Partitioning of metals in the tissues and cytosolic fraction of Cerastoderma edule.

The concentrations of Cd, Cu and Zn have been determined in the tissues and the cytosolic fraction of the common cockle, Cerastoderma edule, collected from sediments in the Tamar, Plym and Avon estuaries (South West, England). Metal concentrations in the tissues of C. edule from the Avon were lower than those from the Tamar and Plym, except for Cu in the digestive gland. Significant statistical relationships were only obtained between the total sedimentary metal concentrations and Cd in the body of C. edule and Cu in the digestive gland. The cytosolic fraction was extracted from each of the tissues and separated for protein analysis thereby allowing determination of the metal contents in high molecular weight (HMW) compounds, metallothionein-like proteins (MTLP) and very low molecular weight (VLMW) compounds. The digestive glands of C. edule from the Avon had relatively low concentrations of MTLP, whereas MTLP concentrations in the digestive gland of cockles from the Tamar and Plym were higher. The cytosolic fraction of C. edule had relatively low total Cd and Cu concentrations associated with MTLP, whereas Zn was preferentially associated with the HMW and the VLMW components. The results are relevant to metal distributions in C. edule and the role of cytosols in the management of metals by C. edule and other invertebrates.

Recovery of an urbanised estuary: Clean-up, de-industrialisation and restoration of redundant dock-basins in the Mersey.

For much of the 20th century, the Mersey in North West England was one of the worst polluted estuaries in Europe. Water from a range of polluting industries plus domestic sewage was discharged into the Mersey Catchment and Estuary. Recovery came through a concerted clean-up campaign and tightening environmental regulations, partly driven by European Commission Directives, coupled with de-industrialisation from the 1970s onward. Recovery of oxygen levels in the Estuary led to the return of a productive ecosystem. This led to conservation designations, but also concerns about transfer of pollutants to higher trophic levels in fish, birds and humans. As part of urban renewal, ecosystems in disused dock basins were restored using mussel biofiltration and artificial de-stratification, facilitating commercial redevelopment and creation of a tourist destination. The degradation and recovery of the Mersey from peak-pollution in the mid-20th century is put in the context of wider environmental change and briefly compared to other systems to develop a hysteresis model of degradation and recovery, often to novel ecosystems.

Oxidative stress, lysosomal damage and dysfunctional autophagy in molluscan hepatopancreas (digestive gland) induced by chemical contaminants.

Autophagy is a highly conserved evolutionary survival or defence process that enables cells and organisms to survive periods of environmental stress by breaking down cellular organelles and macromolecules in autolysosomes to provide a supply of nutrients for cell maintenance. However, autophagy is also a part of normal cellular physiology that facilitates the turnover of cellular constituents under normal conditions: it can be readily augmented by mild environmental stress; but becomes dysfunctional with severe oxidative stress leading to cellular pathology. The molluscan hepatopancreas or digestive gland provides a versatile and environmentally relevant model to investigate lysosomal autophagy and stress-induced dysfunctional autophagy. This latter process has been implicated in many animal and human disease conditions, including degenerative and neurodegenerative diseases, as well as obesity related conditions. Many environmental pollutants have also been found to induce dysfunctional autophagy in molluscan hepatopancreatic digestive cells, and in this study, the marine blue mussel Mytilus galloprovincialis was exposed for 7 days to: 0.1 µM, 1 µM and 10 µM concentrations of fluoranthene and phenanthrene (PAHs); chlorpyrifos and malathion (organophosphorus compounds); atrazine (triazine herbicide); copper (transition metal) and dodecylbenzene sulphonic acid (LAS, surfactant). The marine snail or periwinkle, Littorina littorea, was also exposed to phenanthrene, chlorpyrifos and copper. Indices of oxidative stress, cell injury and dysfunctional autophagy were measured (i.e., lysosomal membrane stability, protein carbonyls, lipofuscin, and lysosomal accumulation of lipid or lipidosis). Evidence of oxidative stress, based on the elevation of lipofuscin and protein carbonyls, was found for all compounds tested; with chlorpyrifos being the most toxic to both species. Dysfunctional autophagy was induced by all of the compounds tested in both species, except for atrazine in mussels. This failure of normal autophagy was consistently associated with oxidative stress. Autophagic dysfunction is an important emerging feature in the aetiology of many disease conditions in animals and humans; and an explanatory conceptual mechanistic model has been developed for dysregulation of autophagy in response to oxidative stress.

