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.     

Seasonal distribution of trace metals in suspended particulate and bottom sediments of four microtidal river estuaries,west coast of India

ABSTRACT

The seasonal distribution of metals (V, Cr, Co, Cu, Ni, Zn, Pb, Mn, Fe, Al and Ti) in suspended and bottom sediments of four minor estuaries (Terekhol, Chapora, Sal and Talpona rivers) of Goa, India was investigated to understand the metal distribution process in the estuarine region. The highest particulate-metal concentrations were found in low-salinity regions of all the estuaries, in the wet season (e.g. in the Terekhol River, the averages in ppm were Co: 53, Ni: 197, Cu: 208, Zn: 212 and Pb: 65) compared to the dry season averages (Co: 27, Ni: 76, Cu: 105, Zn: 164 and Pb: 13 ppm). The estuarine-mixing diagrams showed non-conservative behaviour in both seasons. The Sal River had the highest particulate-metal concentration (Co: 106, Ni: 300 and Zn: 323 ppm), suggesting an anthropogenic input. The enrichment factor for suspended matter was higher than bottom sediments with extremely high enrichment for Mn (>10). The Geo-accumulation index displayed unpolluted to polluted class for all metals. The study highlights the important role played by small estuaries in seasonal metal release and accumulation along the coastal region.     

Changes in metal contamination levels in estuarine sediments around India – An assessment

This review is the first attempt to comprehend the changes in metal contamination levels in surface estuarine sediments with changing time around India. Contamination factor, geoaccumulation index, pollution load index, effects range low and effects range median analysis were used to evaluate the quality of the estuarine sediments (by using the available literature data). This study suggests that estuarine sediments from the east coast of India were comparatively less contaminated by metals than the west coast. Sediments from those estuaries were found to be more contaminated by metals on which major cities are located. An improvement in estuarine sediment quality (in terms of metal contamination) over time around India was noticed. This study provides managers and decision-makers of environmental protection agency with a better scientific understanding for decision-making in controlling metal pollution in estuarine sediments around India.     

Using attached macroalgae to assess ecological status of British estuaries for the European Water Framework Directive

The EC Water Framework Directive requires that ecological quality be assessed in transitional waters using the abundance and species composition of macroalgae. In estuaries, which form the majority of transitional waters, species composition is not a suitable measure. This arises from two features: (i) there is a continuous, natural change in species composition along the gradient of estuarine conditions which makes it difficult to know where within an estuary the species composition should be assessed, (ii) the inner estuarine macroalgal community of mat-forming species is very tolerant to both natural and anthropogenic stress and species poor which makes it insensitive to environmental variations in terms of species composition. An alternative feature is proposed based on the extent of upstream penetration of perennial fucoid algae. This proposal is founded on a series of case studies of the changes in fucoid limits, within a number of estuaries in the British Isles, consequent upon changes in pollution status over the last three decades. This also has to take into account variations of fucoid penetration owing to natural factors such as range of salinity variation and turbidity. The abundance criterion is taken to mean the absence of macroalgal blooms or "green tides", because general abundance of species is hard to quantify meaningfully in the upper estuarine mat-forming species and in the lower estuary is subject to great variation owing to the physical variability of estuary types.     

Bioaccumulation of metals by Fucus ceranoides in estuaries of South West England

Fucus ceranoides tolerates abiotic conditions encountered across the full range of estuarine salinities. We examined the bioaccumulation of metals in individuals and metal concentrations in accompanying sediment samples collected at different locations along estuaries of South West England. Intra- and inter-estuarine variations in metal accumulation by F. ceranoides, after correction for particulate contamination using Fe as a proxy, were attributed to variations in the availabilities and concentrations of aqueous metals. Greatest accumulation was observed in estuaries that remain most heavily impacted by historical mining activities and for metals that were mobilised to the greatest extent during these operations (As, Cu, Sn, Zn). Arsenic concentrations displayed a seaward increase in estuaries in which multiple samples were taken, whereas Cd concentrations were always greatest in samples collected from the most landward locations. Ongoing research aims to better understand the mechanisms and kinetics of metal interactions with F. ceranoides and their dependence on salinity.     

