A biomarker of contaminant exposure is effective in large scale assessment of ten estuaries

Quantification and characterization of microplastics ingested by mangrove oysters across West Africa

Microplastic ingestion by marine organisms presents a challenge to both ecosystem functioning and human health. We characterized microplastic abundance, shape, size, and polymer types ingested by the West African mangrove oyster, Crassostrea tulipa (Lamarck, 1819) sampled from estuaries and lagoons from the Gambia, Sierra Leone, Ghana, Benin, and Nigeria using optical microscopy and Fourier transform infrared (FTIR) techniques. A total of 780 microplastics were isolated in the whole tissues of the 250 oysters (n = 50 oysters per country). The abundance and distribution of microplastics in the oysters followed the pattern: the Gambia > Ghana > Sierra Leone > Nigeria > Benin. The Tanbi wetlands in the Gambia recorded the highest average of 10.50 ± 6.69 per oyster while the Ouidah lagoon in Benin recorded the lowest average of 1.80 ± 1.90 per oyster. Overall, microplastic numbers varied significantly (p < 0.05) among the five countries. Microfibers, particularly those within 1001-5000 μm size, dominated the total microplastic count with a few fragments and films. No spherical microplastics were isolated in the oysters. In the Sierra Leone and Benin oysters, fragments and films were absent in the samples. Microplastic between the 1001 and 5000 μm size class dominated the counts, followed by 501-1000 μm, 101-500 μm, and 51-100 μm. Five polymer groups namely polyethylene, polyester, nylon, polypropylene, and polyamide were identified across the five countries, with polyethylene occurring in oysters from all five countries and polyester occurring in all but the oysters from Nigeria. This diversity of polymers suggests varied sources of microplastics ingested by the studied oysters. The absence of microspheres across the five supports findings from other studies that they are the least ingested and highly egested by the oysters.

The distribution of metal and petroleum-derived contaminants within sediments around oil and gas infrastructure in the Gippsland Basin, Australia

As oil and gas infrastructure comes to the end of its working life, a decommissioning decision must be made: should the infrastructure be abandoned in situ, repurposed, partially removed, or fully removed? Environmental contaminants around oil and gas infrastructure could influence these decisions because contaminants in sediments could degrade the value of the infrastructure as habitat, enter the seafood supply if the area is re-opened for commercial and/or recreational fishing, or be made biologically available as sediment is resuspended when the structures are moved. An initial risk hypothesis, however, may postulate that these concerns are only relevant if contaminant concentrations are above screening values that predict the possibility of environmental harm or contaminant bioaccumulation. To determine whether a substantive contaminants-based risk assessment is needed for infrastructure in the Gippsland Basin (South-eastern Australia), we measured the concentration of metals and polycyclic aromatic hydrocarbons (PAHs) in benthic sediments collected around eight platforms earmarked for decommissioning. The measurements were compared to preset screening values and to background contaminant concentrations in reference sites. Lead (Pb), zinc (Zn), PAHs and other contaminants were occasionally measured at concentrations that exceeded reference values, most often within 150 m of the platforms. The exceedance of a few screening values by contaminants at some platforms indicates that these platforms require further analysis to determine the contaminant risks associated with any decommissioning option.

Contaminant pulse following wildfire is associated with shifts in estuarine benthic communities

Novel combinations of climatic conditions due to climate change and prolonged fire seasons have contributed to an increased occurrence of "megafires". Such large-scale fires pose an unknown threat to biodiversity due to the increased extent and severity of burn. Assessments of wildfires often focus on terrestrial ecosystems and effects on aquatic habitats are less documented, particularly in coastal environments. In a novel application of eDNA techniques, we assessed the impacts of the 2019-2020 Australian wildfires on the diversity of estuarine benthic sediment communities in six estuaries in NSW, Australia, before and after the fires. Estuaries differed in area of catchment burnt (0-92%) and amount of vegetative buffer that remained post-fire between burnt areas and waterways. We found greater dissimilarities in the composition and abundance of eukaryotic and bacterial sediment communities in estuaries from burnt catchments with no buffer compared to those with an intact buffer or from unburnt catchments. Shifts in composition in highly burnt catchments were associated with increased concentrations of nutrients, carbon, including fire-derived pyrogenic carbon, and copper, which was representative of multiple highly correlated trace metals. Changes in the relative abundances of certain taxonomic groups, such as sulfate-reducing and nitrifying bacterial groups, in the most impacted estuaries indicate potential consequences for the functioning of sediment communities. These results provide a unique demonstration of the use of eDNA to identify wildfire impacts on ecological communities and emphasize the importance of vegetative buffers in limiting wildfire-associated impacts.

Microplastic in oysters: A review of global trends and comparison to southern Australia

Microplastics have been documented in a plethora of marine environments and organisms. These small plastics threaten ecosystem health, with implications for seafood species' health. Oysters are an important cultural and economic aquaculture species globally. Due to their filter feeding mechanisms, they can act as an indicator species and proxy for environmental contamination. This makes them an ideal organism for investigating microplastic pollution. Here, we first systematically reviewed the global literature investigating microplastic in oysters. Globally, 94.4% of all oysters had microplastics, with an average of 1.41 ± 0.33 per gram of soft tissue wet weight (gww). The review showed that wild-caught oysters contained more than double the amount of microplastic than aquaculture raised specimens, likely reflecting the clean and productive waters in which oyster aquaculture systems are commonly located. Second, we quantified microplastic presence and polymer type in commercially farmed oysters (Crassostrea gigas and Saccostrea glomerata) across a broad spatial scale, covering eight sites in southern Australia. Microplastics were present in 49.4% of all sampled oysters, with specimens from all locations containing microplastics. On average, whole oysters contained 0.83 ± 0.08 microplastics per individual or 0.09 ± 0.01 microplastics gww. Using Fourier-Transform Infrared Spectroscopy, we identified that 62% of the verified microplastics were vexar plastic netting, a low-density polyethylene commonly used in aquaculture production. Understanding the abundance and source of microplastic in these key seafood species is essential to determine if oysters are vulnerable to these contaminants and pose a risk to the oyster aquaculture industry as an important food resource.