Sediment contaminant surveillance in Milford Haven Waterway.

Sediment contaminants were monitored in Milford Haven Waterway (MHW) since 1978 (hydrocarbons) and 1982 (metals), with the aim of providing surveillance of environmental quality in one of the UK's busiest oil and gas ports. This aim is particularly important during and after large-scale investment in liquefied natural gas (LNG) facilities. However, the methods inevitably have changed over the years, compounding the difficulties of coordinating sampling and analytical programmes. After a review by the MHW Environmental Surveillance Group (MHWESG), sediment hydrocarbon chemistry was investigated in detail in 2010. Natural Resources Wales (NRW) contributed their MHW data for 2007 and 2012, collected to assess the condition of the Special Area of Conservation (SAC) designated under the European Union Habitats Directive. Datasets during 2007-2012 have thus been more comparable. The results showed conclusively that a MHW-wide peak in concentrations of sediment polycyclic aromatic hydrocarbons (PAHs), metals and other contaminants occurred in late 2007. This was corroborated by independent annual monitoring at one centrally located station with peaks in early 2008 and 2011. The spatial and temporal patterns of recovery from the 2007 peak, shown by MHW-wide surveys in 2010 and 2012, indicate several probable causes of contaminant trends, as follows: atmospheric deposition, catchment runoff, sediment resuspension from dredging, and construction of two LNG terminals and a power station. Adverse biological effects predictable in 2007 using international sediment quality guidelines were independently tested by data from monitoring schemes of more than a decade duration in MHW (starfish, limpets) and in the wider SAC (grey seals). Although not proving cause and effect, many of these potential biological receptors showed a simultaneous negative response to the elevated 2007 contamination following intense dredging activity in 2006. Wetland bird counts were typically at a peak in the winter of 2005-2006 previous to peak dredging. In the following winter 2006-2007, shelduck in the Pembroke River showed their lowest winter count, and spring 2007 was the largest ever drop in numbers of shelduck broods across MHW between successive breeding seasons. Wigeon counts in the Pembroke River were low in 2006-2007 and in late 2012 after further dredging nearby. These results are strongly supported by PAH data reported previously from invertebrate bioaccumulation studies in MHW 2007-2010, themselves closely reflecting sediment trends for PAHs in the Pembroke River and Angle Bay.

Intersex in the clam Scrobicularia plana (Da Costa): Widespread occurrence in English Channel estuaries and surrounding areas.

Estuarine clams Scrobicularia plana were sampled from 108 intertidal locations around the English Channel and adjacent areas. Although S. plana is believed to be a strict gonochorist, 58% of the populations sampled included intersexed individuals (described as male clams exhibiting ovotestis). Over the entire region, on average, 8.6% of male clams exhibited intersex, although proportions of affected males ranged from 0% to 53% depending on location. The severity of intersex was assessed using a simple classification scale, with the majority of individuals showing low levels of impact. Sex ratios were significantly skewed at some sites. There were no significant relationships between incidence or severity of intersex; or with size or parasitism of individual clams. Intersex in S. plana is a useful tool to assess endocrine disruptive effects in estuaries, although mechanisms of impact and causative agents remain uncertain.

Recovery from TBT pollution in English Channel environments: A problem solved?

Following recognition of effects in the 1980s, tributyltin (TBT) has been monitored at sites in the English Channel to evaluate the prognosis for biota - spanning the introduction of restrictions on TBT use on small boats and the recent phase-out on the global fleet. We describe how persistence and impact of TBT in clams Scrobicularia plana has changed during this period in Southampton Water and Poole Harbour. TBT contamination (and loss) in water, sediment and clams reflects the abundance and type of vessel activity: half-times in sediment (up to 8y in Poole, 33y in Southampton) are longest near commercial shipping. Recovery of clam populations - slowest in TBT-contaminated deposits - provides a useful biological measure of legislative efficacy in estuaries. On rocky shores, recovery from imposex in Nucella lapillus is evident at many sites but, near ports, is prolonged by shipping impacts, including sediment legacy, for example, in the Fal.

