Heavy metals in surface sediments from nine estuaries along the coast of Bohai Bay,Northern China

Concentrations of heavy metals in river water and sediment were investigated in nine estuaries along the coast of Bohai Bay, Northern China. Multivariate statistical techniques such as principal component analysis and cluster analysis, in combination with metal concentration analysis and correlation analysis, were used to identify the possible sources of the metals and the pollution pattern in nine estuaries along the coast of Bohai Bay. The environmental risks of metals, evaluated by sediment quality guidelines and background values, revealed Hg contamination in the estuaries. However, levels of Cd in estuarine sediments were low, and they were less than those levels in river sediments, partly due to the high mobility and dilution of river or seawater. Cd did not contribute to sediment deposits in estuaries. High organic matter from effluents from large municipal sewage treatment plants was predominantly responsible for restricting Hg mobility from the river to Bohai Bay.     

Assessing metal toxicity in sediments using the equilibrium partitioning model and empirical sediment quality guidelines: A case study in the nearshore zone of the Bohai Sea,China

Surface sediments were collected from five nearshore (wastewater discharges, aquaculture facilities and a seaport) sites in Bohai Bay and Laizhou Bay, China. The equilibrium partitioning (EqP) model and empirical sediment quality guidelines (SQGs) were applied to assess the potential metal toxicity in the collected sediments. The results show that, based on the EqP model, 35% of stations exhibited potential metal toxicity. Several metals (Cu, Ni and Cr) exceeded the empirical SQGs (9–93% of the time), however these guidelines may not be suitable for use in the Bohai Sea owing to the background concentrations. The EqP model is a more useful method for assessing potential metal toxicity in Bohai Sea sediment than the empirical SQGs. Additionally, we have provided new understanding about methods for assessing sediment metal toxicity in the Bohai Sea that may be useful in other coastal areas in China.     

Development of a benthic index to assess sediment quality in the Tampa Bay Estuary

The identification, remedial treatment, and monitoring of contaminated sediments are among the priorities for managers of the Tampa Bay Estuary. Tampa Bay, as an urbanized estuary, is subject to the input of watershed sources of chemical contaminants, including metals, pesticides, and organic chemicals. Although the use of biological indicators and their incorporation into multi-metric indices is not new, the refinement and applications of such techniques for determining environmental condition still require further development and exploration. We present a single Tampa Bay Benthic Index (TBBI) that was developed specifically for Tampa Bay. Stepwise discriminant analysis was applied to a comprehensive list of potential benthic metrics. Results from the stepwise procedure identified the metrics that best discriminated between "healthy" and "degraded" conditions, as defined by sediment contaminant effect levels and dissolved oxygen. Discriminant analysis was then applied to the resultant three variables to determine the linear combination for the index.     

Foraminiferal evidence of submarine sediment transport and deposition by backwash during the 2004 Indian Ocean tsunami

Micropaleontological analysis of nearshore to offshore sediments recovered from the southwestern coast of Thailand was performed to clarify the submarine processes of sediment transport and deposition during the 2004 Indian Ocean tsunami. The distribution pattern of benthic foraminifers showed seaward migration after the tsunami event. Agglutinated foraminifers, which are characteristic of an intertidal brackish environment, were identified in the post-tsunami samples from foreshore to offshore zones. These suggest that sediments originally distributed in foreshore to nearshore zones were transported offshore due to the tsunami backwash. On the other hand, the distribution pattern of planktonic and benthic species living in offshore zones showed slight evidence of landward migration by the tsunami. This suggests that landward redistribution of sediments by the tsunami run-up did not occur in the offshore seafloor of the study area. Our results and a review of previous studies provide an interpretation of submarine sedimentation by tsunamis. It is possible that tsunami backwashes induce sediment flows that transport a large amount of coastal materials seaward. Thus, traces of paleotsunami backwashes can be identified in offshore sedimentary environments as the accumulation of allochthonous materials. This can be recognized as changes in benthic foraminiferal assemblages.     

