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Carbon and Nitrogen Spatial Segregation and Stoichiometry in the Surface Sediments of Southern Chilean Inlets (41°–56°S)
Abstract
The surface sediment of the Chilean Inlets Region has been extensively studied during three major cruises: Cimar Fiordo Cruise 1 in the Upper Area (41°20′S to 46°40′S), Cimar Fiordo Cruise 2 in the Middle Area (46°40′to 47°10′S) and Cimar Fiordo Cruise 3 in the Lower Area (52°19′S to 55°58′S). Total and organic carbon were analysed in 174 sediment samples with an LECO CR-12 elemental analyser. Organic nitrogen was determined using the micro-Kjeldhal technique. Methods were calibrated against standard reference materials certified by the National Institute of Standards and Technology, U.S.A.The study areas were geographically segregated into nine zones according to carbon and nitrogen concentration and distribution. Three of the areas, with comparatively high organic carbon (>1·6%) and organic nitrogen (>0·2%) abundance, were associated with geographically protected inlets and productive planktonic zones. A further four areas with comparatively low organic carbon (In the Upper Area the zonal definition followed a north–south pattern due to the presence of the Corcovado Gulf, which is under the oceanic influence of the West Wind Drift current. Conversely, the Middle Area followed an east–west pattern arising from the ‘Campo de Hielo Norte’ and ‘Campo de Hielo Sur’ glacial fields. A southward trend of diminishing organic carbon content was also noted throughout the Inlets Region.Based on the computed carbon-nitrogen ratios for the previous zones, (C:N range of 5·4 to 11·4), the origin of the organic matter present in the surface sediment was deduced. The C:N values can be chiefly associated to sediment of marine origin, with some degree of remineralization. The edaphic input did not appear to play an important role. Furthermore, the results suggest that the anthropogenic influence on the region is minimal, and thus could be considered as a pristine environment.
... Leaf litter, a local source of organic carbon, stores more carbon and has greater carbon-nitrogen ratios than detritus introduced to mangrove ecosystems by tides (Bouillon et al. 2004). In addition to the mangrove trees themselves, marine phytoplankton are a major source of organic carbon, which can contribute to the carbon content of the sediment and create low carbon-nitrogen ratios (Silva andPrego 2002, Tue et al. 2012). Phytoplankton carries out long-term carbon storage (Gonneea et al. 2004). ...
... Thus, our sediment samples contained a large proportion of non-carbon materials. Sources of non-carbon mangrove sediment include rock erosion and weathering, marine organisms, and calcium-rich shells (Silva and Prego 2002). ...
... One possible explanation for the greater organic-carbon storage in our subsurface than surface samples is that mangrove roots store carbon, which in turn increases carbon content in deeper sediments around them (Tue et al. 2012). Sediments containing high amounts of organic carbon are usually associated with rapid mangrove growth and areas of high primary productivity in the water column (Silva and Prego 2002). At Deep Creek and Kemps Creek, sediment at depths of 5-15 cm stored more carbon than the surface layers, which may be due to the presence of root systems in this depth range. ...
A growing body of evidence suggests that mangrove ecosystems may serve as strong sinks for atmospheric carbon, storing carbon in both mangrove biomass and in the sediment they trap. The quantity of sequestered carbon in Caribbean mangrove ecosystems has yet to be described. The purpose of this study was to determine carbon storage estimates in mangrove sediments to compliment previous work of mangrove carbon storage in The Bahamas. A CN elemental analyzer was used to determine the carbon and nitrogen content as well as carbon nitrogen ratios of the sediment. Litter decomposition rates were also determined using litterbags, which were either kept at the sediment's surface or buried five centimeters below. Results show variable amounts of carbon among the sites, ranging from 13,945-54,853 g of carbon per square meter. Litter decomposition rates were greater belowground than at the surface at every site suggesting that litter must be buried for the form of carbon storage to change. Carbon storage may be correlated with site maturity and soil depth, with more mature forests and deeper depths storing greater amounts of carbon. This study helps complete the picture of tremendous value Caribbean mangroves hold in storing carbon that can help mitigate rising atmospheric carbon.
... The Interior Sea of Chiloé (ISCh) comprises a continuous series of deep basins formed by glacial erosion during the Quaternary and tectonic sinking of the central valley, which in combination with the subsequent rise in sea level and flooding of basins created a system of channels, fjords and interior gulfs (Silva and Prego, 2002, and references therein). The Reloncaví Sound (thereafter RS) and the Ancud Gulf (thereafter AG) are semi-enclosed deep basins (300-400 m), which act as sediment traps and also have a greater concentration of phytoplankton, primary production and zooplankton biomass than the adjacent and southernmost Corcovado Gulf (thereafter CG) (Silva and Prego, 2002;Lara et al., 2016). ...
... The Interior Sea of Chiloé (ISCh) comprises a continuous series of deep basins formed by glacial erosion during the Quaternary and tectonic sinking of the central valley, which in combination with the subsequent rise in sea level and flooding of basins created a system of channels, fjords and interior gulfs (Silva and Prego, 2002, and references therein). The Reloncaví Sound (thereafter RS) and the Ancud Gulf (thereafter AG) are semi-enclosed deep basins (300-400 m), which act as sediment traps and also have a greater concentration of phytoplankton, primary production and zooplankton biomass than the adjacent and southernmost Corcovado Gulf (thereafter CG) (Silva and Prego, 2002;Lara et al., 2016). In general, circulation follows an estuarine pattern where water from the inner sea is exchanged with the Pacific Ocean mainly by the narrow, shallow Chacao Channel (4 km, 50 m depth) and the wider, deeper Boca del Guafo passage (66 km, 150 m depth; Silva et al., 2011). ...
... These ecosystems are characterized by complex marine-terrestrialatmospheric interactions that result in high biological production (Aracena et al., 2011). In the interior parts of the system, the principal sources of particulate material are the biological productivity in the surface waters, fluvial runoff and coastal erosion (Silva and Prego, 2002, and references therein). However, strong seasonality imposes an external influence on the phytoplankton which displays seasonal variation in biomass, primary production, and species composition (González et al., 2010;Lara et al., 2016). ...
... Palabras clave: microorganismos silíceos, diatomeas, sedimentos, producción exportada, canal Puyuhuapi, fiordos chilenos. Some chemical aspects of the Chilean fjord sediments have been studied by Ahumada et al. (1996), Silva et al. (1997), Silva et al. (1998b), Pantoja et al. (2002), Rojas (2002), Silva & Prego (2002), Sepúlveda et al. (in press), among others. Geochronology studies have been performed by Salamanca (1996), using 210 Pb, who registered sedimentation rates of 0.19-0.41 ...
... In general, the distribution of the nutrients in the water column has been described as having a two layer structure, with very low concentrations in the surface waters, a strong nutricline at about 10-20 m depth and higher values at depth (Silva et al. 1997). The sediments are composed of silt and clay and are relatively rich in organic matter (10 %), with average values of total organic carbon (1.62 %) and total nitrogen (0.17 %) (Silva & Prego 2002). ...
... The C org was on average >1 % (with values ranging 0.7-3.3 %, except for the sections that contain the sand layer and the leaf remains), agreeing with the results recorded by Silva et al. (1997Silva et al. ( , 1998b and Silva & Prego (2002) for the northern fjord zone between Puerto Montt and the Moraleda Channel. ...
We present a 100-year reconstruction of siliceous export production from sediments of the Puyuhuapi Channel (44° S, 70° W) in the Chilean fjords. We use accumulation rates and concentrations of diatoms and silicoflagellates, organic carbon (Corg) and biogenic opal (SiOPAL) as proxies of export production, and fluctuations in the contribution of freshwater diatoms as proxies of rainfall in the hinterland and river runoff. Box core sediments collected at two sites within the Puyuhuapi Channel were analyzed: Station 35 (at the head of the fjord; 56 m water depth) and Station 40 (in the middle of the Channel; 270 m water depth). Surface sedimentation rates were 0.75 cm yr-1 at Station 35 and 0.25 cm yr-1 at Station 40. SiOPAL content averaged ∼ 4% at both sites. Diatom accumulation rates as well as the contribution of freshwater diatoms were higher at the head of the fjord (1.59 1010 valves m-2 yr-1 and 22 %, respectively) than in its middle (1.08 1010 valves m-2 yr-1 and 14%, respectively). Diatom abundances were two orders of magnitude higher than silicoflagellate contribution at both sites. In general, diatoms typical of high nutrient environments characterize the Puyuhuapi Channel sediments: at both sites, spores of the genus Chaetoceros dominated the diatom assemblage (> 40% of total diatoms; spores of Chaetoceros radicans/cinctus, Ch. constrictus/vanheurcki, Ch. debilis and Ch. diadema). Downcore analysis reveals an overall increase in the production of siliceous microorganisms from the late 19th century to the early 1980s, and then a decrease until the late-1990s. We associate a decrease in freshwater diatom contribution since the mid-1970s which we associate with a concomitant decline in rainfall in the Chilean fjords. We suggest that this decline is related to the global atmospheric and oceanic warming of the past ∼ 25 years.
... Previous studies indicate that surface sediments of the Reloncaví, Puyuhuapi and Aysén Fjords have high organic carbon contents (i.e. >3%; Silva and Prego, 2002), where a significant part is supplied by the major rivers (i.e. Puelo, Cisnes, Aysén Rivers). ...
... The lack of a hypoxic zone in the fjord heads of the Central Patagonian Zone can be explained by lower autochthonous carbon production and/or organic matter input to the water column and the sediments compared with the Northern Patagonian Zone (Silva and Prego, 2002;Silva et al., 2011), despite the Baker River. The freshwater discharges of the Baker River may possibly be the most important source of terrestrial organic matter in the area (Table 2), on the other hand, its more eroded river basin may also provide more sediment but smaller proportions of plant material than other river basins . ...
... The freshwater discharges of the Baker River may possibly be the most important source of terrestrial organic matter in the area (Table 2), on the other hand, its more eroded river basin may also provide more sediment but smaller proportions of plant material than other river basins . Moreover, this area is heavily influenced by glacier melt water and river discharge loaded with inorganic glacial material or glacier silt (Silva and Prego, 2002;Aracena et al., 2011). Indirect evidence of this is the low total organic carbon content in surface sediment in these fjords, which is due to dilution by the input of glacier silt (Silt + Clay $ 100%; Corg. ...
Chilean Patagonia is one of the largest estuarine systems in the world. It is characterized by a complex geography of approximately 3,300 islands, a total surface area of 240,000 km2, and 84,000 km of coast line, including islands, peninsulas, channels, fjords, and sounds. The Chilean Patagonia Interior Sea is filled with a mixture of sea, estuarine, and fresh waters, and is characterized by a two layer vertical general circulation. Dissolved oxygen (DO) conditions in these fjords were analyzed based on historic salinity, dissolved oxygen and nutrient data from 1,200 oceanographic stations. Horizontal advection of adjacent well oxygenated Subantarctic Waters (5-6 mL L-1) was the mayor source of DO in the deep layers of the Interior Sea. Incoming DO was consumed by the respiration of autochthonous and allochthonous particulate organic matter, as ocean water flows towards the continental fjord heads, reaching near-hypoxic (2-3 mL L-1) or hypoxic levels (< 2 mL L-1). As DO declined nutrient concentrations increased towards the fjord heads (from ∼ 1.6 μM PO4-3 and ∼ 16 μM NO3- to ∼ 2.4 μM PO4-3 and ∼ 24 μM NO3-). Overall, DO conditions in the Interior Sea were mostly the result of a combination of physical and biogeochemical processes. In all eastern channels and fjords, a low DO zone developed near the fjord heads (< 4 mL L-1) as a result of larger allochthonous particulate organic matter inputs transported by local rivers. This enhanced organic matter input to the deep layer increased DO consumption due to respiration and overwhelmed the oxygen supplied by horizontal advection. Out of the 90 Chilean Patagonian gulfs, channels and fjords analyzed, 86 systems were oxic (> 2 mL L-1) and four hypoxic (< 2 mL L-1), but only at their heads. None were found to be anoxic (0 mL L-1). We found these DO conditions to be permanent features of the Chilean Patagonia Interior Sea.
... Palabras clave: microorganismos silíceos, diatomeas, sedimentos, producción exportada, canal Puyuhuapi, fiordos chilenos. Some chemical aspects of the Chilean fjord sediments have been studied by Ahumada et al. (1996), Silva et al. (1997), Silva et al. (1998b), Pantoja et al. (2002), Rojas (2002), Silva & Prego (2002), Sepúlveda et al. (in press), among others. Geochronology studies have been performed by Salamanca (1996), using 210 Pb, who registered sedimentation rates of 0.19-0.41 ...
... In general, the distribution of the nutrients in the water column has been described as having a two layer structure, with very low concentrations in the surface waters, a strong nutricline at about 10-20 m depth and higher values at depth (Silva et al. 1997). The sediments are composed of silt and clay and are relatively rich in organic matter (10 %), with average values of total organic carbon (1.62 %) and total nitrogen (0.17 %) (Silva & Prego 2002). ...
... The C org was on average >1 % (with values ranging 0.7-3.3 %, except for the sections that contain the sand layer and the leaf remains), agreeing with the results recorded by Silva et al. (1997Silva et al. ( , 1998b and Silva & Prego (2002) for the northern fjord zone between Puerto Montt and the Moraleda Channel. ...