Bioaccumulation surveillance in Milford Haven Waterway.

Biomonitoring of contaminants (metals, organotins, polyaromatic hydrocarbons (PAHs), PCBs) was undertaken in Milford Haven Waterway (MHW) and a reference site in the Tywi Estuary (St Ishmael/Ferryside) during 2007-2008. Bioindicator species encompassed various uptake routes-Fucus vesiculosus (dissolved contaminants); Littorina littorea (grazer); Mytilus edulis and Cerastoderma edule (suspension feeders); and Hediste (=Nereis) diversicolor (sediments). Differences in feeding and habitat preference have subtle implications for bioaccumulation trends though, with few exceptions, contaminant burdens in MHW were higher than the Tywi reference site, reflecting inputs. Elevated metal concentrations were observed at some MHW sites, whilst As and Se (molluscs and seaweed) were consistently at the higher end of the UK range. However, for most metals, distributions in MH biota were not exceptional. Several metal-species combinations indicated increases in bioavailability upstream, which may reflect the influence of geogenic/land-based sources-perhaps enhanced by lower salinity. TBT levels in MH mussels were below OSPAR toxicity thresholds and in the Tywi were close to zero. Phenyltins were not accumulated appreciably in M. edulis, whereas some H. diversicolor populations appear subjected to localized (historical) sources. PAHs in H. diversicolor were distributed evenly across most of MHW, although acenaphthene, fluoranthene, pyrene, benzo(a)anthracene and chrysene were highest at one site near the mouth; naphthalenes in H. diversicolor were enriched in the mid-upper Haven (a pattern seen in M. edulis for most PAHs). Whilst PAH (and PCB) concentrations in MH mussels were mostly above reference and OSPAR backgrounds, they are unlikely to exceed ecotoxicological thresholds. Bivalve Condition indices (CI) were highest at the Tywi reference site and at the seaward end of MH, decreasing upstream-giving rise to several significant (negative) relationships between CI and body burdens. Despite the possible influence of salinity gradient as a complicating factor, multivariate analysis indicated that a combination of contaminants could influence the pattern in condition (and the biomarkers metallothionein and TOSC). Integrating bioaccumulation data with biological and biochemical endpoints is seen as a useful way to discriminate environmental quality of moderately contaminated areas such as MHW and to prioritise cause and effect investigations.

Influence of a collapsed coastal landfill on metal levels in sediments and biota--a portent for the future?

In May 2008 a coastal landslide deposited landfill debris onto the shore near Lyme Regis, UK. Six months later, intertidal sediments and biota from the area were sampled to determine whether the landslip had affected distribution and bioavailability of metals in the area and if there were any biological effects. Highest sediment concentrations for the majority of metals occurred near the landslip zone and in several cases exceeded Threshold Effects or Probable Effects Levels (As, Cu, Hg, Ni, Pb, Zn). The 1 M HCl-extractable fraction of Cd, Pb and Zn in sediments also increased near the landslip. Metal bioaccumulation by intertidal biota showed variability between different species and metals, but there were several instances of increased accumulation near the landslip through increased availability from seawater, sediment and dietary sources. In most cases, metal concentrations in molluscs exceeded Oslo and Paris Commission (OSPAR) background concentrations (BCs) together with background assessment concentrations (BACs) at some sites. Kidney tissues in winkles (Littorina littorea) were measured for evidence of oxidative stress using the Total Oxyradical Scavenging Capacity (TOSC) assay. Responses to peroxynitrite, peroxyl and hydroxyl radicals suggested raised levels of TOSC in animals from the sites close to or east of the landfill waste. There have been very few studies of direct impact of landfills on the marine environment and this study could serve as a practical model for similar events driven by sea level rise.