Evaluation of diffusive gradients in thin-films (DGTs) as a monitoring tool for the assessment of the chemical status of transitional waters within the Water Framework Directive

In this contribution, the potential use of diffusive gradients in thin-films (DGTs) for the chemical evaluation of transitional water bodies within the Water Framework Directive (WFD) has been studied. The water metal concentration has been evaluated in 13 estuaries in the southeastern Bay of Biscay. The DGTs were deployed in triplicate at two stations in each estuary, delimiting the tidal influence. The DGT results were in the ranges of 2-1570 ng L(-1) for cadmium, 66-515 ng L(-1) for copper, 30-3650 ng L(-1) for nickel and 0.8-95.5 μg L(-1) for zinc. The DGTs provided reliable average labile metal concentrations in highly dynamic systems that were comparable with DGT measurements in coastal and estuarine waters worldwide. In addition, it was possible to discriminate those estuaries more susceptible to environmental impacts, being consistent with the historical contamination of each estuary. Based on the obtained results, a sampling strategy for the monitoring of transitional water bodies using DGTs is proposed.     

Mine-derived metal pollution in the Isle of Man

The sediments of rivers draining areas of past mining activity in the Isle of Man contained greatly enhanced levels of zinc, lead and, to a lesser extent, copper and cadmium. This contamination extended into the estuarine harbours where it was reflected in the metal content of four species of bivalve molluscs. Of the latter, Mytilus edulis was the most useful indicator species in that it occurred in all five estuarine harbours but Scrobicularia plana, although of more limited distribution, concentrated much higher levels of zinc and lead. Individual variation of metal levels was high in all species of bivalves examined; a negative correlation of dry weight: metal content was demonstrated in many cases, but other factors may also contribute to such variation.     

Development of a fish-based index to assess the ecological quality of transitional waters: The case of French estuaries

The Water Framework Directive requires the assessment of the ecological status of transitional waters considering the fish component. An original methodology, based on a pressure-impact approach, was established to develop a multimetric fish-based index to characterize the ecological quality of French estuaries. An index of contamination, based on the chemical pollution affecting aquatic systems, was used as a proxy of anthropogenic pressure. The fish metric selection was based on their response to disturbances tested via statistical models (generalized linear models) taking into account sampling strategy and estuarine features. Four metrics, for which discriminating responses to level of pressure were demonstrated, were retained to constitute the estuarine multimetric fish index. This new tool appeared particularly relevant to detect the contamination effects on fish communities in estuaries. It could help managers to take decisions in order to maintain or reach the good status required by the Water Framework Directive for 2015.     

A biomonitoring study: Heavy metals in macroalgae from eastern Aegean coastal areas

The concentrations of metals were measured in macroalgae species seasonally at eight coastal stations along the eastern Aegean coast. Sediment and seawater samples were also collected to detect their metal contents in order to gain more information on the environmental conditions of the area and possible bioaccumulation patterns. The aim of this study is, to gather more information on the use of selected species as cosmopolitan biomonitors for the eastern Aegean; to provide information on the marine environmental quality by the use of macroalgae and to determine which algae species are suitable as biomonitoring species for the study area. The relative abundance of metals in macroalgae decreases in the order: Fe-Zn-Cu-Cr-Cd-Hg-Pb and seawater: Fe-Zn-Pb-Cu-Cr-Cd-Hg. In sediment the distribution order from higher to lower was Fe-Cr-Zn-Pb-Cu-Hg-Cd. The brown algae Cystoseira sp., the green algae Ulva sp. and Enteromorpha sp. possess high potential as cosmopolitan biomonitors for trace metals in the Aegean Sea.     

