Distribution of trace metals in surface seawater and zooplankton of the Bay of Bengal, off Rushikulya estuary, East Coast of India

Distribution, ecological, and health risk assessment of trace elements in the surface seawater along the littoral of Tangier Bay (Southwestern Mediterranean Sea)

In the current study, an environmental assessment of surface seawater in Tangier Bay was conducted by analyzing physicochemical parameters and trace elements, such as As, Cr, Zn, Cd, Pb, and Cu. The results showed mean concentrations (μg/l) of 22.50 for As, 0.46 for Cr, 8.57 for Zn, 15.41 for Cd, 0.23 for Pb, and 1.83 for Cu. While most trace elements met the guidelines, elevated levels of Cd raised concerns about long-term exposure. Pollution indices, including the contamination factor, degree of contamination, and water quality index, indicate the impact of human activities, dividing sites into arsenic-cadmium contamination, wastewater influence, and low pollution levels. Statistical methods, such as ANOVA, revealed no significant differences in trace element levels across the bay. PCA and HCA revealed that Cr, Cu, and Zn originated from common anthropogenic sources, whereas Pb and Cd originated from distinct sources. As indicates that natural geological processes influence its origin.

Impact of anthropogenic activities on the abundance of microplastics in copepods sampled from the southeast coast of India

In recent year, the use of plastics has become inevitable due to its unique properties that allow for the production of durable and non-durable goods. Post use, plastics enter the waste stream and now can be found in all compartments of the biosphere as microplastics (MPs). This study presents the abundance of MPs in surface water and within copepods in the southwestern Bay of Bengal during dry (June 2022) and wet season (November 2022). The MPs in the surface water were found in all three regions [Chennai, Tuticorin and Nagapattinam (four locations in each region)] and maximum in wet season (53 particles/m3). Moreover, during dry season the mean ingestion of MPs by copepods in Chennai (0.103 ± 0.04 particles/individual), Tuticorin (0.11 ± 0.07 particles/individual) and Nagapattinam (0.036 ± 0.01 particles/individual) is high compared to the wet season. The maximum level of MPs found in both surface water and ingestion by copepods in Tuticorin and Chennai is subjective to the high maritime activities than Nagapattinam region. Whatever, the anthropogenic activities in the study region increase the bioavailability of MPs pollutant in the copepods and transported to higher trophic levels, endangering marine life and human health. Hence, further studies are needed to determine their potential impact on marine food chain in this alarming situation.

Uptake and trophic transfer of selenium into phytoplankton and zooplankton of the southern Baltic Sea

Selenium (Se) is an essential trace element and displays a narrow range of concentration between essentiality and toxicity. Se plays an important role in ameliorating mercury toxicity in organisms. Despite this there are only a few reports concerning Se concentration in plankton, the first link in the trophic chain that determines the uptake and transfer of Se to subsequent trophic levels. This paper aimed to determine Se concentration in water, phytoplankton, and zooplankton in the Baltic Sea, and factors affecting Se absorption from the environment and its transfer to higher trophic levels. Sea water and plankton samples were collected from the Gulf of Gdańsk during 5 cruises (4 seasons: 2019-2022) at 4 research stations. An additional cruise was undertaken in July 2020 in the open waters of the southern Baltic Sea. The median Se concentrations in the Gulf of Gdańsk was 0.25 μg·dm-3. While the median of Se concentration in phytoplankton was 1.11 μg·g-1 and in zooplankton was 1.25 μg·g-1. The biomass of organisms in the phytoplankton and zooplankton in the Gulf of Gdańsk showed an important role in shaping Se concentration. Seasonal trends in Se concentration in zooplankton could be the result of taxa composition changes, changes to dietary intake of Se, changes in growth dilution, or potentially some combination of factors. The highest biomagnification rate occurred in the summer. In contrast, in autumn and winter, when plankton biomass was dominated by the ciliate species Mesodinium rubrum, the highest Se concentration in plankton was measured. Further scientific studies are needed into the active biocomponents of the Se concentration process, including Se speciation, to more fully understand the dynamics of Se concentrations in the pelagic food webs of this and other freshwater and marine systems.

Non-coding RNA therapeutics: Towards a new candidate for arsenic-induced liver disease

Arsenic, a metalloid toxicant, has caused serious environmental pollution and is presently a global health issue. Long-term exposure to arsenic causes diverse organ and system dysfunctions, including liver disease. Arsenic-induced liver disease comprises a spectrum of liver pathologies, ranging from hepatocyte damage, steatosis, fibrosis, to hepatocellular carcinoma. Various mechanisms, including an imbalance in redox reactions, mitochondrial dysfunction and epigenetic changes, participate in the pathogenesis of arsenic-induced liver disease. Altered epigenetic processes involved in its initiation and progression. Dysregulated modulations of non-coding RNAs (ncRNAs), including miRNAs, lncRNAs and circRNAs, exert regulating effects on these processes. Here, we have reviewed the underlying pathogenic mechanisms that lead to progressive arsenic-induced liver disease, and we provide a discussion focusing on the effects of ncRNAs on dysfunctions in intercellular communication and on the activation of hepatic stellate cells and malignant transformation of hepatocytes. Further, we have discussed the roles of ncRNAs in intercellular communication via extracellular vesicles and cytokines, and have provided a perspective for the application of ncRNAs as biomarkers in the early diagnosis and evaluation of the pathogenesis of arsenic-induced liver disease. Further investigations of ncRNAs will help us to understand the nature of arsenic-induced liver disease and to identify biomarkers and therapeutic targets.

Heavy metals concentration in zooplankton (copepods) in the western Bay of Bengal

Along the coastline, urbanisation and industrialization pose significant challenges to marine habitats and biodiversity. Most wastewater that reaches the marine environment contains toxic metals, which, as they are non-biodegradable, accumulate in the biota and enter the marine food chain. This study presents the concentration of nine heavy metals (Fe, Zn, Cu, Co, Cr, Mn, Ni, Pb, and Cd) in zooplankton (copepods) during the Spring Intermonsoon/Pre-Monsoon (April 2019) in the western Bay of Bengal (BoB). Higher Fe concentrations were found in copepods both nearshore (42,352 µg/g) and offshore (9835 µg/g). However, the relative amounts of heavy metals in copepods from 16 locations (eight nearshore and eight offshore) varied in the order of Fe > Zn > Cu > Co > Cr > Mn > Ni > Pb > Cd. The copepods in the nearshore locations had higher concentrations of heavy metals than those offshore. Compared to earlier data on heavy metals, particularly those that are physiologically non-essential and toxic, the current study demonstrates higher amounts of these metals in copepods in the inshore BoB [Ni (avg. 58.7 ± 5.5 µg/g), Pb (avg. 25.6 ± 4.7 µg/g), and Cd (avg. 16.4 ± 0.9 µg/g)]. Considering the strong East India Coastal Currents in the western BoB, trace metal-concentrated copepods could be transported too far along the Indian coastline from the current study area.

