Trophic Transfer Of Metals Research Articles

Selenium alleviates cadmium and copper toxicity in Gracilaria lemaneiformis (rhodophyta) with contrasting detoxification strategies

Selenium (Se) is a beneficial element for plants, and can be used to mitigate the toxicity of heavy metals. However, the detoxification of Se in macroalgae, a crucial part of aquatic ecosystem productivity, has rarely been reported. In the present study, a red macroalga Gracilaria lemaneiformis was exposed to non-essential metal cadmium (Cd) or essential metal copper (Cu) with addition of different levels of Se. We then examined the changes in growth rate, metal accumulation, metal uptake rate, subcellular distribution, as well as thiol compound induction in this alga. Se addition alleviated Cd/Cu-induced stress in G. lemaneiformis by regulating cellular metal accumulation and intracellular detoxification. Specifically, supplementation of low-level Se displayed a significant decrease in Cd accumulation, and thus alleviated the growth inhibition induced by Cd. This may be caused by the inhibitory effect of endogenous Se instead of exogenous Se on Cd uptake. Although Se addition increased bioaccumulation of Cu in G. lemaneiformis, the important intracellular metal chelators, phytochelatins (PCs), were massively induced to alleviate Cu-induced growth inhibition. High-dose Se addition did not deteriorate but failed to normalize the growth of algae under metal stress conditions. Reduction in Cd accumulation or induction of PCs by Cu could not suppress the toxicity of Se above safe levels. Se addition also altered metal subcellular distribution in G. lemaneiformis, which might affect the subsequent metal trophic transfer. Our results demonstrated that the detoxification strategies of Se between Cd and Cu were different in macroalgae. Elucidating the protective mechanisms of Se against metal stress may help us better apply Se to regulate metal accumulation, toxicity, and transfer in aquatic environment.

The transfer of trace metals in the soil-plant-arthropod system.

Essential and non-essential trace metals are capable of causing toxicity to organisms above a threshold concentration. Extensive research has assessed the behaviour of trace metals in biological and ecological systems, but has typically focused on single organisms within a trophic level and not on multi-trophic transfer through terrestrial food chains. This reinforces the notion of metal toxicity as a closed system, failing to consider one trophic level as a pollution source to another; therefore, obscuring the full extent of ecosystem effects. Given the relatively few studies on trophic transfer of metals, this review has taken a compartment-based approach, where transfer of metals through trophic pathways is considered as a series of linked compartments (soil-plant-arthropod herbivore-arthropod predator). In particular, we consider the mechanisms by which trace metals are taken up by organisms, the forms and transformations that can occur within the organism and the consequences for trace metal availability to the next trophic level. The review focuses on four of the most prevalent metal cations in soil which are labile in terrestrial food chains: Cd, Cu, Zn and Ni. Current knowledge of the processes and mechanisms by which these metals are transformed and moved within and between trophic levels in the soil-plant-arthropod system are evaluated. We demonstrate that the key factors controlling the transfer of trace metals through the soil-plant-arthropod system are the form and location in which the metal occurs in the lower trophic level and the physiological mechanisms of each organism in regulating uptake, transformation, detoxification and transfer. The magnitude of transfer varies considerably depending on the trace metal concerned, as does its toxicity, and we conclude that biomagnification is not a general property of plant-arthropod and arthropod-arthropod systems. To deliver a more holistic assessment of ecosystem toxicity, integrated studies across ecosystem compartments are needed to identify critical pathways that can result in secondary toxicity across terrestrial food-chains.