Biomarker responses and genotoxicity in the mud snail (Bullacta exarata) as indicators of coastal contamination

In the present study different biomarker responses and genotoxicity were determined in wild mud snails (Bullacta exarata) collected from 3 sampling sites in Bohai Bay in northeastern China, which is a region that is under considerable anthropogenic influence. Significant spatial variability of superoxide dismutase (SOD) and metallothionein (MT)-like proteins were recorded, while glutathione transferase (GST), catalase (CAT), and vitellin-like proteins (Vn's) were not observed. Furthermore, genomic DNA that was amplified with 4 fluorescence-labeled primer pairs showed variable genetic distances among the 3 wild mud snail populations found in Bohai Bay, which may be correlated with differences in the types of environmental genotoxicants, such as heavy metals and polycyclic aromatic hydrocarbons. This multi-biomarker approach provided an improved understanding of the potential toxicological impact of contaminated sediments on benthic organisms.     

Foraminiferal responses to polluted sediments in the Montevideo coastal zone, Uruguay

A study of foraminiferal assemblages was carried out in 24 sediment samples collected from the Montevideo coastal zone (south-eastern coastal region of South America) to assess the response of the benthic foraminifera to the polluted sediments. The area is affected by different pollutants such as sewage, hydrocarbons and heavy metals derived from different sources. Biological data were analyzed with multivariate techniques of cluster analysis and a principal component analysis (PCA) was performed for abiotic factors. The results allowed the recognition of different species assemblages corresponding to different sub-environments, which reflected the prevalent ecological conditions. The Montevideo Bay, particularly, its inner part showed an extremely poor foraminiferal fauna-including a totally azoic station-and high percentages of abnormal tests, when compared with the adjacent Punta Carretas and Punta Yeguas zones. Mean faunal density showed a strong relationship with organic matter, oxygen and heavy metal concentrations, as well as redox potential and pH values of each sub-environment. Although the adjacent zones presented a moderate pollution degree, it was noticed that a positive effect on the foraminiferal density specially on Ammonia tepida, caused by the sewage pipe located in Punta Carretas, a pure organic contamination. Differences among foraminiferal assemblages seemed to be related to the combined action of the several kinds of pollutants and the natural abiotic variables, like the rapid salinity changes that occurred in this area.     

Distribution and ecological relevance of fine sediments in organic-enriched lagoons: the case study of the Cabras lagoon (Sardinia, Italy)

In organic-enriched sedimentary systems, like many Mediterranean coastal lagoons, a detailed analysis of sediment grain size composition and partitioning within the muds is crucial to investigate sedimentological trends related to both hydrodynamic energy and basin morphology. In these systems, sediment dynamics are particularly important because the partitioning and transport of fine sediments can strongly influence the redistribution and accumulation of large amounts of organic matter, and consequently the distribution of benthic assemblages and the trophic status and functioning of a lagoon. Nevertheless, studies on benthic-sediment relationships have been based mainly on a rather coarse analysis of sediment grain size features. In muddy systems, however, this approach may impede a proper evaluation of the relationships and effects of the distribution of fine sediment and organic matter on the biotic benthic components. Here we show that the distribution of sedimentary organic matter (OM) and total organic carbon (TOC) in the Cabras lagoon (Sardinia, Italy) can be explained (i.e., predicted) as a function of a nonlinear increase in the amount of the cohesive fraction of sediments (< or = 8 microm grain size particles) and that this fraction strongly influences the structure, composition and distribution of macrobenthic assemblages. Even in such a homogeneously muddy system, characterized by "naturally" occurring impoverished communities, impaired benthic assemblages were found at < or = 8 microm, OM, TOC contents of about 77%, 11% and 3.5%, respectively. A review of studies conducted in Mediterranean coastal lagoons highlighted a lack of direct integrated analysis of sediment features and the biotic components. We suggest that, especially in organic-enriched coastal lagoons, monitoring programs should primarily investigate and consider the cohesive fraction of sediments in order to allow a better assessment of benthic-sediment relationships and ecological quality of the system.     