Distribution and accumulation of metals and metalloids in planktonic food webs of the Mediterranean Sea (MERITE-HIPPOCAMPE campaign)

Particle-size classes (7 fractions from 0.8 to 2000 μm) were collected in the deep chlorophyll maximum along a Mediterranean transect including the northern coastal zone (bays of Toulon and Marseilles, France), the offshore zone (near the North Balearic Thermal Front), and the southern coastal zone (Gulf of Gabès, Tunisia). Concentrations of biotic metals and metalloids (As, Cd, Cr, Cu, Fe, Mn, Ni, Sb, V, Zn) bound to living or dead organisms and faecal pellets were assessed by phosphorus normalisation. Biotic metals and metalloids concentrations (except Cr, Mn, and V) were higher in the offshore zone than in the coastal zones. In addition, biotic Sb and V concentrations appeared to be affected by atmospheric deposition, and biotic Cr concentrations appeared to be affected by local anthropogenic inputs. Essential elements (Cd, Cu, Fe, Mn, Ni, V, Zn) were very likely controlled both by the metabolic activity of certain organisms (nanoeukaryotes, copepods) and trophic structure. In the northern coastal zone, biomagnification of essential elements was controlled by copepods activities. In the offshore zone, metals and metalloids were not biomagnified probably due to homeostasis regulatory processes in organisms. In the southern coastal zone, biomagnification of As, Cu, Cr, Sb could probably induce specific effects within the planktonic network.

Ecological risk assessment of metals in the Arctic environment with emphasis on Kongsfjorden Fjord and freshwater lakes of Ny-Ålesund, Svalbard

The concentrations of five heavy metals (Cd, Cr, Cu, Pb, and Zn) in the sediments, water, phytoplankton, zooplankton, and macroalgae from Kongsfjorden Fjord and the freshwater lakes of Ny-Ålesund in the Svalbard archipelago were determined in order to describe the anthropogenic impacts related to the Ny-Ålesund town. Water samples from nine stations, sediment samples from 23 stations, plankton samples from five stations, and six species of macroalgae were collected and subjected to heavy metal analysis using atomic absorption spectrophotometry (AAS). Only Cu and Zn were detected in the water samples. The plankton samples had only Zn, Cu, and Cr. The average metal concentrations in macroalgae fell in the decreasing order of Cu > Zn > Cr > Cd > Pb. In sediment samples, the metal order was as follows: Zn > Cu > Cr > Pb > Cd. Multivariate statistical analyses including principal component analysis (PCA) and hierarchical cluster analysis (HCA) were used to identify the source of the metal contamination. The metals were found to originate from a blend of both anthropogenic and geogenic sources. Pollution monitoring indices including geoaccumulation index (I_geo), contamination factor, contamination degree (C_deg), pollution load index (PLI), and potential ecological risk (PER) were calculated using the metal data. In the study area, I_geo values of the metals showed pollution grades from 0 (uncontaminated) to 6 (extremely contaminated). C_deg fell in classes from 1 (low contamination) to 4 (very high contamination). PLI values ranged between 0 and 5.68. PER values expressed that except for a few stations located at higher elevations in the glacial outwash plains, all other sites were highly polluted. The high level of pollution indices in the sites can be attributed to the anthropogenic activities persistent in the study area.

Intensive marine finfish aquaculture impacts community structure and metal bioaccumulation in meso-zooplankton

Commercial aquaculture has a profound impact on coastal marine environments. Here, we investigate the spatial impact of intensive commercial finfish aquaculture on local meso-zooplankton communities and the bioaccumulation of aquaculturally-derived metals (and other elements) within zooplankton samples in the Vourlias Bay, Greece. The results indicate alterations to zooplankton community composition correlate with increased eutrophic compound concentrations in the water column in closer proximity to aquaculture stations (100-300 m from fish cages). During the summer sampling, higher concentrations of accumulated metals within zooplankton samples were found at reference stations furthest from fish cages (>1000 m). During the winter sampling, however, spatial differences in accumulated metal concentrations were limited. We suggest metals are rapidly accumulated at lower trophic levels near aquaculture stations and are then dispersed to greater distances while ascending the trophic chain. This research provides good evidence for future investigations into zooplankton as an environmental impact bioindicator for aquaculture.

Spatiotemporal patterns and influencing factors of dissolved heavy metals off the Yangtze River Estuary, East China Sea

Dissolved heavy metal pollution in the ocean is becoming an environmental concern. Their distribution patterns are complex and influenced by multiple factors in the coastal ocean. Therefore, more investigations are needed to understand their behavior in the seawater. This study systematically investigated the distribution of Cu, Pb, Cd, As, Zn and seawater properties in the surface and bottom water off the Yangtze River Estuary, East China Sea in spring, summer and autumn, 2019. The results showed significant spatiotemporal distribution that three-zone-pattern of estuary, nearshore, and offshore can be divided. While sources, hydrodynamics, biological uptake and sediment resuspension affected the overall distribution, dissolved oxygen and pH dominantly influenced the estuary and offshore respectively, with more complex factors in the nearshore. Low ecological risks were assessed during the study, but global warming, ocean acidification and hypoxia are essential concerns to understand the biogeochemistry of dissolved heavy metals in the ocean.

Characterization of major and trace elements in coastal sediments along the Egyptian Mediterranean Sea

The present study was conducted to provide a comprehensive picture of marine sediment characterization in terms of geochemistry and the extent of pollution. A total of 99 surface coastal sediments were collected from coastal areas along with the Egyptian Mediterranean Sea. The samples were analyzed by neutron activation analysis (NAA) and the mass fractions in mg/kg of 39 trace elements were determined. The normalized mass fractions show significant amounts of Cl (26.4%), Sn (12%), Zr (7.3%), Hf (5.9%), Ti (4.7%), Cr (4.2%), Ca (3.4%), Si (3.1%), Sr (2.9%). The mass fractions of the rare earth elements REEs (La, Ce, Nd, Sm, Eu, Tb, Dy, Yb, and Lu) are almost double compared to literature data. Principal component analysis PCA and positive matrix factorization PMF were used to decipher the sources of pollutions. Sediment quality was quantified using different pollution indices such as enrichment factor (EF), modified pollution index (MPI), pollution load index (PLI) and the new approach to calculate total pollution index (TPI). The results of the study recognized four locations with significant pollution, namely the coastal area along Al Manzalah Lake, the Nile River estuaries at Ras Elbar and its western coastal area, at the outlet of Elbrullus Lake, and finally the Abu Qir Bay. The obtained result can serve as a geochemical background of the sediments of the study coastal area, which allows following the quality of marine sediments along with the Egyptian Mediterranean Sea.