Trophic transfer of heavy metals in the marine food web based on tissue residuals

Trophic transfer of metals has been well researched in aquatic food webs; however, most studies have examined the presence of metal residuals in the entire body of marine organisms and but not in specific tissues. In this study, we determined the concentrations of Cu, Cr, Pb, Zn, Cd, and Ni in various organs of 17 marine species, including crustaceans, gastropods, bivalves, and fishes, with different trophic levels (TLs), which were collected from the Liaodong Bay, China, in July 2019. Results showed that the liver, gill, and muscle tissues of marine species are ideal indicators for analyzing Cu, Cr, Pb, Zn, Cd, and Ni contamination in marine environments. When the entire bodies of these marine species were considered, a bio-dilution in Cu, Cr, Pb, Zn, Cd, and Ni was observed in the studied food web. In contrast, the metal tissue-specific bio-magnification in the entire studied food web showed different results. In the liver and gill tissues, negative correlations were found between the concentrations of cadmium and TLs, while copper bio-dilution was also observed in gill tissue. In the muscle tissues, Cu, Pb, and Ni showed bio-dilution and trophic magnification factors of Cu, Pb, and Ni ranged from 0.44 to 0.73. This study highlights the importance of tissue-specific considerations to obtain further accurate information on metal trophodynamics and trophic transfers in marine food webs, thereby enhancing the risk assessment of many elements in wildlife and human health.

Trophic transfer of metals in a seagrass food web: Bioaccumulation of essential and non-essential metals

Metal concentrations are reported for a seagrass ecosystem receiving industrial inputs. δ13C and δ15N isotope ratios were used to establish trophic links. Copper concentrations (dry mass) ranged from <0.01 μg/g in fish species to 570 μg/g (μ = 49 ± SD = 90 μg/g) in the oyster Saccostrea glomerata. Zinc concentrations ranged from 0.6 μg/g in the seagrass Zostera capricorni to 10,800 μg/g in the mud oyster Ostrea angasi (μ = 434 ± 1390 μg/g). Cadmium concentrations ranged from <0.01 μg/g in fish species to 268 μg/g in Ostrea angasi (μ = 6 ± 25 μg/g). Lead concentrations ranged from <0.01 μg/g for most fish species to 20 μg/g in polychaetes (μ = 2 ± 3 μg/g). Biomagnification of metals did not occur. Organisms that fed on particulate organic matter and benthic microalgae had higher metal concentrations than those that fed on detritus. Species physiology also played an important role in the bioaccumulation of metals.

Trace Metals Bioavailability Approach in Intertidal Estuarine Sediments and Bioaccumulation in Associated Nereidid Polychaetes.

Polychaetes that inhabit the sediments of estuaries are important prey to many species all around the world. Laeonereis acuta is a deposit feeder living in estuaries along the Atlantic coast of South America. Ragworms accumulate metals from the sediment, and represent a means of entry of sediment contaminants into the trophic network. The concentrations of Zn, Pb, Cu, Cr and Cd were determined in polychaetes and sediments (total and extractable) from six estuarine beaches of Río de la Plata. The associations between total and extractable concentrations in sediment and accumulated concentrations in L. acuta were analyzed. Sediments extracted by weak acid digestion appear to be a good proxy model of bioavailable metal fractions in the sediment. The association between metals in sediment and polychaetes denotes the role of L. acuta as an important link in metal trophic transfer from sediments to potential fish and bird predators of the worm.

Bioaccumulation and trophic transfer of metals, As and Se through a freshwater food web affected by antrophic pollution in Córdoba, Argentina