An environmental assessment of the Charleston Ocean Dredged Material Disposal Site and surrounding areas after partial completion of the Charleston Harbor Deepening Project

A project to deepen shipping and entrance channels in Charleston Harbor was conducted from 1999 to 2002. This generated approximately 22 million cubic yards of sediment for offshore disposal. Assessments of biological and physical conditions in the Charleston Ocean Dredged Material Disposal Site and surrounding areas were conducted prior to deepening (1993-94), and partway through the disposal period (2000). Results from the 2000 survey are presented and compared to the baseline survey. The study area was composed of the disposal zone and surrounding areas and divided into 20 one square mile strata. Within each stratum, benthic grab samples were collected from ten random sites for analysis of sediment composition and contaminants and macrobenthic assemblages. No contaminant levels were above effects range low levels. Results revealed that sediments in the western strata had significantly higher silt/clay content in the 2000 survey when compared to baseline sediments, while sediments east of the disposal zone were similar to baseline. Analyses were performed on a subset of the benthic data that compared baseline to 2000 conditions in western and eastern strata. The benthic communities in western strata were altered following disposal operations. The benthic community east of the disposal area was not different from baseline conditions. These alterations in the benthic community were attributed to changes in bottom habitat characteristics rather than pollution effects.     

Human-induced changes in recent sedimentation rates in Bohai Bay,China: Implications for coastal development

In many countries, coastal planners strive to balance the demands between civil, commercial strategy and environmental conversation interests for future development, particularly given the sea level rise in the 21 st century. Achieving a sustainable balance is often a dilemma, especially in low-lying coastal areas where dams in inland river basin are trapping significant amounts of fluvial sediments. We recently investigated the shore of Bohai Bay in northern China where there has been a severe increase in sea level following a program of large-scale coastal reclamation and infrastructure development over the last five decades. To investigate this trend, we obtained sediment cores from near-shore in Bohai Bay, which were dated by ~(137)Cs and ~(210)Pb radionuclides to determine the sedimentation rates for the last 50 years. The average sedimentation rates of Bohai Bay exceeded 10 mm yr~(-1) before 1963, which was much higher than the rate of local sea-level rise. However, our results showed an overall decreasing sedimentation rate after 1963, which was not able to compensate for the increasing relative sea-level rise in that period. In addition, our results revealed that erosion occurred after the 1980 s in the shallow sea area of Bohai Bay. We suggest that this situation places the Bohai Bay coast at a greater risk of inundation and erosion within the next few decades than previously thought, especially in the large new reclamation area. This study may be a case study for many other shallow sea areas of the muddy coast if the sea level continues to rise rapidly and the sediment delivered by rivers continues to decrease.     

Benthic foraminiferal assemblages from Moreton Bay, South-East Queensland, Australia: Applications in monitoring water and substrate quality in subtropical estuarine environments

We assess species composition, assemblage structure and distribution of the benthic foraminiferal assemblages from diverse substrates in Moreton Bay, South-East Queensland, Australia. Analysis of 47 surface sediment samples revealed 69 species, three distinct foraminiferal assemblages and six sub-assemblages. The assemblages from the western Bay are characterized by stress tolerant taxa and the lowest diversity, whereas the assemblages from the eastern Bay are characterized by symbiont-bearing taxa and high diversity. We found a correlation between foraminiferal assemblages and substrate conditions that was indicative of strong environmental gradients (substrate type, water quality and salinity), from an urban-impacted assemblage in the westernmost part of the Bay, to a hyposaline, estuarine-influenced assemblage in the western Bay to a nearly normal marine to hypersaline assemblage in the eastern Bay. The FORAM Index was consistent with the changes in water and sediment quality gradient, from the western shoreline to the eastern Bay. Thus the foraminiferal assemblages of Moreton Bay make excellent bio-indicators of environmental changes in a subtropical, estuarine setting in eastern Australia.     

How representative are subfossil assemblages of Chironomidae and common benthic invertebrates for the living fauna of Lake De Waay,the Netherlands?