We present a 100-year reconstruction of siliceous export production from sediments of the Puyuhuapi Channel (44° S, 70° W) in the Chilean fjords. We use accumulation rates and concentrations of diatoms and silicoflagellates, organic carbon (Corg) and biogenic opal (SiOPAL) as proxies of export production, and fluctuations in the contribution of freshwater diatoms as proxies of rainfall in the hinterland and river runoff. Box core sediments collected at two sites within the Puyuhuapi Channel were analyzed: Station 35 (at the head of the fjord; 56 m water depth) and Station 40 (in the middle of the Channel; 270 m water depth). Surface sedimentation rates were 0.75 cm yr-1 at Station 35 and 0.25 cm yr-1 at Station 40. SiOPAL content averaged ~ 4 % at both sites. Diatom accumulation rates as well as the contribution of freshwater diatoms were higher at the head of the fjord (1.59 10(10) valves m-2 yr-1 and 22 %, respectively) than in its middle (1.08 10(10) valves m_2 yr_1 and 14 %, respectively). Diatom abundances were two orders of magnitude higher than silicoflagellate contribution at both sites. In general, diatoms typical of high nutrient environments characterize the Puyuhuapi Channel sediments: at both sites, spores of the genus Chaetoceros dominated the diatom assemblage (> 40 % of total diatoms; spores of Chaetoceros radicans/cinctus, Ch. constrictus/vanheurcki, Ch. debilis and Ch. diadema). Downcore analysis reveals an overall increase in the production of siliceous microorganisms from the late 19th century to the early 1980s, and then a decrease until the late-1990s. We associate a decrease in freshwater diatom contribution since the mid-1970s which we associate with a concomitant decline in rainfall in the Chilean fjords. We suggest that this decline is related to the global atmospheric and oceanic warming of the past ~ 25 years
... These features, combined with the wave-sheltered environment and the presence of multiple sills within most fjords, promote retention of organic matter (Pickrill, 1980(Pickrill, , 1987Stanton & Pickard, 1981;Nuwer & Keil, 2005), resulting in most fjords being net carbon sinks (Pickard & Stanton, 1980;Nuwer & Keil, 2005). In addition, high rainfall of up to 8 m year −1 (Naiman & Sibert, 1978;Sansom, 1984;Silva & Prego, 2002) provides optimum conditions for temperate rainforest production, and the subsequent flow of forest-derived organic matter into the fjord marine environment (Glasby, 1978;Nuwer & Keil, 2005;Sepúlveda et al., 2009). Data on rates of primary production are limited, but temperate rainforests that cover the often extensive catchments of fjords can often exceed 0.65 kg C.m −2 .year ...
... −1 (Table 1). This case study is concerned primarily with carbon flow in forested temperate fjords, and so will focus on those in New Zealand, Canada and Chile where extensive native forest remains (Scott, Mark & Sanderson, 1964;Silva & Prego, 2002;Vargas et al., 2011) (2) Main vectors of carbon POC and DOC released from the forest vegetation form the main vectors for carbon flow across ecosystem boundaries between temperate forests and fjords (Fig. 3). Forest organic matter enters the fjords via fluvial transport of particulate and dissolved organic matter (Nuwer & Keil, 2005;Sepúlveda et al., 2009;Silva, Vargas & Prego, 2011;Vargas et al., 2011), and sudden deposition events such as landslides (St-Onge & Hillaire-Marcel, 2001;Timothy, Soon & Calvert, 2003). ...
... However, data on the export of DIC, and on the scale of movement of both DOC and DIC, are limited or lacking in all the systems we examined. Land run-off also plays a critical role in the transport of terrestrial POC and DOC into coastal systems, particularly in fjords (Sansom, 1984;Burrell, 1988;Silva & Prego, 2002), but the extent of the influence of these vectors is likely to be limited. Once imported into a recipient system, POC influences productivity via mesograzers (Crawley & Hyndes, 2007;Ince et al., 2007), which are consumed by higher trophic levels, or the release of DOC from macrophytes that becomes available to microbial activity and uptake by microalgae or macrophytes (Berg & Jorgensen, 2006;Vonk et al., 2008). ...
Worldwide, coastal systems provide some of the most productive habitats, which potentially influence a range of marine and terrestrial ecosystems through the transfer of nutrients and energy. Several reviews have examined aspects of connectivity within coastal seascapes, but the scope of those reviews has been limited to single systems or single vectors. We use the transfer of carbon to examine the processes of connectivity through multiple vectors in multiple ecosystems using four coastal seascapes as case studies. We discuss and compare the main vectors of carbon connecting different ecosystems, and then the natural and human-induced factors that influence the magnitude of effect for those vectors on recipient systems. Vectors of carbon transfer can be grouped into two main categories: detrital particulate organic carbon (POC) and its associated dissolved organic and inorganic carbon (DOC/DIC) that are transported passively; and mobile consumers that transport carbon actively. High proportions of net primary production can be exported over meters to hundreds of kilometers from seagrass beds, algal reefs and mangroves as POC, with its export dependent on wind-generated currents in the first two of these systems and tidal currents for the last. By contrast, saltmarshes export large quantities of DOC through tidal movement, while land run-off plays a critical role in the transport of terrestrial POC and DOC into temperate fjords. Nekton actively transfers carbon across ecosystem boundaries through foraging movements, ontogenetic migrations, or 'trophic relays', into and out of seagrass beds, mangroves or saltmarshes. The magnitude of these vectors is influenced by: the hydrodynamics and geomorphology of the region; the characteristics of the carbon vector, such as their particle size and buoyancy; and for nekton, the extent and frequency of migrations between ecosystems. Through a risk-assessment process, we have identified the most significant human disturbances that affect the integrity of connectivity among ecosystems. Loss of habitat, net primary production (NPP) and overfishing pose the greatest risks to carbon transfer in temperate saltmarsh and tropical estuaries, particularly through their effects on nekton abundance and movement. In comparison, habitat/NPP loss and climate change are likely to be the major risks to carbon transfer in temperate fjords and temperate open coasts through alteration in the amount of POC and/or DOC/DIC being transported. While we have highlighted the importance of these vectors in coastal seascapes, there is limited quantitative data on the effects of these vectors on recipient systems. It is only through quantifying those subsidies that we can effectively incorporate complex interactions into the management of the marine environment and its resources.
... The similarity measure used was the Normalized Euclidean Distance. Environmental variables (water depth, substrate) and some sediment chemical features of the SPI (organic carbon and nitrogen, total phosphate) were obtained from Ahumada et al. (1996) and Silva and Prego (2002). Comparable information for the SM area is relatively scarce. ...
... These differences are attributed to certain environmental properties of the areas, mainly those related to the stability of the bottom sediments. Silva and Prego (2002) indicated that glaciers provide cold oligotrophic waters rich in silt to the inlets, features which may explain the scarcity of benthic abundance and biomass production, as was suggested for the phytoplankton scarcity found in several of the fjords considered in our study (Vera et al., 1996). ...
... An important additional difference to sites located in the SPI area is the higher amount of inorganic carbon in surface sediments of the Straits of Magel- lan (Silva and Prego, 2002), which according to Brambati et al. (1991) can be attributed to the presence of calcite in the remains of bivalves, gastropods, crustaceans and foraminiferans. Unfortunately, information on chemical and physical processes of pelagobenthic coupling (Cattaneo-Vietti et al., 1999) and in the bottom sediments is scarce for the area of study, and this represents a limiting factor to explain the (dis)similarities we found between the study areas. ...
Macrobenthic associations were investigated at 29 sampling stations with a semi-quantitative Agassiz trawl, ranging from the South Patagonian Icefield to the Straits of Magellan in the South Chilean fjord system. A total of 1,895 individuals belonging to 131 species were collected. 19 species belong to colonial organisms, mainly Bryozoa (17 species) and Octocorallia (2 species). The phylum Echinodermata was the most diverse in species number (47 species), with asteroids (25 species) and ophiuroids (13 species) being the best represented within this taxon. Polychaeta was the second dominant group in terms of species richness (46 species). Multidimensional scaling ordination (MDS) separated two station groups, one related to fjords and channels off the South Patagonian Icefield and the second one to stations surrounding the Straits of Magellan. 45 species account for 90% of the dissimilarity between these two groups. These differences can mainly be explained by the influence of local environmental conditions determined by processes closely related to the pres-ence/absence of glaciers. Abiotic parameters such as water depth, type of sediment and chemical features of the superficial sediment were not correlated with the numbers of individuals caught by the Agassiz trawl in each group of sampling stations .
... The coastline of southern Chile (below 41 @BULLET S) is comprised of a continuous series of deep basins, channels and islands formed by glacial erosion during the Quaternary and tectonic sinking of the Central Chilean Valley. This area extends from Puerto Montt City (42 @BULLET 30'S) to Cape Horn (55 @BULLET 58'S), in a rugged region composed by a myriad of islands, fjords and channels with a relief ranging from 500 to 2000 m (Silva 2002). The bottom topography of the inlets is made irregular by frequent sills, which act as barriers for the circulation of bottom waters, favoring high sedimentation and a depression in dissolved oxygen, although anoxia is never attained (Silva, 2002). ...
... This area extends from Puerto Montt City (42 @BULLET 30'S) to Cape Horn (55 @BULLET 58'S), in a rugged region composed by a myriad of islands, fjords and channels with a relief ranging from 500 to 2000 m (Silva 2002). The bottom topography of the inlets is made irregular by frequent sills, which act as barriers for the circulation of bottom waters, favoring high sedimentation and a depression in dissolved oxygen, although anoxia is never attained (Silva, 2002). These factors, plus highly variable climatic conditions and minimal anthropogenic influence (Silva 2002), produce ecosystems that can be considered structurally and functionally unique (Palma 2004). ...
... The bottom topography of the inlets is made irregular by frequent sills, which act as barriers for the circulation of bottom waters, favoring high sedimentation and a depression in dissolved oxygen, although anoxia is never attained (Silva, 2002). These factors, plus highly variable climatic conditions and minimal anthropogenic influence (Silva 2002), produce ecosystems that can be considered structurally and functionally unique (Palma 2004). The AysénAys´Aysén fjord is located in the middle of this exceptional territory (45 @BULLET 12'S), with a length of 65 km, and an average width of 6.5 km (Fig. 1). ...
... The CPFC is subdivided into three major areas: North Patagonia (42°-46.5°S), Central Patagonia (46.5°-53°S), and South Patagonia (53°-56°S) (Silva and Prego, 2002;Aracena et al., 2011). Located in the central part of the CPFC, the Katalalixar National Reserve (KNR) is an archipelago surrounded mostly by brackish waters and interconnected by channels and fjords, representing a geographical puzzle of landscapes. ...
... Central Patagonia (46.5°-53°S), and South Patagonia (53°-56°S). This categorization was based on oceanographic (Silva and Prego, 2002;Aracena et al., 2011) and geological information, considering that the CPFC extends over a latitude of about 14°(42°to 56°S) and reaches up to three degrees of longitude in its widest part. The CPFC is only interrupted by two major geographical features, the Gulf of Penas and the Strait of Magellan, which may produce a zoogeographical subdivision (Rovira and Herreros, 2016). ...
Knowledge about the composition, diversity, and geographic distribution of marine species is important for successful conservation planning in the future. The ecological and zoogeographic patterns of benthic communities in Central Patagonia have been scarcely studied, due to the remoteness of the area combined with harsh weather conditions. During the past years, five scientific expeditions were executed in order to study the biodiversity, ecological, and biogeographical patterns of benthic invertebrates in the Katalalixar National Reserve (KNR) waters, Central Patagonia (~48°S). Our analyses comprised images from 26 video transects using a remotely operated vehicle, completed with biological sampling at four stations by means of SCUBA diving, covering a bathymetric range from 10 to 220 m depth. Stations covered the entire longitudinal range of the KNR, from inner channels to the Pacific Ocean. A total of 187 benthic invertebrate taxa were identified as OTUs (operational taxonomic units), with mollusks being the most conspicuous taxonomic group (18.7%), followed by sponges, echinoderms (16.6% each), and arthropods (14.4%). A higher OTU richness (42 to 51 OTUs) was observed in the central and western parts of the KNR waters. Analyses of the β-diversity indicated a similar level of species turnover between shallow, intermediate, and deep strata, as well as an important turnover between different locations. Dissimilitudes in the assemblage structure of invertebrates were explained mainly by changes in substrate types and longitude. Most of the species (49%) found in the KNR waters showed a wide latitudinal distribution range along the Eastern South Pacific Ocean (ESP) and the Chilean Patagonia of fjords and channels (CPFC) (~18°S and ~56°S), whereas 9.4% of the species have a wide distribution range between the CPFC and south of the Antarctic polar front (SAPF) (~42°S and ~65°S). Since only 16.7% of the species identified in the KNR are distributed exclusively in CPFC waters, it may be considered a transition area for marine invertebrates. It is distributed between northern ESP and SAPF. Knowledge of species composition and distribution patterns along spatial and environmental gradients is essential for any sustainable management, monitoring, and future conservation plans to protect the fragile and diverse marine ecosystems of Chilean Patagonia.