The concentration of metals (Al, Cr, Mn, Fe, Ni, Cu, Zn, Ag, Cd, Hg, Pb, U), As and Se in different ecosystem components (water, sediment, plankton, shrimp, and fish muscle) has been determined in a eutrophic reservoir in the Province of Córdoba (Argentina). Los Molinos Lake (LML) was sampled during the dry (DS) and wet seasons (WS) in order to examine the bioaccumulation and transfer of these inorganic elements through the food web. Stable nitrogen isotope (δ15N) was used to investigate trophic interactions. According to this, samples were divided into three categories: plankton, shrimp (Palaemonetes argentinus) and fish (Silverside, Odontesthes bonariensis). The bioaccumulation factor (BAF) was calculated for the organisms, and it was determined that the elements analyzed undergo bioaccumulation, especially in organisms such as plankton. The invertebrates were characterized by the highest BAF for Cu and Zn in both seasons, As (DS), and Cd and Hg (WS). The fish muscle was characterized by the highest BAF for Se (WS), Ag and Hg (DS). On the other hand, a significant decrease in Al, Cr, Mn, Fe, Ni, Cu, Zn, As, Se, Cd and U concentrations through the analyzed trophic web during both seasons was observed. Moreover, a significant increase in Hg levels was observed with increasing trophic levels in the DS, indicating its biomagnification.Despite the increasing impact of metals, As and Se pollution in the studied area due to urban growth and agricultural and livestock activities, no previous study has focused on the behavior and relationships of these pollutants with the biotic and abiotic components of this aquatic reservoir. We expect that these findings may be used for providing directions or guidance for future monitoring and environmental protection policies.

Investigations of temperature and pH variations on metal trophic transfer in turbot (Scophthalmus maximus).

Studying dietary metal transfer kinetics is essential to gain a better understanding in global metal accumulation rates and its impacts in marine fish. While there exists a solid understanding on the influence of various biotic factors on this transfer, metal assimilation in fish might be also affected by abiotic factors, as has been observed in marine invertebrates. The present study therefore aims to understand the potential effects of two climate-related master variables, temperature and pH, on the assimilation efficiency (AE) of essential (Co and Zn) and non-essential (Ag) metals in the turbot Scophthalmus maximus using radiotracer tools. Juvenile turbots were acclimated for 8weeks at two temperatures (17 and 20°C) and pH (7.5 and 8.0) regimes, under controlled laboratory conditions, and then fed with radiolabelled shrimp (57Co, 65Zn and 110mAg). Assimilation efficiencies of Co and Ag in juvenile turbot, determined after a 21-day depuration period, were not affected by pre-exposition to the different environmental conditions. In contrast, temperature did significantly influence Zn AE (p<0.05), while pH variations did not affect the assimilation of any of the metals studied. In fact, temperature is known to affect gut physiology, specifically the membrane properties of anterior intestine cells where Zn is adsorbed and assimilated from the ingested food. These results are relevant to accurately assess the influence of abiotic factors in AEs of metals in fish as they are highly element-dependent and also modulated by metabolic processes.

Interactive effects of metal pollution and ocean acidification on physiology of marine organisms

Abstract Changes in the global environment such as ocean acidification (OA) may interact with anthropogenic pollutants including trace metals threatening the integrity of marine ecosystems. We analyze recent studies on the interactive effects of OA and trace metals on marine organisms with a focus on the physiological basis of these interactions. Our analysis shows that the responses to elevated CO2 and metals are strongly dependent on the species, developmental stage, metal biochemistry and the degree of environmental hypercapnia, and cannot be directly predicted from the CO2-induced changes in metal solubility and speciation. The key physiological functions affected by both the OA and trace metal exposures involve acid-base regulation, protein turnover and mitochondrial bioenergetics, reflecting the sensitivity of the underlying molecular and cellular pathways to CO2and metals. Physiological interactions between elevated CO2 and metals may impact the organisms’ capacity to maintain acid-base homeostasis and reduce the amount of energy available for fitness-related functions such as growth, development and reproduction thereby affecting survival and performance of estuarine populations. Environmental hypercapnia may also affect the marine food webs by altering predator-prey interactions and the trophic transfer of metals in the food chain. However, our understanding of the degree to which these effects can impact the function and integrity of marine ecosystems is limited due the scarcity of the published research and its bias towards certain taxonomic groups. Future research priorities should include studies of metal x PCO2 interactions focusing on critical physiological functions (including acid-base, protein and energy homeostasis) in a greater range of ecologically and economically important marine species, as well as including the field populations naturally exposed (and potentially adapted) to different levels of metals and CO2 in their environments.