Estuarine modification of nutrient and sediment exports to the Great Barrier Reef Marine Park from the Daintree and Annan River catchments

Nutrient and suspended sediment concentrations were measured in the dry season and during the rising and falling stages of flood events in the Annan and Daintree rivers to estimate catchment exports. These flood events were also sampled along the salinity gradient in the estuary and nearshore shelf to quantify the modification of terrestrial sediment and nutrient loads as they pass through estuaries into the Great Barrier Reef lagoon. In the Daintree River TSS concentrations were found to increase between the catchment and the estuary plume. The source of TSS may have been scour of the estuarine channel or from land use in the catchment of the lower estuary. In the dry season nitrogen enters the Annan and Daintree estuaries predominantly in the form of PON and DON in roughly equal proportions. Nitrogen exports to the GBR are mostly in the form of DON. In the wet season the majority of nitrogen enters the estuaries as DON and leaves as PON. Nitrogen removal in the estuaries and plumes appears to be biologically mediated once suspended sediment concentrations decrease to a point where phytoplankton growth is not light limited. In the dry season phosphorus enters and leaves the estuaries primarily in organic form. PIP is the dominant form of phosphorus in river water, but leaves the estuary more evenly distributed between all forms. These estuarine processes result in less nitrogen and phosphorus being delivered to the GBR lagoon than is exported from the catchment. The differences between these estuaries highlights the need for further work to explore modifications in estuaries that drain into the Great Barrier Reef lagoon.     

Investigation of the mud crab (Scylla serrata) as a potential bio-monitoring species for tropical coastal marine environments of Australia

Mud crabs, Scylla serrata, were sampled from four estuaries (the Normanby, Herbert, Burdekin and Fitzroy Rivers) along the coast of northern Queensland, Australia, representing a pollution gradient from low to high contamination based upon previous chemical monitoring. Four biomarkers; glutathione-S-transferase (GST) activity, cholinesterase (ChE) inhibition and the urinary metabolite concentrations of naphthalene (NPH) and benzo-a-pyrene (BaP) were evaluated in S. serrata hepatopancreas, haemolymph and urine. Site-specific evidence of elevated GST activity and BaP metabolite concentrations and significant ChE inhibition was detected. Biomarker responses from this field study provide evidence of contaminant exposure of S. serrata from river estuaries along the coast of northern Queensland and indicate that further investigation is warranted. Based on the current results, and with further work on characterising the dose-response and seasonal variation in this species, mud crabs have great potential as indicator species for water quality and ecosystem monitoring programs across tropical coastal regions of Australia.     

Spatial patterns of submerged macrophytes and heavy metals in the hypertrophic, contaminated, shallow reservoir Lake Qattieneh/Syria

Our investigation on macrophytes in Lake Qattieneh, a large, shallow reservoir in western Syria, is a first assessment of ecological status of this lake. We studied spatial distribution patterns of aquatic macrophyte vegetation and heavy metal concentrations to determine if they can be used as indicators of point sources of pollution. Industrial and municipal point sources at the lake shore increase nutrient load and contamination by heavy metals. Water analyses revealed high concentrations of some heavy metals at some littoral sites: Ni 88.7 μg L⁻¹, Cr 49.99 μg L⁻¹, Co 14.38 μg L⁻¹, and Cu 11.65 μg L⁻¹. Despite hypertrophic conditions and high heavy metal contamination, we recorded several submerged macrophyte species with heterogeneous spatial distribution patterns. Whereas Potamogeton pectinatus L. dominates in the eastern part of the lake, near industrial point sources, both Myriophyllum spicatum L. and Potamogeton lucens L. form extended patches in the western part of the lake. The shallow, littoral areas near villages are dominated by Ranunculus trichophyllus Chaix in Villars and Ceratophyllum demersum L. The west-east gradient in nutrient and heavy metal concentrations in waters and sediments are reflected by the spatial distribution of submersed species. While the heavy metal concentrations of the water body vary considerably in different seasons, the contents in submersed macrophytes integrate seasonal variations of longer time periods. Spatial distribution and tissue accumulation of littoral macrophyte species reflect the environmental conditions at respective sites such as heavy metal contents in water and sediment.     