... Within this model ẟ 13 C org values were used as the tracer as it has been shown to be a more reliable and robust tracer of OC source than either N/C or δ 15 N when used alongside a binary mixing model (Faust & Knies, 2019;Hinojosa et al., 2014;. The binary mixing model was chosen over a Bayesian approach (Fernandes et al., 2014; to allow comparisons to global F terr estimates calculated using the binary mixing model approach (i.e., Cui, Bianchi, Jaeger, & Smith, 2016;Faust & Knies, 2019;Hinojosa et al., 2014;Silva & Prego, 2002). (1) ...
... Both the outer sill depth and tidal range can be seen as proxies for the restrictiveness of the fjord which likely governs both the input of OC mar and the retention of OC terr within the fjord as conceptualized by Fuast and Knies Hage et al., 2022;Ingall et al., 2005;Louchouarn et al., 1997;Nuwer & Keil, 2005;Smith & Walton, 1980;Smittenberg, Pancost, et al., 2004;St-Onge & Hillaire-Marcel, 2001 Chile 1.79 ± 0.76 −29.0-−19.1 1.3-9.0 Bertrand et al., 2012;Mayr et al., 2014;Rebolledo et al., 2019;Ríos et al., 2020;Ruiz-Ruiz et al., 2021;Sepúlveda et al., 2005Sepúlveda et al., , 2011Silva et al., 2011;Silva & Prego, 2002Norway 8.82 ± 4.20 −23.8-−20.9 4.69-6.9 ...
The sediments within fjords are critical components of the mid‐ to high‐latitude coastal carbon (C) cycle, trapping and storing more organic carbon (OC) per unit area than other marine sedimentary environments. Located at the land‐ocean transition, fjord sediments receive OC from both marine and terrestrial environments; globally, it has been estimated that 55%–62% of the OC held within modern fjord sediments originates from terrestrial environments. However, the mid‐latitude fjords of the Northern Hemisphere have largely been omitted from these global compilations. Here we investigate the mechanism driving the distribution of OC originating from different sources within the sediments of 38 Scottish fjords. From an array of fjord characteristics, the tidal range and outer sill depth were identified as the main drivers governing the proportions of marine and terrestrial OC in the sediments. Utilizing this relationship, we estimate that on average 52% ± 10% of the OC held within the sediments of all Scotland's fjords is terrestrial in origin. These findings show that the Scottish fjords hold equivalent quantities of terrestrial OC as other global fjord systems. However, the analysis also highlights that the sediments within 29% of Scottish fjords are dominated by marine derived OC, which is driven by local fjord geomorphology and oceanography.
... The carbon, nitrogen and phosphorus contents and their molar ratios in sea-water and marine sediments are regularly used to determine the origin and transformation of organic matter (OM). These ratios can be influenced by a series of environmental factors highlighted by climate, terrigenous input, bathymetry, and bottom circulation [1][2][3][4][5][6][7][8][9]. There is evidence that organic C and N contents display decreasing trends in sediments along depth gradients (200 to 3000 m), such as off the Mississippi River Delta in the Gulf of Mexico [3]. ...
... The availability of carbon and nitrogen sources, the oxidation conditions, and the diagenesis of the organic matter pool may play an important role in the OC:ON ratios. When the OC:ON ratios of Block III were recalculated, the resulting values were higher than those reported by Redfield et al. [50] but fell within the range of those published by several authors [1,5,6,8,29,51]. ...
The surficial sediments recovered from 12 sites located near the channel axis of the Florida Straits and the lower slope off NW Cuba were analyzed for total organic carbon (TOC), nitrogen (TN), phosphorus (TP), elemental C:N:P ratios, C and N isotopic values, and 14 C dating. The depth profiles of TOC, TN, and TP (0-18 cm) displayed a downcore trend and a significant variation. The TOC values were low (0.15 to 0.62%; 66 to 516 µmol g-1). Sites near the island's lower slope had lower TOC average concentrations (158-333 µmol g-1) than those closer to the channel axis (averaging 341-516 µmol g-1 ; p <0.05). The TN concentrations near the lower slope attained 0.11% (80 µmol g-1), whereas, towards the channel axis, they decreased to 0.07% (55 µmol g-1 ; p<0.05). The C:N ratios ranged from 1.9 to 10.2. The mean molar C:N ratio (5.4) indicated a marine hemipelagic deposition. The TP was lower at sites near the lower slope (38.4 to 50.0 µmol g-1 ; 0.12% to 0.16%) than those near the channel axis (50.0 to 66 µmol g-1 ; 0.15 to 0.21%). C:P fluctuated from 7.7 to 14.1 in the surficial sediment layer. The bulk organic δ 13 C org and δ 15 N values confirmed pelagic organic sources, and the 14 C dating revealed that the sediments were deposited during the Holocene (1000-5000 yr BP). We suggest that the hydrodynamic conditions in the Straits influence vertical and advective fluxes of particulate organic material trapped in the mixed-layer, which reduces the particulate matter flux to the seabed.
... Thus, the overall B and productivity estimated were higher for the ISCh than MCh, coinciding with reports on the trend of declining B and diversity of zooplankters toward higher latitudes described when analyzing larger spatial scales (from Northern to Southern Patagonia) (Palma and Silva 2004). The same latitudinal trend was found for the OM recorded in the sediments (5.3 and 3.8 %, respectively; Silva and Prego 2002), where the carbon flows into detritus were 40 % higher in the ISCh than MCh, exemplifying a more efficient pelagic-benthic coupling. In other studies, the average POC concentrations determined in the upper 50 m of the water column (spring-summer) decreased from around 200 to 600 mg C m −3 in Reloncavi Fjord to 76 mg C m −3 in the Strait of Magellan (Fabiano et al. 1999), which also coincides with the decrease in the percentage of organic carbon in the sediments from the same areas (5.3-3.8 %; Silva and Prego 2002) and which is also similar to the decreasing trend in the detritus flows found here. ...
... The same latitudinal trend was found for the OM recorded in the sediments (5.3 and 3.8 %, respectively; Silva and Prego 2002), where the carbon flows into detritus were 40 % higher in the ISCh than MCh, exemplifying a more efficient pelagic-benthic coupling. In other studies, the average POC concentrations determined in the upper 50 m of the water column (spring-summer) decreased from around 200 to 600 mg C m −3 in Reloncavi Fjord to 76 mg C m −3 in the Strait of Magellan (Fabiano et al. 1999), which also coincides with the decrease in the percentage of organic carbon in the sediments from the same areas (5.3-3.8 %; Silva and Prego 2002) and which is also similar to the decreasing trend in the detritus flows found here. ...
The fjords and channels of the Chilean Patagonia are unique, and their high biological diversity is mainly associated with physicochemical characteristics of local water masses. The topography, depth, and extension of the Patagonian basins affect the extent to which water is exchanged between the inner and outer parts of the fjords, determining the marine productivity, biomass levels and energy flows through the pelagic food web. Coastal basins with high connectivity to the adjacent ocean and nutrient supply (e.g., the Inner Sea of Chiloe (ISCh)) might be predicted to have higher productivity and biomass than the relatively shallow, small-sized fjords and channels (e.g., Moraleda Channel (MCh)). To determine the ecotrophic and ecosystem-level similarities and differences of these two basins, we built two static and mass-balanced trophic models using Ecopath software. The models of planktonic communities were based on data collected during three scientific cruises conducted in 2006 and 2007. Diet, secondary production, and consumption rates were obtained from previously published data. The models’ results suggested that areas adjacent to the ocean (ISCh) had 61 % higher biomass, 44 % more biomass consumed, and a 17 % greater efficiency in the transfer of energy than inshore (MCh) areas. By characterizing the trophic position and linkages of the planktonic groups with a multi-taxa approach, we were able to analyze the roles of key species and functional groups that modulate the described biomass and energy flows under different conditions in two basins of the Chilean Patagonian coastal system.
... Fjords in Northern Patagonia have previously registered low δ 15 N values in water columns and sediments (Silva and Prego, 2002;Silva et al., 2011;Rebolledo et al., 2019), as well as in benthic macroalgae (Mayr et al., 2011). In general, nutrient inputs in fjord waters enriched with nitrate and orthophosphate are derived from oceanic Sub Antarctic Water masses (SAAW) (Silva and Palma, 2008). ...
Benthic marine food webs, which recycle organic matter and sustain unique biodiversity, are an important component of estuarine Patagonian fjords; however, these may be heavily influenced by salmon farming activities. Under the above conditions, this study collected several food sources (sediment organic matter, suspended particulate organic matter, macroalgae) and 26 benthic invertebrate species, and analyzed them using a Bayesian mixing model. Briefly, carbon and nitrogen stable isotopes analyses revealed that the highly variable isotopic niche widths respond to food supplies from marine and terrestrial organic matter. In addition, particulate and dissolved waste from salmon farming activities were found to modify isotopic composition ratios in many suspension feeders. Particularly, our results indicate high δ¹⁵N values in the sponge Cliona chilensis and the encrusting coral Incrustatus comauensis, which appear to be potential ecological indicators for evaluating stoichiometry imbalances and trace organic pollution sources in fjord environments.
... PMO and QLN presented a more differentiated pattern of meristic and morphometric variation ( Fig. 4 and Table A5) related to the chemical and physical features of the ISCh, which comprises a complex arrangement of semi-enclosed basins such as inlets, fjords, and estuaries (Zapata-Hernández et al. 2016). Based on their locations, this indicates that PMO individuals developed a purely estuarine form and grew in a productive environment with higher values of organic matter (Silva and Prego 2002), while individuals in QLN had an intermediate marine-estuarine form because of the more dynamic interaction between ISCh and the HCS in this place (Zapata-Hernández et al. 2016). ...
We evaluated the influence of areas with dissimilar upwelling intensity along the Humboldt Current System on the morphological variation of the economically important sea silverside Odontesthes regia by using geometric morphometric (GM) and meristic data of populations sampled off Northern Peru, Central Peru, Southern Peru-Northern Chile, and Central-Southern Chile (CSCH). Multivariate analyses of variance, a UPGMA tree, and discriminant analyses of meristic counts separated CSCH individuals, which had slightly higher numbers of gill rakers and radius of the anal fin. Permutation tests and canonical variate analyses of GM data distinguished all populations and highlighted deformations in the head and fins. Variations in GM and meristic analyses were significantly correlated with values of the sea surface temperature and surface chlorophyll-a concentrations. Morphological differences among populations might be associated with the spatial coastal upwelling dynamic of the Humboldt Current System, which highlights the role that this system plays in relation to the phenotypic variation of fish.
... The Almirantazgo Fjord which is located at the northeastern corner of Dawson Island and close to the southern end of Inútil Bay (IB in Fig. 1a) is an additional source of low salinity waters to the central basin via the Whiteside Channel (Aracena et al., 2015). Calving glaciers form Cordillera Darwin icefield (CDI in Fig. 1a, e. g. Silva and Prego, 2002;Aracena et al., 2015) and runoff fresh waters (e.g., Antezana, 1999) salinities ~ 28 are observed at the head of the fjord. Within the fjord the upper 60 m of the water column salinity increases towards the MS to about 30.5 (Fig. 6). ...
We analyze historical hydrographic data together with recent high-resolution hydrographic and underwater glider observations collected in the Magellan Strait to determine the water mass characteristics and exchanges between the continental shelves of the southeast South Pacific and southwest South Atlantic around southern South America. The near-surface salinity distribution and water mass analyses indicate a strong interoceanic connectivity associated with diluted subantarctic waters of the Pacific Ocean through the Magellan Strait which in turn are further diluted largely by inflows from the Almirantazgo Fjord via the Whiteside Channel. The lowest salinity waters reach the Atlantic shelf via the Magellan Strait. This core of low salinity waters (S < 31.5) are observed on the northern portion of the strait's Atlantic mouth and creates a strong baroclinic signal that leads to intense eastward geostrophic velocities suggesting a net Pacific to Atlantic transport (0.038–0.074 Sv, 1 Sv = 10⁶ m³ s⁻¹). This flow plays a significant role on the thermohaline characteristics and extent of the subantarctic shelf waters that occupy the Atlantic shelf. The low salinity inflow from the Magellan Strait combines with saltier inflows through the Le Maire Strait and farther east that feed the Atlantic shelf.
... Polygordius can select muddy and sandy sediments during settlement, with a preference for sandy fractions during flume experiments (Snelgrove et al. 1999), and Polygordius jouinae could be a potential bioindicator of enriched sandy sediment in the east coast of United States (Ramey & Bodnar, 2008). Confirming these observations, the sediment characterization of CIMAR Fjord Cruise 3 (1997) reported that the sediments around Dawson Island, Inútil Bay, and Beagle Channel were composed mainly of mud with a small fraction of sand, with 0-2.4% organic carbon, 0-0.4% inorganic carbon, and 0-0.2% Kjieldhal nitrogen (Silva & Prego, 2002;Silva, 2008). ...