Assessment of potential variability of cadmium and copper trace metals using hindcast estimates

Trace metals are vital to primary productivity and play an essential role as main components in regulating oceanic biogeochemical cycles. Dissolved and particulate trace metals within the water column may vary due to primary production, temperature, and nutrient changes, factors that may also vary spatially and temporally. Furthermore, assessment of trace metals mainly relies on in situ observation, and so wide-area investigation of trace-metal concentration may be challenging and subject to technical constraints. A specific approach is therefore necessary that combines biogeochemical proxies, satellite data, and trace-metal linear correlation. This study aims to assess the potential spatio-temporal variability of sea surface cadmium (Cd) and copper (Cu) concentrations in Indonesian seas and surrounding areas. The correlations of Cd and Cu concentrations with primary production and nutrient data were used to convert hindcast satellite data into estimates of the metals' concentrations. The potential variability of trace metals can be determined by overlaying both data. Indonesia's Fisheries Management Areas (FMAs) were used for data clustering and analysis. The results show that Cd and Cu trace metals have similar distribution patterns throughout the year. However, dissolved Cu has a more diverse coverage area than dissolved Cd, including within the Halmahera, Seram, and Maluku Seas (FMAs 716 and 717), the Makassar Strait (FMA 717), and the Java-Sumatra upwelling area (FMA 573). Both Cd and Cu concentrations in the Java-Sumatra upwelling region follow the periodic upwelling pattern. Overall, both Cd and Cu show a declining trend in concentration from 2012 to 2019. It is estimated that dissolved Cd concentration declined from 1500-2000 pmol/kg in 2012 to 1000-1500 pmol/kg in 2019 for all locations. Dissolved Cu concentration decreased from 30-35 nmol/kg in 2012 to 25-30 nmol/kg in 2019. Estimated dissolved Cd and Cu follow the linear functions of silicate (SiO₄), nitrate (NO₃), and primary productivity. The fluctuation of anthropogenic activities and global warming are likely to indirectly impact the decline in metal concentrations by affecting nutrients and primary productivity.

Statistical analysis and susceptibility properties of heavy/light metal pollution in surface seawater of Izmir Bay

The inner bay of Izmir is known as the part between Sasalı/Karşıyaka coastline and Güzelbahçe/Bayraklı. It is used extensively in transportation. There is constant ferry transportation and an international port operates in this region. There are also a few streams that flow into the inner bay. Therefore, the inner bay can be exposed to continuous chemical pollutants, and these wastes can intensively be observed in its natural structure. In this study, the magnetic susceptibility values and elemental analyses of the samples taken from the surface sea waters of the inner bay coastline were performed. Silicon, strontium, and manganese elements were mostly observed in the samples. The greatest susceptibility values were seen in the Bostanlı ferry port and Göztepe ferry. In addition, the standard deviation and correlation coefficient values of the samples were calculated and discussed. According to the correlation coefficient value, it can be said that there is a positive correlation between metal ion ratios and magnetic susceptibility.

Release of heavy metals under pre-set redox potentials in Musa estuary sediments, northwestern of Persian Gulf

Sediments are capable of adsorbing and desorbing heavy metals (HMs) under various environmental conditions. This study investigated the impact of pre-set redox potential (Eh) on the release dynamics of HMs (Co, Cr, Cu, Ni, Pb, V, and Zn) from sediment in an automated biogeochemical microcosm. The release of Co, Pb, and V under reducing conditions increased that may increase the potential risks in the aquatic environment. This phenomenon could be attributed to the decrease in pH, the reductive dissolution of FeMn oxides, and the complex of HMs with dissolved organic carbon (DOC). However, the soluble Cr, Cu, Ni, and Zn decreased at redox potentials as low as -150 mV. Co, Ni, Pb, and Zn were observed in mobile fractions while Cu primarily existed in the residual fraction (indicating lithogenic source). HPI and HEI indexes showed that water quality concerning HMs would become more unsuitable for aquatic life by reducing Eh.

Trace metals concentration in water hyacinth implicates the saltwater barrage altered hydrography of Kochi backwaters, southwest Coast of India

This study in the Kochi backwaters (KBW) presents the distribution of 9 trace metals (Fe, Zn, Cu, Mn, Ni, Co, Cr, Cd, Pb) in different parts (root, stolon and leaf) of the common water hyacinth Eichhornia crassipes during three different seasons [Pre-Monsoon (PRM), Southwest Monsoon (SWM), and Northeast Monsoon (NEM)]. The hyacinth was collected from 4 sections upstream of the KBW where a saltwater barrage [Thannermukkom Barrage (TB)] prevents saltwater intrusion. Results showed that regardless of seasons, all the trace metals concentration in different parts of Eichhornia varied in the following order: roots > stolon > leaves. All the trace metals except Fe showed their highest concentration during the PRM when TB introduces stagnancy of the water upstream through flow restrictions. Instead, Fe was high during the SWM associated with increased river influx at that time. Overall results showed that the hydrographical alterations of TB upstream of KBW have clear imprints on the trace metals concentrated in the hyacinth Eichhornia crassipes.

Metal and metallothionein levels in zooplankton in relation to environmental exposure: spatial and temporal variability (Saronikos Gulf, Greece)

Metal and metallothionein (MT) in mixed zooplankton were investigated as means of monitoring metal availability regarding environmental exposure. Spatial and temporal variability of Cd, Cu, Ni, Zn, Fe, Mn and Pb in zooplankton and seawater were studied in Saronikos Gulf (Aegean Sea, Eastern Mediterranean), once every second month during an annual cycle (2011-2012). Particulate organic carbon and chlorophyll α were also measured in seawater samples. Median zooplankton metal concentrations were 0.65, 32.4, 7.1, 864, 1420, 40.2 and 26.8 μg g^-1 dw for Cd, Cu, Ni, Zn, Fe, Mn and Pb, respectively, and 109 μg g^-1 ww for MTs. Metal levels in zooplankton and MTs were higher at sites influenced by human-derived pressures. Additionally, metal concentrations in pelagic fish flesh from the Greek MED-POL data base were used for bioconcentration and biomagnification factors calculation. Bioconcentration from water to zooplankton was higher than metal transfer from either seston to zooplankton or zooplankton to fish.

Evaluation of factors influencing the trace metals in Puducherry and Diu coasts of India through multivariate techniques

In recent years, urban and industrial development initiatives at Puducherry and Diu such as tourism, shipping, and fisheries have led to sediment contamination by trace metals, and contributed to this investigation that extended from 2016 to 2017. Strong factor loadings of Cd (0.94), Ni (0.84), Al (0.84), Cr (0.83), Co (0.82), and Fe (0.78) illustrated the variability at Puducherry, whereas Cr (0.88), Cd (0.86), Ni (0.83), Co (0.77), Cu (0.77), and Fe (0.77) showed variability at Diu. The mean rank order distribution of the top three metals in sediment was Fe > Al > Mn, which exhibited higher variability. The highest contamination factor was observed for Cd at Diu, whereas the lowest was observed at Puducherry for Al. Similarly, the risk index also exhibited considerable risk which could be attributed to Cd contamination in the sediment at Diu compared with that at Puducherry. The results obtained are essential to establish a reference for better comparison and management of the tropical environments.