Internal distribution of Cd in lettuce and resulting effects on Cd trophic transfer to the snail: Achatina fulica

The mechanisms underlying Cd trophic transfer along the soil–lettuce–snail food chain were investigated. The fate of Cd within cells, revealed by assessment of Cd chemical forms and of subcellular partitioning, differed between the two examined lettuce species that we examined (L. longifolia and L. crispa). The species-specific internal Cd fate not only influenced Cd burdens in lettuce, with higher Cd levels in L. crispa, but also affected Cd transfer efficiency to the consumer snail (Achatina fulica). Especially, the incorporation of Cd chemical forms (Cd in the inorganic, water-soluble and pectates and protein-integrated forms) in lettuce could best explain Cd trophic transfer, when compared to dietary Cd levels alone and/or subcellular Cd partitioning. Trophically available metal on the subcellular partitioning base failed to shed light on Cd transfer in this study. After 28-d of exposure, most Cd was trapped in the viscera of Achatina fulica, and cadmium bio-magnification was noted in the snails, as the transfer factor of lettuce-to-snail soft tissue was larger than one. This study provides a first step to apply a chemical speciation approach to dictate the trophic bioavailability of Cd through the soil–plant–snail system, which might be an important pre-requisite for mechanistic understanding of metal trophic transfer.

Effects of metal burden and food avoidance on the transfer of metals from naturally contaminated prey to a marine predator Nassarius siquijorensis

Nassarid snails are important opportunistic scavengers widely found in marine intertidal shores and trophic transfer is a predominant source of metal accumulation in these species, thus there is a significant need to understand the controls of metal trophic transfer. In the present study, we took advantage of a severely contaminated estuary and collected two prey organisms (oysters Crassostrea angulata and barnacles Fistulobalanus albicostatus) with different contamination histories. These naturally contaminated prey were fed to a marine neogastropod Nassarius siquijorensis for a period of up to 7 weeks. We then investigated the influences of prey type, metal burden, and subcellular distribution in the prey on the metal accumulation, trophic transfer, and potential toxicity on N. siquijorensis. We demonstrated an obvious negative relationship between the trophic transfer and the metal concentration in prey or the metal dosage. N. siquijorensis exhibited food avoidance behavior to the Cu contaminated food, which effectively reduced the metal ingestion and resulted in a decrease of trophic transfer, as well as a potential toxic effect from dietary exposure. On the other hand, our results also implied the metal-specific impact of subcellular metal distribution in prey on the trophic transfer to N. siquijorensis. Our study suggested that metal burden and feeding avoidance should be considered in studying the trophic transfer of metals in marine benthic food chain.

Examining waterborne and dietborne routes of exposure and their contribution to biological response patterns in fathead minnow ( Pimephales promelas)

The objectives of the current study were: (i) to gain a better understanding of the relative importance of water and diet as routes of exposure causing toxicity in fathead minnow (FHM) exposed to metal mining effluents (MME) using a full factorial water/food experimental design (Experiment 1), and (ii) to assess differences in the effects of food quality on toxicity by comparing FHM fed both a live and frozen diet of Chironomus dilutus (Experiment 2). The results showed significant increases in general water quality parameters (e.g., hardness, conductivity) and various metals in the effluent treatment waters compared to control waters, with maximum increase seen in the multi-trophic streams. Metals accumulation (Rb, Al, Se, Sr, Tl, Ce, Co, Cu, Pb) effects of both waterborne and multi-trophic exposures were significant in one or more fathead minnow tissue type (muscle, gonads, liver, larvae) relative to those in the control systems. Condition factor and liver somatic index (LSI) of FHM were also significantly affected in both exposures by one or both routes of exposure (water and/or diet). In addition, cumulative total egg production and cumulative spawning events were significantly affected by both waterborne and dietborne exposures, with maximum effect found in the multi-trophic streams. These results suggest that under environmentally relevant exposure conditions, trophic transfer of metals may lead to greater reproductive effects and increased metal toxicity in fish. It also indicates that metals are assimilated in tissues differently depending on the quality of the food (live vs. frozen). Overall, it appears that the multi-trophic bioassay provides an important link between the laboratory and field, which may allow for a more realistic assessment of the true impact of MME's in the environment.