Toxicological effects of tris(1,3-dichloro-2-propyl) phosphate in oyster Crassostrea gigas using proteomic and phosphoproteomic analyses

As a typical organophosphorus pollutant, tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) has been widely detected in aquatic environment. Previous studies showed that protein phosphorylation might be a vital way of TDCIPP to exert multiple toxic effects. However, there is a lack of high-throughput investigations on how TDCIPP affected protein phosphorylation. In this study, the toxicological effects of TDCIPP were explored by proteomic and phosphoproteomic analyses together with traditional means in oysters Crassostrea gigas treated with 0.5, 5 and 50 μg/L TDCIPP for 28 days. Integration of omic analyses revealed that TDCIPP dysregulated transcription, energy metabolism, and apoptosis and cell proliferation by either directly phosphorylating pivotal proteins or phosphorylating their upstream signaling pathways. The U-shaped response of acetylcholinesterase activities suggested the neurotoxicity of TDCIPP in a hormesis manner. What's more, the increase in caspase-9 activity as well as the expression or phosphorylation alterations in eukaryotic translation initiation factor 4E, cell division control protein 42 and transforming growth factor-β1-induced protein indicated the disruption of homeostasis between apoptosis and cell proliferation, which was consistent with the observation of shedding of digestive cells. Overall, combination of proteomic and phosphoproteomic analyses showed the capability of identifying molecular events, which provided new insights into the toxicological mechanisms of TDCIPP.

Establishing Baseline Assessment Levels for Monitoring Coastal Heavy Metals Using Foraminiferal Shells: A Case Study from the Southeastern Mediterranean

One of the challenges in monitoring the marine coastal environments is quantifying the magnitude and duration of pollution events. This study introduces a new concept of defining heavy metal (HM) baseline assessment levels (BALs) in coastal environments using foraminiferal shells. We demonstrated the potential of this approach by examining a nature reserve along the Mediterranean coast of Israel. Our previous investigation of this site in 2013–2014 using foraminiferal single-chamber LA-ICPMS created a large dataset consisting of HM measurements of two species, Lachlanella and Pararotalia calcariformata. This database was used to establish the BAL of Zn, Cu and Pb, associated with anthropogenic sources. In February 2021, a significant tar pollution event affected the entire Mediterranean coast of Israel, derived from an offshore oil spill. This event provided a unique opportunity to test the applicability of the foraminiferal BAL by comparing it to whole-shell ICPMS measurements of the two species collected in winter and summer 2021. Results reveal a significant increase (2–34-fold) in the three HMs between 2013–2014 and 2021, with Pb/Ca displaying the most prominent increase in both species. This suggests a possible linkage between the oil spill event and the significantly elevated metal/Ca ratios in 2021.

Tracking the impacts of nutrient inputs on estuary ecosystem function

Estuaries are one of the most impacted coastal environments globally, subjected to multiple stressors from urban, industry and coastal development. With increasing anthropogenic activity surrounding estuarine systems, sewage inputs have become a common concern. Stable isotope analysis provides a well-established tool to investigate the incorporation of nitrogen into marine organisms and identify major nutrient sources. Benthic macroinvertebrate communities are often used as bioindicators in ecological studies as they typically display predictable responses to anthropogenic pressures, however have a suite of limitations and costs associated with their use. 16S rDNA amplicon sequencing techniques allow for investigation of the microbial communities inhabiting complex environmental samples, with potential as a tool in the ecological assessment of pollution. These communities have not yet been adequately considered for ecological studies and biomonitoring, with a need to better understand interactions with environmental stressors and implications for ecosystem function. This study used a combination of stable isotope analysis to trace the uptake of anthropogenic nitrogen in biota, traditional assessment of benthic macroinvertebrate communities, and 16S rDNA genotyping of benthic microbial communities. Stable isotope analysis of seagrass and epiphytes identified multiple treated and untreated sewage inputs, ranges of 5.2-7.2‰ and 1.9-4.0‰ for δ¹⁵N respectively, as the dominant nitrogen source at specific locations. The benthic macroinvertebrate community reflected these inputs with shifts in dominant taxa and high abundances of polychaetes at some sites. Microbial communities provided a sensitive indication of impact with a breadth of information not available using traditional techniques. Composition and predicted function reflected sewage inputs, particularly within sediments, with the relative abundance of specific taxa and putative pathogens linked to these inputs. This research supports the growing body of evidence that benthic microbial communities respond rapidly to anthropogenic stressors and have potential as a monitoring tool in urban estuarine systems.

Light-trapped caddisflies to decipher the role of species traits and habitats in Hg accumulation and transfer

We present a novel meta-community approach to explore the influence of species traits, such as adult body size, larval feeding type and microhabitat, as well as larval macrohabitat (main river channel vs. floodplain water bodies) on the concentration of total Hg accumulated ([THg]) in assemblages of adult caddisflies. We analyzed [THg] in 157 light-trapped adult caddisflies in a floodplain sector of the French upper Rhône River and used a linear mixed effect model to decipher the role of species traits and habitats in Hg accumulation. Variation of [THg] between species was best explained by the larval feeding type, whereas the contributions of adult size and larval micro and macro-habitat were minor. Results showed that [THg] in species associated with floodplain macrohabitats in the larval stage was lower than in those associated with the main river channel. This difference could depend on complexation of Hg by DOM (in the floodplain) and MES (in the main channel). This research provides a first evidence of the potential of an entire caddisfly assemblage for the assessment of contamination in large alluvial rivers. The implications of the results are discussed in view of the possible role of caddisflies as vectors of Hg to riparian predators.

Microplastic contamination in Indian edible mussels (Perna perna and Perna viridis) and their environs

This study investigated the microplastic (MPs) contamination of the mussels, P. viridis and P. perna of different sizes, and their environment viz. water and sediment. MPs were recovered from the soft tissues of both species. The mean abundance of MPs ranges from 0.87 ± 0.55 to 10.02 ± 4.15 items/individual; 0.1 ± 0.03 to 2.05 ± 0.33 items/g; 31.57 ± 7.63 to 59.25 ± 14.32 items/l in water, and 79.54 ± 18.66 to 108 ± 40.36 items/kg in sediment. Smaller mussels (3-6 cm) are capable of ingesting higher quantities of MPs per gram of tissue weight, and the rate of MP uptake decreases when the mussels grow in size. These might be due to the faster filtration rate in smaller mussels. MPs of fiber type and blue color in the size range of 500 μm to 1 mm are predominant in mussels. Eleven different polymeric groups were identified, of which PE is the most common, followed by PP. The distribution patterns of MP abundance, shape, size, color, and polymer in mussels more closely resemble those in water. There is no significant difference in MP quantities between P. perna and P. viridis (p > 0.05). FTIR-ATR spectroscopy and SEM analysis show that most of the MPs have been strongly weathered. EDAX analysis detects heavy metals like As, Ni, Fe, Zn, and Cd associated with MPs. This study shows that the MPs contents of both the mussel species are transferred from seawater to their edible meat. This study again proved that mussels can act as bio indicator of MPs pollution.