A review of sediment dynamics in the Severn Estuary: influence of flocculation.

This paper provides a review and critique of the distributions and characteristics of non-cohesive and cohesive sediments within the Severn Estuary, with particular reference to floc properties. The estuary is hyper-tidal and, consequently, highly turbid along most of its length and it generally has two turbidity maxima. In the upper reaches of the estuary, suspended particulate matter (SPM) concentrations can be in excess of 10 g l(-1) for river flows up to 50 m(3)s(-1), rising to over 50 g l(-1) during periods of lower river flow. The lower estuary turbidity maximum originates in the vicinity of Bridgwater Bay where SPM concentrations may vary between 0.1-200 g l(-1). The formation of fluid mud is coupled to the spring-neap cycle and strong vertical gradients in SPM concentrations produce turbulence damping and drag reduction effects, and hence impair the ability of the flow to transport sediments. Flocculation is an important mechanism for controlling the behaviour of fine sediments and mean settling velocities of flocs vary between 0.8-6 mm s(-1). A secondary consequence of flocculation is the formation of mud:sand mixtures in turbid suspensions. Improved understanding of the significance of flocculation processes is crucial as they may exert an influence on the mechanism by which adsorbed contaminants are transported in the system.

Contaminants in fine sediments and their consequences for biota of the Severn Estuary.

When the first MPB special issue was published 25 years ago it was suggested that high body burdens of metals and selected organic pollutants in the Severn Estuary were the result of anthropogenic loadings from a variety of sources. The objective of this synopsis is to illustrate recent trends for contaminants (metals, PAHs, PCBs) in sediments and benthic biota and to consider the evidence for improved environmental quality over the last quarter of a century. Contaminants in sediments and sediment-dwelling fauna such as Hediste(=Nereis)diversicolor are, generally, evenly distributed over the estuary - which is the consequence of extensive re-suspension and redistribution of fine sediment by strong tidal currents. Such dispersal tends to mask the influences of individual discharges and physical characteristics are considered to be the major drivers affecting biodiversity in the Severn Estuary, often overshadowing contaminant concerns. Following the closure of major industries and the introduction of stricter pollution control, many inputs have ceased or been reduced and there are indications that environmental concentrations are now lower. Bioaccumulation of most contaminants has declined accordingly (with the possible exception of Cr). Intuitively, better environmental quality should be linked to ecological improvements. However, due to the dynamic nature of the system (and a lack of biological-effects data) it is difficult to establish direct relationships between inputs, body burdens and biological/ecological consequence. Uniquely, the long-term integrated monitoring program of AstraZeneca (Avonmouth) indicates that recovery of faunal diversity and abundance has occurred in mid-sections of the estuary in recent years implying that contaminants have indeed been a forcing feature for Severn biota. In this context, we highlight contaminant issues and biogeochemical changes which may need to be addressed in connection with the development of proposals for tidal energy schemes.

Hepatic metallothionein and total oxyradical scavenging capacity in Atlantic cod Gadus morhua caged in open sea contamination gradients.

Biological effects monitoring has seldom been undertaken in offshore pelagic environments. Cages containing hatchery-reared Atlantic cod Gadus morhua were deployed on expected contamination gradients, along a transect from the River Elbe in the German Bight, and in the vicinity of an oil field in the North Sea (Statfjord). Six weeks later, the cod were retrieved and samples taken for a range of biological effects techniques. In this study, metallothionein (MT) and total oxyradical scavenging capacity (TOSC) were measured in liver samples from the caged cod, together with metals (as a measure of bioaccumulation). Both MT and TOSC were highest in cod from the German Bight. In the Statfjord samples MT and TOSC decreased with distance from the oil platform indicating induction in response to anthropogenic sources. The bioavailability of metals appears to be a major factor in MT synthesis, and the measurement of MT and associated metals is shown to be a useful tool for biological exposure and effects monitoring in pelagic systems. There also appears to be a strong linkage between MT and TOSC levels, indicating overlapping capabilities as stress biomarkers. Results suggest that in addition to its role as a specific indicator of metal exposure, MT in cod could act as a more general biomarker of oxidative stress under certain conditions.