Oceanic karma? Eco-ethical gaps in African EEE metal cycle may hit back through seafood contamination

The increasing global demand for electric and electronic equipment (EEE) such as smartphones, tablets and electric car batteries has resulted in an increase in heavy metal releases to the environment at different steps during its manufacture (e.g. mining, extraction, production and e-waste). Some critical raw materials (CRMs) that supply the worldwide demand of technology are mainly sourced from Africa, but their resulting heavy metal pollution can reach citizens from other regions of the world through seafood caught in African waters, which would act as a vector. In this study, we review heavy metal contents in African fish and, as proof of concept, we analyse heavy metal content in three tuna species (Thunnus alalunga, T. albacares and T. obesus) caught in different regions inside the Sustainable Fisheries Partnership Agreements (SFPAs) by Spanish fleets and commercialised in Spain. Thunnus alalunga and T. albacares from African waters had higher concentrations of heavy metals (especially Hg but also As and Pb) in muscle than samples of the same species caught in other waters. Metal profiles in tunas from African waters were significantly correlated with those of continental and coastal fish from nearby areas impacted by mines and e-waste, as found in the literature review. Based on these results we identify research priorities that should be addressed in order to improve the social and environmental sustainability of EEE metal manufacture in Africa.

Prescribing sea water quality criteria for arsenic, cadmium and lead through species sensitivity distribution

Water quality standards are essential for regulation of contaminants in marine environment. Seawater quality criteria (SWQC) for arsenic (As), cadmium (Cd) and lead (Pb) have not been developed for India. The aim of this study is to derive the SWQC for the metals based on Species Sensitivity Distribution (SSD). Eight species of sensitive marine organisms belonging to five phyla were assessed for their sensitivity to toxicity of As, Cd and Pb. Median effective concentrations (EC₅₀) and Median Lethal Concentrations (LC₅₀) were derived from the acute toxicity bio-assays. No Observed Effect Concentrations (NOEC), Lowest Observed Effect Concentrations (LOEC) and chronic values were derived from chronic toxicity bio-assays. Diatoms were more sensitive to As with 96 h EC₅₀ of 0.1 mg/l and copepods were more sensitive to Cd and Pb with 96 h EC₅₀ of 0.019 mg/l and 0.05 mg/l respectively. Estimated NOECs ranged from 4.87 to 21.55 µg/l of As, 1.0 to 120 µg/l of Cd and 5.67 to 91.67 µg/l of Pb. Similarly, chronic values (µg/l) were in the range of 6.71-26.1, 1.38-170, and 7.67-91.67 of As, Cd and Pb respectively. The Criterion Maximum Concentration (CMC), Criterion Continuous Concentration (CCC) and Predicted No Effect Concentration (PNEC) values were prescribed as SWQC. The CMC (µg/l) of 19, 1.7 and 17 for As, Cd, and Pb were derived respectively for acute exposure during accidental marine outfalls. The CCC (µg/l) for As was 4.6, 1.1 for Cd and 5.9 for Pb are recommended as SWQC for protection of 95% of marine organisms. PNEC (µg/l) of 3.8 for As, 0.92 for Cd and 4.3 for Pb are suggested for highly disturbed ecosystems, shell fishing and mariculture uses of water bodies. These values are recommended as a baseline for site specific water quality criteria for the coastal waters of the country.

Distribution and ecological- and health-risk assessment of heavy metals in the seawater of the southeast coast of India

The objective of the present study was to conduct an ecological and health risk assessment of heavy metals in the seawater of the southeast coast of India. The distribution profile of heavy metals in the surface seawater was Fe (79.60 ± 21.57 μg/L) > Zn (9.31 ± 1.33 μg/L) > Cu (5.19 ± 2.00 μg/L) > Ni (2.45 ± 0.76 μg/L) > Mn (1.20 ± 1.00 μg/L) > U (0.44 ± 0.23 μg/L) > Pb (0.36 ± 0.06 μg/L) > Cr (0.31 ± 0.57 μg/L) > Cd (0.11 ± 0.05 μg/L) > Co (0.07 ± 0.20 μg/L). Cu level for most of the samples exceeded the USEPA criteria for acute CMC (criterion maximum concentration) and chronic CCC (criterion continuous concentration). Other studied metals, Cd, Cr, Pb, and Ni, remained below the acute CMC and chronic CCC guidelines. The seawater pollution index (I_wp) of Cr, Ni, Zn, Cd, and Pb complied with the category-I seawater (<1, unpolluted). The ERI values (0.46-3.99) of the seawater of the studied coast mostly fell under the ecologically low risk category with respect to heavy metals. Dermal Hazard index values were orders of magnitude lower than one, indicating no potential health concern due to dermal exposure.

Impact of a large hydraulic barrage on the trace metals concentration in mesozooplankton in the Kochi backwaters, along the Southwest coast of India

This study delineates the impact of a man-made hydrological barrage [Thannermukkom barrage (TB)] on the concentration of selected trace metals (Fe, Zn, Cu, Co, Cr, Mn, Ni, Pb) in mesozooplankton from the Kochi backwaters (KBW). The overall results point out that during Pre-Southwest Monsoon (PRM), the concentration of trace metals in mesozooplankton was high in the upstream due to the closure of the barrage, which essentially causes stagnancy of the waters. Trace metal concentrations in the downstream and upstream regions of KBW were found to be lower during Post- Southwest Monsoon (PSWM) compared to the rest of the seasons. In general, trace metals in mesozooplankton from the KBW showed the following order of concentration: Fe > Mn > Zn > Ni > Cu > Cr > Co > Pb. A comparison with earlier data across the globe showed that trace metal concentration in mesoplankton in the KBW is lower than the values reported from other parts of the world.