Quantitative and qualitative determination of microplastics in oyster, seawater and sediment from the coastal areas in Zhuhai, China

Microplastics as a new class of environmental contaminants have become the hot issue of global concern. We conducted quantitative and qualitative experiments to investigate microplastics in oyster, seawater and sediment along the Zhuhai coastline. The soft tissues of oysters were digested with potassium hydroxide (10%) and hydrogen peroxide (30%), seawaters and sediments with hydrogen peroxide (30%) to degrade organic matter, and analyzed using a digital camera, optical microscopy and micro-ATR-FTIR. The abundance of microplastics were in the range of 0.14-7.90 n/g in oysters (wet weight), 10.00-27.50 n/L in seawaters and 0.053-0.26 n/g in sediments. The fiber and fragment shape, black color, 101-500 μm of size and polyethylene composition were all classified as the major constituents of microplastics. The level of contaminants in oysters was correlated to those in their surrounding environments. Therefore, oysters may serve as a promising sentinel species for the indication of microplastic pollution in the coastal zone of Zhuhai.

Making seawalls multifunctional: The positive effects of seeded bivalves and habitat structure on species diversity and filtration rates

The marine environment is being increasingly modified by the construction of artificial structures, the impacts of which may be mitigated through eco-engineering. To date, eco-engineering has predominantly aimed to increase biodiversity, but enhancing other ecological functions is arguably of equal importance for artificial structures. Here, we manipulated complexity through habitat structure (flat, and 2.5 cm, 5 cm deep vertical and 5 cm deep horizontal crevices) and seeding with the native oyster (Saccostrea glomerata, unseeded and seeded) on concrete tiles (0.25 m × 0.25 m) affixed to seawalls to investigate whether complexity (both orientation and depth of crevices) influences particle removal rates by suspension feeders and colonisation by different functional groups, and whether there are any ecological trade-offs between these functions. After 12 months, complex seeded tiles generally supported a greater abundance of suspension feeding taxa and had higher particle removal rates than flat tiles or unseeded tiles. The richness and diversity of taxa also increased with complexity. The effect of seeding was, however, generally weaker on tiles with complex habitat structure. However, the orientation of habitat complexity and the depth of the crevices did not influence particle removal rates or colonising taxa. Colonisation by non-native taxa was low compared to total taxa richness. We did not detect negative ecological trade-offs between increased particle removal rates and diversity and abundance of key functional groups. Our results suggest that the addition of complexity to marine artificial structures could potentially be used to enhance both biodiversity and particle removal rates. Consequently, complexity should be incorporated into future eco-engineering projects to provide a range of ecological functions in urbanised estuaries.

Sublethal effects of contaminants on marine habitat-forming species: a review and meta-analysis

Contaminants may affect ecosystem functioning by reducing the fitness of organisms and these impacts may cascade through ecosystems, particularly if the sensitive organisms are also habitat-forming species. Understanding how sub-lethal effects of toxicants can affect the quality and functions of biogenic habitats is critical if we are to establish effective guidelines for protecting ecosystems. We carried out a global systematic review and meta-analysis critically evaluating contaminant effects on properties of habitat-formers linked to ecosystem functioning. We reviewed a total of 95 publications. However, 40% of publications initially captured by the literature search were identified as having flaws in experimental design and ~11% did not present results in an appropriate way and thus were excluded from the quantitative meta-analysis. We quantitatively reviewed 410 studies from 46 publications, of which 313 (~76%) were on plants and seaweeds, that is macro-algae, saltmarsh plants and seagrasses, 58 (~14%) studied corals and 39 (~10%) looked at toxicant impacts on bivalves, with 70% of those on mussels and the remaining studies on oysters. Response variables analysed were photosynthetic efficiency, amount of chlorophyll a (as a proxy for primary production) and growth of plants, seaweeds and corals as well as leaf area of plants. We also analysed filtration, growth and respiration rates of bivalves. Our meta-analysis found that chemical contaminants have a significant negative impact on most of the analysed functional variables, with the exception of the amount of chlorophyll a. Metals were the most widely harmful type of contaminant, significantly decreasing photosynthetic efficiency of kelps, leaf area of saltmarsh plants, growth of fucoids, corals and saltmarsh plants and the filtration rates of bivalves. Organic contaminants decreased the photosynthetic efficiency of seagrass, but had no significant effects on bivalve filtration. We did not find significant effects of polycyclic aromatic hydrocarbons on any of the analysed functional variables or habitat-forming taxa, but this could be due to the low number of studies available. A meta-regression revealed that relationships between concentrations of metal contaminants and the magnitude of functional responses varied with the type of metal and habitat-former. Increasing concentrations of contaminants significantly increased the negative effects on the photosynthetic efficiency of habitat-formers. There was, however, no apparent relationship between ecologically relevant concentrations of metals and effect sizes of photosynthetic efficiency of corals and seaweeds. A qualitative analysis of all relevant studies found slightly different patterns when compared to our quantitative analysis, emphasising the need for studies to meet critical inclusion criteria for meta-analyses. Our study highlights links between effects of contaminants at lower levels of organisation (i.e. at the biochemical and/or physiological level of individuals) and ecological, large-scale impacts, through effects on habitat-forming species. Contaminants can clearly reduce the functioning of many habitat-forming marine species. We therefore recommend the adoption of routine measures of functional endpoints in monitoring and conservation programs to complement structural measures.

Biomarker responses in oysters Crassostrea hongkongensis in relation to metal contamination patterns in the Pearl River Estuary, southern China

The Pearl River Estuary (PRE) is the third largest estuary in China, where estuarine organisms are under metal stress at various biological levels. Based on the metal concentrations measured in oyster Crassostrea hongkongensis, we documented a change in dominance of metal contamination from Cd, Cr, Cu, Ni and Zn to Ag, Cd, Cu and Zn. In general, metal concentrations were higher in upstream stations and displayed a clear up-downstream gradient. Compared to the historical values, we noted the reductions in Cd, Cr and Ni concentrations, and the changing inputs due to evolving industrial activities were responsible for shaping the metal contamination profile in the PRE region. Along with metal concentrations, a suite of biomarkers was analyzed. Among the metals measured in the oyster tissues, Ag, Cd, Cu, Ni and Zn showed the strongest associations with pro-oxidant and oxidative stress responses (superoxide dismutase, lipid peroxidation and lysosomal membrane destabilization) and detoxification responses (glutathione and metallothionein), suggesting that the present metal contamination still exerts significant amount of stress in biota in the PRE. Metal contamination in estuaries in China is still severe compared to other countries, therefore continuous efforts should be taken to monitor the changing metal profiles with necessary control and remediation measures.