Intersex in the clam Scrobicularia plana: a sign of endocrine disruption in estuaries?

The phenomenon of endocrine disruption is currently a source of growing concern. Feminization of male fish in UK rivers has been shown to occur extensively and has been linked with exposure to endocrine-disrupting compounds present in the environment. Much less is known of the extent and scale of endocrine disruption in estuarine and marine ecosystems, particularly in invertebrates. We present evidence that intersex, in the form of ovotestis, is occurring in the common estuarine bivalve Scrobicularia plana, which is considered to be inherently gonochoristic. We report varying degrees in the severity of ovotestis in male S. plana, and have adopted and developed a grading method to assess the extent of this intersex condition. These findings indicate that S. plana offers potential for widespread screening and investigation of endocrine disruption, helping to focus remediatory strategy.

Effect of TBT on Ruditapes decussatus juveniles.

The effects of sublethal concentrations of tributyltin (TBT) on growth of juvenile clams Ruditapes decussatus were determined during exposure to TBT concentrations of 50, 100 and 250 ng l(-1) (as Sn) for a period up to two years. Length and weight of clams increased continuously in all treatments throughout the experimental period, and, overall, rates were not significantly influenced by TBT exposure, although final length and weight were inversely related to increasing TBT concentration. Juvenile R. decussatus therefore appear to be less sensitive to TBT than larval stages. Some juveniles exposed to TBT developed abnormal shell growth, laterally, changing the typical flattened shape of clams into a more "rounded" form. This characteristic was more visible in the anterior margins of valves than posteriorly, and mainly observed in clams exposed to TBT at 50 ng l(-1) (as Sn).

Distribution of organotin compounds in tissues of mussels Mytilus edulis and clams Mya arenaria.

Concentrations and composition of butyltin (BT) and phenyltin (PT) compounds were compared in tissues of mussels Mytilus edulis and clams Mya arenaria collected from the Mersey Estuary. Tributyltin (TBT) concentrations were consistently highest in digestive gland and low in muscular tissues such as siphons (Mya) and adductor muscle (Mytilus). Lowest concentrations were found in the periostracum surrounding the siphons of Mya. Ratios of monobutyltin (MBT), dibutyltin (DBT) and TBT to total BT content of Mytilus tissues were in the ranges 25-34%, 21-28% and 44-51%, respectively. Much higher proportions of TBT:total BT were characteristic of Mya (>80% in the digestive gland, remaining tissue and gonad) implying that slow degradation rates account for the relatively high levels of TBT in this species. TPT was the only phenyltin compound detected (albeit at relatively low levels), and, like TBT, was present in highest concentrations in the digestive gland of clams--suggesting an important dietary component in the accumulation of OTs in these bivalves.

Bioaccumulation of trace metals in the amphipod Chaetogammarus marinus (Leach, 1815) from the Avon and Tamar estuaries (UK): comparison of two-compartment and hyperbolic toxicokinetic models.

Bioaccumulation of Cd, Cr, Cu, Co, Pb, Ni and Zn was investigated in the eulittoral gammaridean amphipod Chaetogammarus marinus (Leach, 1815) from the Avon and Tamar estuaries (UK). The main goals were to provide information on accumulation strategies of the organisms tested and to verify toxicokinetic models as a predictive tool. The organisms accumulated metals upon exposure and it was possible to estimate significant model parameters of two-compartment and hyperbolic models, with the exception of Zn. Both types of models yielded significant model estimates in two independent toxicokinetic studies using gammarids from the Avon and Tamar estuaries, respectively. Kinetic BCFs at theoretical equilibrium were 58-102 for Cd, 95-215 for Cr, 400-963 for Cu, 38-59 for Co, 150-750 for Pb and 33-63 for Ni, and were in most cases distinctly lower than the range reported in the literature for other amphipods. To demonstrate the potential of toxicokinetic models as a predictive tool, attempts were made, further to verify time-dependent model data (Tamar) with independent experimental data (Avon). In this case only for Cd were both in good agreement, whilst for all other elements the models overestimated the measured values. The second approach was to verify time-dependent model data (Tamar) with measured values from an independent concentration-dependent uptake study (Tamar) or, alternatively, to estimate the model parameters simultaneously for both studies. A good agreement between observed and predicted values was obtained for all elements for the simultaneous two-compartment models. Only for Cd was a simultaneous estimation of the hyperbolic model more promising. A tentative estimation showed the following sequence of sensitivity of C. marinus to an increase of soluble metal exposure: 0.6 microg Cd l(-1), 1.7 microg Cr l(-1), 16 microg Cu l(-1), 3.5 microg Co l(-1), 0.8 microg Pb l(-1) and 7 microg Ni l(-1). Available information can be used to quantify a measure of agreement or disagreement between bioaccumulation in different amphipods. This can be regarded as an important step in the calibration of biomonitors which is necessary to assess the potential for bioaccumulation on a large geographical scale.