The distribution of benthic invertebrates and their subfossil remains was examined within the basin of De Waay, a dimictic, eutrophic lake in the Netherlands. We focused on Chironomidae, but also report the abundances of 11 invertebrate groups that potentially produce chitinous remains that are preserved in the fossil record, although their remains could only be identified at a coarser taxonomic resolution. Most living invertebrates sampled in different seasons were constrained to the littoral zone, with the exception of a few taxa (Ceratopogonidae, Chaoborus flavicans, and Chironomus) that are adapted to low oxygen conditions in the seasonally anoxic profundal zone. In contrast, assemblages of invertebrate remains in lake surface sediments were similar in the entire lake basin, suggesting that considerable numbers of invertebrate remains are transported and redeposited off-shore in Lake De Waay, due to its steep bathymetry. These results indicate that a single sediment sample obtained from the centre of this lake contains subfossil invertebrate remains originating from the entire lake basin. In Lake De Waay, the majority of taxa found in the living assemblages were identified as remains in lake surface sediments, at least for the Chironomidae that could be identified at a similar taxonomic level in living and subfossil assemblages. Of the total 44 chironomid taxa found in Lake De Waay, 35 taxa occurred in the living assemblages and 34 taxa occurred in the subfossil assemblages. Thirty chironomid taxa occurred both as living and subfossil specimens, and on average these 30 taxa represent 94% of the specimens encountered in a sediment sample. Five rare chironomid taxa present as living larvae were not detected in the subfossil assemblages. Conversely, eight rare and four common chironomid taxa were found in subfossil remains, but not in living assemblages. Our results indicate that subfossil assemblages in surface sediment samples provide spatially integrated and representative samples of the living assemblage. However, a combined approach examining both the living benthic invertebrate fauna and invertebrate remains in lake surface sediments will potentially give a more complete and detailed overview of benthic invertebrates in a lake ecosystem than an approach based exclusively on one of these groups.     

Effects of nutrient enrichment derived from fish farming activities on macroinvertebrate assemblages in a subtropical region of Hong Kong

To study the correlation between nutrient enrichment derived from fish farming activities and changes in macrobenthic assemblages, a one-year field study was conducted in Kau Sai Bay marine fish culture zone of Hong Kong. Bimonthly sediment samples were collected at six stations: two at the fish cages, two near the boundary of the fish culture area, and two reference sites further away from the culture area. Sediment physico-chemical characteristics in terms of silt/clay fraction, moisture content, total organic carbon (TOC), total Kjeldahl nitrogen (TKN) and total phosphorus (TP) were analyzed. The macrobenthos (>0.5 mm) present in the sediment were sorted, identified and enumerated. On average, TOC, TKN and TP levels at the fish cage stations were 82.8%, 128.5% and 1315.7% higher than those at the reference stations, respectively. As a result, the N:P molar ratio was greatly reduced from 8.75 at the reference stations to 1.83 at the fish cage stations. Univariate and multivariate analyses revealed that diversity of macrofauna was significantly reduced and community structure differed at the fish cage stations relative to the reference sites. The intermediary stations near the fish culture area showed a transitional state of disturbance. Faunal diversity was negatively correlated with nutrient level, reflecting the adverse impacts of nutrient enrichment derived from fish farming activities on the benthic assemblages. Whilst in subtropical Asia-Pacific trash fish is the major feed for fish culture resulting in a higher nutrient loading and nutrient ratio accumulated in the sediment beneath the fish rafts, the effects of nutrient enrichment on macrobenthic assemblages are comparable to that in temperate waters owing to relatively high sediment metabolism rate and smaller fish culture scale in Hong Kong.     

Total petroleum hydrocarbons and heavy metals in the surface sediments of Bohai Bay,China: Long-term variations in pollution status and adverse biological risk

Surface sediments collected from 2001 to 2011 were analyzed for total petroleum hydrocarbons (TPH) and five heavy metals. The sediment concentration ranges of TPH, Zn, Cu, Pb, Cd and Hg were 6.3–535 μg/g, 58–332 μg/g, 7.2–63 μg/g, 4.3–138 μg/g, 0–0.98 μg/g, and 0.10–0.68 μg/g, respectively. These results met the highest marine sediment quality standards in China, indicating that the sediment was fairly clean. However, based on the effects range-median (ERM) quotient method, the calculated values for all of the sampling sites were higher than 0.10, suggesting that there was a potential adverse biological risk in Bohai Bay. According to the calculated results, the biological risk decreased from 2001 to 2007 and increased afterwards. High-risk sites were mainly distributed along the coast. This study suggests that anthropogenic influences might be responsible for the potential risk of adverse biological effects from TPH and heavy metals in Bohai Bay.     