Assessment of the ecological and human health risks from metals in shrimp aquaculture environments in Central Java, Indonesia

The occurrence and contamination level of seven important toxic metals (Cd, Cu, Co, Cr, Hg, Pb, and Zn) and three additional metals (Al, Fe, and Mn) in the water, sediment, and shrimp muscle in aquaculture areas located in Central Java, Indonesia, were investigated. The results suggest that the majority of metals have higher concentrations in the inlet followed by the outlet and ponds. Cd dissolved in the waters exhibited the highest level in Pekalongan (3.15 ± 0.33 μg L^-1). Although Pb was not detected in the water, it was detected in the sediment, and the concentration ranged from 7.6 to 15.40 mg kg^-1 dw. In general, the heavy metal concentrations in the sediments were found to decrease in the sequence Al > Fe > Mn > Zn > Cr > Cu > Co > Pb. Concentrations below the effects range low level based on the Canadian sediment quality guidelines were found for Cr, Cu, Pb, and Zn, whereas moderate sediment pollution (25-75 mg kg^-1 dw) was observed for Cr (all regions), Cu (except in the Pekalongan region), and Zn (Brebes and Tegal regions) according to the US EPA standard. The status of the waters was evaluated by calculating a pollution index derived mostly from Mn and Zn. The ecological risk (geoaccumulation index (I_geo), contamination factor (CF), pollution load index (PLI), and potential ecological risk index (ERI)) determined in the sediments indicated that all studied areas had low to moderate contamination. The concentrations of all metals in shrimp were generally below the maximum limits for seafood, except for Zn (in all stations), Pb, and Cr (Tegal and Pekalongan). The hazard index values for metals indicated that consuming shrimp would not have adverse effects on human health.

Ecological risk assessment of trace metals and comprehensive contamination indicators in the coastal waters of Macao, South China Sea

Few systematic and scientific assessments have been conducted on marine environmental quality in the coastal waters of Macao, a major city in the Pearl River Delta, China. In this study, we investigated the spatial distribution of trace metals (TMs) and comprehensive contamination indicators of marine water in Macao and evaluated their ecological risks. The total amount of typical TMs (∑TMs) in surface water ranged from 2.71 μg/L to 201 μg/L. ∑TMs (Hg, As, and Cd) in sediments ranged from 0.34 mg/kg to 54.8 mg/kg. TM contamination in surface water was influenced by spatial position and tidal current direction. The spatial distribution and correlation analysis of TMs and comprehensive contamination indicators were assessed, and ecological risk assessment indicated that the surface water and sediments in coastal waters of Macao are of relatively good quality, although high sulfide levels could be detected in surface water.

Chromium in Benoa Bay, Bali - Indonesia

The chromium (Cr) pollution in Bali gained public attention because the textile and screen-printing industry was reportedly dumping their waste into the river. Benoa Bay is the estuary of six rivers in Bali and is thought to be contaminated by Cr. In this research, we investigated the presence of Cr in surface water, sediment and plankton (as a base trophic level) in Benoa Bay, Bali. Thirty stations were used to investigate Cr in Benoa Bay. The results showed that at almost all stations, surface waters of Benoa Bay were not contaminated by Cr, meanwhile Cr was detected in plankton and sediment. This research found that the range of Cr concentrations was sediment > plankton > water. The Bioaccumulation Factor (BCF) between plankton-water was much higher than plankton-sediment.

Neurobehavioural and biochemical responses associated with exposure to binary waterborne mixtures of zinc and nickel in rats

Environmental and occupational exposure to metal mixtures due to various geogenic and anthropogenic activities poses a health threat to exposed organisms. The outcome of systemic interactions of metals is a topical area of research because it may cause either synergistic or antagonistic effect. The present study investigated the impact of co-exposure to environmentally relevant concentrations of waterborne nickel (75 and 150 μg NiCl ₂ L^-1) and zinc (100 and 200 μg ZnCl₂ L^-1) mixtures on neurobehavioural performance of rats. Locomotor, motor and exploratory activities were evaluated using video-tracking software during trial in a novel arena and thereafter, biochemical and histological analyses were performed using the cerebrum, cerebellum and liver. Results indicated that zinc significantly (p < 0.05) abated the nickel-induced locomotor and motor deficits as well as improved the exploratory activity of exposed rats as verified by track plots and heat map analyses. Moreover, zinc mitigated nickel-mediated decrease in acetylcholinesterase activity, elevation in biomarkers of liver damage, levels of reactive oxygen and nitrogen species as well as lipid peroxidation in the exposed rats when compared with control. Additionally, nickel mediated decrease in antioxidant enzyme activities as well as the increase in tumour necrosis factor alpha, interleukin-1 beta and caspase-3 activity were markedly abrogated in the cerebrum, cerebellum and liver of rats co-exposed to nickel and zinc. Histological and histomorphometrical analyses evinced that zinc abated nickel-mediated neurohepatic degeneration as well as quantitative reduction in the widest diameter of the Purkinje cells and the densities of viable granule cell layer of dentate gyrus, pyramidal neurones of cornu ammonis 3 and cortical neurons in the exposed rats. Taken together, zinc abrogated nickel-induced neurohepatic damage via suppression of oxido-inflammatory stress and caspase-3 activation in rats.

Assessment of trace metal contamination in the marine sediment, seawater, and bivalves of Parangipettai, southeast coast of India

Industrial and domestic discharge into the coastal environment has driven us to propose an integrated approach to delineate stations contaminated with metals on the Parangipettai coast by collecting sediment and seawater samples monthly at 18 stations from 2015 to 2017. Descriptive statistics revealed that the concentrations of some metals in the sediment and seawater samples were beyond the permissible level. Further, factor analysis showed a sampling adequacy of 0.90 with high positive loading for Ni (0.94), Cd (0.91), Co (0.90), Pb (0.89), and Zn (0.87) in sediment samples. The degree of contamination by metals was evaluated using pollution indices. The results of the contamination index revealed that some stations in the study area were moderately polluted, and those of the ecological index showed that open sea was under low risk while other stations were in the moderate-to-high-risk category. The results obtained are essential to establish the reference condition for a comparative study in similar environments in the tropical regions.

Evaluation of trace metals in seawater, sediments, and bivalves of Nellore, southeast coast of India, by using multivariate and ecological tool

Urbanization in recent years has driven us to investigate metal contamination on Nellore coast by collecting seawater, sediment, and bivalve samples monthly at five stations from 2015 to 2017. Non-metric multidimensional scaling and cluster analysis indicated that open sea (OS) samples were markedly different from the samples collected at other stations. Strong factor loadings of Al (0.76), Mn (0.79), and Cd (0.78) showed variability in seawater, while those for Fe (0.76), Ni (0.77), Zn (0.85), and Pb (0.81) showed variability in sediment. The mean values of Fe (346 ppm) and Mn (21 ppm) were high in bivalves compared to the mean values of other metals. A higher contamination factor was observed for Cd at Buckingham Canal, while the lowest was observed for sediment in OS. The order of trace metals in sediments according to risk index was Cd > Pb > Cu > Cr > Zn. The results obtained are essential to establish a reference for better comparison of tropical environments.

