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Benthic community data from eight stations around Pulau Semakau, an island south of Singapore, were collected during three surveys and analysed to determine changes in community structure under different sediment regimes resulting from construction activity at the eastern part of Pulau Semakau. Multidimensional Scaling (MDS) Configurations indicate...
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... activities such as the dumping of earth spoils, land reclamation and commercial fishing have impacted marine ecosystems seriously in recent years. Some of these impacts are increased sedimentation, changes in physical and chemical parameters of the marine system, and disturbances in biology communities. The study of benthic communities is a particularly useful and sensitive tool for identifying sediment-related stress (Alongi, 1990). The analysis of changes in benthic community structure has now become one of the main methods of detecting and monitoring the biological effects of marine disturbance. Many studies have been made on the impacts of pollution resulting from human activities on benthic communities (Nicolaidou et al., 1989; Hall et al., 1990, 1992; Olsgard & Hasle 1993; Hatcher et al., 1994). Pulau Semakau is situated south of mainland Singapore ( Fig. 1), and was surrounded by large areas of patch reefs and an extensive fringing reef. Dumping of earth spoils started in 1988 to convert the eastern sea of the island into a landfill site (Anonymous, 1989; Liu, 1989). An extensive bund to connect Pulau Semakau and neighbouring Pulau Sakeng to enclose the sub-marine landfill site was constructed and sediment screens were placed to prevent the spread of sediment after 1995 (Nathan, 1993, 1995). This study aims to describe the impacts from this construction activity by examining the changes in the structure of the soft-bottom communities with regard to environmental changes in space and time. Am- bient physical-chemical parameters were monitored and the nutrient analysis in this study focused on ammonium, nitrate, nitrate, nitrite concentration and organic-inorganic ratio in benthic water, bottom sediment and input sediment. Multidimesional Scaling (MDS) was used to analyse the soft-bottom benthic community by ordination to identify changes in the community over space and time. One-way ANOVA and correlation coefficient were also employed to determine significant devi- ations among stations and the relationship between community and environment ...
Citations
... The sandy clay type of soil composition is also found in the saline soils of Bangladesh (Rahman et al., 1993). Usually, the soil texture variation in the estuarine coastal area is produced during sedimentation process (Chou et al., 2004). The higher percentage of sand in soil in the study area suggests that the estuarine habitat of Bakkhali river probably a depositional coast. ...
Morphology, habitat, shoot density and standing crop (above and below ground biomass) of salt marsh Porteresia coarctata at Bakkhali estuary, Cox’s Bazar were investigated from January 2006 to June 2006. Permanent plots of 50 m x 50 m from exposed (station I) and protected (station II) areas were selected. P. coarctata was found growing as monospecific stand and four-species association with seagrass Halophila beccarii, patches of mangroves (Avicennia alba, A. marina and Acanthus ilicifolius) and the seaweed Ulva intestinalis in the intertidal sandy clay substrate. P. coarctata also grew in three-species association with mangrove and seaweed, or with seagrass and seaweed as well as in two-species association with seagrass and Imperata cylindrica. The range of mean leaf length, internodes length of rhizome and individual shoot height were found 8.10-14.49 cm, 0.91-1.41 cm and 12.90-20.94 cm, respectively. The mean shoot density varied from 925.0 to 1545.0 shoots m-2. The mean above and below ground biomass were 23.28-38.02 g DW (Dry Weight) m-2 and 60.26-97.39 g DW m-2, respectively. The pore water salinity, pH and NH4-N were recorded 17.0-41.66‰, 6.0-6.47 and 1.80-3.70 µg l-1, respectively. The variation of morphological parameters, shoot density and standing crop of P. coarctata between the two sampling stations attributed to the differences in habitat, soil organic matter and tidal action i.e., wave and current between the stations.
... Warming and precipitation increases are estimated to be strongest during winters (Ruosteenoja and Jylhä, 2007), which will most likely enhancethe sediment yields from watersheds to water basins, especially outside the vegetation period when soil is more prone to erosion. Increased sediment concentration in water bodies reduces light penetration, and thus, primary production (Pedersen et al., 2012) and increased sedimentation rates have been recorded to smother benthic fauna (Chou et al., 2004). In addition, the duration of ice cover during the winter season is estimated to decrease in the Baltic Sea region (Jevrejeva et al., 2004;Vihma and Haapala, 2009), exposing shorelines for longer periods of erosion (Ryabchuk et al., 2011). ...