Integration of meroplankton abundance and hydrographic data was employed to relate the Polygordius exolarvae spatial dynamics with different salinity gradients in order to define the factors that regulate the abundance and spatial distribution along the large estuarine system from southern Chile. The present study aims: i) record the abundance and spatial distribution of Polygordius neustonic exolarvae along of the estuaries with different gradients of salinity located between Guafo Channel, southern Chiloé Island (44° S) to Navarino Island (55° S), Chile; ii) connect this distributional pattern to oceanographic parameters to determine if members of this genus have adapted to euryhaline or stenohaline conditions, and iii) establish a comparison between the abundance of Polygordius and others meroplanktonic taxa collected during CIMAR Cruises 16, 18 and 20 Fjords. Neustonic samples were collected during three oceanographic cruises along southern Chilean fjord/channel systems (~ 1,700 km) with different freshwater supply regimes (CIMAR 16: October/November, 2010, 52° to 55° S; CIMAR 18: June/July, 2012, 44° to 47° S; CIMAR 20: October, 2014, 47° to 50° S), providing evidence to relate the influence of surface salinity on the Polygordius exolarvae spatial distribution of abundance. Polygordius exolarvae (average length=2.9 ± 0.8 mm), the most abundant meroplanktonic taxa within the neustonic community (54.04% of total abundance; 66,228 individuals; NTotal=26 stations), was represented at 81% of stations sampled in CIMAR 16 (mean salinity=30.7 psu), showing higher abundance (1,518 ind. x 5 min of horizontal drag) than for other polychaete larvae (10 types) and other meroneustonic taxa; 60% of the abundance of exolarvae during CIMAR 16 was collected around Dawson Island, Magellan Strait. In CIMAR 18 cruise (mean salinity=24.28 psu), abundance of exolarvae was low (3 ind. x 5 min of horizontal drag) and were collected only at 5 stations along the Moraleda Channel (NTotal=31 stations); no exolarvae were collected duringTCotaIlMAR 20 (Ntotal=39 stations) (mean salinity= 23.26 psu). Polygordius exolarvae have narrow haline/thermal requirements during their pelagic life, where sills and island mass effect could produce a restricted and aggregated spatial distribution in some areas of the study zone.
... This highlights the feedback control between the so-called macro-and micro-nutrients. In Chilean fjords, nitrogen is mainly contributed as nitrate (NO 3 − ) by vertical entrainment of nutrient-rich sub-Antarctic water from adjacent oceanic areas (Silva et al., 1998;Silva and Prego, 2002). During assimilation by phytoplankton, NO 3 − follows a series of metabolic processes in which it is reduced to NH 4 + , a process which requires the availability of Fe. ...
Salmon aquaculture in Chile has been a rapidly growing industry, generating increasing inputs of organic matter and inorganic nutrients into the ecosystem. We studied the potential impacts of ammonium input by this industry on the cycling of iron (Fe) in a Chilean fjord. The distribution of different Fe fractions at varying ammonium concentrations was monitored in a twenty-two day mesocosm experiment. The setup involved brackish water and seawater; each had a control and four ammonium concentrations. Measurements were performed for total (TFe Ch ) and dissolved (DFe Ch ) chelex labile Fe fractions, and particulate Fe (PFe). Results for both brackish and seawater showed similar trends but differences in magnitude. Over time, DFe Ch decreased with increasing ammonium concentration, while TFe Ch showed up to a three-fold increase positively correlated with ammonium addition, chlorophyll and particulate organic carbon. Overall, PFe values increased over time with 37%–89% of this fraction estimated to be of lithogenic origin. When normalized to particulate organic carbon and chlorophyll, PFe was negatively correlated with ammonium showing an exponential decrease. The PFe measured in the 20–140 μm fraction, showed a hyperbolic relationship with particulate phosphorus, suggesting a change in the ratio for these elements in this size fraction. The increase and dominance of diatoms over time in both water types, together with the observed PFe trend, suggest that large phytoplankton potentially act as the main carrier phase of potential scavenged Fe via the available surfaces of sinking cells. Positive correlations between changes in TFe Ch and changes in chlorophyll and particulate organic carbon suggest a biological role in controlling the particulate labile Fe fraction, hence resulting in a potential increase of bioavailable Fe. Increasing ammonium addition in the fjords of Chile caused by salmon aquaculture may affect the phytoplankton assemblage composition and therefore the PFe to organic carbon ratio. Possible changes in biogeochemical Fe cycling may result from nutrient enhanced diatom-dominated blooms acting as more efficient vectors for downward export of organic matter.
... Coupling between freshwater inputs (from rivers and glaciers), nutrients, and biological responses of coastal systems in the outflow region of Patagonia's inner seas has been a major oceanographic issue in the past fifteen years, especially given actual scenarios of climatic-driven hydrological regime changes (León-Muñoz et al. 2018). Early studies have pointed out that Patagonian fjords are thought to be sinks for atmospheric CO 2 (Torres et al. 2011), and they are important aquatic systems where high concentrations of organic matter and biogenic opal contents in the sediments have been associated with high primary productivity estimates (Aracena et al. 2011;Silva and Prego 2002). A combination of physical (stratification) and chemical (nutrients) properties has been reported to determine high primary production in spring and summer (up to 4 g C m −2 d −1 ) in the inner sea of northern Patagonia (Iriarte et al. 2007;Jacob et al. 2014). ...
It is relevant to understand the processes and factors that modulate the efficiency of the carbon pump throughout the ecosystem of Patagonian fjords. Spatial variability of primary productivity and bacteria-microplankton biomass was assessed in relation to inorganic nutrients and stratification across nearshore zones of southern Patagonia (50–53°S) in austral spring 2009. Estimates of primary productivity (300–500 mg C m⁻² d⁻¹) and phytoplankton biomass (9–180 mg chlorophyll-a m⁻²) were low at offshore and inshore waters. Synergistic effects of low silicic acid concentrations and poor light penetration because of salinity-driven stratification of glacier meltwater in springtime appeared to negatively affect phytoplankton carbon biomass and primary production in this sub-Antarctic region. The knowledge of the relative importance of nutrient sources and light is especially significant for Patagonian glacier-fjord systems that are expected to receive higher freshwater inputs and will be more stratified in the future.
... The Almirantazgo Fjord which is located at the northeastern corner of Dawson Island and close to the southern end of Inútil Bay (IB in Fig. 1a) is an additional source of low salinity waters to the central basin via the Whiteside Channel (Aracena et al., 2015). Calving glaciers form Cordillera Darwin icefield (CDI in Fig. 1a, e. g. Silva and Prego, 2002;Aracena et al., 2015) and runoff fresh waters (e.g., Antezana, 1999) salinities ~ 28 are observed at the head of the fjord. Within the fjord the upper 60 m of the water column salinity increases towards the MS to about 30.5 (Fig. 6). ...
El Estrecho de Magallanes (EM) es un canal interoceánico que conecta los océanos Pacífico y Atlántico Sur en el extremo sur de Sudamérica. Sus características batimétricas y morfológicas cumplen un importante rol en el flujo, la mezcla interoceánica y la distribución de las masas de agua. El objetivo de este trabajo es analizar las características físicas de las aguas en el EM y su variabilidad espacio-temporal. Las distribuciones de temperatura y salinidad obtenidas a partir de datos históricos, de observaciones de alta resolución y datos obtenidos con un planeador marino autónomo indican escenarios oceanográficos diferentes para cada microcuenca. La microcuenca occidental presenta una capa superficial relativamente fría (~6 ° C) y de baja salinidad (<29) en los primeros 100 m que se extiende hasta la isla Carlos III; en la microcuenca central la columna de agua es menos estratificada ( temperatura entre 6.5 y 6.8 °C y salinidad entre 30.5 y 31) y la microcuenca oriental presenta temperaturas y salinidades más altas (7°C; S∼32) que el pasaje intermedio, pero menos salina y más cálida que las aguas de la plataforma Atlántica (PA). En la microcuenca central existen aportes locales de aguas fluviales y glacio-fluviales que serían transportadas por advección-difusión hacia el margen norte de la boca oriental y continúan su extensión en la PA, formando una lengua de baja salinidad (S<33.5) que se extiende más de 1000 km hacia el NE, denominada Corriente Patagónica.
... On the other hand, Cosmasterias lurida and P. magellanicus (representative of group a stations) were mainly distributed in the channels area, with a higher dispersion of the asteroid and an increment of uniformity that is reflected in a higher number of species and a lower abundance of each one of them. Other studies have suggested that oligotrophic waters (nutrient -poor) and a high discharge of sediments limits richness and abundance in the fjords and channel's benthic ecosystems during the aestival period (Silva & Prego, 2002). However, there are seasonal fluctuations that have not been studied and which might better explain the trends observed in the marine ecosystems, especially those related to areas that are near the South Ice Fields (Ríos, Mutschke, Montiel, Gerdes, & Arntz, 2005). ...
The existence of latitudinal marine biodiversity gradients from low to high-southern latitudes is a controversial issue regarding the marine biogeographic division in the Southeastern Pacific. In this region, the Northern Patagonian Icefield is considered a break point for faunistic elements derived from more northern or southern biogeographical realms. However, the division seems to be better defined by distribution patterns and endemism of specific marine taxa. There have been no exhaustive latitudinal benthic inventories compiled along the southern-eastern Pacific Chilean coastline. This study focuses on the spatial distribution variability and relative abundance of the sublittoral echinoderm assemblages and uses them to establish an evaluation of zoogeographic relationship in the Southeastern Pacific and Atlantic Oceans. This is the first time echinoderms have been used for this purpose. A total 3 665 echinoderm specimens were collected in two cruises. Within this organism pool, 29 species were distinguished, belonging to the asteroids (17 species), echinoids (6 species), ophiuroids (4 species) and holothurians (2 species); crinoids were not found. The dominant species were the asteroid Ctenodiscus procurator, the echinoid Pseudechinus magellanicus, the ophiuroid Ophiuroglypha lymani, and the irregular sea urchin Tripylaster philippii. The spatial distribution patterns for the echinoderm clusters along the study area showed only weak geographical trends. Stations belong in three groups: with influence of glacier processes, influence of waters of the open Pacific Ocean, and a third group of stations without any links to specific locations. Rev. Biol. Trop. 65(Suppl. 1): S60-S72. Epub 2017 November 01.
... Additionally, OC data from the grab samples show a relationship between the composition of the OC and the salinity gradient within the fjord (supporting information). , Bianchi, Hutchings, et al. (2016) À28.1 to À23.3 Cui, Bianchi, Savage, et al. (2016) Norther Patagonia Chile À28.2 to À19.1 1.3 to 9.0 Sepúlveda et al. (2011) À26.7 to À20.1 Silva et al. (2011) Southern Patagonia À22.1 to À19.7 Silva and Prego (2002) Note. Listed for comparison are published equivalent isotopic values from the surface sediment of fjords around the world. ...
Fjords are recognized as globally important sites for the burial and long-term storage of carbon (C) within sediments. The proximity of fjords to the terrestrial environment in combination with their geomorphology and hydrography results in the fjordic sediments being subsidized with organic carbon (OC) from the terrestrial environment. It has been well documented that terrestrial OC (OCterr) is an important component of coastal sediments yet our understanding of the quantity of OCterr stored in these sediments remains poorly constrained. Utilizing Bayesian isotopic sediment fingerprinting techniques to the surface sediments of Loch Sunart we estimate that 42.0 ± 10.1 % of the OC is terrestrial in origin. Through combining these outputs with sedimentary OC stock estimates we have calculated the surface sediments (0-15 cm) hold 0.1 Mt OCterr and estimate that the postglacial sediment held within the fjord contains 3.96 Mt OCterr. When these totals are compared to the quantity of OC stored in the adjacent terrestrial environment it is clear that the fjord's catchment stores a greater amount of OCterr in the form of vegetation and soil. Though when normalized for area the results suggest that the marine sediments are a more effective long-term store of OCterr than the adjacent terrestrial environment. This striking result highlights the importance of the terrestrial environment as a source of OC to the coastal ocean and that the OCterr subsidy to the marine sediments is a significant mechanism for the long-term storage of OC in coastal marine sediments.
... temperature, quality, quantity and availability of food, trophic source, and type of substrate) that may limit secondary production of populations (Downing 1984; Brey America is characterized by about 84,000 km of broken coastline, including islands, peninsulas, channels, fjords, and sounds (Silva and Prego 2002). In this region, one of the characteristic features is the extremely high variability concerning abiotic conditions related to seasonal variations on solar irradiance (Antezana 1999;Pizarro et al. 2000). ...
The sub-Antarctic Magellan region in southern Chile belongs to the most extensive fjord regions of the world. Coastal and marine environments are exposed to natural and anthropogenic perturbations. Research on the marine ecosystems have received some attention, however, research on the flow of energy is rather limited. To trace energy flow and resource distribution across communities is of considerable concern to current ecological studies for understanding how marine benthic ecosystems are organized, the base of which food sources they are built upon and how benthic organisms utilize resources. Heterogeneous environmental conditions along the Sub-Antarctic Magellan region, however, suggest the possibility of great heterogeneity in community structure and population dynamics. Studies of the trophic structure and energy flow are essential in this context. The aim of this thesis is to increase the knowledge of the ecological role of benthic species to communities living in the sub-Antarctic Magellan region. The main objectives of this research are (i) to investigate the trophic ecology of conspicuous species and their ecological role in the marine benthic communities of the Magellan region, (ii) to describe the trophic structure of two shallow-water benthic community types in the Strait of Magellan in order to establish baseline descriptions of trophic relationships for community structure and function, and (iii) to estimate benthic secondary production in this sub-Antarctic region as a proxy for energy flow along latitudinal gradients. The main results indicate that both local/regional environmental conditions and biological features cause clear differences in the trophic structure and energy flow patterns. This research gives valuable insight into ecological functioning of marine benthic communities present in the sub-Antarctic Magellan region and offers useful information to build food web models.