Impact of offsite sediment transport and toxicity on remediation of a contaminated estuarine bay

Sediment of Ostrich Bay, an arm of Dyes Inlet on Puget Sound, was historically contaminated with ordnance compounds from an onshore US Navy facility. An initial recommendation for a sediment cover to mitigate benthic risks was followed by studies of sediment transport and deposition to determine whether contaminated sediment from Dyes Inlet or other offsite sources in Puget Sound may contribute to Ostrich Bay impacts. A Sediment Trend Analysis (STA) identified net sediment transport pathways throughout the bay and inlet by examining changes in grain size distributions in multiple adjacent samples. Results indicated that fine-grained sedimentary material transports into and deposits throughout the Dyes Inlet system, with no erosion or transport out of Ostrich Bay. Echinoderm larvae mortality bioassay results were elevated in fine-grained sediments of both Ostrich Bay and Dyes Inlet. Ordnance compounds were undetected, and although sediment mercury concentrations were elevated at 0.48-1.4 mg/kg in both waterbodies, the relationship with toxicity was weak. Results of the studies and sedimentation modeling indicate that impacted sedimentary material deposits throughout the Dyes Inlet/Ostrich Bay system from unknown sources and will prevent natural recovery of Ostrich Bay as well as negate long-term effectiveness of active remedial measures. Stakeholders have recognized that remediation of the bay can be achieved only after the toxicity of depositing sediment decreases.     

Effects of heavy metal contamination on the macrobenthic fauna in estuaries: the case of the Seine estuary

Heavy metal contamination levels are generally higher in estuaries than in the open sea. Some estuaries, the Seine estuary for example, have particularly high pollution levels of metals, yet continue to support a very high benthic biomass and remain quite productive. Measurements of sediment contamination are highly variable due to diverse chemical analysis methods, sediments origin and sources of contaminants found in the estuaries. Salinity appears to be the principal factor controlling contaminant distribution in the sediment and the overlying and/or interstitial waters; it also affects the bioavailability of contaminants in estuarine sediments. Of course, the response to contaminants varies greatly among species and assemblages. Trace metals explain only a small part of the variation in benthic community structure. Some species, such as the shrimp Crangon crangon, appears vulnerable to metal pollution, while other species, such as Scrobicularia plana, are able to tolerate quite high levels of cadmium in their tissue. This paper demonstrates the wide variability of benthic responses to contamination, which is probably due to the high spatio-temporal heterogeneity of the estuary. To reduce the problems due the heterogeneity and variability observed to date in the available results, it will be necessary to encourage integrated estuarine studies, in which sedimentologists, chemists, and biologists work together on the same campaigns at the same sites.     

Benthic marine pollution around McMurdo Station, Antarctica: A summary of findings

McMurdo Station is the United States Antarctic Research Program's (USARP) centre for scientific and logistical support for most of the continent and is the largest settlement in Antarctica. Over 30 years of human presence with shipping, air-transport, scientific, and municipal activities have resulted in severe but localized nearshore marine benthic pollution. This review will summarize the results of 3 years of research which has documented concentrations of chemical contaminants, changes in community patterns, and the toxicity of sediments to invertebrate species and infaunal communities. The primary contaminants are petroleum hydrocarbons in the sediments of Winter Quarters Bay, the site of shipping activities and a former dumpsite. Total hydrocarbon levels in sediments in Winter Quarters Bay were comparable to the most polluted harbours in temperate latitudes. However, a steep gradient of pollution existed: stations less than 1 km away were nearly pristine. Benthic invertebrate communities changed dramatically along this contamination gradient. The results of both field and laboratory bioassay experiments with contaminated sediments found that biological changes observed in benthic communities around McMurdo Station were most likely caused by hydrocarbons, PCBs, and PCTs. A primary goal of polar pollution research is to determine the response and tolerance of Antarctic biota to physical and chemical anthropogenic disturbance, and the mitigation of negative effects. To this end, future work should include continued monitoring of changes in chemical and community patterns, studies of the physiological responses of Antarctic invertebrates to chemical contamination, and further comparisons of anthropogenic and natural disturbances to benthic communities.     

Impacts of dredged material disposal on a tropical soft-bottom benthic assemblage

The soft-bottom benthic macrofauna in a spoil-ground of dredged material in Cleveland Bay, North Queensland, Australia, was studied to detect possible impacts of the disposal of sediments. The spatial distribution of the assemblage was studied in relation to the source of the impact at 28 stations on four occasions during 1998 and 1999. Additionally, environmental variables were measured on each occasion at each station. Macrobenthic assemblages inside the spoil-ground were different from assemblages outside the spoil ground only immediately after (15 days) the disposal of dredged material. Given the decrease in the abundance of organisms and number of species, it is suggested that this effect was due to direct burial of the macrobenthic assemblage inside the spoil-ground. Macrobenthic assemblages inside the spoil ground were not different from assemblages outside the spoil ground 3 months after dumping. These results suggest that the soft-bottom macrobenthic assemblages may respond quickly to the disturbance associated with the dumping of dredged material.     