Subcellular compartmentalization of cadmium, nickel, and lead in Gammarus fossarum: Comparison of methods

Knowledge of the subcellular behavior of toxicants, mainly metals, in living organisms is fundamental for understanding their toxicological consequences at individual and trans-generation levels and throughout the food web. However, different partitioning methodologies are available in the literature, particularly concerning the cytosolic fraction. Different cytosolic compounds, metallothionein-like proteins (MTLPs), and non-metallothionein-like proteins (non-MTLPs) could be separated by size exclusion chromatography or by heat treatment and centrifugation. Our results show changes of metal partitioning in the cytosolic fraction according to the methodologies used. After heat treatment, the majority of cytosolic cadmium (Cd) was found with MTLPs compounds and the opposite results were observed with size exclusion chromatography. Metal partitioning could also play an important role in the metal trophic transfer. Therefore, metal partitioning in Gammarus fossarum, an ecologically relevant species and good metal bioaccumulator, defining the trophically available metal fraction, is also discussed.

Relevance of intracellular partitioning of metals in prey to differential metal bioaccumulation among populations of mummichogs ( Fundulus heteroclitus)

Intracellular partitioning of trace metals is critical to metal tolerance in aquatic organisms and may also influence metal trophic transfer in ecosystems. In this study, we tested the relevance of metal (Cd, Cu, Pb, and Zn) intracellular partitioning in prey as an indicator of metal trophic availability to benthic forage fish, mummichogs ( Fundulus heteroclitus), in chronically metal-polluted salt marshes in New York, USA. Two common prey of mummichogs in the study area, Palaemonetes pugio and Nereis acuminata, generally stored increasingly higher proportions of non-essential metals (particularly Pb) in insoluble (less trophically available) cellular components, as the whole body burdens increased. In contrast, intracellular partitioning of essential metals (Cu and Zn) in invertebrate prey varied relatively little among sites. Differential Cd and Pb intracellular partitioning patterns within P. pugio among sites were significantly associated with Cd and Pb whole body burdens in mummichogs, respectively (i.e., prey-driven bioreduction of metals), while bioaccumulation of Cu and Zn in mummichogs was similar among populations. The findings in this study suggest that metal intracellular partitioning within prey may be partially responsible for metal trophic availability to a predator in metal-polluted habitats, while there was also evidence that some predator-dependent processes may offset differential trophic availabilities from prey.

Bioaccumulation of silver, cadmium and mercury in the abalone Haliotis diversicolor from water and food sources

Most abalone farms in China are confronted with increasing pollution, including metal pollution. Macroalgae such as Gracilaria, widely used as abalone forage, can very appreciably concentrate metals, thus there is an increasing concern for metal trophic transfer in abalones. The route and rate of Ag, Cd and Hg uptake in the abalone Haliotis diversicolor were quantified by determining each metal's uptake rate from the dissolved phase, its assimilation efficiency (AE) from different macroalgae and its efflux rate constant. The uptake rate constants in abalones from the dissolved phase were 1.78 L g − 1 d − 1 for Ag, 0.056 L g − 1 d − 1 for Cd and 0.32 L g − 1 d − 1 for Hg. The corresponding AEs were 58–83%, 33–59%, and 65–78%. The AEs of Ag and Hg decreased significantly with increasing metal concentration in the ingested macroalgae, which may be caused by the decreasing desorption of metals in the gut. The AEs for Cd varied little when the Cd concentration in the diet varied. The efflux rate constants were 0.003 d − 1 for Ag, and 0.010–0.011 d − 1 for Cd and Hg, respectively, and were comparable following uptake from water and food. The low efflux rate of Ag was mainly due to its binding with metal-rich granules and cellular debris. Modeling calculations suggest that, under typical conditions, dietary uptake is the dominant route for Ag, Cd and Hg accumulation in abalones. The trophic transfer factors for all three metals were greater than one, implying a potential for biomagnification due to their high dietary assimilation. These results suggest that metals in abalones can be a food safety issue due to the potential for trophic transfer from macroalgae.