Recovery of polluted ecosystems: the case for long-term studies.

Recovery of marine ecosystems from pollution has tended to receive less attention than the study of new or continuing impacts, but such studies are important in charting recovery from acute incidents and following legislation to deal with chronic contamination. Recovery is inevitably a long-term process, and where such studies have been made they are often too short-lived. Interest quickly wanes following an acute incident and governmental bodies rapidly switch to new legislative priorities for chronic inputs. We review three case studies: recovery of dogwhelk populations after local extinction by tributyl tin leachates from anti-fouling paints; recovery of rocky shore communities from oil spills; and recovery of estuarine ecosystems from industrial and urban development. We then make some generalisations about recovery processes before making a plea for long-term studies of polluted areas.

Effect of temperature and size on metallothionein synthesis in the gill of Mytilus galloprovincialis exposed to cadmium.

Although the degree of metal contamination is expected to be a primary determinant of metallothionein (MT) induction in marine mussels, at least at polluted sites, variability caused by temperature, and biotic factors such as size, may need to be considered when interpreting field data. To test the effects of these variables, mussels, Mytilus galloprovincialis, of different sizes (small: 3.5 +/- 0.5 cm and large: 5.2 +/- 0.7 cm) were exposed to Cd (100 microg l(-1)) at different water temperatures (5, 18 and 25 degrees C) for 34 days. Resultant Cd and MT concentrations in gills were shown to be size dependent and increased significantly with temperature. At the highest temperature tested (25 degrees C) there appears to be a disproportionate effect on Cd accumulation, which raises MT synthesis to exceptionally high levels. The effect of size on MT concentrations was also temperature-dependent: at 18 and 25 degrees C, large mussels exhibited higher MT levels than smaller individuals, whilst at 5 degrees C there were no significant differences between contaminated and control mussels, in either size-group, as a result of the reduced level of MT production at this temperature. When considering the use of MT levels in mussels as a biochemical indicator of metal contamination, the potential influence of factors such as size and temperature on MT-metal relationships needs to be considered. Samples should be of uniform size as far as possible, and collection should be limited to a fixed season (avoiding climatic extremes) to ensure that the effects of these factors on baseline levels of MT is minimised.

Routes of TBT uptake in the clam Ruditapes decussatus. I. Water and sediments as vectors of TBT uptake.

This study assesses the relative importance of water and sediments as vectors of TBT uptake in the sediment-dwelling suspension feeder, Ruditapes decussatus. Accumulation of TBT was determined in R. decussatus exposed for 60 days to moderately high but environmentally realistic levels of TBT in water (100 ng Snl(-1)) and sediments (0.8 microg Sn g(-1) dw), separately or in combination, using constant-flow systems. The results indicate that this species accumulates TBT predominantly from water. Although some accumulation from sediments does occur, the processing of large amounts of water needed to sustain the filter-feeding habits of this species is a prime determinant of TBT uptake. The route of exposures reflected in tissue distributions of TBT in R. decussatus. However, gills are the most important site for accumulation of TBT from water, irrespective of whether contaminated sediments are present or not.