Copper and ocean acidification interact to lower maternal investment, but have little effect on adult physiology of the Sydney rock oyster Saccostrea glomerata

It remains unknown how molluscs will respond to oceans which are increasingly predicted to be warmer, more acidic, and heavily polluted. Ocean acidification and trace metals will likely interact to increase the energy demands of marine organisms, especially oysters. This study tested the interactive effect of exposure to elevated pCO₂ and copper on the energetic demands of the Sydney rock oyster (Saccostrea glomerata) during reproductive conditioning and determined whether there were any positive or negative effects on their offspring. Oysters were exposed to elevated pCO₂ (1000 μatm) and elevated copper (Cu 50 μg L^-1 [0.787 μM]) in an orthogonal design for eight weeks during reproductive conditioning. After eight weeks, energetic demands on oysters were measured including standard metabolic rate (SMR), nitrogen excretion, molar oxygen to nitrogen (O:N) ratio, and pH_e of adult oysters as well as the size and total lipid content of their eggs. To determine egg viability, the gametes were collected and fertilised from adult oysters, the percentage of embryos that had reached the trochophore stage after 24 h was recorded. Elevated pCO₂ caused a lower extracellular pH and there was a greater O:N ratio in adult oysters exposed to copper. While the two stressors did not interact to cause significant effects on adult physiology, they did interact to reduce the size and lipid content of eggs indicating that energy demand on adult oysters was greater when both elevated pCO₂ and copper were combined. Despite the lower energy, there were no negative effects on early embryonic development. In conclusion, elevated pCO₂ can interact with metals and cause greater energetic demands on oysters; in response oysters may lower maternal investment to offspring.

Testing biomarker feasibility: a case study of Laeonereis culveri (Nereididae, Annelida) exposed to sewage contamination in a subtropical estuary

The feasibility of biomarkers to accurately detect pollution in estuaries and coastal areas appears to be overestimated in the scientific literature, and is likely stemming from a bias towards publishing only positive results. Herein, we test the applicability of antioxidant capacity and lipid peroxidation to detect potential in situ sewage impacts on a subtropical estuary. We experimentally assessed variation in malondialdehyde (MDA, an indicator of lipid peroxidation) and total antioxidant capacity against peroxyl radicals (ACAP) through transplantations of the worm Laeonereis culveri from control to sewage-polluted areas. Variations in biomarkers were more related to natural environmental variability and small-scale heterogeneity among areas than to experimental exposure to sewage. Use of oxidative stress biomarkers is promising but further experimental work under real-life conditions is necessary to further validate and establish their accuracy and feasibility for practical purposes.

Trace metals in oysters: molecular and cellular mechanisms and ecotoxicological impacts

Oysters are important benthic bivalves in coastal and estuarine environments. They are widely farmed due to their rapid growth and taste; they are also widely applied in environmental monitoring of coastal pollution due to their accumulation of contaminants. Most importantly, oysters are among the few marine organisms that are considered to be hyper-accumulators of many toxic metals, such as cadmium, copper and zinc. As such, there is a tremendous call to study the interactions between metals and oysters, especially due to the increasing metal pollution in many coastal and estuarine waters. Over the past decades, many studies have focused on metal accumulation in oysters as well as the ecotoxicological effects of metals on oysters. In this review, we summarize the recent progress in our understanding of the molecular and cellular mechanisms of metal accumulation, sequestration and toxicity in oysters. Applications of modern technologies such as omics and nanoscale imaging have added significantly to our knowledge of metal biology in oysters. Variations between different metals also demonstrate the diversity of the interactions between oysters and metals. Despite this recent progress, however, there is a need for further study of the molecular mechanisms of metal uptake and toxicity as well as the joint effects of metal mixtures on oyster populations. Oysters have higher numbers of stress responsive genes than most animals, which may have been induced by gene duplication during the evolution of their intertidal environmental adaptations. The divergent expression of stress responsive genes may explain the different tolerances for metals among different species. These fundamental studies may eventually provide promising solutions for reducing toxic metal concentrations in oysters for safe consumption by humans. To conclude, the complexity of life history and metal chemistry of oysters coupled with emerging pollution and application of modern techniques represents an important and exciting research area in modern ecotoxicology.

Integrated toxicity evaluation of metals in sediments of Jiaozhou Bay (China): Based on biomarkers responses in clam Ruditapes philippinarum exposed to sediment extracts

To evaluate the integrated toxicity of metals in sediments of Jiaozhou Bay, we exposed clam (Ruditapes philippinarum) to sediments extracts obtained using of sediment extraction with deionised water adjusted to pH 4 which simulated the weak acidity in the digestive juice of clams and tested the selected biomarkers responses in clams for exposure over 15 days. At the same time, the contents of metals in sediments were assessed with method of the mean sediment quality guideline quotient (SQG-Q). The integrated biomarker response version 2 (IBR_v2) was used to assess the integrated toxicity induced by metals in sediment extracts based on biomarkers response in clams: the results demonstrated that site S7 located in the mouth of Nanxin'an River show higher IBR_v2 values compared to the other sites. The IBR_v2 values exhibited the good consistency with SQG-Q values.

Assessment of metal contamination in estuarine surface sediments from Dongying City, China: Use of a modified ecological risk index

Surface sediments and clam Meretrix meretrix were collected from a northern estuarine region in Dongying City, China. Sediments were analysed for heavy metals (Hg, As, Cd, Cr, Cu, Pb, and Zn) and the clams were tested for metallothioneins (MTs) and lysosomal membrane stability (LMS). The heavy metal total concentrations decreased in the order of Cr>Zn>Cu>Pb>As>Cd>Hg. The results of Bureau Communautaire de Référence (BCR) sequential extraction of heavy metals showed that the geochemical speciation of all heavy metals was dominated by residual fraction. According to the responses of biomarkers in M. meretrix, the modified potential ecological risk index (PERI-B) can more accurately reflect heavy metals pollution. PERI-B showed all sediment samples have low or moderate risk, except at site S10 (considerable risk), and the main contribution of ecological risk heavy metals were Cd and Hg.