Major, trace, and rare-earth elements in the zooplankton of the Laptev Sea in relation to community composition

We investigated the concentrations of major, trace, and rare-earth elements in zooplankton in relation to species community composition from the eastern part of the Lena Delta to the continental slope of the Laptev Sea in September 2015. The elemental composition of zooplankton inhabiting different areas demonstrated similarities. Cross-shelf changes were found for only 4 (Li, Zn, As, and U) of the 56 elements analyzed. Zinc was the only element concentration of which successively reduced across coastal-open ocean gradient. Considering own and literary data, we can assume that the cross-shelf decrease of zinc accumulation in zooplankton is a universal pattern, manifested in different climatic and biogeochemical environmental conditions and with different species compositions of the zooplankton community. Cross-shelf changes were also established for Li, As, and U. However, the concentrations of these elements increased along the gradient. We assume that increased As concentration in zooplankton across the shelf-continental slope gradient of the Laptev Sea is associated with a change in the feeding behavior of the species of the zooplankton community. However, a sharp increase in the concentrations of Li and U in zooplankton was associated with the appearance of Calanus copepods in the community. The average total concentration of rare-earth elements and yttrium in zooplankton of the Laptev Sea was 752.8 ng g^-1 of dry weight. We found record high levels of rare-earth elements for zooplankton of the inner shelf, near the eastern part of the Lena Delta. From the inner shelf to the continental slope of the Laptev Sea, La, Ce, and Nd were the dominant rare-earth elements. The elemental composition of zooplankton in the Arctic Seas is characterized by a much lower content of major and trace elements in comparison with the zooplankton and total plankton of the ocean.

Effect of algal and bacterial diet on metal bioaccumulation in zooplankton from the Pearl River, South China

The biomagnification of metals (Cd, Co, Cr, Cu, Fe, Mn, Pb and Zn) and the metalloid As in aquatic systems is a global health concern. In this study, concentrations of fatty acid biomarkers in zooplankton were analyzed from the Pearl River, South China between September 2016 and July 2017. The objective was to examine how particulate matter, algae and bacteria food sources affect metal bioaccumulation using fatty acid facilitation. In the zooplankton fraction, positive correlations were observed between Pb concentration and Eicosapentaenoic acid (EPA), Zn and Docosahexaenoic acid (DHA) (diatoms and Cryptophyceae biomarkers), Fe with Palmitoleic acid (C16:1n-7, diatom marker), and a weak association of Mn with α-linolenic acid (C18:3n-3). Cu concentration in the zooplankton increased significantly with an endogenous biotic biomarker Stearic acid (C18:0, bacteria biomarker), while Cd concentrations increased with increasing Oleic acid (C18:1n-9, green alga biomarker) concentration. There was a positive correlation between Cr concentration and the sum of Pentadecylic and Margaric acids (C15:0 + C17:0, bacteria biomarkers). Seven of the nine metals examined showed associations with fatty acids in the zooplankton. The bioaccumulation of Co, Cu, Pb, Fe, Mn and Zn concentration was correlated to the individual biomasses of Brachionus calyciflorus, Filinia longiseta, Schmackeria forbesi, Limnoithona sinenisis, Thermocyclops brevifurcatus, and Diaphanosoma dubium. For selected zooplankton taxa, the algal biomasses of Euglenophyceae, Chlorophyceae, Cryptophyceae, and Bacillariophyceae were correlated. Zooplankton were affected by selected species of phytoplankton and bacteria numbers in the Pearl River. These results show that metal accumulation in zooplankton is not only correlated with diet but is also in part, species specific with metal type. Thus, the bioaccumulation or scavenging of metals across trophic levels is a fundamental and complex component of metal cycling in aquatic environments.

Distribution, Source and Risk Assessment of Heavy Metal(oid)s in Water, Sediments, and Corbicula Fluminea of Xijiang River, China

A total of 43 water and sediment samples, and 34 Corbicula fluminea samples were collected in Xijiang River in southern China to determine the spatial distribution and sources of 12 metals/metalloids (V, Co, Cr, Ni, Cu, Mn, Zn, Cd, Pb, As, Sb, and Tl) and to assess the pollution levels and ecological risks of the pollutants. The results showed that the levels of the metals/metalloids (except for Tl) in the river water from almost all of the sampling sites met the Chinese national surface water quality standards. However, the concentrations of the metals/metalloids in the sediments exceeded the background values by a factor of 1.03–56.56 except for V, Co, and Mn, and the contents of Zn, Cd, and Pb in the Corbicula fluminea soft tissue exceeded the limits of the Chinese Category I food Quality Standards. The spatial distribution analysis showed that the concentrations of the contaminants in the lower reaches of Xijiang River were higher than in the upper reaches. The bioaccumulation factor (BAF), biota-sediment accumulation factor (BSF), geo-accumulation index (I_geo), and the potential ecological risk index (RI) were obtained to assess the pollution levels and ecological risks. The results indicated that Cu, Cd, and Zn were the most prone to bio-accumulation in the Corbicula fluminea soft tissue, and the lower reaches showed a much higher pollution level and risk than the upper reaches. The metals/metalloids in the sediments posed serious threat on the aquatic ecosystem, of which Cd, As, and Sb are the most risky contaminants. The results of principal component analysis (PCA) indicated Cr, Ni, Cu, Mn, Cd, Pb, and As in the sediments came from relevant industrial activities, and V and Co originated from natural sources, and Sb from mining activities, Zn and Tl came from industrial activities and mining activities.

Suitability of the shallow water hydrothermal system at Ambitle Island (Papua New Guinea) to study the effect of high pCO2 on coral reefs

Volcanic CO₂ seeps were successfully used to predict coral reef response to ocean acidification, although toxic elements, often characteristic of hydrothermal vents were rarely reported. We measured the physicochemical conditions, seawater carbonate chemistry and trace elements in Tutum Bay, Papua New Guinea. There, intense emission of hydrothermal fluids and CO₂ expose the coral reef to a seawater pH_T between 7.6 and 7.7. Arsenic and silica were enriched by up to six times in surface seawater, while bottom concentrations were lower and thus similar to coral reefs worldwide. Manganese, cesium, iron and zinc concentrations fell into the range of other coastal environments. Our measurements suggest that Tutum Bay is a suitable site to study the response of coral reefs to high pCO₂. Considering that arsenic is a common metal in hydrothermal fluids, its characterization should be included in any study that uses volcanic CO₂ seeps as natural laboratories for ocean acidification.

Evidence for mitigation of coral bleaching by manganese

Unprecedented mass coral bleaching events due to global warming and overall seawater pollution have been observed worldwide over the last decades. Although metals are often considered as toxic substances for corals, some are essential at nanomolar concentrations for physiological processes such as photosynthesis and antioxidant defenses. This study was designed to elucidate, the individual and combined effects of nanomolar seawater enrichment in manganese (Mn) and iron (Fe), on the main physiological traits of Stylophora pistillata, maintained under normal growth and thermal stress conditions. We provide, for the first time, evidence that Mn is a key trace element for coral symbionts, enhancing cellular chlorophyll concentrations, photosynthetic efficiency and gross photosynthetic rates at ambient temperature. Our experiment also highlights the key role of Mn in increasing coral resistance to heat stress-induced bleaching. While Mn-enriched corals did not bleach and did not reduce their rates of photosynthesis and calcification, control corals experienced significant bleaching. On the contrary to Mn, Fe enrichment not only impaired calcification but induced significant bleaching. Such information is an important step towards a better understanding of the response of corals to seawater enrichment in metals. It can also explain, to some extent, species susceptibility to environmental stress.

