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Schematic diagram illustrating typical zonation with depth used for analysis in this study. Cores split into three zones based on dominant processes affecting labile carbon preservation. Zones included a surface active zone (SAZ), diagenetic zone (DZ) and accumulation zone (AZ). The SAZ is dominated by new deposition, mixing, lateral transport and oxic degradation and modification of organic carbon. The DZ was dominated by anoxic degradation processes, while the AZ shows little subsequent degradation of labile organic carbon and was thus more characteristic of deeper more abundant accumulating deposits.
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The primary focus of this paper is to better understand carbon burial on the Louisiana continental margin using spatial scales that covered various shelf depositional areas far-field and near-field (sediment and organic carbon inputs relative to river mouth proximity) and covering a variety of sedimentation rates. Box-cores samples were collected i...
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... were broken into three zones relating to the dominant forces thought to affect organic carbon burial. The Surface Active Zone (SAZ) was defined based on 7 Be, 234 Th, and porosity charac- teristics of the upper core (Fig. 2). The SAZ was dominated by deposition, modification, sediment mixing and oxic degradation of organic carbon. More specifically, there is evidence that the sedi- ment layer is less than about 1 year in age (deposited in the last river flood year) or has been exposed to oxygen within that time. This covers both the physical mixing ...
Context 2
... were broken into three zones relating to the dominant forces thought to affect organic carbon burial. The Surface Active Zone (SAZ) was defined based on 7 Be, 234 Th, and porosity charac- teristics of the upper core (Fig. 2). The SAZ was dominated by deposition, modification, sediment mixing and oxic degradation of organic carbon. More specifically, there is evidence that the sedi- ment layer is less than about 1 year in age (deposited in the last river flood year) or has been exposed to oxygen within that time. This covers both the physical mixing ...
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... Using primary productivity rates, total organic carbon (TOC) and comparisons with δ 13 C org values, Trefry et al. (1994) estimated that ∼ 20 %-50 % of the particulate organic carbon (POC) flux off the Mississippi River (MR) is buried on the Louisiana shelf and that < 40 % is derived terrestrially. Studies on organic matter sources in the northern GoM generally focused on total OM concentrations, or the differentiation of terrestrial and marine OM sources, mostly using bulk OM properties (TOC and δ 13 C org values) and concentrations and/or ratios of plant (lignin) and/or algal (photosynthetic pigments) biomarkers (e.g., Goñi et al., 1997Goñi et al., , 1998Bianchi et al., 2002;Chen et al., 2003;Wysocki et al., 2006;Waterson and Canuel, 2008;Sampere et al., 2008Sampere et al., , 2011. These studies showed that TerrOM concentrations follow the expected trend of highest concentrations close to the MR and a subsequent decrease with increasing distance from the river mouth. ...
... The MR mouth is located close to the Mississippi Canyon, the formation of which is generally linked to channel entrenchment of the MR during sea level low stands (Coleman et al., 1982). Subsequently, a portion of the sediments discharged by the MR is transported downslope into the Mississippi Canyon (Coleman, 1988;Bianchi et al., 2006;Sampere et al., 2008Sampere et al., , 2011, resulting in higher sediment export rates compared to the Atchafalaya River . These differences in morphology also influence physical shelf processes such as water column stratification; the steeper morphology of the MR allows for a well-defined pycnocline, whereas the shallower shelf (< 20 m) close to the AR mouth prevents the development of a stratified water column (Hetland and Di-Marco, 2008). ...