In this study, we investigated sedimentation differences between two distinctive cold seasons, in terms of hydrometeorological and hydrodynamic conditions, in a coastal area of the Northern Baltic Sea in 2018–2020. A combination of sediment trap data, hydrometeorological data and hydrodynamic modelling provided a unique set-up to discover differences in sedimentation rates and compositions. Our study shows that the averaged sedimentation accumulation rate (SAR) was nearly three times higher during warmer cold season (30.9 g m⁻² day⁻¹), characterised by higher precipitation, especially rain and discharge, as well as snowless and open water conditions, compared to regular cold season (10.6 g m⁻² day⁻¹). While sedimentation was higher during the warmer season, the mean sediment grain size (D50) was higher during the regular cold season with permanent snow and ice cover. Similarly, while sediments of the regular cold season were organically rich, the total amount of organic matter accumulation was larger during the warmer cold season. Sediments consisted mostly of clastic matter (85–89%), of which the mean grain size varied from clay to fine silt (0.3–3.0 μm). Sedimentation differences between the cold seasons can be explained by differences in precipitation, river flow, wind-induced resuspension and a low air pressure system forcing sea level changes. Sedimentation differences along the study bay were found to be connected to channel cross-sectional area and flow conditions caused by river input and sea level changes.
... Multiple investigations have identified natural and anthropogenic impacts, including increased OM and sedimentation rates, that alter benthic communities by limiting diversity and allowing more aggressive, opportunistic organisms to excel (Pearson and Rosenberg, 1978;Alongi, 1989;Norkko et al., 2006). As sandy sediment becomes buried and replaced by higher porosity, organic-rich sediment, benthic community abundance and diversity decrease because biota are unable to cope with OM degradation and resulting hypoxia/anoxia (Chou et al., 2004;Hale et al., 2016). Various forms of the Pearson-Rosenberg (P-R) model have shown that decreasing numbers of taxa, abundances of organisms and biomass are functions of increased OM and contaminants (Pearson and Rosenberg, 1978;Thompson and Lowe, 2004;Hyland et al., 2005). ...
... Sediment type and grain size also have been shown to be major factors affecting community diversity and abundance (Lin et al., 2018). For example, Chou et al. (2004) concluded that family richness and abundance decreased in benthic habitats with 10-65% increases in silt + clay. ...
Organic-rich sediments in estuaries and the coastal ocean are often a product of land clearing, runoff of excess nutrients and other human activities. They can harbor pollutants, oxygen-consuming microbes and toxic hydrogen sulfide (H2S), thereby creating a hostile environment for infauna. In one barrier island lagoon, the Indian River Lagoon (IRL), Florida, layers of organic-rich sediments have increased substantially in thickness and areal extent over the past 60 years. Geochemical properties of these muddy sediments have been described; however, less is known about their habitability. We analyzed infauna and geochemical properties of 102 samples taken during wet and dry seasons at 17 locations spanning 60 km of the lagoon. We quantified infaunal abundance and diversity (Shannon-Wiener, H′) and determined Pearson’s correlation coefficients for effective number of species (ENS = eH′) vs. sediment porosity (ϕ = 0.69–0.95), organic carbon (1–8%), nitrogen (0.1–0.7%), silt + clay (16–99%), porewater H2S (5–3,600 μM), and other environmental variables. Small bivalves accounted for 70% of the organisms collected, followed by gastropods, polychaetes and other biota. The bivalves were predominantly Macoma spp., Mulinia lateralis and Parastarte triquetra with average abundances of 3,896, 2,049, and 926 individuals per m², respectively. High abundance of some species, such as Macoma, showed that these opportunists had adapted to poor quality sediments. More than two-thirds of the 35 species collected were present at <100 individuals per m² of sediment. Cluster analysis identified four groups of stations with significantly different geochemical properties. Permutation analyses of variance indicated that the four groups also represented statistically different infaunal communities. Diversity decreased with increasing sediment concentrations of organic carbon, nitrogen and silt + clay; however, community richness at our most prolific station along the perimeter of muddy deposits was ∼7 times lower than found previously in sandy sediments from the IRL. The results identified areas where infaunal communities have experienced the greatest stress due to accumulation of organic-rich sediments. Results from this study help support management plans for remediation of organic-rich mud and improvement of sediment and water quality, especially in areas identified with low ENS.