A comprehensive evaluation of the environmental quality of a coastal lagoon (Ravenna, Italy): Integrating chemical and physiological analyses in mussels as a biomonitoring strategy

This study aimed at evaluating the environmental quality of a coastal lagoon (Pialassa Piomboni, NW-Adriatic, Italy) by combining analyses of biomarkers of environmental stress and bioaccumulation of contaminants in marine mussels (Mytilus galloprovincialis) transplanted for 28days to six selected sites. Assessed biomarkers encompassed lysosomal endpoints, oxidative stress and detoxification parameters, specific responses to metals, neuro- and genotoxic substances; chemical analyses focused on PAHs, metals, pesticide and pharmaceuticals. Results showed up to a 67-fold bioaccumulation of 4- to 6-ring PAHs, including pyrene, fluoranthene, chrysene and benzo(ghi)perylene in transplanted mussels compared to reference conditions (T0). A 10-fold increase of Fe, Cr and Mn was observed, while pesticides and pharmaceuticals were not or slightly detected. The onset of a significant (p<0.05) general stress syndrome occurred in exposed mussels, as outlined by a 50-57.7% decrease in haemocytes lysosomal membrane stability and an increased lysosomal volume (22.6-26.9%) and neutral lipid storage (18.9-48.8%) observed in digestive gland. Data also revealed a diffuse lipofuscin accumulation (86.5-139.3%; p<0.05) in digestive gland, occasionally associated to a catalase activity inhibition in gill, indicating an increased vulnerability toward pro-oxidant factors. Higher levels of primary DNA damage (258%; p<0.05) and PAH accumulation were found in mussels exposed along the eastern shoreline, hosting a petrochemical settlement. Bioaccumulated metals showed a positive correlation with increased metallothionein content (85-208%; p<0.05) observed in mussels from most sites. Overall, the use of physiological and chemical analyses detected chronic alterations of the mussel health status induced by specific toxicological pathways, proving a suitable approach in the framework of biomonitoring programs of coastal lagoons.

Assessing the impacts of bait collection on inter-tidal sediment and the associated macrofaunal and bird communities: The importance of appropriate spatial scales

Bait collection is a multibillion dollar worldwide activity that is often managed ineffectively. For managers to understand the impacts on protected inter-tidal mudflats and waders at appropriate spatial scales macrofaunal surveys combined with video recordings of birds and bait collectors were undertaken at two UK sites. Dug sediment constituted approximately 8% of the surveyed area at both sites and is less muddy (lower organic content) than undug sediment. This may have significant implications for turbidity. Differences in the macrofaunal community between dug and undug areas if the same shore height is compared as well as changes in the dispersion of the community occurred at one site. Collection also induces a 'temporary loss of habitat' for some birds as bait collector numbers negatively correlate with wader and gull abundance. Bait collection changes the coherence and ecological structure of inter-tidal mudflats as well as directly affecting wading birds. However, as β diversity increased we suggest that management at appropriate hectare/site scales could maximise biodiversity/function whilst still supporting collection.

The response of Isidorella newcombi to copper exposure: Using an integrated biological framework to interpret transcriptomic responses from RNA-seq analysis

This study describes the transcriptomic response of the Australian endemic freshwater gastropod Isidorella newcombi exposed to 80±1μg/L of copper for 3days. Analysis of copper tissue concentration, lysosomal membrane destabilisation and RNA-seq were conducted. Copper tissue concentrations confirmed that copper was bioaccumulated by the snails. Increased lysosomal membrane destabilisation in the copper-exposed snails indicated that the snails were stressed as a result of the exposure. Both copper tissue concentrations and lysosomal destabilisation were significantly greater in snails exposed to copper. In order to interpret the RNA-seq data from an ecotoxicological perspective an integrated biological response model was developed that grouped transcriptomic responses into those associated with copper transport and storage, survival mechanisms and cell death. A conceptual model of expected transcriptomic changes resulting from the copper exposure was developed as a basis to assess transcriptomic responses. Transcriptomic changes were evident at all the three levels of the integrated biological response model. Despite lacking statistical significance, increased expression of the gene encoding copper transporting ATPase provided an indication of increased internal transport of copper. Increased expression of genes associated with endocytosis are associated with increased transport of copper to the lysosome for storage in a detoxified form. Survival mechanisms included metabolic depression and processes associated with cellular repair and recycling. There was transcriptomic evidence of increased cell death by apoptosis in the copper-exposed organisms. Increased apoptosis is supported by the increase in lysosomal membrane destabilisation in the copper-exposed snails. Transcriptomic changes relating to apoptosis, phagocytosis, protein degradation and the lysosome were evident and these processes can be linked to the degradation of post-apoptotic debris. The study identified contaminant specific transcriptomic markers as well as markers of general stress. From an ecotoxicological perspective, the use of a framework to group transcriptomic responses into those associated with copper transport, survival and cell death assisted with the complex process of interpretation of RNA-seq data. The broad adoption of such a framework in ecotoxicology studies would assist in comparison between studies and the identification of reliable transcriptomic markers of contaminant exposure and response.

The freshwater bivalve Corbicula australis as a sentinel species for metal toxicity assessment: An in situ case study integrating chemical and biomarker analyses

A weight of evidence approach in environmental assessment includes the use of biomonitor organisms to measure biologically available contaminant concentrations and lethal and sublethal responses in an exposure, dose, and response framework. Corbicula australis was assessed as a test species for metal toxicity using in situ river sediment exposures at 4 locations in the Molonglo River (New South Wales, Australia), which has a legacy of sediment metal contamination, following 8 decades of mining in its upper reaches. A sediment metal contamination gradient was evident from 12.5 km to 47 km downstream of the mine, as follows: zinc (851-130 mg/kg) > lead (104-7 mg/kg) > copper (31-5 mg/kg) > cadmium (2-0.3 mg/kg). Exposed C. australis accumulated the following metals in tissue: zinc (1358-236 μg/g) > copper (24-20 μg/g) > cadmium (4.7-0.7 μg/g) = lead (4.2-1.8 μg/g). Biomarker responses showed increased sublethal impairment with increased tissue metal concentrations. Total antioxidant capacity was mildly impaired, with corresponding increased lipid peroxidation and lysosomal membrane destabilization at the higher tissue metal concentrations. Corbicula australis proved to be an effective biomonitor organism for sediment metal assessment, as it is able to accumulate metals relative to sediment concentrations and showed a pattern of increased sublethal impairment with increased tissue metal concentration. It is recommended as a suitable species for incorporation into local freshwater monitoring and assessment programs. Environ Toxicol Chem 2017;36:709-719. © 2016 SETAC.