... The proportion of lithogenic particles is generally higher at the heads of the fjords than in the oceanic area, due to local runoff (Sepúlveda et al., 2011;Silva et al., 2011;Vargas et al., 2011;Bertrand et al., 2012a;Montade et al., 2012). In glacierinfluenced fjords, sediments have a very low OM content due to dilution by large amounts of inorganic matter (i.e., glacial clay) originating from glacier erosion (Silva and Prego, 2002;Silva et al., 2011). Both freshwater and marine diatoms are abundant in fjord sediments, allowing reconstructions of variability in freshwater input (tied to precipitation on land and river runoff into the fjords) and siliceous productivity through time (e.g., Sepúlveda et al., 2005;Rebolledo et al., 2011). ...
Wepresent reconstructions of late Holocene changes in the source of organicmatter and siliceous export production
in the Relocanví Fjord (41°S, 72°W),Northern Chilean Patagonia, based on organic carbon content, δ13Corg, N/
C ratio, diatomassemblages and biogenic silica contents fromthree sediment cores. The age models are based on
a combination of 210Pb profiles, AMS 14C dating, and on the first occurrence of the diatom Rhizosolenia setigera f.
pungens, as a stratigraphic marker in the fjords. The cores span the last 300 to 700 yr. Diatoms dominate the siliceous
assemblages in the three cores (98% on average). Our results suggest that precipitation seasonality in the
region of Reloncaví was high in CE 1300–1400 and CE 1700–1850, with a clear decreasing trend since CE 1850.
The latter trend is in agreement with instrumental records and tree-ring reconstructions. These fluctuations
seem to be associated with the Southern Annular Mode (SAM).
... The proportion of lithogenic particles is generally higher at the heads of the fjords than in the oceanic area, due to local runoff (Sepúlveda et al., 2011;Silva et al., 2011;Vargas et al., 2011;Bertrand et al., 2012a;Montade et al., 2012). In glacierinfluenced fjords, sediments have a very low OM content due to dilution by large amounts of inorganic matter (i.e., glacial clay) originating from glacier erosion (Silva and Prego, 2002;Silva et al., 2011). Both freshwater and marine diatoms are abundant in fjord sediments, allowing reconstructions of variability in freshwater input (tied to precipitation on land and river runoff into the fjords) and siliceous productivity through time (e.g., Sepúlveda et al., 2005;Rebolledo et al., 2011). ...
We present reconstructions of late Holocene changes in the source of organic matter and siliceous export production in the Relocanví Fjord (41°S, 72°W), Northern Chilean Patagonia, based on organic carbon content, δ13Corg, N/C ratio, diatom assemblages and biogenic silica contents from three sediment cores. The age models are based on a combination of 210Pb profiles, AMS 14C dating, and on the first occurrence of the diatom Rhizosolenia setigera f. pungens, as a stratigraphic marker in the fjords. The cores span the last 300 to 700 yr. Diatoms dominate the siliceous assemblages in the three cores (98% on average). Our results suggest that precipitation seasonality in the region of Reloncaví was high in CE 1300–1400 and CE 1700–1850, with a clear decreasing trend since CE 1850. The latter trend is in agreement with instrumental records and tree-ring reconstructions. These fluctuations seem to be associated with the Southern Annular Mode (SAM).
... Possible effects of low Si ⁄ concentrations on the productivity and floristic composition of southern PAIS Aracena et al. (2011) reported that the spring concentration of DSi in seawater, the percentage of biogenic opal on surface sediments and the primary productivity of the PAIS south of the Gulf of Penas (i.e., southern than the austral limit of the LOFZ) were significantly lower than northern Patagonia. Similar to the primary productivity patterns, zooplankton biomass (Palma and Silva, 2004) and surface sediment organic matter content (Silva and Prego, 2002) decreases from northern to southern Patagonia. ...
... This average value is similar to the base line concentration for the microbasins in this zone and to that reported for cruises carried out in 1995 (Silva et al., 1998b). The sediments in this area have average organic matter values as compared with the semi-enclosed areas of the highly productive Chilean coast such as Concepción Bay (i.e., 12-18% organic matter) (Rudolph et al., 2002) and with areas that maintain a high exchange with the adjacent oceanic zone such as Corcovado Gulf (i.e., 1-2% organic matter) (Silva et al., 1998b;Silva & Prego, 2002). ...
A study of the ecotoxicological quality of surface sediment was carried out on samples collected in the main fjords and interior channels between Reloncaví and Corcovado gulfs. The surface sediment samples were taken with a box corer and analyzed for organic matter content and grain size. Dissolved oxygen was measured in water samples taken 10 m off the bottom. The ecotoxicological evaluation of the sediments was performed using fertilization assays with gametes of Arbacia spatuligera (EPA/600/4-91/003). A fertilization rate of 95%, similar to that of the controls, was achieved. Therefore, the sediments at the sampled stations located in the middle of the channels were classified as non-toxic. Only the sediment at Station 26 (i.e., sector Dalcahue) was classified as "slightly toxic" (90 ± 4.1%). The samples were taken from the central zones of the studied channels and fjords. Since toxicologically these central areas are not polluted, any possible effects of aquaculture activities are expected to be more local in scope. Calidad ecotoxicológica de los sedimentos entre los golfos Reloncaví y Corcovado, Chile RESUMEN. Mediante el análisis de muestras de sedimento superficial, tomadas en los principales fiordos y canales interiores entre el golfo de Reloncaví y golfo Corcovado, se realiza el estudio de su calidad ecotoxicologica. Las mues-tras superficiales de sedimentos se obtuvieron con un box corer. Se analizó el contenido de materia orgánica y textura de los sedimentos, y oxígeno en la columna de agua disuelto de muestras de agua tomadas a 10 m del fondo. Además, se realizó la evaluación ecotoxicológica de los sedimentos mediante pruebas de fecundación con gametos de Arbacia spatuligera (EPA/600/4-91/003), resultados que indican que sobre el 95% de ovas fueron fecundadas, valor semejante a los controles, lo que permite clasificar a los sedimentos de las estaciones ubicadas en el centro de los canales como no tóxicos. Sólo el sedimento de la estación 26 (i.e., sector Dalcahue) mostró un 90 ± 4,1%, lo que se clasificaría como sedimento "levemente tóxico". Las muestras fueron recolectadas en las zonas centrales de los canales y fiordos mues-treados. Se concluye que estas zonas, desde el punto de vista toxicológico, no están contaminadas por lo que se estimó que un posible efecto de las actividades de la acuicultura sería más localizado. Palabras clave: calidad de sedimentos, ensayos de fecundación, contaminación, acuicultura, zona austral, Chile.
... Stations 14, 51, and 76 had a few C:N values over 10, although in general, values remained between 7 and 10. Similar C:N values were observed by Silva & Prego (2002), throughout the entire Chilean fjord area, from Puerto Montt (41°S) to Cape Horn (56°S). ...
Eleven surface sediment cores were taken with a Rumohr corer during the oceanographic cruise Cimar 8 Fiordos (July 2002; between the Corcovado Gulf and Pulluche Channel). These cores were used to determine the vertical distribution of organic carbon, total nitrogen, and their atomic ratio (C/N) for use as a diagenesis indicator. The grains observed were mostly clay-silt in four of the sediment cores and more heterogeneous in the other seven cores. Organic carbon and total nitrogen concentrations were higher in the four clay-silt cores than in the sandy cores, although in terms of their vertical distribution, both concentrations were relatively homogenous at most stations. Nevertheless, exponential decreases characteristic of first-order diagenetic degradation were observed in cores from three stations. The C:N ratio fluctuated between 7 and 10, indicating that the organic material in the sediments was mostly marine in origin. Values were lower at more oceanic stations and greater at more coastal stations; the contribution of terrigenous materials was greater at the latter. We inferred a slower break down of organic carbon as compared to total nitrogen from a steady-state first-order degradation kinetics model, that was applied to stations where both fractions had exponential vertical distributions. Remineralization percentages were between 23 and 34% (organic carbon) and 33 and 43% (total nitrogen) and accumulation percentages were between 77 and 66% (organic carbon) and 67 and 57% (total nitrogen).
... SCH se analiza en función de antecedentes en la zona comprendida entre Valparaíso y Puerto Montt. Fuentes bibliográficas: Gallardo et al. (1995Gallardo et al. ( , 1996Gallardo et al. ( , 2004, Silva et al. (1995), Valdenegro & Silva (2003), Thiel et al. (2007), Silva & Palma (2010 de materia orgánica disponible en los sedimentos (Antezana, 1999;Fabiano et al. 1999;Hamamé & Antezana, 1999;Silva & Prego, 2002), mientras que las zonas someras y estuarinas podrían ser más afectadas por cambios en la salinidad y tipo sustrato (Bertrán, 1989;Cañete et al. 1999;Díaz-Jaramillo et al. 2008;Cañete et al. 2010). Adicionalmente, Cañete et al. (1999) sugirieron la posibilidad de que la fauna de poliquetos compartida entre la Antártica y la zona austral de Chile podrían alcanzar zonas someras de los fiordos a través del fondo, proponiendo la hipótesis de que estas especies deberían presentar una gran adaptabilidad fisiológica para resistir cambios de presión, niveles variables de salinidad y diferentes regímenes térmicos, características ambientales habituales en las diferentes subcuencas que se encuentran en la zona de canales interiores. ...
A bibliographic revision on the records of the distribution of the polychaete Cistenides elhersi, obtained during different CIMAR Fjord cruises (50 m), was conducted in order to test the potential effects of salinity gradients and temperature on the vertical distribution of benthic estuarine fauna. Aditionally, a new record of C. elhersi is reported in low salinity (25 psu) shallow waters of Skyring Sound ((52°33’16" S, 71°51’34" W; 0.3 to 2 m depth) Magellan region, with presence of the grass Ruppia flifolia. This record suggest the eurybathic, euryhaline and eurythermal of this polychaete in the austral zone of Chile. Additional studies are suggested in order to identify other ecological services provided by seagrass beds.
... In many subarctic and high-latitude estuaries, glaciers discharge cold, oligotrophic, and silt-laden water, influencing the salt and nutrient budgets, sediment load, and turbidity in the coastal environment (Pickard, 1971;Silva and Prego, 2002; reviewed by Wiencke et al., 2007). The effects of such changing environmental conditions on high-latitude kelp bed communities are not well understood. ...
Glaciers have pronounced long-and short-term effects on nearshore marine ecosystems. Concerns exist about possible changes that may occur to nearshore habitats with the pronounced climatic alterations in subarctic and high-latitude environments. The present research studied the effects of glacial discharge on kelp bed community structure by comparing environmental conditions on one more exposed and one less exposed shore in a subarctic Alaskan estuary.Inorganic sedimentation, abrasion, and percent sand/silt substrate were significantly higher on the more exposed shore than the less exposed shore. Light intensity, salinity, nitrate concentrations, and hard substrate cover were significantly lower on the more exposed shore. Kelp bed communities on the more exposed shore contained only one kelp species, Saccharina latissima, versus five kelp species on the less exposed shore. Taxonomie richness and overall organism abundance were significantly lower on the more exposed shore. Salinity, nitrate, inorganic sedimentation, and abrasion were identified as important drivers of kelp communities that are dynamically influenced by glacial discharge. In contrast, other drivers, such as hard substrate and rugosity, reflect existing differences between the two shore environments that are not influenced on short timescales by glacial discharge. While it is currently difficult to separate the relative roles of these two types of drivers on kelp bed communities, increased rates of glacial discharge due to climate change may exacerbate specifically the effects of the dynamic drivers and further decrease species richness in kelp bed communities in high-latitude estuaries.
... its multiple islands and peninsulas, and numerous waterways (Silva and Prego, 2002). Formed by erosion, due to the advancement and retreat of glaciers in the last ice age, this study area has a particularly irregular geography (Borgel, 1970(Borgel, -1971, which makes direct communication between water masses of oceanic origin and fresh-river water difficult at the head of the continental fjords. ...
... The AFS is separated from the CIS by the Gulf of Corcovado (Fig. 1). This Gulf is a relatively shallow (<180 m) and regular basin corresponding to an interior sea, which receives lower freshwater inputs than adjacent areas and it is well connected to the ocean through the 150 m deep and 45 km wide Guafo Entrance (Silva & Prego 2002). Thus, the Gulf of Corcovado represents a large and important physical and oceanographic barrier, where divergent water fluxes connect the CIS and the AFS micro-basins to the open ocean (Aiken 2008;Sievers & Silva 2008). ...
Chile is the second largest producer of farmed salmon in the world. After reaching a peak harvest of 631 000 tonnes in 2008, a severe sanitary and production crisis triggered a major legal and operational reorganization, and an imminent expansion of the industry into the Aysén Fjords System (AFS). This expansion has caused increasing national and international concern about its potential negative impact upon this pristine area, which holds a mosaic of unique ecosystems and three World Biosphere Reserves. This paper reviews and provides some upper bounds to potential impacts under two feasible production scenarios. It is concluded that severe but highly localized mid‐term damage to the sea‐floor bottom may affect up to 6200 ha. Although this surface area represents only 0.5% of the AFS, the high heterogeneity and limited scientific knowledge of local ecosystems increase the risks of damaging sensitive habitats, communities or populations. While additional inputs of up to 60 000 t of nitrogen and 8000 t of phosphorus can be predicted, the estimation of carrying capacities is a pendant and urgent task to be accomplished in this area. If current escape rates are not reduced, the average number of escaped salmon may exceed 4.4 million individuals each year, able to consume up to 6600 t of pelagic prey from local ecosystems. We recommend following a strict precautionary approach, not granting new farming leases until sufficient information about the risk and magnitude of these impacts is obtained and transformed into effective management actions.