Spatio-temporal variations in physico-chemical parameters and potentially harmful elements (PHEs) of Uchalli Wetlands Complex (Ramsar site), Pakistan

Uchalli Wetlands Complex (UWC) is located in District Khushab, Pakistan, which comprised of three lakes named Khabeki, Uchalli, and Jahlar. The UWC Pakistan is one of the Ramsar sites of international importance. However, the information regarding water quality parameters and concentration of potentially harmful elements (PHEs) is relatively short. Present study focused on spatio-temporal variations in the physico-chemical parameters and PHE (Cd, Pb, Ni, Cu, Zn, Cr, As, Mn) concentrations in water and fish samples using inductively coupled plasma. Sampling was done in summer (August 2016) and winter (January 2017) seasons. The overall concentrations of PHEs in water were in the following order: Mn > Zn > Cu > Cr > Ni > Cd > Pb > As for Khabeki; As >Ni > Cr > Mn > Zn > Cu > Cd > Pb for Uchalli; and Mn > Zn > Ni > Cu > As > Cr > Cd > Pb for Jahlar Lake. PHE concentration in fish followed the order Ni > Cd > Mn > Pb > Cu > Zn > Cr > As. PHEs analysis showed that Mn; Ni and As; and Ni and Mn in summer were above the Pakistan Environmental Quality Standards (PEQS) and World Health Organization (WHO) standards in Khabeki, Uchalli, and Jahlar Lakes respectively while in winter, Mn; Cd, Ni, and As; and Ni and Mn were higher than standard values in Khabeki, Uchalli, and Jahlar Lakes respectively. In fish samples, only Cd (0.0942) was higher in summer as compared to winter (0.0512) while other seven PHEs observed were higher in winter. Conclusively, the metal pollution index showed that water quality of UWC is not very fit for human consumption directly. The bioconcentration factor results indicated potential to accumulate PHEs, i.e., Cd (29.4375 and 9.4814), Pb (16.66 and 4.375), and Ni (4.9875 and 6.206), in fish during both sampling campaigns. Target hazard quotient (THQ), target carcinogenic risk (TR), hazard index (HI), estimated daily intake (EDI), and international safe standard limits of PHEs for fish species indicated that fish from UWC is safe for human consumption. Variations in physic-chemical parameters and PHE concentration were observed spatially and temporally that could be caused by precipitation amount or natural geochemistry of the lakes' crust. The water quality was not suitable for direct human consumption. Fish was only found in Khabeki Lake that had potential to accumulate Cd, Pb, and Ni more as compared to other studied PHEs.

Arsenic and Trace Metals in Three West African rivers: Concentrations, Partitioning, and Distribution in Particle-Size Fractions

Despite increasing mining activities, and fertilizer and pesticide use in agriculture, little information is available on the status of metal(loid) contamination in rivers in West Africa. Sixty water samples were collected from three significant rivers (the Bandama, Comoé, and Bia Rivers) in Côte d'Ivoire, the world's top cocoa producer, to examine As, Pb, Cu, Fe, Cd, and Zn concentrations, partitioning, and distribution in suspended particle-size fractions. The results showed higher total metal(loid) concentrations during the dry and flood seasons than during the rainy season. Significant As and Pb concentrations, moderate Cu and Fe concentrations, and low Zn concentrations were observed during the flood season. The metal(loid) concentrations decreased upstream to downstream primarily due to increased deposition through flocculation. Inverse or no obvious spatial trends often were observed, indicative of local contamination from anthropogenic activities. The suspended solid phase and the strength of metal affinity to the particles controlled the metal(loid) concentrations. Furthermore, total metal(loid) concentrations increased significantly with decreasing suspended particle-size fractions. The results underline that As and Pb contents in the Comoé and Bia Rivers threaten the health of at least 3 million people in southeastern Côte d'Ivoire. Filtering river waters before use will significantly reduce human health risks.

Heavy metals and arsenic content in water along the southern Caspian coasts in Iran

Due to the importance of pollution monitoring in marine ecosystems and lack of a coherent and systematic investigation of heavy metal ions along the southern shores of the Caspian Sea, in the present study, the amount of these metals and As ions in coastal waters along its 780-km-long coast in Iran have been studied. Heavy metals (cobalt, nickel, copper, zinc, cadmium, mercury, lead) and a poisonous metalloid (arsenic) were selected in 59 sampling stations and determined using differential pulse polarography method. The multivariate statistical tools were applied to describe and interpret the experimental data. The overall mean concentrations of studied metals (in microgram per liter; μg L^-1) in the samples were found in the order Zn (10.9) > Ni (7.4) > Cu (5.5) > Pb (1.9) > Hg (1.4) > As (1.3) > Co (1.1) > Cd (0.2). The results when compared with reported international standards confirmed that the sampled waters do contain some of these elements above the suggested maximum permissible limits. Hg and Cu were detected in 54.2 and 72.9% of the samples, almost all above the permissible limits. Ni, Zn, Pb, and Co were detected in 100, 96.6, 93.2, and 88.1%, respectively, while 8.5, 22.0, 3.4, and 1.7% were above the permissible limits. Cd and As were present in 61 and 93% of the samples, and their concentrations were higher than the rate presented by Russian System of Management Chemicals (RSMC). In addition, spatial distribution of heavy metal concentrations showed that Gorgan Bay is an ecosystem serving as a filter, trapping natural and anthropogenic materials that are brought from industrial, commercial, and urbanized areas. The multivariate data analysis reveals that Caspian Sea is contaminated by both anthropogenic as well as pedo-geochemical sources.