Inputs, dynamics and potential impacts of silver (Ag) from urban wastewater to a highly turbid estuary (SW France)

Although silver (Ag) has been listed as a priority pollutant for the aquatic environment by the European Union (Directive 2006/11/EC), the use of Ag-based products with antimicrobial effects is increasing in Europe, as well as North America and Asia. This study investigates personal care products (PCP) as a potential source of Ag in wastewater, as well as the dynamics and fate of Ag in the influent and effluent of a major urban wastewater treatment plant (WWTP) located on the fluvial part of the Gironde Estuary. Typical household PCPs marked as using Ag contained concentrations of up to 0.4 mg kg^-1 making them likely contributors to urban Ag released into the aquatic environment. Silver concentrations in influent wastewater generally occurred during mid-week working hours and decreased during the night and on weekends clearly indicating the dominance of urban sources. Up to 90% of the total Ag in wastewater was bound to particles and efficiently (>80%) removed by the treatment process, whereas 20% of Ag was released into the fluvial estuary. Silver concentrations in wastewater effluents clearly exceeded estuarine concentrations and may strongly amplify the local Ag concentrations and fluxes, especially during summer rainstorms in low river discharge conditions. Further work should focus on environmental effects and fate of urban Ag release due to immediate localized outfall and/or the adsorption on estuarine particles and subsequent release as dissolved Ag chloro-complexes within the estuarine salinity gradient.

Antioxidant and detoxification responses of oysters Crassostrea hongkongensis in a multimetal-contaminated estuary

The contaminated oysters discovered in the Pearl River Estuary (Guangdong province, China) contained high levels of metals in their tissues, especially Cu and Zn, indicating that this large and densely urbanized estuary in Southern China suffers from serious metal pollution. The present study aimed to investigate the impacts of multimetal pollution in the Pearl River Estuary on oyster antioxidant and detoxification systems. The responses of various biochemical biomarkers in the ecologically important oyster Crassostrea hongkongensis collected from 7 sites in the Pearl River Estuary were quantified. Significant correlations were demonstrated between the accumulation of Cu and Zn and oxidative stress (lipid peroxidation) and oxidative stress defenses (catalase, glutathione peroxidase) in the oyster gills. Significant correlations between the accumulation of Cd and Cu and detoxification (glutathione and glutathione transferase) in the gills were also documented. Interestingly, metallothionein concentrations were positively correlated with Cd, but negatively correlated with Cu, Ni, and Zn concentrations in the gills. These measurements indicated that Cu in the Pearl River Estuary induced various biochemical responses in the oysters and influenced the susceptibility of oysters to environmental stress. The present study has provided the first evidence of antioxidant and detoxification responses in native contaminated oysters from a field environment seriously contaminated by metals. Coupling biomarkers with tissue metal concentration measurements was a promising approach to identify the metals causing biological impacts in a multimetal-contaminated estuary. Environ Toxicol Chem 2016;35:2798-2805. © 2016 SETAC.

Physiological and cellular responses of oysters (Crassostrea hongkongensis) in a multimetal-contaminated estuary

The Pearl River estuary, southern China, suffers from multiple sources of metal contamination as a result of the rapid industrial development in the region; but the biological impacts of contamination remain unknown. In the present study, a euryhaline oyster, Crassostrea hongkongensis, was collected from different sites of the Pearl River estuary; and various physiological (heart rate, alkaline phosphatase as homeostatic regulation, and glycogen as energy reserve) and cytological (lysosomal membrane stability) biomarkers were quantified to assess this species as a potential bioindicator of metal pollution in contaminated areas. Large variations of metal accumulation levels in the oysters were documented, especially for copper (Cu), zinc (Zn), cadmium (Cd), chromium, and nickel (Ni). Among these metals, the authors demonstrated significant correlations between the digestive gland metal accumulation of Cu, Zn, and Ni and the cellular homeostasis (alkaline phosphatase) and glycogen reserves. Heart rate was positively correlated with Cd but negatively correlated with Cu and Zn concentrations in the gills. Lysosomal membrane stability was significantly inhibited at the most contaminated sites but had no relationship with the accumulated metal concentrations. These measurements indicate that multimetal contamination in the Pearl River estuary impacts the physiological and cytological performance of oysters. Environ Toxicol Chem 2016;35:2577-2586. © 2016 SETAC.

Oxidative stress in two tropical species after exposure to diesel oil

Recent offshore petroleum exploration has increased the risks of oil spills worldwide. We investigated biomarker responses to diesel oil exposure in two tropical and subtropical species, the clam Anomalocardia flexuosa and the polychaete Laeonereis culveri. Animals were exposed to oil-spiked sediment at two different concentrations (0.5 L and 1.0 L m^-2). Activities of antioxidant enzymes catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx); glutathione transferase (GST); and lipid peroxides (LPO) were assessed in bivalve digestive glands and polychaete whole-body homogenates at 36 and 60 h of exposure. Significant variation in enzymatic antioxidant activity depended on the sampling time after exposure. No similar response patterns, either increases or decreases, were detected for the two target species, and biomarker responses were species-specific. L. culveri showed clearer patterns in its antioxidant response and should be prioritized over other species in biomonitoring studies involving oil exposure. Understanding the temporal variability of these biomarkers is a necessary action before implementing them as indicators measures in oil contamination biomonitoring programs. Our results provide a better understanding of biomarker responses in subtropical species, evidencing their potential use as sentinels of oil contamination.

Sub-lethal effects of water-based drilling muds on the deep-water sponge Geodia barretti

Offshore oil and gas activities can result in the discharge of large amounts of drilling muds. While these materials have generally been regarded as non-toxic to marine organisms, recent studies have demonstrated negative impacts to suspension feeding organisms. We exposed the arctic-boreal sponge Geodia barretti to the primary particulate components of two water-based drilling muds; barite and bentonite. Sponges were exposed to barite, bentonite and a natural reference sediment at a range of total suspended solid concentrations (TSS = 0, 10, 50 or 100 mg/L) for 12 h after which we measured a suite of biomarker responses (lysosomal membrane stability, lipid peroxidation and glutathione). In addition, we compared biomarker responses, organic energy content and metal accumulation in sponges, which had been continuously or intermittently exposed to suspended barite and natural sediment for 14 d at relevant concentrations (10 and 30 mg TSS/L). Lysosomal membrane stability was reduced in the sponges exposed to barite at 50 and 100 mg TSS/L after just 12 h and at 30 mg TSS/L for both continuous and intermittent exposures over 14 d. Evidence of compromised cellular viability was accompanied by barite analysis revealing concentrations of Cu and Pb well above reference sediments and Norwegian sediment quality guidelines. Metal bioaccumulation in sponge tissues was low and the total organic energy content (determined by the elemental composition of organic tissue) was not affected. Intermittent exposures to barite resulted in less toxicity than continuous exposure to barite. Short term exposures to bentonite did not alter any biomarker responses. This is the first time that these biomarkers have been used to indicate contaminant exposure in an arctic-boreal sponge. Our results illustrate the potential toxicity of barite and the importance of assessments that reflect the ways in which these contaminants are delivered under environmentally realistic conditions.