Rivers play a key role in the global carbon cycle by transporting terrestrial organic matter (TerrOM) from land to the ocean. Upon burial in marine sediments, this TerrOM may be a significant long-term carbon sink, depending on its composition and properties. However, much remains unknown about the dispersal of different types of TerrOM in the marine realm upon fluvial discharge since the commonly used bulk organic matter (OM) parameters do not reach the required level of source- and process-specific information. Here, we analyzed bulk OM properties, lipid biomarkers (long-chain n-alkanes, sterols, long-chain diols, alkenones, branched and isoprenoid glycerol dialkyl glycerol tetraethers (brGDGTs and isoGDGTs)), pollen, and dinoflagellate cysts in marine surface sediments along two transects offshore the Mississippi–Atchafalaya River (MAR) system, as well as one along the 20 m isobath in the direction of the river plume. We use these biomarkers and palynological proxies to identify the dispersal patterns of soil–microbial organic matter (SMOM), fluvial, higher plant, and marine-produced OM in the coastal sediments of the northern Gulf of Mexico (GoM). The Branched and Isoprenoid Tetraether (BIT) index and the relative abundance of C32 1,15-diols indicative for freshwater production show high contributions of SMOM and fluvial OM near the Mississippi River (MR) mouth (BIT = 0.6, FC321,15 > 50 %), which rapidly decrease further away from the river mouth (BIT < 0.1, FC321,15 < 20 %). In contrast, concentrations of long-chain n-alkanes and pollen grains do not show this stark decrease along the path of transport, and especially n-alkanes are also found in sediments in deeper waters. Proxy indicators show that marine productivity is highest close to shore and reveal that marine producers (diatoms, dinoflagellates, coccolithophores) have different spatial distributions, indicating their preferred niches. Close to the coast, where food supply is high and waters are turbid, cysts of heterotrophic dinoflagellates dominate the assemblages. The dominance of heterotrophic taxa in shelf waters in combination with the rapid decrease in the relative contribution of TerrOM towards the deeper ocean suggest that TerrOM input may trigger a priming effect that results in its rapid decomposition upon discharge. In the open ocean far away from the river plume, autotrophic dinoflagellates dominate the assemblages, indicating more oligotrophic conditions. Our combined lipid biomarker and palynology approach reveals that different types of TerrOM have distinct dispersal patterns, suggesting that the initial composition of this particulate OM influences the burial efficiency of TerrOM on the continental margin.
... For instance, the upwelling-driven primary productivity controls the OM enrichment in the Wufeng Formation at out-shelf of the upper Yangtze platform, while preservation condition is the primary controlling factor of the OM accumulation at the restricted inner-shelf (Lu et al., 2019). Most previous research has focused on the OM burial process in the current sedimentary system (Einsele et al., 2001;Sampere et al., 2011;Wang et al., 2015;Jiang et al., 2020). Recently, Huang et al. (2021b) reported an astronomical paced deeptime OM burial and proposed a model for obliquity-forced OM accumulation in the middle to high latitudes. ...
Organic matter (OM) sequestration acts as a significant sink of the CO2 in Earth's carbon cycle and is tightly associated with the climate and depositional environments. However, the dominant factors controlling OM burial in different depositional settings and the orbitally forced variations in the lacustrine OM accumulation remain poorly constrained. Here, we investigate the depositional environment of the Lucaogou Formation in southern Junggar Basin, northwestern China and further decipher the astronomically forced OM accumulation in different depositional environments. Sedimentological and cyclostratigraphic studies show that both shallow lake and semi-deep to deep lake deposits recorded significant Milankovitch signals among of which ~405 kyr, ~91 kyr, 34.5–37.4 kyr, and 17.3–22.8 kyr are interpreted to be long eccentricity, short eccentricity, obliquity, and precession cycles, respectively. A linkage among the lithofacies, natural gamma ray (NGR), and total organic carbon (TOC) content suggests that the depositional environment and OM accumulation were in pace with the hydrological cycle and lake-level changes, in response to the astronomically forced changes in the ice volume and monsoonal intensity. In the semi-deep to deep lake, TOC content tightly tracks the lithofacies and shows an in-phase relationship with NGR. However, this phase relationship has changed with sedimentary facies. The gypsiferous shale deposited in the restricted environment during lowstand intervals has higher TOC content than highstand dolomitic mudstone, demonstrating an anti-phase relationship with NGR data. Our study indicates that the OM sequestration is a dynamically cumulative process of supply and degradation. The different responses of the OM sequestration to the climate change in different environments suggest that detailed sedimentological studies are essential for the cyclostratigraphic analysis.
... Owing to highly constant peak characteristics, the chl a-derivative phaeophytin as well as diadinoxanthin, and its derivate diadinochrome ('D+D') could be identified with high probability in most of the cores, as could prasinoxanthin albeit less frequently. The fact that other studies already detected D+D (Repeta 1989, Brotas and Plante-Cuny 2003, Krajewska et al. 2017) and prasinoxanthin in sediments (Sampere et al. 2011, Kang et al. 2016, Zhang et al. 2019) supports the tentative identification of these pigments. Hence, D+D were summarised, and all four pigments included in the following analysis. ...
... Despite the fact that phytoplanktic cryptophytes and prasinophytes typically prefer deeper lakes, cryptophyte remains as well as the peaks of the prasinoxanthin-like pigment also appear in the younger sediments of shallow lakes (Fig. 2). Both indicate developments triggered by warming and further support to identify the latter as prasinoxanthin, which was also found to increase in other sediments (Sampere et al. 2011, Kang et al. 2016, Zhang et al. 2019). ...