Estimating nutrient budgets in tropical estuaries subject to episodic flows

Most Australian estuaries are subject to riverine discharge regimes that are highly episodic. This characteristic poses difficulties for estimating nutrient budgets of such systems based on sampling regimes that do not resolve the discharge variation and the changes in nutrient distributions that they cause. This paper presents a method for calculating nutrient budgets in estuaries having episodic hydrology. The method utilises a simple hydrodynamic transport model that is calibrated using measured salinities and which is used to describe the transport properties of the estuary as they respond to river discharge. Using this transport model, the temporal variation in nutrient concentrations within the estuary can be resolved between sampling surveys even when the discharge events are of short duration. An inverse method is then applied to calculate internal fluxes of nutrients from measurements obtained on successive sampling surveys. The approach is demonstrated through an application to the Fitzroy Estuary in Queensland, Australia.     

Concentration and distribution of hydrophobic organic contaminants and metals in the estuaries of Ukraine

In this study of Ukrainian estuaries, sediments and tissues from the Dnieper and Boh estuaries and Danube Delta on the mainland, Sevastopol and Balaklava Bays on the Crimean Peninsula, and coastal Black Sea along the Crimean Peninsula were collected in 2006. Contaminant analyses included several metals, the hydrophobic organic chemicals (HOCs) polychlorinated biphenyls, several chlorinated pesticides, and polycyclic aromatic hydrocarbons. When compared to estuarine sediments globally, the Ukrainian sediments were found to be moderately contaminated. However, several metals, especially mercury, were often shown to be elevated in the tissues of the Ukrainian organisms in comparison to organisms from other estuarine locations. Sediment quality guidelines indicate some of the estuarine sediments could be sufficiently contaminated to cause adverse toxicological effects. This investigation represents the first extensive study of HOC and metal baseline concentrations and distributions in Ukrainian estuaries and seeks to characterize exposures to aquatic organisms living in these systems.     

Dredging related metal bioaccumulation in oysters

Bivalves are regularly used as biomonitors of contaminants in coastal and estuarine waters. We used oysters to assess short term changes in metal availability caused by the resuspension of contaminated sediments. Sydney Rock Oysters, Saccostrea glomerata, were deployed at multiple sites in Port Kembla Harbour and two reference estuaries for 11 weeks before dredging and for two equivalent periods during dredging. Saccostrea experienced large increases in accumulation of zinc, copper and tin during dredging in the Port relative to oysters deployed in reference estuaries. Lead and tin were found to be permanently elevated within Port Kembla. We present a clear and un-confounded demonstration of the potential for dredging activities to cause large scale increases in water column contamination. Our results also demonstrate the usefulness of external reference locations in overcoming temporal confounding in bioaccumulation studies.     

Contribution of primary producers to mercury trophic transfer in estuarine ecosystems: Possible effects of eutrophication