The mismatch of bioaccumulated trace metals (Cu, Pb and Zn) in field and transplanted oysters (Saccostrea glomerata) to ambient surficial sediments and suspended particulate matter in a highly urbanised estuary (Sydney estuary, Australia)

A significant correlation between sedimentary metals, particularly the 'bio-available' fraction, and bioaccumulated metal concentrations in the native Sydney rock oyster (Saccostrea glomerata) tissues has been successfully demonstrated previously for Cu and Zn in a number of estuaries in New South Wales, Australia. However, this relationship has been difficult to establish in a highly modified estuary (Sydney estuary, Australia) where metal contamination is of greatest concern and where a significant relationship would be most useful for environmental monitoring. The use of the Sydney rock oyster as a biomonitoring tool for metal contamination was assessed in the present study by investigating relationships between metals attached to sediments and suspended particulate matter (SPM) to bioaccumulated concentrations in oyster tissues. Surficial sediments (both total and fine-fraction), SPM and wild oysters were collected over 3 years from three embayments (Chowder Bay, Mosman Bay and Iron Cove) with each embayment representing a different physiographic region of Sydney estuary. In addition, a transplant experiment of farmed oysters was conducted in the same embayments for 3 months. No relationship was observed between sediments or SPM metals (Cu, Pb and Zn) to tissue of wild oysters; however, significant relationship was observed against transplanted oysters. The mismatch between wild and farmed, transplanted oysters is perplexing and indicates that wild oysters are unsuitable to be used as a biomonitoring tool due to the involvement of unknown complex factors while transplanted oysters hold strong potential.

Metal-contaminated resuspended sediment particles are a minor metal-uptake route for the Sydney rock oyster (Saccostrea glomerata)--A mesocosm study, Sydney Harbour estuary, Australia

Resuspension of surficial sediments is considered a key process influencing bioaccumulation of metals in filter-feeders in the contaminated Sydney Harbour estuary (Australia). However, previous investigations were unable to establish a significant relationship between metals in sediments or suspended particulate matter (SPM) and oyster tissue concentrations. This study used a 60-d laboratory mesocosm experiment to expose Sydney rock oysters, Saccostrea glomerata, to a natural range of SPM concentrations with different SPM-metal concentrations. Dissolved metal concentrations were low and the availability of algae provided as food was constant for all treatments. Tissue metal concentrations of Cu, Pb and Zn increased significantly, however, no relationship was determined between tissue metal concentrations in the oyster and either SPM or SPM-metal concentrations. The results indicated that exposure to resuspended contaminated sediment particles contributed little to the observed metal uptake. Dissolved or algae food sources appear to be more important for metal accumulation in these oysters.

Time changes in biomarker responses in two species of oyster transplanted into a metal contaminated estuary

The Jiulong Estuary in Southern China suffers from serious metal pollution, leading to the appearance of 'colored' oysters in this estuary. In this study, two species of oysters Crassostrea hongkongensis and Crassostrea angulata were transplanted to three sites in the Jiulong Estuary over a two-month period. The time-series changes of various biomarkers were measured, coupled with simultaneous quantification of metal bioaccumulation (Ag, Cd, Cr, Cu, Ni and Zn). Cu and Zn accumulation increased linearly and reached up to 2% and 1.5% dry tissue weight by the end of exposure. Negative correlations between the tissue Cu or Zn accumulation and catalase or superoxide dismutase activities strongly indicated that Cu and Zn in 'colored' oysters induced the adjustments of oyster antioxidant systems. Metallothionein (MT) detoxification was insufficient for sequestering all the absorbed metals and its concentrations in the oysters were suppressed following an initial increase, primarily due to the high metal accumulation in the tissues. Interestingly, gradual recoveries of lysosomal membrane stability after the initial strong inhibitions were observed in both oysters. We also documented an increasing 'watering' of oyster tissues presumably as a result of rupturing of tissue cells under metal stress. This study demonstrated the complexity of biomarker responses under field condition, therefore the time changes of biomarker responses to metals need to be considered in evaluating the biological impacts of metal pollution on estuarine organisms.

Evaluation of impacted Brazilian estuaries using the native oyster Crassostrea rhizophorae: Branchial carbonic anhydrase as a biomarker

In this study, we investigated the use of branchial carbonic anhydrase activity in a sessile filter feeding species, the oyster Crassostrea rhizophorae, as a biomarker. The oysters were collected in three human impacted Brazilian estuaries, following a crescent latitudinal gradient: in Pernambuco state (Itamaracá), in Espírito Santo state (Piraquê), and in Paraná state (Paranaguá), in August/2003 (Winter in the southern hemisphere) and February/2004 (Summer). Three sites were chosen in each estuary for oyster sampling: Reference (R), Contaminated 1 (C1, close to industrial/harbor contamination), and Contaminated 2 (C2, near to sewage discharges). Comparing to values in oysters sampled in reference sites, there was apparent inhibition in carbonic anhydrase activity (CAA) in gills of oysters from C1 of Itamaracá and from C2 of Piraquê, both cases in Summer. On the other hand, increased CAA was noted in C2 oysters of Itamaracá in winter, and of Paranaguá, in both seasons. Branchial CAA in C. rhizophorae was thus very responsive to coastal contamination. Data are consistent with its usefulness as a supporting biomarker for inexpensive and rapid analysis in the assessment of estuaries using a sessile osmoconformer species, but preferably allied to other biomarkers and with knowledge on the suite of contaminants present.