The biological communities of mountain lakes are suspected to be highly sensitive to global warming and associated catchment changes. To identify the parameters determining algal community responses, subfossil pigments from 21 different mountain lakes in the Bavarian‐Tyrolean Limestone Alps were investigated. Sediment cores were radio‐isotopically dated, and their pigment preservation evaluated. General additive models (GAM) of pigment compositions were calculated with temperature as the explanatory variable and generalised linear models with several lake parameters explaining log‐transformed GAM p‐values.
Lake depth and trophic state were identified as major control variables of the algal community and productivity changes. Shifts in a deep oligotrophic alpine lake (lg(p) = –1.04) were half as strong as in a shallow mesotrophic alpine lake (lg(p) = –1.86) with faster warming and higher productivity forcing the development of biomass. Phytoplankton and macrophyte pigments increased clearly with warming, at lower altitudes, and decreased at the treeline, so that periphytic pigments dominated alpine sediments. This pattern is probably the result of interactions of UV radiation and allochthonous inputs of DOM. Our findings suggest that (sub)alpine shallow lakes with higher nutrient levels are most vulnerable to climate change‐driven changes whereas deep, nutrient‐poor lakes appear more resilient.
... Sediment deposition and resuspension within marine environments are processes that are fundamental to shaping the seabed environment and of key interest to several fields. For example, understanding the location and rate of sediment accumulation is important for monitoring pollutants and microplastics (Corcoran et al., 2015;Kankaanpää et al., 1997), understanding the organic carbon cycle (Burdige, 2007;Nilsson et al., 2019;Sampere et al., 2011) and understanding changes in erosion and deposition of sediments (Peizhen et al., 2001). Many areas are subject to both sedimentation and erosion events, and the sedimentation rate or sediment accumulation rate (SAR), as a linear measure (cm yr − 1 ), refers to the net of these two actions over a given time period. ...
... For example, over 1000 SAR samples have been collected globally (Restreppo et al., 2020), and while these are outside the physical domain of interest, were appropriate predictor variables available they could still be incorporated into the observational space used to inform the model. Other associated issues with ground truth SAR data may include interpretation of 137 Cs tracer band curves, for samples converted from mass, whether the dry weight or wet weight was measured and whether samples were corrected for sediment compaction (Jenkins, 2018;Sampere et al., 2011). Data within the EMODnet database had well documented metadata for the majority of samples, which could have allowed these issues to be considered. ...
Sedimentation rate data are applied in a range of studies such as understanding the sediment carbon budget and accumulation of pollutants in marine sediments. Over many years, sedimentation rate samples have been collected within the Baltic Sea. However, to understand patterns in sedimentation rates more broadly across this sea basin requires converting these point data into continuous spatial predictions. The generation of continuous maps remains problematic and under-studied. This study explores the feasibility of machine learning to estimate sedimentation rates, using 137 Cs measurements from the Baltic Sea. A random forest model was applied to predict sedimentation rates based on a range of predictor variables that related to the hydrodynamic regime, bathy-metric complexity of the seabed, substrate type and proximity to sediment sources. The accuracy of this prediction was tested against an independent set of sedimentation rate samples that had been withheld from model training. The model was also compared against a simple spatial interpolation to assess whether machine learning produces an improvement on previously applied methods. Overall, the modelling approach explained 41.9% of the variance, far surpassing the spatial interpolation method (4.2% variance explained). This study is a first step towards the spatial prediction of sediment accumulation rates in a repeatable and validated way, but further refinement is desirable to improve the accuracy of the predictions. We discuss the potential sources of model error that could have limited the success of this approach and suggest how some of these could be addressed. Our results indicate that short-term sedimentation rates are highest in small coastal basins, while rates in the deep basins of the Baltic Sea are generally low, thereby seemingly contradicting long held views of the deep-basins as the major depocentres in the Baltic Sea. This apparent contradiction might be attributed to the higher spatial detail of our analysis and differences in the time scales of analysis, indicating that sedimentation patterns in the Baltic Sea might be complex in space and time.