... The average POC concentrations in the upper 25 m of the water column (247 mg C m À3 ) were in the lower range of the reported values for the northern Reloncaví Fjord (200-600 mg C m À3 ) but higher than values recorded in the southern Strait of Magellan (76 mg C m À3 ; Fabiano et al., 1999). This latitudinal decrease appears to parallel the percentage of organic carbon in the sediments from the same areas (from 5.3% to 3.8%, respectively, Silva and Prego, 2002). These gradients could be due to more efficient pelagic-benthic coupling in northern than in southern Patagonian fjords, which may result from higher spring-summer PP in northern than in southern fjords. ...
Patagonian fjord systems, and in particular the fjords and channels associated with the Baker/Pascua Rivers, are currently under conspicuous natural and anthropogenic perturbations. These systems display very high variability, where limnetic and oceanic features overlap generating strong vertical and horizontal physicochemical gradients. The CIMAR 14-Fiordos cruise was conducted in the Chilean fjords located between 47° and 50°S during the spring (October–November) of 2008. The main objectives were to study vertical and horizontal gradients in physical, chemical and biological characteristics of the water column, and to assess plankton dynamics and trophic carbon fluxes in the fjords and channels of central-south Patagonia.
... This average value is similar to the base line concentration for the microbasins in this zone and to that reported for cruises carried out in 1995 (Silva et al., 1998b). The sediments in this area have average organic matter values as compared with the semi-enclosed areas of the highly productive Chilean coast such as Concepción Bay (i.e., 12-18% organic matter) (Rudolph et al., 2002) and with areas that maintain a high exchange with the adjacent oceanic zone such as Corcovado Gulf (i.e., 1-2% organic matter) (Silva et al., 1998b;Silva & Prego, 2002). ...
A study of the ecotoxicological quality of surface sediment was carried out on samples collected in the main fjords and interior channels between Reloncaví and Corcovado gulfs. The surface sediment samples were taken with a box corer and analyzed for organic matter content and grain size. Dissolved oxygen was measured in water samples taken 10 m off the bottom. The ecotoxicological evaluation of the sediments was performed using fertilization assays with gametes of Arbacia spatuligera (EPA/600/4-91/003). A fertilization rate of 95%, similar to that of the controls, was achieved. Therefore, the sediments at the sampled stations located in the middle of the channels were classified as nontoxic. Only the sediment at Station 26 (i.e., sector Dalcahue) was classified as "slightly toxic" (90 ± 4.1%). The samples were taken from the central zones of the studied channels and fjords. Since toxicologically these central areas are not polluted, any possible effects of aquaculture activities are expected to be more local in scope.
... This area is under the influence of the Humboldt Current and the Cape Horn Current, both of which are branches of the West Wind Drift Current (WWD). The Subantarctic water can penetrate into the inlets (Silva et al., 1998), whose depth may locally exceed 1000 m. The hydrographical regime is characterised by a strong freshwater input due to high precipitation and concomitant runoff, both producing a strong and shallow pycnocline (Dávila et al., 2002). ...
The zoogeography of polychaete annelids was described for the Magellan region. This work considered information available from 19 expeditions carried out in the last 124 years of polychaete taxonomic research around the southernmost tip of the South American continental shelf. The polychaete fauna of the Magellan region comprised a total of 431 species belonging to 108 genera and 41 families. MDS and ANOSIM analyses showed the Magellan region to be divided into two subregions, one on the Pacific side of the tip of South America and one on the Atlantic side. These subregions showed a low percentage of “endemic species” (< 10%) whereas > 70% of the species recorded for the whole Magellan region showed a wide distribution range, and there were especially high affinities with Antarctic and Subantarctic areas. We suggest that the opening of the Straits of Magellan created a new pathway for enhanced exchange of faunal elements between the Pacific and the Atlantic. Transport of larvae via easterly directed currents of the West Wind Drift plays an important role in current distribution patterns of polychaete fauna around the tip of South America.
... En el caso de las muestras terrígenas del borde de los ríos, la relación C:N fue alta y en general superior a 10 (Figs. 4d-4f). Silva et al. (1998), Silva & Prego (2002) y Silva (2008), indican que de acuerdo a las característica químicas orgánicas generales de los sedimentos marinos superficiales (MOT, C-org y N-org), muestreados durante el crucero C1F, la zona Puerto Montt a laguna San Rafael, puede ser segregada en cuatro zonas. Una zona norte, ubicada entre Puerto Montt y el grupo de las islas Desertores, Apiao, Quehi y Lemuy con concentraciones preferentemente altas (MOT > 5%, C-org > 1,6% y N-org > 0,2%) y una zona central, ubicada entre estas islas y la boca norte del canal Moraleda (incluyendo Boca del Guafo y la zona oceánica), con concentraciones preferentemente bajas (MOT < 5%, C-org < 1,6% y N-org < 0,2%), una zona sur con concentraciones preferentemente altas entre la boca norte del canal Moraleda y el canal Pulluche (incluyendo la boca Wickham y bahía Anna Pink) y finalmente una zona sur glaciar, con concentraciones preferentemente bajas, entre el canal Pulluche y la laguna San Rafael (Figs. 2-6 de Silva et al., 1998). ...
... Extensive networks of temperate fjords with intact forest occur on the west coasts of South America (Patagonia) and North America (British Columbia and Alaska). These regions similarly experience very high precipitation and levels of sedimentation (Silva and Prego 2002;Nuwer and Keil 2005;Sepú lveda et al. 2009), although to the best of our knowledge similar studies of OM flux through infaunal communities have not been conducted to date. Such knowledge would be particularly relevant given the exploitation of higher trophic level species in these regions that are likely supported by such macroinfaunal communities, and potential changes to sediment chemistry caused by the dramatic increase in aquaculture developments in the Chilean fjords (Pascual et al. 2009). ...
In the New Zealand fjords, hydrogen sulfide production from decomposing forest litter is used by chemoautotrophs to fix CO(2[aq]) and support benthic food webs. We used quantitative surveys and stable isotope analyses to investigate the contribution of chemoautotrophy to shallow (50 m) and deep (400 m) benthic communities in Doubtful and Bradshaw Sounds. Prevalence of bivalve-chemoautotroph symbioses varied between shallow sites where large-bodied (<= 50 mm) Solemya parkinsonii (Solemyidae) were common, and deep-basin sites where small-bodied (< 2 mm) Nucinella maoriana (Manzanellidae) dominated assemblages. delta(13)C and delta(15)N of sediment indicated that the basal carbon source supporting chemosynthesis was likely decomposing forest litter at 50 m, and decomposing marine algae at 400 m. An isotopic mass balance model weighted to community composition and biomass indicated that the majority of carbon supporting communities at 50 m originated from chemoautotrophy. Concentration of fatty acid biomarkers for heterotrophic bacteria (C(15) and C(17)) were correlated with the estimated amount of carbon from terrestrial sources, indicating that decomposing forest litter is important in the system. Analysis of the trophic level of these macroinfaunal communities normalized to biomass indicated that the communities sampled from 50 m were on average chemoautotrophic, whereas those sampled at 400 m were on average heterotrophic. The reliance of benthic invertebrate communities on decomposing forest litter and chemoautotrophy, particularly in shallow habitats, demonstrates close connectivity between terrestrial and marine ecosystems in this region and illustrates how diverse food webs can be supported in the shaded and quiescent inner fjord environments.
... SCH se analiza en función de antecedentes en la zona comprendida entre Valparaíso y Puerto Montt. Fuentes bibliográficas: Gallardo et al. (1995 Gallardo et al. ( , 1996 Gallardo et al. ( , 2004), Silva et al. (1995), Valdenegro & Silva (2003), Thiel et al. (2007, de materia orgánica disponible en los sedimentos (Antezana, 1999; Fabiano et al. 1999; Hamamé & Antezana, 1999; Silva & Prego, 2002), mientras que las zonas someras y estuarinas podrían ser más afectadas por cambios en la salinidad y tipo sustrato (Bertrán, 1989; Cañete et al. 1999; Díaz-Jaramillo et al. 2008; Cañete et al. 2010). Adicionalmente, Cañete et al. (1999) sugirieron la posibilidad de que la fauna de poliquetos compartida entre la Antártica y la zona austral de Chile podrían alcanzar zonas someras de los fiordos a través del fondo, proponiendo la hipótesis de que estas especies deberían presentar una gran adaptabilidad fisiológica para resistir cambios de presión, niveles variables de salinidad y diferentes regímenes térmicos, características ambientales habituales en las diferentes subcuencas que se encuentran en la zona de canales interiores. ...
A bibliographic revision on the records of the distribution of the polychaete Cistenides elhersi,
obtained during different CIMAR Fjord cruises (50 m), was conducted in order to test the potential effects
of salinity gradients and temperature on the vertical distribution of benthic estuarine fauna. Aditionally, a
new record of C. elhersi is reported in low salinity (25 psu) shallow waters of Skyring Sound ((52°33’16”
S, 71°51’34” W; 0.3 to 2 m depth) Magellan region, with presence of the grass Ruppia filifolia. This record
suggest the eurybathic, euryhaline and eurythermal of this polychaete in the austral zone of Chile.
Additional studies are suggested in order to identify other ecological services provided by seagrass beds.
Key words: estuaries, Polychaeta, Fjord benthos, Ruppia, Cimar-Fiordo, subantarctic wetland.
... This area is under the influence of the Humboldt Current and the Cape Horn Current, both of which are branches of the West Wind Drift Current (WWD). The Subantarctic water can penetrate into the inlets (Silva et al., 1998), whose depth may locally exceed 1000 m. The hydrographical regime is characterised by a strong freshwater input due to high precipitation and concomitant runoff, both producing a strong and shallow pycnocline (Dávila et al., 2002). ...
The zoogeography of polychacte annelids was described for the Magellan region. This work considered information available from 19 expeditions carried out in the last 124 years of polychaete taxonomic research around the southernmost tip of the South American continental shelf. The polychaete fauna of the Magellan region comprised a total of 431 species belonging to 108 genera and 41 families. MDS and ANOSIM analyses showed the Magellan region to be divided into two subregions, one on the Pacific side of the tip of South America and one on the Atlantic side. These subregions showed a low percentage of "endemic species" (< 10%) whereas > 70% of the species recorded for the whole Magellan region showed a wide distribution range, and there were especially high affinities with Antarctic and Subantarctic areas. We suggest that the opening of the Straits of Magellan created a new pathway for enhanced exchange of faunal elements between the Pacific and the Atlantic. Transport of larvae via easterly directed currents of the West Wind Drift plays an important role in current distribution patterns of polychaete fauna around the tip of South America.
... Similar results have also been obtained in the Canadian Arctic and Alaskan fjords, where epifauna is restricted to areas with low sedimentation rates (Evans et al., 1980; Carney et al., 1999). An important additional difference to sites located in the SPI area is the higher amount of inorganic carbon in surface sediments of the Straits of lan (Silva and Prego, 2002), which according to Brambati et al. (1991) can be attributed to the presence of calcite in the remains of bivalves, gastropods , crustaceans and foraminiferans. Unfortunately , information on chemical and physical processes of pelagobenthic coupling (Cattaneo-Vietti et al., 1999) and in the bottom sediments is scarce for the area of study, and this represents a limiting factor to explain the (dis)similarities we found between the study areas. ...
: Macrobenthic associations were investigated at 29 sampling stations with a semi-quantitative Agassiz trawl, ranging from the South Patagonian Icefield to the Straits of Magellan in the South Chilean fjord system. A total of 1,895 individuals belonging to 131 species were collected. 19 species belong to colonial organisms, mainly Bryozoa (17 species) and Octocorallia (2 species). The phylum Echinodermata was the most diverse in species number (47 species), with aster-oids (25 species) and ophiuroids (13 species) being the best represented within this taxon. Polychaeta was the second dom-inant group in terms of species richness (46 species). Multidimensional scaling ordination (MDS) separated two station groups, one related to fjords and channels off the South Patagonian Icefield and the second one to stations surrounding the Straits of Magellan. 45 species account for 90% of the dissimilarity between these two groups. These differences can main-ly be explained by the influence of local environmental conditions determined by processes closely related to the pres-ence/absence of glaciers. Abiotic parameters such as water depth, type of sediment and chemical features of the superficial sediment were not correlated with the numbers of individuals caught by the Agassiz trawl in each group of sampling sta-tions.
... Ramirez and Guzmán (2005), during the spring of 1995, registered the presence of a biological front that affected almost the totality of the water column at the latitude considered in this study as a boundary line to separate the northern and southern areas of the Interior Sea of Chiloe. Silva and Prego (2002), on the other hand, found high concentrations of organic matter and organic carbon and nitrogen in surface sediments in the area encompassed between 41.5-42.8u S and low concentrations in the area encompassed between 42.8-44.1u ...