... turbidity, which can negatively impact the survival of coral reefs (Chou, Yu & Loh, 2004;Dikou & Van Woesik, 2006). ...
Okinawa is the largest and most populated island of the Ryukyu Archipelago in southern Japan and is renowned for its natural resources and beauty. Similar as to what has been happening in the rest of the country, Okinawa Island has been affected by an increasing amount of development and construction work. The trend has been particularly acute after reversion to Japanese sovereignty in 1972, following 27 years of postwar American administration. A coastline once characterized by extended sandy beaches surrounded by coral reefs now includes tracts delimited by seawalls, revetments, and other human-made hardening structures. Additionally, part of coastal Okinawa Island was obtained by land-filling shallow ocean areas (land reclamation). Nevertheless, the current extension of the artificial coastline, as well as the level of fragmentation of the natural coastline are unclear, due to the lack of both published studies and easily accessible and updated datasets. The aims of this research were to quantify the extension of coastline alterations in Okinawa Island, including the amount of land-filling performed over the last 41 years, and to describe the coastlines that have been altered the most as well as those that are still relatively pristine. The analyses were performed using a reference map of Okinawa Island based on GIS vector data extracted from the OpenStreetMap (OSM) coastline dataset (average node distance for Okinawa Island = 24 m), in addition to satellite and aerial photography from multiple providers. We measured 431.8 km of altered coastline, equal to about 63% of the total length of coastline in Okinawa Island. Habitat fragmentation is also an issue as the remaining natural coastline was broken into 239 distinct tracts (mean length = 1.05 km). Finally, 21.03 km 2 of the island's surface were of land reclaimed over the last 41 years. The west coast has been altered the most, while the east coast is in relatively more natural conditions, particularly the northern part, which has the largest amount of uninterrupted natural coastline. Given the importance of the ecosystem services that coastal and marine ecosystems provide to local populations of subtropical islands, including significant economic income from tourism, conservation of remaining natural coastlines should be given high priority.
... Encrusting sponges have already been shown to be winners in stressed environments, being good competitors for space (Bell and Barnes, 2000;Bell, 2002;Nepote et al., 2017). Appearance of turf and sediment (Chou et al., 2004;Nepote et al., 2017) can be related to enhanced sediment arrival to the cave, as its peculiar topography allows circulation and transport through most of the cave and increased deposit in relatively confined sectors . Turf and sediment covered the 2 and 3dimensional forms and the bare substrate, thus favouring the structural homogenization of the cave community, as illustrated by the decline in the multivariate dispersion until 2009, and the loss of the complex structure of the habitat. ...
Marine caves are unique and vulnerable habitats exhibiting high biodiversity and heterogeneity, but threatened by multiple global and local disturbances. Marine caves, although widely distributed along the Mediterranean coast, suffer for the lack of quantitative data on their structure and function, which hinder their conservation status assessment. Thanks to the availability of a nearly 30-year-long series of data (1986-2013), we evaluated ecosystem change in the Bergeggi marine cave (Ligurian Sea, NW Mediterranean), a cave with a complex shape and high habitat heterogeneity. Non-taxonomic descriptors were adopted, namely growth forms (GF) and trophic guilds (TG), which are informative about ecosystem structure and functioning, respectively. The cave experienced a general trend of change during the last three decades, mainly due to the decline in the cover of sessile organisms (especially 3-dimensional forms) matched by an increase of turf and sediment, thus causing the structural and functional homogenization of the cave community. While change before 2004 had been attributed to climatic factors (especially to the summer heat waves of 1999 and 2003), the most important rate of change was observed between 2009 and 2013, coinciding with recent major beach nourishments and the extension of the neighbouring Vado Ligure harbour, thus providing evidences on the importance of local disturbances deriving from coastal interventions. Monitoring the status of cave ecosystems is urgently needed, and the use of effective indicators, such as the specific traits here adopted (morphology and feeding strategy), could provide effective tools to assist marine cave conservation.