... In contrast, the momentum of the river outflow at high discharge is strong enough to overcome this effect and transport water and sediment offshore. As a result, sediment trapped in estuaries or backwater reaches during low discharge seasons is biogeochemically processed until the next high discharge, such that the inorganic (Allison and Pratt, 2017;Meiggs and Taillefert, 2011;Sutula et al., 2004) and organic (Cowie and Hedges, 1984;Cowie and Hedges, 1992;Sampere et al., 2011) content of surrounding shelf sediments is affected seasonally. In turn, the lithologic input to continental shelves is greater during high discharge as a result of increased erosion upstream (Meiggs and Taillefert, 2011). ...
... The bioturbation coefficient at the sediment-water interface was predicted from an empirical relationship as a function of water depth (Boudreau, 1997), and the maximum bioturbation depth was set empirically at each station according to the Fe(OH) 3 profile. Organic carbon degradation that produces NH 4 + and DIC as by-product is described by Michaelis-Menten rate laws with respiratory inhibition (Soetaert et al., 1996;Wang and Van Cappellen, 1996) using C:N ratios from the literature (Sampere et al., 2011;Waterson and Canuel, 2008). Reduced compounds produced during remineralization (i.e., NH 4 + , Mn 2+ , Fe 2+ , ΣH 2 S) are partly removed from the system by precipitation of sulfide (FeS) or carbonate minerals (MnCO 3 , FeCO 3 ) and oxidation in the presence of O 2(aq) or other oxidants (MnO 2 , Fe(OH) 3 ) using explicit kinetic formulations (Wang and Van Cappellen, 1996). ...
... The Mississippi River supplies a large load of particulate material during its high discharge period from the winter to early spring that is eventually deposited on the Louisiana shelf (Corbett et al., 2006;Corbett et al., 2004;Devereux et al., 2019). These sediments form mobile muds that are often remobilized by physical mixing generated by tidal currents or storms (Sampere et al., 2011). This process eventually sorts material by size, morphology, or composition , transports terrestrial organic carbon (Waterson and Canuel, 2008) and inorganic material (Trefry and Presley, 1982) to the deep sediment, and may increase diagenetic reactivity by a priming effect (Bianchi, 2011). ...
Pore water and solid phase geochemical profiles of sediment cores collected along two transects on the western and eastern sides of the Mississippi River mouth in the northern Gulf of Mexico were incorporated into a reactive transport model to determine the role of manganese and iron in the remineralization of carbon. Reactive transport model calculations indicate that sedimentation rates control the intensity of anaerobic carbon remineralization and select for the dominant anaerobic carbon remineralization pathways. Although sulfate reduction dominates the shelf station (65 m water depth), denitrification and microbial manganese reduction appear equally significant anaerobic respiration processes along the continental slope the closest to the Mississippi River, whereas microbial iron reduction does not represent an important process in these sediments. These findings suggest that the differential kinetics of manganese and iron redox transformations influence carbon remineralization processes on the continental slope. The fast kinetics of Fe2+ oxidation near the sediment-water interface and high sedimentation rates maintain Fe under the form of Fe(III) oxides and thermodynamically prevent sulfate reduction from dominating carbon remineralization processes on the slope, whereas the much slower Mn2+ oxygenation kinetics allows diffusion of Mn2+ across the sediment-water interface of the shelf station closest to the river mouth. Exposure to oxygenated bottom waters and entrainment within mobile muds typical of deltaic sediments during high riverine discharge likely promote the formation and downslope transport of Mn(III/IV) oxides within the nepheloid layer. This phenomenon appears to form a manganese ‘conveyor belt’ that selectively enriches Mn(III/IV) oxides relative to Fe(III) oxides in the deep sediment. In contrast, the intensity of anaerobic carbon remineralization processes along the eastern continental slope the farthest from the Mississippi River plume is much lower due to the low organic and lithogenic inputs, and denitrification dominates anaerobic respiration. Overall, these findings suggest that manganese cycling and its role in carbon remineralization processes in continental slope sediments exposed to large riverine inputs may be more important than previously considered.
... To better describe the mechanisms underlying empirical relationships, substantial effort has been made to estimate primary production Lohrenz et al., 1997;Walker & Rabalais, 2006), the distribution of organic carbon across the shelf (Bianchi et al., 2002;Fry et al., 2014;Lehrter et al., 2013;Trefry et al., 1994;Wang et al., 2004), and the respiration that drives hypoxia formation in bottom water (Dortch et al., 1994;Lehrter et al., 2012;Murrell & Lehrter, 2011;Rowe & Chapman, 2002). The relationship among these processes has been conceptualized as intense production associated with the river discharge plume, followed by transport, respiration, and production associated with nutrient recycling in association with westward or downcoast transport along the continental shelf (Bianchi et al., 2010;Boesch et al., 2009;Corbett et al., 2006;Gordon et al., 2001;Rowe & Chapman, 2002;Sampere et al., 2011). ...