Biodilution of heavy metals in a stream macroinvertebrate food web: Evidence from stable isotope analysis

Analysis of carbon (δ13C) and nitrogen (δ15N) stable isotopes provides an increasingly important means of understanding the complex trophic structure of macroinvertebrate communities in streams. We coupled a stable isotope approach with a contaminant analysis of six metals (Pb, Ag, Zn, Hg, Cu, As) to trace the accumulation and dilution of metals from an abandoned mine across trophic levels of the benthic community in Ginzan Creek, Japan. The δ15N signature increased with trophic level, with mean increases of 4.70‰ from producers to primary consumers and 3.06‰ from primary to secondary consumers. Tissue Pb and Ag concentrations were negatively correlated with δ15N, indicating biodilution of both metals through the food web. Although macroinvertebrate taxon body mass was negatively correlated with tissue metal concentration at several sites, it did not increase with trophic level (as δ15N) in any of the sites, suggesting that changes in body mass were not the cause of biodilution. Our findings suggest invertebrates at higher trophic levels may exhibit increasingly efficient excretion of metals. Autotrophic epilithon (mean δ13C=−21.3‰) had a much higher concentration of mined metals than did riparian vegetation (mean δ13C=−29.3‰); nonetheless, a carbon-mixing model indicated that taxa feeding on autochthonous carbon sources did not accumulate more metal than allochthonous feeders. It is likely that the notably high metal concentration of allochthonous FPOM plays an important role in the trophic transfer of metals. Our data suggest the strong potential for stable isotope analysis to enhance our understanding of metal transfer through stream macroinvertebrate food webs.

Cadmium uptake by the European eel: Trophic transfer in field and experimental investigations

Due to its status of threatened species and being heavily contaminated by metals, the European eel ( Anguilla anguilla) was selected to investigate cadmium contamination levels of fish settled along a historically cadmium-contaminated hydrosystem, the Garonne–Gironde continuum (France), according to its various location sites and fish length. Results have shown an important site effect on cadmium concentrations in liver but not in gills, highlighting the possible predominance of the trophic exposure route. Subsequently, uncontaminated eels were experimentally exposed to cadmium by water uptake and/or trophic route(s). Eels were fed with different preys: white shrimps collected in an unpolluted area in the Gironde estuary, and cadmium-enriched shrimps. Data obtained tend to show that the use of cadmium-enriched food during experimental investigations triggers an underestimation of the metal trophic transfer rate. These two complementary approaches provide some elements to suggest that the trophic route plays an important role in cadmium contamination of wild eels.

Cadmium biodynamics in the oligochaete Lumbriculus variegatus and its implications for trophic transfer

It has become increasingly apparent that diet can be a major source of trace metal bioaccumulation in aquatic organisms. In this study, we examined cadmium uptake, efflux, and subcellular compartmentalization dynamics in the freshwater oligochaete Lumbriculus variegatus. L. variegatus is an important component of freshwater food webs in Europe and North America and is potentially useful as a standard food source for laboratory-based trophic transfer studies. Cadmium accumulation and depuration were each followed for 10 days. Rate constants of uptake ( k u) and efflux ( k e) were estimated and subcellular Cd compartmentalization was followed over the course of uptake and efflux. The partitioning of Cd into operationally-defined subcellular compartments was relatively consistent throughout the 20-day experiment, with the majority of Cd accumulating in the cytosol. No major changes in Cd compartmentalization were observed over uptake or depuration, but there appeared to be some exchange between heat-stable and heat-labile cytosolic protein fractions. Cadmium accumulation from solution was strongly affected by ambient calcium concentrations, suggesting competition between Cd and Ca for uptake sites. Finally, we demonstrate the ability to manipulate the whole body calcium content of L. variegatus as a potential tool for examining calcium influences on dietary Cd dynamics. The potential for this species to be an important conduit of Cd to higher trophic levels is discussed, along with its potential as a standardized food source in metal trophic transfer studies.