This study characterizes the spatial and temporal distribution of chlorophyll a (Chl a) and sea surface temperature (SST) in the Interior Sea of Chiloe in Chile at a moderate spatial resolution using SeaWiFS and MODIS‐Aqua time series data from the Goddard Earth Science (GES) Data and Information Services Center (DISC) imported into the GES DISC Interactive Online Visualization and Analysis System (‘Giovanni’). The Interior Sea of Chiloe is home to Chile's salmon farming industry, the world's second largest salmonid producer. This study undertakes the characterization of the main patterns of spatial and temporal variability of Chl a and SST in the Interior Sea of Chiloe using a continuous set of time series ocean colour and SST data. Both Chl a and SST exhibit a marked spatial and temporal distribution, with values being significantly higher in the northern area (41.4–42.7° S; total area 41.4–43.5° S) and during the spring–summer period. Peak Chl a concentrations tend to occur in a temporal interval from October to April (austral spring–austral autumn), whereas monthly averaged peak SST values occur consistently in the month of February (austral summer). Chl a concentrations exhibit strong interannual variations, with monthly averaged peak Chl a concentrations experiencing a twofold increase between the year with the lowest and highest Chl a peak concentration in the time series. Results suggest that at the present scale of analysis two spatial domains can be distinguished, regarding the differential behaviour of SST and Chl a in the northern and southern areas of the Interior Sea of Chiloe. The concurrent analysis of Chl a time series data with accumulated rainfall time series data as a proxy of solar radiation, on the other hand, supports previous hypothesis suggesting solar radiation to be a limiting factor for phytoplankton development in the Interior Sea of Chiloe. The role of geomorphological factors on pattern formation and the results presented in this study in relation to results from seasonal oceanographic cruises in the area are briefly discussed.
The kelp forests of southern Patagonia have a large diversity of habitats, with remote islands, archipelagos, peninsulas, gulfs, channels, and fjords, which are comprised of a mixture of species with temperate and sub-Antarctic distributions, creating a unique ecosystem that is among the least impacted on Earth. We investigated the distribution, diversity, and abundance of marine macroinvertebrate assemblages from the kelp forests of southern Patagonia over a large spatial scale and examined the environmental drivers contributing to the observed patterns in assemblage composition. We analyzed data from 120 quantitative underwater transects (25 x 2 m) conducted within kelp forests in the southern Patagonian fjords in the Kawésqar National Reserve (KNR), the remote Cape Horn (CH) and Diego Ramírez (DR) archipelagos of southern Chile, and the Mitre Peninsula (MP) and Isla de los Estados (IE) in the southern tip of Argentina. We observed rich assemblages of macroinvertebrates among these kelp forests, with a total of 185 unique taxa from 10 phyla and 23 classes/infraorders across the five regions. The number of taxa per transect was highest at IE, followed by MP, CH, and KNR, with the lowest number recorded at DR. The trophic structure of the macroinvertebrate assemblages was explained mostly by wave exposure (28% of the variation), followed by salinity (12%) and the KNR region (11%). KNR was most distinct from the other regions with a greater abundance of deposit feeders, likely driven by low salinity along with high turbidity and nutrients from terrigenous sources and glacial melt. Our study provides the first broad-scale description of the benthic assemblages associated with kelp forests in this vast and little-studied region and helps to establish baselines for an area that is currently lightly influenced by local anthropogenic factors and less impacted by climate change compared with other kelp forests globally.
The distribution, composition, and transport of both dissolved and particulate organic carbon (DOC and POC) were studied across a terrestrial - marine transition system in the Chilean North-Patagonia (41°S). At the land-fjord boundary we reported: (i) high concentrations of both silicic acid (up to 100 μM) and integrated chlorophyll a (62 mg m⁻²), (ii) dominance of nanophytoplankton (63%), humic-, terrigenous-derived, and protein-like DOC (19 and 36%, respectively), and (iii) a shallow photic zone (12 m depth). In contrast, the estuarine-ocean boundary was characterized by (i) high concentrations of nitrate and phosphate (20 and 2 μM respectively) and low chlorophyll a concentration (11 mg m⁻²), (ii) dominance of microphytoplankton (59%) and tyrosine-like C3 autochthonous DOC (34%), and (iii) a deep photic zone (29 m depth). Allochthonous DOC input at the fjord head and the ocean accounted for 60% and 10% of total DOC, respectively. The input of humic-like substances was enhanced by intense forestry and agriculture activity around the Puelo River watershed, contributing from 50% to 14% of total DOC along the fjord - ocean transect. In contrast, autochthonous tyrosine-like substances increased from 25% to 41% of total DOC, highlighting the role of bacterial metabolism in regulating DOM composition. The high correlation (R² = 0.7) between the UVC-humic:UVA-humic ratio and salinity suggest that processes associated to freshwater input impinged on the DOC chemical characteristics and origins. Overall, our observations support the view that climate warming (freshwater input) and anthropogenic practices (aquaculture) boost the mobilization of terrestrial carbon pools and their intrusion into coastal ocean areas, a process that should be given more attention in climate prediction models.
The horizontal distribution of the organic matter, organic and inorganic carbon, organic nitrogen content, and surface sediment texture was determined between Puerto Montt and Boca del Guafo using samples collected during the cruises CIMAR 10 Fiordos (2004), CIMAR 11 Fiordos (2005) and CIMAR 12 Fiordos (2006). Two zones were identified: the northern zone (from Puerto Montt to the Desertores-Apiao-Quehui-Lemuy island group) had mostly high concentrations (TOM >5%; C-org >1.6%; C-inorg >0.4% and N-org > 0.2%) the southern zone (from the same island group to Boca del Guafo) had mostly low concentrations (TOM 7.5%, C-org > 2.4%, C-inorg > 0.4% and N-org > 0.2%. The texture of the marine sediments was mostly sand and silt + clay; gravel was scarce and less than 4% in some samples. The terrigenous sediment from the river edges was mostly sandy. The sediment origins (marine versus terrigenous), as a first approach, were inferred from the values of the C:N ratio. The sediments were mostly marine in origin, except in the continental fjords, where the terrigenous component was important.
To investigate the melting history of the Patagonian Ice Sheet (PIS) during the last deglaciation, we reconstructed Al2O3, flux in sediments from the Magellanes fjord (53°S) and southern Patagonia (55°S: Drake Passage) over the past 12 and 31 kiloyears (kyr), respectively. We confirm that the melting history of the PIS is recorded as changes in sedimentological signals and find that the melting ceased between ∼1() and 8 Calendar kyr before present (cal kyr BP). The timing of major melting events of the PIS was similar to that of the Northern Hemisphere ice sheets.
Progress in the oceanographic knowledge of Chilean interior waters, from Puerto Montt to Cape Horn. N. Silva & S. Palma (eds.). 2008 Comité Oceanográfico Nacional -Pontificia Universidad Católica de Valparaíso, Valparaíso, pp. 69-75. The knowledge on the physical and chemical characteristics of the surface sediments in Chile's austral channels and fjords prior to the beginning of the CIMAR Program in 1995 was scarce, limited to the results obtained by the Italian cruises on board the R/V Cariboo in the summers of 1988-1989 and 1989-1990 (Brambati et al., 1991; Lenardon, 1991; Mosca & Fontolan, 1991). These cruises focused on the Strait of Magellan, Magdalena, Cockburn, Brecknock, Ballenero, Brazo Norte, and Beagle channels. The area between Puerto Montt and Cape Horn was practically unexplored from a sedimentological point of view. Along with the other measurements and samples taken during the CIMAR Fiordos cruises in the austral region, the surface sediments were sampled intensively: 74 samples were taken between Puerto Montt and Laguna San Rafael (northern zone; CIMAR 1 Fiordos), 64 between Golfo de Penas and Strait of Magellan (central zone; CIMAR 2 Fiordos), and 36 between Strait of Magellan and Cape Horn (southern zone; CIMAR 3 Fiordos) (Fig. 1). This information was used to make the first physical (texture) and chemical (organic matter, organic and inorganic carbon, organic nitrogen) characterization of the sediments in this vast area of austral channels and fjords. The sediment textures did not present a defined relationship with depth. At times, fine sediments (silt-clay) were observed in deep areas (300-1,000 m) and, at other times, these textures were found in shallow areas (100-200 m). The same was true for gravels and sands. Nevertheless, a direct association was found between bottoms covered with fine sediments and proximity to glaciers. In the fjords near the Campos de Hielo Norte and the Campos de Hielo Sur, the sediment texture was almost 100 % clayey-mud (Silva et al., 1998, 2001; Silva & Ortiz, 2003).
The present study determined the main sources of Zn enrichment at the head of Aysén Fjord. The study considered the analysis of the river sediments that enter the fjord (fluvial record), the marine sediments at the head of the fjord (estuarine area record), and the sediments from stations along the fjord (horizontal concentration gradient). The Zn content was analyzed, as were Cd, Cu, and Pb as references. A different chemical attack was performed in order to estimate the total Zn and a sequential extraction techniques to estimate the "species" or fractions. The quantification was done using a polarographic analyzer (POL 1�0) coupled to a Trace Lab �0TM with square wave voltammetry and standard addition. Moreover, the sediment grain size, total organic matter, total organic carbon, and total phosphorus were analyzed. The results confirmed the highest zinc concentrations in the surface sediments at the head of the fjord. The profiles showed the highest concentrations of Zn at the surface. The fractional chemical attack indicated that residual Zn (60-80%) was the most abundant fraction. The Zn fractions associated with oxy-hydroxides and organo-metallics were similar (10-20%) and greater than the exchangeable fractions (�-10%). The residual Zn was associated with the lithogenic fraction and the rest corresponded to fluvial contributions main baseline components, whereas the remaining inflow corresponded to contributions associated with fluvial, advective, and anthropogenic components at the head of the fjord. The identification of the sources of Zn enrichment provides information relevant for implementing management policies to protect the area and indicates the changes due to anthropogenic sources.
The first systematic study of physical oceanographic characteristics of the fjord inlets of Chile was carried out by the Institute of Oceanography of the University of British Columbia during March 1970 as Phase V of the Hudson 70 Round-the-Americas Expedition. Observations were made of temperature, salinity, and dissolved oxygen at 175 stations in 32 inlets and in the passage outside them, and soundings were made along 3500 km of track. The sounding data are presented as longitudinal sections, and water properties are summarized in temperature-salinity and temperature-dissolved oxygen correlation plots and characteristic diagrams; comparisons are made with observations for the British Columbia and Alaska inlets. (Author)
Distinguishes three areas: 1) formed by the Primera and the Segunda Angosturas, was marked by highg nannoplankton values; 2) the basin of Punta Arenas, was marked by lower values than the first and by a preponderant diatom population; 3) described as "Pacific' characterized by lowest values and by a more homogeneous composition of phytoplankton populations. -from Authors
The Strait of Magellan is made up of 5 main morphological-sedimentological units: 3 are located in the Atlantic arm and two in the Pacific. The first unit consists of the first two basins that open onto the Atlantic Ocean and that are separated by a narrow (Primera Angostura) and by the northernmost tip of Punta Arenas Basin. The second morphological-sedimentological unit basically consists of the Punta Arenas Basin, which follows the first two basins through as additional narrow (Segunda Angostura). This is the largest basin and has a depth of 400-500 m. The energy levels, which tend to decrease gradually from the north to the south, affect the distribution of sands become finer. Starting from the Punta Arenas Basin, a network of bays and channels branch off forming the third physiographical unit which is characterized by both ancient tillite deposits and fluvio-glacial mud. The Pacific arm is characterized by two narrow, prolonged basins (fourth and fifth unit). These basins are the deepest (about 1000 m) and are mainly filled by modern muds though locally ancient, partly reworked tillite sediments are to be found. -from Authors
Analyses for dissolved oxygen, nitrate and total CO 2 in the interstitial water have been combined with solid phase sediment analyses of carbon and nitrogen to calculate the rates of reaction and stoichiometry of decomposing organic matter in central Equatorial Pacific pelagic sediments. The diagenesis is dominated by aerobic respiration and nitrification. Organic carbon and total nitrogen decrease exponentially with depth in both red clay and carbonate ooze sediments. In addition, there is a correlation between surface organic carbon and total nitrogen with distance from the equator. Fixed NH 4 is relatively constant with depth and constitutes 12 to 64% of the total nitrogen. The remainder is considered to be organic nitrogen. The C / N ratio of the decomposing organic matter was obtained using three approaches. Using the correlations of organic carbon with total nitrogen or organic nitrogen the molar ratios varied from 3.4 to 18.1. The average of all stations was 12.6 using total nitrogen and 13.7 using organic nitrogen. The Redfield ratio is 6.6. Approaches using interstitial water chemistry gave lower ratios. The average value using correlations between dissolved oxygen and nitrate was 8.1. The same approach using total CO 2 and nitrate gave an average of 9.1. Due to difficulties in unambiguously interpreting the solid phase data we favor the ratios obtained from the pore water analyses. The rate of organic matter decomposition can be obtained from model calculations using the dissolved oxygen and solid organic carbon data. Most gradients occur in the upper 10 to 20 cm of the sediments. Assuming that bioturbation is more important than sedimentation we have calculated first order rate constants. The average values using organic carbon and dissolved oxygen was 3.9 kyr - and 4.2 kyr - respectively using a biological mixing coefficient of 100 cm 2 kyr -1 . These rate constants decrease in direct proportions to the mixing coefficient.