The hypoxic zone on the Louisiana Continental Shelf (LCS) forms each summer due to nutrient‐enhanced primary production and seasonal stratification associated with freshwater discharges from the Mississippi/Atchafalaya River Basin (MARB). Recent field studies have identified highly productive shallow nearshore waters as an important component of shelf‐wide carbon production contributing to hypoxia formation. This study applied a three‐dimensional hydrodynamic‐biogeochemical model named CGEM (Coastal Generalized Ecosystem Model) to quantify the spatial and temporal patterns of hypoxia, carbon production, respiration, and transport between nearshore and middle shelf regions where hypoxia is most prevalent. We first demonstrate that our simulations reproduced spatial and temporal patterns of carbon production, respiration, and bottom‐water oxygen gradients compared to field observations. We used multiyear simulations to quantify transport of particulate organic carbon (POC) from nearshore areas where riverine organic matter and phytoplankton carbon production are greatest. The spatial displacement of carbon production and respiration in our simulations was created by westward and offshore POC flux via phytoplankton carbon flux in the surface layer and POC flux in the bottom layer, supporting heterotrophic respiration on the middle shelf where hypoxia is frequently observed. These results support existing studies suggesting the importance of offshore carbon flux to hypoxia formation, particularly on the west shelf where hypoxic conditions are most variable.
... LAR values are affected by porosity changes due to sediment consolidation or lack of consolidation as in fluid muds. Some studies (e.g., Sampere et al. 2011) recalculate deposited thicknesses to 75%, a benchmark which is appropriate for muddy sediments and fluid muds in particular. Studies that compare linear rates between sand and muddy sediments (porosities usually ' 30% versus ' 75%, respectively) are prone to these effects. ...
Abundant data on sediment accumulation rates exist for the continental margin in the region of the Mississippi Delta. They were obtained during numerous studies by many institutions and researchers using a range of methods: radioisotope and other tracers, identified events, and biostratigraphy. For several reasons, it is necessary to integrate the data across the region: to test and validate numerical models of sedimentation, and to devise methods for a Big Data integration of similar rates on a global scale. We have collated over 700 records of sediment accumulation rate in theMississippi region. They were taken over time intervals (viz. Integration times, measurement intervals) that range over five orders of magnitude, from 2 days to 1000 years. This range stems from use of diverse analytical methods such as tracers with different half-lives, and also from varying sample lengths and times. A Sadler Effect relationship is found to apply across the data: intercept 1.71 in log10(cm/yr), slope-0.55, R2 0.66, N 717. It corroborates ad hoc observations in the area by analysts, that short-period rates tend to be higher than longterm rates. Investigations are made on how the Sadler Effect coefficients vary by environment: by water depth, physiographic province, and sediment mud contents. For most environments the coefficients cluster around the general result, though coefficients for prodelta, deep basin, bay, canyon, and upper slope areas are separate enough to be remarked on. The statistics indicate that measurement interval is responsible for most of the inter-analysis variability. Therefore a transform of the data to a 1-year basis (the Sadler Effect intercept) is proposed, removing measurement-interval effects and providing a general framework for integrating the rates. This is in conformance with a random-walk model for the Sadler Effect of steady, constant deposition plus a spectrum of unsteady nondeposition events. Precise values of the coefficients are different in some environments. After the transform, variations in the rates by spatial and environmental factors are revealed more clearly.
... High OC/SA loadings (> 1 mg OC/m 2 ) are commonly found in certain estuarine sedimentary environments (e.g. fjords) and/or Aller and Blair (2006), Feng et al. (2016), Kastner and Goñi (2003), Keil et al. (1997), Kuehl et al. (1986), Showers and Angle (1986), Sun et al. (2017), Williams et al. (2015) Northern Gulf of Mexico GOM Bianchi et al. (2002), Goñi et al. (1998aGoñi et al. ( , 1998b, Goñi (2003, 2004), Gordon et al. (2001), Sampere et al. (2011aSampere et al. ( , 2011bSampere et al. ( , 2008, Wakeham et al. (2009) Amazon AMA Aller and Blair (2006), Feng et al. (2016), Kastner and Goñi (2003), Keil et al. (1997), Kuehl et al. (1986), Showers and Angle (1986) Wakeham et al. (2009) depositional shelf/slope settings underlying areas of high productivity (e.g. upwelling zones), both of which are characterized by low-O 2 levels in bottom waters (Fig. 2B). ...