Transfer and efflux of cadmium and silver in marine snails and fish fed pre‐exposed mussel prey

Subcellular metal distribution may play an important role in the bioaccumulation and trophic transfer of metals in marine food chains. In the present study, we preexposed the green mussel Perna viridis to Ag and Cd and quantified their trophic transfer efficiencies to two predators (whelks [Thais clavigera] and fish [Terapon jarbua]). For the mussels, more Ag was distributed in the metal-rich granule (MRG) fraction following Ag exposure, and more Cd was distributed in the metallothionein-like protein following Cd exposure. In addition, Cd was mainly bound with the proteins having a molecular size of approximately 20 kDa. After being fed with metal-exposed mussels, the assimilation efficiencies of Ag decreased significantly (from 77 to 29-60% in whelks and from 9 to 2% in fish) with an increasing percentage of Ag deposited in the MRG fraction of the prey. In contrast, the assimilation efficiencies of Cd remained comparable (81-85% in whelks and 6-8% in fish), because its partitioning in the soluble fraction of different treatments of the prey was similar. The efflux of Ag and Cd in the two predators was comparable after feeding on preexposed mussel prey. Our results imply that the subcellular distribution of metals in prey may affect the dietary assimilation of metals in predators, but such influence is clearly metal-specific. The present study may lead to a better understanding of metal trophic transfer in different marine food chains.

Metal trophic transfer from algae to cladocerans and the relative importance of dietary metal exposure

We initially investigated effects and uptake of cadmium and copper on Pseudokirchneriella subcapitata (primary producer; formerly known as Selenastrum capricornutum). Our major efforts focused on the effects of metal-laden (i.e., Cd, Cu) P. subcapitata when used to provide dietary metal exposure to Ceriodaphnia dubia (primary consumer). Major test endpoints included feeding rate, survival, and reproduction. Metal body burden in C. dubia increased dose dependently at dietary exposure concentrations of 0.6 microg/g algal dry weight or less for cadmium and 74.7 microg/g algal dry weight or less for copper. However, it decreased sharply when dietary concentrations exceeded 0.6 microg/g algal dry weight for cadmium and 74.7 microg/g algal dry weight copper. Both dietary cadmium and copper affected all the major test endpoints. Whereas reproduction was observed to be the most sensitive endpoint, survival was observed to be the least sensitive endpoint. These results demonstrated the potential importance of dietary exposure for consideration in metal regulations or risk assessment.

Interspecific variation in heavy metal body concentrations in biota of Sunderban mangrove wetland, northeast India

The coastal environment of West Bengal, recognized as the most diversified and productive ecosystem among all the maritime states of India, faces organic pollution from domestic sewage and urban and industrial effluents leading serious impacts on biota. The present paper aims at providing information on concentration level of heavy metals among the tissues of benthic polychaetes, bivalve molluscs and finfishes collected from Sundarban mangrove wetland, northeast coast of India. An overall common trend in bioaccumulation was revealed with the following decreasing order: Zn>Mn>Cu>Cr>Se>Hg with few exceptions. Both species dependent variability and temporal variations were pronounced. A high degree of organ specificity was evident in the bivalves where gill and mantle exhibited higher metal accumulation due to ion exchange property of the mucous layer covering these organs. Variability between closely related species is a reflection of different uptake rates, physiology and impact of environmental factors. The results of this analysis suggest that mollusks can play a significant role in trace metal trophic transfer studies, especially as their representatives are intertidally and subtidally ubiquitous.