Dissolved trace elements in Hooghly (Ganges) River Estuary, India: Risk assessment and implications for management

The study presents a spatio-seasonal distribution of 13 trace elements in the surface water (0-5 cm) along the north-south gradient of Hooghly River Estuary, India, and subsequently evaluates the human health risk by adopting USEPA standards. An overall homogeneous spatial distribution of elements was pronounced, whereas an irregular and inconsistent seasonal pattern were recorded for the majority of the elements. The concentration range (μg/l) of the elements and their relative variability were obtained as follows in the decreasing order: Al (55,458-104,955) > Fe (35,676-78,427) > Mn (651.76-975.78) > V (85.15-147.70) > Si (16.0-153.88) > Zn (26.94-105.32) > Cr (21.61-106.02) > Ni (19.64-66.72) > Cu (34.70-65.80) > Pb (26.40-37.48) > Co (11.16-23.01) > As (0.10-8.20) > Cd (1.19-5.53). Although Pb, Ni, Cr, Al, Fe, and Mn exceeded the WHO prescribed threshold limit for drinking water, Metal Pollution Index values (8.02-11.86) superseded the upper threshold limit endorsing adverse impact on biota. The studied elements were justified to have a non-carcinogenic risk as derived from hazard quotient and hazard index values. However, the trace elements As, Cd, Pb, and Cr exceeded the upper limit of cancer risk (10^-4), thereby leading to carcinogenic risk concern for both children and adult population groups, where children are more susceptible than the adults. Hence, evaluation of bioavailable fractions of the elements is required for proper management of this stressed fluvial system.

Enhancement of coral calcification via the interplay of nickel and urease

Corals are the main reef builders through the formation of calcium carbonate skeletons. In recent decades, coral calcification has however been impacted by many global (climate change) and local stressors (such as destructive fishing practices and changes in water quality). In this particular context, it is crucial to identify and characterize the various factors that promote coral calcification. We thus performed the first investigation of the effect of nickel and urea enrichment on the calcification rates of three coral species. These two factors may indeed interact with calcification through the activity of urease, which catalyzes the hydrolysis of urea to produce inorganic carbon and ammonia that are involved in the calcification process. Experiments were performed with the asymbiotic coral Dendrophyllia arbuscula and, to further assess if urea and/or nickel has an indirect link with calcification through photosynthesis, results were compared with those obtained with two symbiotic corals, Acropora muricata and Pocillopora damicornis, for which we also measured photosynthetic rates. Ambient and enriched nickel (0.12 and 3.50 μg L^-1) combined with ambient and enriched urea concentrations (0.26 and 5.52 μmol L^-1) were tested during 4 weeks in aquaria. We demonstrate in the study that a nickel enrichment alone or combined with a urea enrichment strongly stimulated urea uptake rates of the three tested species. In addition, this enhancement of urea uptake and hydrolysis significantly increased the long-term calcification rates (i.e. growth) of the three coral species investigated, inducing a 1.49-fold to 1.64-fold increase, respectively for D. arbuscula and P. damicornis. Since calcification was greatly enhanced by nickel in the asymbiotic coral species - i.e. in absence of photosynthesis - we concluded that the effect of increased urease activity on calcification was mainly direct. According to our results, it can be assumed that corals in some fringing reefs, benefiting from seawater enriched in nickel may have advantages and might be able to use urea more effectively as a carbon and nitrogen source. It can also be suggested that urea, for which hotspots are regularly measured in reef waters may alleviate the negative consequences of thermal stress on corals.

Effect of selenium on Penaeus monodon and Perna viridis: Enzyme activities and histopathological responses

The study was carried out to evaluate enzyme activities and histopathological changes due to the effect of acute and chronic definitive toxicity of selenium (Se) on the post larvae (PL) of giant tiger shrimp (Penaeus monodon), and green mussel (Perna viridis). The 96-h Median Lethal concentration (LC₅₀) for the PL of shrimp was 3.36 mg L^-1 and the chronic value for the long-term survival endpoint in a 21-d exposure was 0.10 mg L^-1. The green mussel 96-h LC₅₀ was 28.41 mg L^-1 and the chronic value for the long-term survival endpoint in a 30-d exposure was 3.06 mg L^-1. Native polyacrylamide gel electrophoresis revealed altered diverse isoforms of esterase, superoxide dismutase and malate dehydrogenase activities in the PL of shrimp and green mussel exposed to sublethal concentration of Se. Cellular anomalies such as deformation and fusion of corneal cells, detachment of corneal cells from cornea facet and increased space between ommatidia were observed in the compound eye of PL of shrimp exposed to Se for 21-d. Shrinkage and clumping of mucous gland, degenerative changes in phenol gland, and ciliated epithelium were observed in the foot of green mussel exposed to Se for 30-d. This study shows that cellular anomalies in the compound eye of PL of P. monodon and foot tissues of P. viridis described would affect the vision of shrimp and byssus thread formation in green mussel.

Inhibition in fertilisation of coral gametes following exposure to nickel and copper

The mining and production of nickel in tropical regions have the potential to impact on ecologically valuable tropical marine ecosystems. Currently, few data exist to assess the risks of nickel exposure to tropical ecosystems and to derive ecologically relevant water quality guidelines. In particular, data are lacking for keystone species such as scleractinian corals, which create the complex structural reef habitats that support many other marine species. As part of a larger study developing risk assessment tools for nickel in the tropical Asia-Pacific region, we investigated the toxicity of nickel on fertilisation success in three species of scleractinian corals: Acropora aspera, Acropora digitifera and Platygyra daedalea. In the literature, more data are available on the effects of copper on coral fertilisation, so to allow for comparisons with past studies, the toxicity of copper to A. aspera and P. daedalea was also determined. Overall, copper was more toxic than nickel to the fertilisation success of the species tested. Acropora aspera was the most sensitive species to nickel (NOEC < 280µg Ni/L), followed by A. digitifera with an EC10 of 2000µg Ni/L and P. daedalea (EC10 > 4610µg Ni/L). Acropora aspera was also the more sensitive species to copper with an EC10 of 5.8µg Cu/L. The EC10 for P. daedalea was 16µg Cu/L, similar to previous studies. This is the first time that the toxicity of nickel on fertilisation success in Acropora species has been reported, and thus provides valuable data that can contribute to the development of reliable water quality guidelines for nickel in tropical marine waters.

First investigation of trace metal distribution in surface seawater and copepods of the south coast of Sfax (Tunisia)

The increased metal loading from anthropogenic sources has affected aquatic ecosystems and has cascaded through food webs worldwide. Therefore, the evaluation of ecological impacts of anthropogenic metal has become increasingly important. In this paper, we monitored the concentration of six trace metals (Cd, Cu, Fe, Ni, Pb, and Zn) in the three copepod groups (cyclopoida, calanoida, and harpacticoida) and in seawater samples collected from the south coast of Sfax (Tunisia). Results showed that the concentration of Fe and Zn for all copepod groups was higher than that for other metals and that of Cd was the lowest in all groups. The mean increase in bioconcentration factor of metals in copepods ranged from 0.05 to 18.93 and followed the sequence Zn (18.93) > Fe (14.34) > Pb (6.41) > Cd (1.53) > Cu (0.10) > Ni (0.05). The copepods in the south coast of Sfax were found to have a great capacity to accumulate trace metals and act as contamination indicators. Comparative studies with those from the Luza zone indicate considerable bioaccumulation of trace metals (Pb and Ni) in all copepod groups namely in cyclopoida.