Biological and chemical composition of Boston Harbor, USA

As part of a planning study of improvements to the navigation channels in Boston Harbor, Massachusetts (USA) biological and chemical composition were determined. During 1985 and 1986, sampling of the sediments and water column took place to understand existing conditions. These sampling efforts involved 21 sediment chemistry stations, 13 benthic infaunal stations, 6 otter trawl and gill net stations. The chemical determinations show high levels of contaminations in the inner channels. The benthic organisms react to this substrate chemical stress and a seasonal oxygen depletion with episodes of tolerance and defaunation. The finfish species follow a similar pattern as the infaunal community.     

Modern pollen assemblages from surface lake sediments in northwestern China and their importance as indicators of vegetation and climate

The modern pollen assemblages of surface lake sediments and topsoils in northwestern China were studied to understand the relationship of modern pollen data with contemporary vegetation and climate, and the differences between the pollen assemblages of surface lake sediments and topsoils. The results show that Chenopodiaceae and Artemisia are dominant elements in the pollen assemblages of northwestern China. Additionally, Ephedra, Cyperaceae, Asteraceae, Poaceae, Picea, Pinus, and Betula are also important pollen taxa. Both pollen assemblages and principal component analysis indicate that pollen data from surface lake sediments and topsoils can be used to differentiate the main vegetation types of this region(desert, steppe, meadow and forest). However, differences exist between modern pollen assemblages of the two types of sediments due to the different relevant source areas of pollen and degrees of pollen preservation. For example, the larger relevant source area of surface lake sediment results in a higher abundance of Betula in pollen assemblage from surface lake sediment, whereas the tendency to disintegrate thin-walled pollen types in topsoil leads to a higher proportion of resistant pollen, such as Asteraceae. Linear regression analysis indicates that the Artemisia/Chenopodiaceae(A/C) ratio in pollen assemblages of surface lake sediments can be used to indicate humidity changes in the study area. However, the A/C ratio in topsoils should be used carefully. Our results suggest that pollen data from surface lake sediments would be better references for interpreting the fossil pollen assemblages of lake cores or lacustrine profiles.     

An overview of toxicant identification in sediments and dredged materials

The identification of toxicants affecting aquatic benthic systems is critical to sound assessment and management of our nation's waterways. Identification of toxicants can be useful in designing effective sediment remediation plans and reasonable options for sediment disposal. Knowledge of which contaminants affect benthic systems allows managers to link pollution to specific dischargers and prevent further release of toxicant(s). In addition, identification of major causes of toxicity in sediments may guide programs such as those developing environmental sediment guidelines and registering pesticides, while knowledge of the causes of toxicity which drive ecological changes such as shifts in benthic community structure would be useful in performing ecological risk assessments. To this end, the US Environmental Protection Agency has developed tools (toxicity identification and evaluation (TIE) methods) that allow investigators to characterize and identify chemicals causing acute toxicity in sediments and dredged materials. To date, most sediment TIEs have been performed on interstitial waters. Preliminary evidence from the use of interstitial water TIEs reveals certain patterns in causes of sediment toxicity. First, among all sediments tested, there is no one predominant cause of toxicity; metals, organics, and ammonia play approximately equal roles in causing toxicity. Second, within a single sediment there are multiple causes of toxicity detected; not just one chemical class is active. Third, the role of ammonia is very prominent in these interstitial waters. Finally, if sediments are divided into marine or freshwater, TIEs perforMed on interstitial waters from freshwater sediments indicate a variety of toxicants in fairly equal proportions, while TIEs performed on interstitial waters from marine sediments have identified only ammonia and organics as toxicants, with metals playing a minor role. Preliminary evidence from whole sediment TIEs indicates that organic compounds play a major role in the toxicity of marine sediments, with almost no evidence for either metal or ammonia toxicity. However, interpretation of these results may be skewed because only a small number of interstitial water (n = 13) and whole sediment (n = 5) TIEs have been completed. These trends may change as more data are collected.