The main differences between seasons were in the surface temperatures. In winter these were low at the fjord's head and increased towards its mouth. The surface salinity was very low at the head of the fjord in both seasons and only minor differences were detected. Differences were also observed in the levels of nutrients and dissolved oxygen and in the temperature and salinity structure. -from English summary
The four main vegetation types (Patagonian steppe, deciduous Magellanic forest, evergreen Magellanic forest and Magellanic tundra) are connected to climatic conditions and soils. -from Author
In the Atlantic sector, benthic species were abundant. In the large Middle sector, diatoms showed an overwhelming dominance, and in the Pacific Sector, number of dinoflagellates was the highest. Chaetoceros septentrionale and Protoperidinium denticulatum are new records for the Magellanic Fjords. -from Author
Oceanographic data collected in March 1970, during the Chile 70 leg of the Canadian expedition Hudson 70 in the southern Chile Region, has been used to describe some of the inlets, channels and gulfs, located between 41°20′S and 46°40′S latitude. Vertical sections of temperature, salinity and dissolved oxygen were prepared to analyze the water characteristic distributions in each inlet. The role of bathymetric constrictions, in the form of sills, in constraining water circulation in various locations is explored. Water mass properties and types are also described.
Highlights the strong influence exerted by the intense tidal currents in the shallow eastern sector of the Strait resulting in the mixing of Atlantic and more diluted internal waters and in the resuspension of inorganic particulate sediments, rich in metals; the presence in the central sector of a water mass generated by the mixing of Atlantic water with continental runoff and glaciofluvial water; the formation in the western sector of a stable two-layer structure consisting of colder and more diluted waters of continental origin in the surface layer, and of warmer and saltier waters of Sub-Antarctic origin in the underlying layer. -from Authors
Our views of remineralization and nutrient cycling in coastal marine ecosystems have changed considerably over the last 30 years. The major trend has been an increasing appreciation for the complexity of processes involved, including some marked changes in our assessment of the importance of bacteria with respect to smaller animals and in our perception of the association between bacteria and particulate matter in the sea. Among the more recent developments in this area is a growing awareness of the importance of the coupling between benthic and pelagic communities in coastal waters. There appears to be a strong linear correlation between the organic matter produced in the overlying water and the amount of organic matter consumed on the bottom in almost all of the coastal environments for which annual data are available. The large amount of organic matter consumed by the benthos (perhaps 25–50 percent of that produced) is associated with a large flux of inorganic nutrients from the sediments to the overlying water. The stoichiometry of net benthic nutrient regeneration differs from that of pelagic regeneration, however, and simple Redfield type models probably cannot be applied. The amount of fixed inorganic nitrogen returned to the water across the sediment-water interface appears to be about half of that expected on the basis of the flux of phosphorus. This behavior, along with the fact that an appreciable amount of organic matter in coastal waters gets remineralized on the bottom, contributes to the low N/P ratio that is characteristic of these areas and may be responsible for the observation that nitrogen is commonly the nutrient most limiting for primary production. Recent direct measurements of the flux of dissolved N2 across the sediment-water interface indicate that denitrification is probably responsible for the loss of fixed nitrogen during decomposition in the sediments. If this is a widespread phenomenon, estuaries, bays, and other coastal waters may be major sinks in the marine nitrogen cycle and important terms in the global nitrogen budget. However, the fact that eutrophication appears to be an increasing problem in many estuaries is dramatic warning that anthropogenic nutrient inputs can overwhelm the recycling and remineralization processes in coastal waters.
The regions with which this review is concerned are the deep fjord regions of Alaska and British Columbia in the northern hemisphere and Chile and New Zealand in the southern. The relative locations in latitude are shown in Fig. 1. The latitude zones for the Pacific fjords are: North America from 50° to 60°N, South America from 40° to 55°S and New Zealand from 45° to 47°S. (The Atlantic fjord regions are generally at higher latitudes, i.e. approximately 50° to 75°N for eastern Canada, 64° to 75°N for Greenland and 60° to 72°N for Norway.)
A rapid technique is presented for measuring organic C and N in carbonate-bearing sediments. Organic C and N were determined with a Yanaco MT-5 CHN analyzer after removing carbonate by acidification of samples in ceramic sample boats with HCl vapor. This procedure eliminates loss of acid-soluble organic matter during carbonate dissolution. The accuracy of this new technique and two earlier methods of determining organic C and N concentrations was verified with standard chemicals and carbonate-bearing sediments (> 80 wt% CaCO,). With the new technique there was no contamination or loss of organic C and N. The method is suitable for acidifying sediments with a wide range of carbonate content.
Ammonium regeneration was studied in sediments collected from two stations located in Concepcion Bay, Chile, a semi-enclosed and shallow system. This system is under the effects of the coastal upwelling processes for about 57% of every year. To understand the importance of the benthic system in ammonium dynamics, quantification is required of, at least, detrital inputs (with sediment traps), ammonium recycling rates (using experimental incubations of intact sediment cores), and ammonium loss through burial in the sediment column. The mean annual ammonium flux of 3·41mmol m−2day−1is comparable to the estimated benthic flux in very high productivity areas. The sediment thus constitutes an important ammonium source for the water column with respect to other sources, such as inputs from salt marshes, rivers and shelf waters. Seasonal variation in ammonium fluxes reflects the seasonality in macrofaunal activity, detrital inputs to the sediment–water interface, and the oxygen content of bottom water. These variables are enhanced in summer and may be an effect of the upwelling process. Ammonium benthic flux measurements and calculated burial rates are utilized to estimate the nitrogen budget of the sediments in the two stations studied. Approximately 76–83% of total nitrogen is regenerated as a product of the remineralization of organic matter produced during upwelling events which settles onto anoxic sediment.
Elemental and molecular organic matter concentrations were analyzed in sediments from the Lower St. Lawrence Estuary and the Saguenay Fjord in order to evaluate the historic evolution of pulp and paper mills solid-waste inputs in the system in the last decades and the relative reactivities of lignin and bulk organic materials in coastal sediments. A qualitative estimation of vascular plant sources to the Saguenay Fjord shows that the sedimentary terrigenous plant material is comprised predominantly of gymnosperm woods. In the deeper sediment horizons of the upper Saguenay basin, low intensive lignin parameters (CV and SV) and high percentages of lignin to total sedimentary organic carbon (> 20%) all indicate elevated concentrations of woody gymnosperm tissues unprecedented in coastal sediments and directly related to the intense activity of the region's pulp and paper industries. The increased control on solid organic wastes from industrial effluents into the Saguenay river in the late 1980s to early 1990s is clearly apparent from increasing intensive parameter values and decreasing lignin fractions to the total sedimentary organic carbon (≈ 6–8%) in the upper basin surface sediments. Elemental and molecular analyses of fjord sediments, all indicate that most of the solid-phase discharge of lignified material by the pulp and paper industry is deposited rapidly close to the mouth of the river without reaching the downstream basins. In the St. Lawrence Estuary, intensive lignin parameters indicate that gymnosperm tissues are a major component of the sedimentary vascular plant material but with a significant fraction composed of angiosperm and nonwoody tissues. These latter types of organic tissues are particularly important components of terrigenous material in sediments deposited prior to the 1910–1920s. Acid/aldehyde ratios in most cores studied do not indicate clear-cut oxidative degradation of lignin material prior to its introduction in the aquatic system. The only exceptions are the two estuarine cores, where slightly elevated acid/aldehyde ratios relative to the range for fresh vascular plant tissues, might indicate mild aerobic fungal degradation of the sedimentary lignin material. Organic carbon, total nitrogen, organic phosphorus and lignin derived phenols all exhibited decreasing concentrations with core depth in the sediments of the Lower St. Lawrence Estuary. First-order degradation rate constants for all four chemical categories ranged between 0.02–0.05 yr−1. The order of apparent reactivity among the different organic compounds is TN ≥ Corg > Porg > lignin at the head of the Laurentian channel and lignin ≈ TN = Corg > Porg further downstream. The surprising diagenetic selectivity observed at the upstream station is probably due to a higher flux of fresh, labile organic matter that reaches the sediment-water interface and degrades preferentially to more refractory materials such as lignin. Further downstream, little diagenetic selectivity was observed below the sediment-water interface indicating an overall refractory nature of the sedimentary organic matter. Finally, the differences in reactivity observed between Corg and Porg at both stations contradict earlier assumptions that no fractionation occurs between organic carbon and phosphorus during anaerobic degradation.
The first systematic study of physical oceanographic characteristics of the fjord inlets of Chile was carried out by the Institute of Oceanography of the University of British Columbia during March 1970 as Phase V of the Hudson 70 Round-the-Americas Expedition. Observations were made of temperature, salinity, and dissolved oxygen at 175 stations in 32 inlets and in the passage outside them, and soundings were made along 3500 km of track. The sounding data are presented as longitudinal sections, and water properties are summarized in temperature-salinity and temperature-dissolved oxygen correlation plots and characteristic diagrams; comparisons are made with observations for the British Columbia and Alaska inlets. (Author)
The bacterial reduction of sulphate to sulphide at the sea bed is a key process in the oceanic sulphur cycle, and is responsible for the oxidation of organic matter which becomes buried below the oxic and sub-oxic zones of the sea bed. The oxic surface layer of the sea bed varies in thickness from a few millimetres in sheltered coastal areas to 1 m in pelagic sediments1,2. Below this layer, organic matter is mineralized mainly by fermenting, denitrifying, sulphate-reducing and methane-producing bacteria. Sulphate reduction is the predominant terminal step in the mineralization processes of sulphate-rich shelf sediments where the sulphate reducers inhibit the methanogens by competing with them for common substrates3–5. Sulphate reduction may therefore have a quantitatively important role in the overall oxidation of organic matter in the sea bed. Recently, concurrent measurements of oxygen uptake and sulphate reduction in a coastal sediment6 have demonstrated the importance of the sulphate-reducing bacteria in the mineralization of organic carbon. I present here the first comparative survey of aerobic and anaerobic mineralization in the sea bed based on direct rate measurements of the two processes. The results demonstrate a surprisingly high contribution from the sulphate-reducers. In coastal sediments, this specialized group of bacteria oxidized as much organic matter to CO2 as did all the aerobic organisms. Their relative contribution decreased three fold over the continental shelf from the shore to a depth of 200 m.
The supply of particulate material to the sea-bed as well as the oxygen consumption and the redox potential of the sea-bed were measured during a one-year period (1979/1980) at 60 and 90 m depth in the inner part of a west Norwegian fjord, Fanafjorden. At both sites, uniform sedimentation rates of total particulate material (825 and 885 g m-2 yr-1, respectively) and particulate inorganic material (576 and 616 g m-2 yr-1, respectively) were found. The sedimentation rates of particulate organic carbon (96 and 107 g m-2 yr-1, respectively) and particulate organic nitrogen (10 and 12 g m-2 yr-1, respectively) were low in winter, higher in summer and autumn, with maxima in May/June, reflecting similar maxima in the phytoplankton biomass in the area, with 6 to 8 wk delay. The oxygen consumption of the sea-floor was lowest in winter/spring and highest in summer. Thirtytwo and 38 g C m-2 yr-1 (respiration quotient=0.85) were metabolized by the sediment at 60 and 90 m, respectively. The simultaneous measurements of sedimentation rates and sediment oxygen uptake throughout a whole year demonstrated that the benthic mineralization is governed by the sedimentation over a longer time-scale, but that seasonal imbalances do occur. A box-model of the flux of particulate organic carbon to the sediment surface is presented, and includes the relevant processes and some quantitative estimates.
Flocculation and de-flocculation have been observed in estuaries and the processes involved are discussed. Salt flocculation plays a minor role, if any. Flocs are mainly formed by a combination of two groups of processes: those bringing particles together, and those keeping them together. The first group is related to the flow conditions in the water and to organisms that clog particles into faeces or pseudofaeces or attach them to mucus. The second is related to the formation of sticky organic matter by a variety of organisms. Two main types of flocs have been observed: microflocs with a diameter up to 125 μm, and macroflocs with a maximum size of 3–4 mm. Microflocs consist of mineral particles and organic matter. Their formation is strongly related to the origin of the organic matter, to the organisms producing it, and to conditions of (temporary) deposition and resuspension. Mucopolysaccharides, produced by bacteria, algae and higher plants and mobilized from the suspended matter at low salinity, are important in glueing particles together. The microflocs, together with single mineral particles, are the basic building units of macroflocs. Macroflocs are fragile and formed in the water under conditions of viscous flow. Their maximum size is determined by turbulent shear, the size of the smallest turbulent whirls on the Kolmogorov scale being of the same order as the maximum floc size. They are easily destroyed during sampling. In estuaries the microflocs of fluvial origin are broken up by organisms consuming the organic matter in the microflocs, and reflocculated into new microflocs with newly formed organic matter of estuarine origin. The size of the microflocs, as seen under a microscope or determined by size analysis, is likely to be determined mainly by the binding strength of the organic matter in relation to the total mass of the floc and the physical disturbance produced during sampling and size analysis.
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Distribució n espacial de la biomasa y productividad fito-plancton en zonas de fiordos y canales australes: influencia de factores fisico-quí in press. Price, B. 1976 Chemical diagenesis in sediment
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