There is an ongoing eutrophication process in the Ria de Aveiro coastal lagoon (Portugal), with progressive replacement of rooted primary producers for macroalgae. Taking advantage of a well-defined environmental contamination gradient, we studied mercury accumulation and distribution in the aboveground and the belowground biomass of several salt marsh plants, including the seagrass species Zostera noltii and the dominant green macroalgal species Enteromorpha sp. The results of these experiments were then placed into the context of the estuarine mercury cycle and transport from the contaminated area.All salt marsh plants accumulated mercury in the root system, with Halimione portulacoides showing the highest levels, with up to 1.3 mg kg⁻¹ observed in the most contaminated area. Belowground/aboveground ratios were generally below 0.4, suggesting that salt marsh plants are efficient immobilizers and retainers of mercury agents. Moreover, due to their sediment accretion capacities, salt marsh plants seem to play an important role in the sequestration of mercury in estuarine sediments.Seagrasses, on the other hand, accumulated considerable amounts of mercury in the aboveground biomass with belowground/aboveground ratios reaching as high as 1.4. These results may be due to their different routes of uptake (roots and foliar uptake) which suggests that seagrass meadows can be an important agent in the export of mercury from contaminated areas, considering the high aboveground biomass replacement rates.Rooted macrophytes accumulate less mercury in their aboveground biomass than macroalgae. The change of primary producer dominance due to eutrophication can originate a 4- to 5-fold increase in primary producer associated mercury. This mercury would be available for export, making it bioavailable to estuarine food webs, which stresses the need to reverse the current eutrophic status of estuarine systems.     

Distribution, magnitude and characterization of the toxicity of Ukrainian estuarine sediments

During the Soviet era, Ukraine was an important industrial and agricultural region of the Soviet Union. This industrial and agricultural activity resulted in contamination of Ukraine’s estuaries with legacy anthropogenic pollutants. Investigations on the toxicological effects of this estuarine contamination have been limited. For this research, we measured the toxicity of contaminated sediments from four Ukrainian estuaries to several aquatic organisms over 3 years. Sediment chemical analyses and whole sediment toxicity identification evaluations (TIEs) were also performed to determine the classes of contaminants contributing to toxicity. Toxic sediments were observed in several of the Ukrainian estuaries and chemical analyses of the sediments demonstrated anthropogenic contaminants were widely distributed. Contaminants were also detected in macrobenthic organisms collected from the sediments. Several lines of evidence, including TIEs, indicated hydrophobic organic chemicals (HOCs) were contributing substantially to observed toxicity. This information can guide environmental managers to prioritize portions of the estuaries requiring remediation.     

Trace element contamination in the estuarine sediments along Tuticorin coast – Gulf of Mannar,southeast coast of India

Sediment samples were collected from Kallar, Korampallam creek and Punnakayal estuaries of Tuticorin coast for assessing the level of contamination by trace elements in these estuarine sediments. The trace element concentration, calcium carbonate, organic carbon and mercury level were analyzed by Inductively Coupled Plasma Atomic Emission Spectrophotometer, Titrimetric method and SnCl₂ reduction method. The results reveals that the enrichment factor, metal pollution index and geo-accumulation index of these estuarine sediments were predominantly polluted by Cd, As, Zn, Hg and Pb. The factor analysis revealed the source of trace element accumulation in the estuarine sediments particularly Mn and Fe are from riverine inputs and As and Hg from untreated industrial effluents. Among the selected estuaries, Korampallam creek was found to be highly contaminated by trace elements due to the discharge of effluents from thermal power plant, Tuticorin alkali chemicals, copper smelting, Petrochemical industries and shipping activities.     

The use of diatom assemblages as ecological indicators in highly stratified estuaries and evaluation of existing diatom indices

Diatom indices are used to evaluate the ecological status of rivers but they have been rarely applied in estuaries. This study aimed to identify the diatom species indicating the main environmental gradients and pressures in a highly stratified estuary; and to evaluate the applicability of existing freshwater diatom indices. Marine influence due to salt-wedge intrusion and sea water mixing appeared as the main factor affecting diatom community. Three diatom assemblages were identified: indicators of riverine conditions (without marine influence), indicators of estuarine conditions (heterogeneous conditions with higher conductivities due to marine influence) and those specifically indicating well-established salt-wedge situations. Nowadays, the main human pressure affecting diatom community in the Ebro Estuary is the hydrological alteration resulting from flow regulation and abstraction. Several limitations were encountered in the application of diatom indices (e.g. inverse response with nutrients; ecologically important species not considered). Therefore, their use in estuaries should be done cautiously.     

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.