... Encrusting sponges have already been shown to be winners in stressed environments, being good competitors for space (Bell and Barnes, 2000;Bell, 2002;Nepote et al., 2017). Appearance of turf and sediment (Chou et al., 2004;Nepote et al., 2017) can be related to enhanced sediment arrival to the cave, as its peculiar topography allows circulation and transport through most of the cave and increased deposit in relatively confined sectors . Turf and sediment covered the 2 and 3dimensional forms and the bare substrate, thus favouring the structural homogenization of the cave community, as illustrated by the decline in the multivariate dispersion until 2009, and the loss of the complex structure of the habitat. ...
Marine caves are unique and vulnerable habitats exhibiting high biodiversity and heterogeneity, but threatened by multiple global and local disturbances. Marine caves, although widely distributed along the Mediterranean coast, suffer for the lack of quantitative data on their structure and function, which hinder their conservation status assessment. Thanks to the availability of a nearly 30-year-long series of data (1986-2013), we evaluated ecosystem change in the Bergeggi marine cave (Ligurian Sea, NW Mediterranean), a cave with a complex shape and high habitat heterogeneity. Non-taxonomic descriptors were adopted, namely growth forms (GF) and trophic guilds (TG), which are informative about ecosystem structure and functioning, respectively. The cave experienced a general trend of change during the last three decades, mainly due to the decline in the cover of sessile organisms (especially 3-dimensional forms) matched by an increase of turf and sediment, thus causing the structural and functional homogenization of the cave community. While change before 2004 had been attributed to climatic factors (especially to the summer heat waves of 1999 and 2003), the most important rate of change was observed between 2009 and 2013, coinciding with recent major beach nourishments and the extension of the neighbouring Vado Ligure harbour, thus providing evidences on the importance of local disturbances deriving from coastal interventions. Monitoring the status of cave ecosystems is urgently needed, and the use of effective indicators, such as the specific traits here adopted (morphology and feeding strategy), could provide effective tools to assist marine cave conservation.
... Some earlier studies were simple surveys of occurrence and distribution of benthic fauna but the areas covered were limited (Lim and Koh 1990;Lim and Gan 1990;Khoo 1990;Chung and Goh 1990;Chuang et al. 1992;Sachidhanandam and Chou 1996). Others studied the change in benthic community with environmental changes over time (Chong and Chou 1992;Goh et al. 1994;Chou et al. 2004;Lu 2005aLu , 2005b. A separate biodiversity assessment at a high wave energy area adjacent to Southern and Sisters Fairways was carried out in 2016. ...
he Singapore Blue Plan 2018 (hereafter ‘The Blue Plan’) is a proposal for the conservation of marine ecosystems, prepared by members of Singapore society, and submitted to the Government for consideration. It was initiated by marine biologists with academics, volunteers, stakeholders, and concerned citizens. The Blue Plan synthesizes the current state of knowledge for marine environments, reviews relevant legislature and advocates comprehensive sustainable methods to manage this important ecosystem
... The extremely large sediment load into the bay is likely to have a significant impact on the benthos. It is well established that elevated sedimentation rates impact both the abundance and diversity of benthic communities (Chou et al., 2004;Naser, 2011). Thrush et al. (2004) summarized, based on the previous field and laboratory studies, that a critical threshold of episodic deposition of 2 cm in an estuary will quickly create anaerobic conditions within the seabed, resulting in the death of the resident faunal community. ...
Hurricane Harvey, one of the worst hurricanes that hit the United States in recent history, poured record-breaking rainfall across the Houston metropolitan area. Based on a comprehensive set of data from various sources, we examined the dramatic responses in hydrodynamic and sedimentary processes of Galveston Bay to this extreme event. Using a freshwater fraction method, the freshwater load into the bay during Harvey and the following month was estimated to be 11.1×10^9 m3, or about 3 times the bay volume, which had completely refreshed the entire bay. Harvey also delivered 9.86×10^7 metric tons of sediment into the bay, equivalent to 18 years of average annual sediment load. At a site inside the San Jacinto Estuary, acute bed erosion of 48 cm followed by deposition of 22 cm of new sediment was observed from the sediment cores. Slow salinity recovery (~2 month) and a thick flood deposit (~10.5 cm average over the entire bay) had likely impacted the ecosystem in the bay and the adjacent inner shelf. Estuaries with similar bathymetric and geometric characteristics, i.e., shallow bathymetry with narrow outlets, are expected to experience similar dramatic estuarine responses while extreme precipitation events are expected to occur more frequently under the warming climate.