Continental margin systems collectively receive and store vast amounts of organic carbon (OC) derived from primary productivity both on land and in the ocean, thereby playing a central role in the global carbon cycle. The land-ocean interface is however extremely heterogeneous in terms of terrigenous input, marine primary productivity, sediment transport processes and depositional conditions (e.g. such as bottom water oxygen level). Continental margins are also highly dynamic, with processes occurring over a broad range of spatial and temporal scales. The rates of OC burial and oxidation are consequently variable over both space and time, hindering our ability to derive a global picture of OC cycling at the land-ocean interface. Here, we review the processes controlling the fate of organic matter in continental margin sediments, with a special emphasis on “hot spots” and “hot moments” of OC burial and oxidation. We present a compilation of compositional data from a set of illustrative settings, including fjords, small mountainous river margins, large deltaic systems and upwelling areas. Bulk OC stable isotope and radiocarbon compositions reveal the diversity and complexity characteristic of OC buried in marginal seas. This primarily relates to differences in marine and terrestrial inputs, the composition of the terrestrial component (e.g. vascular plant OC, soil, and petrogenic OC inputs), and processes modulating the fate of OC within the marine environment (e.g. priming). This widely contrasting behavior of OC among these systems illustrates that the reactivity of OC is a product of its chemical composition and regional conditions. Interpreted in the context of bulk compositional data as well as that obtained on specific molecular markers (e.g. lignin-derived phenols), the possibility exists to tease apart complex mixtures of terrestrial and marine inputs, and to shed light on the role of the myriad of depositional and post-depositional processes. Finally, we discuss a set of hot topics that warrant further investigation – such as the role of photochemistry, fungi, halogenation and reactive iron in dictating the fate of OC in the (changing) coastal ocean.
... Vertical fluxes of OC in the Mississippi River plume as high as 1.80 g C m −2 d −1 have been observed during spring (Redalje and Fahnenstiel, 1994), but are lower during other seasons (0.29-0.95 g C m −2 d −1 ) and away from the immediate plume (0.18-0.40 g C m −2 d −1 ). In fact, the highest OC burial rates in sediments (∼300 g C m −2 y −1 ) occur near the mouth of Southwest Pass (Sampere et al., 2011). ...
The purpose of this review is to highlight progress in unraveling carbon cycling dynamics across the continuum of landscapes, inland waters, coastal oceans, and the atmosphere. Earth systems are intimately interconnected, yet most biogeochemical studies focus on specific components in isolation. The movement of water drives the carbon cycle, and, as such, inland waters provide a critical intersection between terrestrial and marine biospheres. Inland, estuarine, and coastal waters are well studied in regions near centers of human population in the Northern hemisphere. However, many of the world's large river systems and their marine receiving waters remain poorly characterized, particularly in the tropics, which contribute to a disproportionately large fraction of the transformation of terrestrial organic matter to carbon dioxide, and the Arctic, where positive feedback mechanisms are likely to amplify global climate change. There are large gaps in current coverage of environmental observations along the aquatic continuum. For example, tidally-influenced reaches of major rivers and near-shore coastal regions around river plumes are often left out of carbon budgets due to a combination of methodological constraints and poor data coverage. We suggest that closing these gaps could potentially alter global estimates of CO2 outgassing from surface waters to the atmosphere by several-fold. Finally, in order to identify and constrain/embrace uncertainties in global carbon budget estimations it is important that we further adopt statistical and modeling approaches that have become well-established in the fields of oceanography and paleoclimatology, for example.
... The Mississippi RiOMar is a Type IIIa system (McKee et al., 2004) because a significant proportion (N10%) of the river plume is transported down-slope indirectly. Particles from the Mississippi, including C org synthesized within the Mississippi River plume (Bianchi et al., 2006;Sampere et al., 2011), accumulate on a prograding delta near the shelf-break (Coleman, 1988) and may spill-over in storms (Bea et al., 1983), or more infrequently, during large-scale mass-slumping of rapidly deposited, over pressurized muds (Coleman et al., 1998;Dugan and Stigall, 2010). The net effect is an accumulation of terrigenous material much farther downslope than normal mixing processes would allow (Konyukhov, 2008), as has been demonstrated in the Ursa basin to the east of GOM12 (Long et al., 2011;Reece et al., 2012). ...