Dietary ingestion of fine sediments and microalgae represent the dominant route of exposure and metal accumulation for Sydney rock oyster (Saccostrea glomerata): A biokinetic model for zinc

Past studies disagree on the extent to which dissolved or dietary uptake contribute to metal bioaccumulation in the filter-feeding Sydney rock oyster (Saccostrea glomerata) in urbanized estuaries. Although most data support the assumption that fine sediments are a major route of metal uptake in these bivalves, some studies based in the Sydney estuary, Australia, have indicated a poor correlation. In the present study, seawater, sediment and microalgae were radiolabelled with (65)Zn tracer and exposed to S. glomerata to assess the influence of dissolved and dietary sources to Zn bioaccumulation. Oysters in the dissolved-phase uptake experiment (5, 25 and 50 μg L(-1) (65)Zn for 4 d followed by 21 days of depuration) readily accumulated (65)Zn for all three concentrations with an uptake rate constant of 0.160±0.006 L dry weight g(-1) d(-1). Oysters in the dietary assimilation experiment (1h pulse-feed of either (65)Zn-radiolabelled suspended fine-fraction (<63 μm) sediment or the microalgae Tetraselmis sp.) accumulated (65)Zn, with assimilation efficiencies of 59 and 67% for fine sediment and microalgae, respectively. The efflux rates were low for the three experiments (0.1-0.5% d(-1)). A bioaccumulation kinetic model predicts that uptake of Zn will occur predominantly through the dietary ingestion of contaminated fine sediment particles and microalgae within the water column, with considerably greater metal bioaccumulation predicted if oysters ingested microalgae preferentially to sediments. However, the model predicts that for dissolved Zn concentrations greater than 40 μg L(-1), as observed during precipitation events, the uptake of the dissolved phase may contribute ≥50% to accumulation. Overall, the results of the present study suggest that all three sources may be important exposure routes to S. glomerata under different environmental conditions, but contributions from dietary exposure will often dominate.

Resuspended contaminated sediments cause sublethal stress to oysters: A biomarker differentiates total suspended solids and contaminant effects

Resuspended contaminated sediments represent an important route of contaminant exposure for aquatic organisms. During resuspension events, filter-feeding organisms are exposed to contaminants, in both the dissolved form (at the gills) and the particulate form (in the digestive system). In addition, these organisms must manage the physical stress associated with an increase in total suspended solids (TSS). To date, few studies have experimentally compared the contributions to biological stress of contaminated and clean suspended solids. The authors mixed field-collected sediments (<63 μm) from clean and contaminated field sites to create 4 treatments of increasing metal concentrations. Sydney rock oysters were then exposed to sediment treatments at different TSS concentrations for 4 d, and cellular biomarkers (lysosomal membrane stability, lipid peroxidation, and glutathione) were measured to evaluate sublethal toxicity. Lysosomal membrane stability was the most sensitive biomarker for distinguishing effects from resuspended contaminated sediments, as increasing amounts of contaminated TSS increased lysosomal membrane destabilization. The authors' results illustrate the importance of considering contaminant exposures from resuspended sediments when assessing the toxicity of contaminants to aquatic organisms.

Effects of cadmium accumulation from suspended sediments and phytoplankton on the Oyster Saccostrea glomerata

Metals are accumulated by filter feeding organisms via water, ingestion of suspended sediments or food. The uptake pathway can affect metal toxicity. Saccostrea glomerata were exposed to cadmium through cadmium-spiked suspended sediments (19 and 93μg/g dry mass) and cadmium-enriched phytoplankton (1.6-3μg/g dry mass) and cadmium uptake and effects measured. Oysters accumulated appreciable amounts of cadmium from both low and high cadmium spiked suspended sediment treatments (5.9±0.4μg/g and 23±2μg/g respectively compared to controls 0.97±0.05μg/g dry mass). Only a small amount of cadmium was accumulated by ingestion of cadmium-enriched phytoplankton (1.9±0.1μg/g compared to controls 1.2±0.1μg/g). In the cadmium spiked suspended sediment experiments, most cadmium was desorbed from sediments and cadmium concentrations in S. glomerata were significantly related to dissolved cadmium concentrations (4-21μg/L) in the overlying water. In the phytoplankton feeding experiment cadmium concentrations in overlying water were <0.01μg/L. In both exposure experiments, cadmium-exposed oysters showed a significant reduction in total antioxidant capacity and significantly increased lipid peroxidation and percentage of destabilised lysosomes. Destabilised lysosomes in the suspended sediments experiments also resulted from stress of exposure to the suspended sediments. The study demonstrated that exposure to cadmium via suspended sediments and to low concentrations of cadmium through the ingestion of phytoplankton, can cause sublethal stress to S. glomerata.

Improving management support tools for reintroducing bivalve species (eastern oyster [Crassostrea virginica Gmelin]) in urban estuaries

Successful reintroduction of "ecologically extinct" bivalve species into anthropogenically impaired urban estuaries is problematic when employing existing management tools used in estuaries where bivalves are present (GIS-based restoration models, expanding existing shellfish beds, placement of shell substrate, physical oceanographic parameters). A significant management challenge is appropriate site selection. We are proposing the inclusion of a biological parameter (evaluation of tissue histopathology) in an inexpensive and rapid site selection model to inform management decision making and identify sites with the greatest potential for reintroduction success. Use of biological biomarkers is not a new concept, but it is important that they be included in a multitiered management approach to bivalve reintroduction. This Case Study tested adult Eastern Oysters (Crassostrea virginica Gmelin) from locations that supported comparable short-term survival rates by evaluating growth and tissue health and/or disease. Biomarkers indicated oyster tissues at one site were normal, the female:male sex ratio was 50:50, and female oysters were in spawning condition. Conversely, oyster tissues at the second site exhibited multiple abnormalities, samples were 100% male, and the incidence of disease was high. Using the biomarker tool, we evaluated 4 additional sites where oysters exhibited short-term (1 year) survival. At 2 locations, we observed chronic health impacts that would preclude reintroduction, including samples from one site where a wild population was surviving. We also analyzed tissue and shell heavy metal contents. Soft tissue metal concentrations in Meadowlands samples were at the high range of scientific literature values, averaging 1.1% of total body weight, whereas tissue metal concentrations at the Keyport site were within acceptable ranges. Although initial survival and growth rates at both locations were comparable, site-specific urban stressors reduced oyster fitness at 1 of the 2 locations. We are proposing an Estuarine Reintroduction Site Selection Model, which includes a biological in situ parameter, to increase the probability of successfully managing a sustainable oyster reintroduction before commencing expensive large-scale restoration activities.

Next generation sequence analysis of the transcriptome of Sydney rock oysters (Saccostrea glomerata) exposed to a range of environmental stressors

Sydney rock oysters (Saccostrea glomerata) were exposed to environmental stressors at contaminated field sites or in a controlled laboratory setting. RNA seq transcriptome data were generated for the gill and digestive gland using Roche's 454 pyrosequencing technology. 28,685 contigs were de novo assembled which encoded 11,671 different protein products. The data will act as a reference for future studies in ecology, immunology and environmental toxicology.