... This finding was not in agreement with those of various investigations conducted at shellfish cultivation sites. Chou et al. (2004) presented that sedimentation rate, sediment composition, and ammonia concentration were the most important factors impacting the macroinvertebrate community. Distinct changes were noted in the abundance, family numbers, and diversity of benthic invertebrate fauna, which corresponded to sedimentation rates. ...
The diversity, distribution, and species richness of benthic invertebrates were examined under extensive bottom cultivation of the tropical oyster Crassostrea belcheri during the summer of 2015 at Ban Don Bay, Suratthani Province, Southern Thailand. Oyster farms that had been operating for 25 years were selected for the study, and four sampling sites were allocated along each transect as (i) at the center of the farm, (ii) inside the farm, (iii) at the farm boundary, and (iv) a reference site. Results indicated that a total of 23 families and 28 species of benthic invertebrate taxa were recorded from the four sampling sites, and the macrobenthic invertebrates inhabiting all study sites consisted mainly of gastropods (11 species), polychaetes (11 species), and bivalves (8 species). No significant differences in total density, diversity index, evenness index, and species richness index of benthic invertebrates were found among each sampling site (P > 0.05). Significant differences in total nitrogen, nitrate, nitrite, total ammonia, sulfide, total phosphorus, organic matter, and grain sizes of sediment were found among each sampling site, but no significant differences in pH and total nitrogen were found. Among the independent variables analyzed, correlation analysis showed relationships between benthic diversity indices and abiotic variables. There were no clear patterns of differences in the detrimental environmental effects between sampling site locations, which indicated a minimal ecological impact of oyster cultivation.
... Nevertheless, while tailings addition resulted in an upward shift of the entire macrofauna community, dead sediment addition resulted in a less clear distinction between surface and subsurface community composition, compared to the control situation. The stress response of macrofauna is species-specific and depends on their mobility, oxygen requirements, and feeding type (Chou et al., 2004;Hinchey et al., 2006;Smit et al., 2008). In a metanalysis, Smit et al. (2008) predicted from marine species sensitivity distributions that instantaneous burial with 5.4 cm of natural sediment would negatively affect about half of the 32 analyzed macrofauna species. ...
The extraction of minerals from land-based mines necessitates the disposal of large amounts of mine tailings. Dumping and storage of tailings into the marine environment, such as fjords, is currently being performed without knowing the potential ecological consequences. This study investigated the effect of short-term exposure to different deposition depths of inert iron ore tailings (0.1, 0.5, and 3 cm) and dead subsurface sediment (0.5 and 3 cm) on a deep water (200 m) fjord benthic assemblage in a microcosm experiment. Biotic and abiotic variables were measured to determine structural and functional changes of the benthic community following an 11 and 16 day exposure with tailings and dead sediment, respectively. Structural changes of macrofauna, meiofauna, and bacteria were measured in terms of biomass, density, community composition and mortality while measures of oxygen penetration depth, sediment community oxygen consumption and ¹³C-uptake and processing by biota revealed changes in the functioning of the system. Burial with mine tailings and natural sediments modified the structure and functioning of the benthic community albeit in a different way. Mine tailings deposition of 0.1 cm and more resulted in a reduced capacity of the benthic community to remineralize fresh ¹³C-labeled algal material, as evidenced by the reduced sediment community oxygen consumption and uptake rates in all biological compartments. At 3 cm of tailings deposition, it was evident that nematode mortality was higher inside the tailings layer, likely caused by reduced food availability. In contrast, dead sediment addition led to an increase in oxygen consumption and bacterial carbon uptake comparable to control conditions, thereby leaving deeper sediment layers anoxic and in turn causing nematode mortality at 3 cm deposition. This study clearly shows that even small levels (0.1 cm) of instantaneous burial by mine tailings may significantly reduce benthic ecosystem functioning on the short term. Furthermore, it reveals the importance of substrate characteristics and origin when studying the effects of substrate addition on marine benthic fauna. Our findings should alert decision makers when considering approval of new deep-sea tailings placement sites as this technique will have major negative impacts on benthic ecosystem functioning over large areas.
