[Somatic condition of the clam Polymesoda solida (Veneroidea: Corbiculidae) in the rainy season of the Salamanca Island Natural Park, Colombian Caribbean]

The estuarine clam Polymesoda solida is the main fishery resource in the Salamanca Island Natural Park. I sampled the clam in three interconnected lagoons (Poza Verde, El Torno and Atascosa) during the rainy period (April to November 2004). Sixty individuals were monthly collected by hand on each lagoon; 30 to analyze two condition indexes (relationship between body and shell weight and between soft dry and wet weight), yield (meat percentage) and length-weight relationships. Maturity of female gonad smears was assessed on the remaining individuals. Measures of salinity, temperature, pH, dissolved oxygen, transparency and depth, were also taken at the collection places. Increases of the condition indexes occurred when the Magdalena River showed some decreases in its level, especially at Poza Verde and El Torno. The condition indexes were higher at 27-33 mm, (range where maturity size was reached). Clams from Poza Verde, the lagoon nearest to the Magdalena River, had the highest values in condition indexes, yield, fresh weight and maturity frequency. Yield was directly correlated to the condition indexes and sexual maturity. The condition index (body weight/shell weight) showed a highest multiple regression coefficient with salinity, pH and transparency (R2=74%), indicating the relevance of the hydrological regime in the regulation of the condition of the organisms. P. solida seems to be more adapted to the lowest salinities of the system (0.0-0.4), corresponding to Poza Verde, where the influence of the Magdalena river is more direct and steady. Additionally, differences found between sites in the assessed variables, emphasize the importance of considering spatial heterogeneity of this kind of lagoon estuaries, and should be taken into account for future fisheries management in the rainy period and conservation of P. solida populations.

Relationship of metal content and bioavailability with benthic macrofauna in Camamu Bay (Bahia, Brazil)

Camamu Bay (Bahia, Brazil) is an Environmental Protected Area with mangroves of economic and ecological importance. The objective of this study was to elucidate, through the distribution of the benthic macrofauna and its relationships with trace metals and bioavailabilty, if the current quality of the mangrove sediments of Camamu Bay is acceptable for the protection of aquatic life. Seven sampling stations were selected as representative of the meso-littoral region of Camamu Bay. It was found 581 macrobenthic organisms distributed in 38 species. The highest values of metals occurred at stations located in areas that influenced by barite extraction, while the lowest concentrations were found in areas with relatively lower anthropogenic influence. Analysis of acid volatile sulphide and simultaneously extracted metals showed the occurrence of the ratio SEM/AVS >1, indicative of possible bioavailability of metals, at only one station. The results suggested that Camamu Bay is a nearly pristine area.

Manganese speciation in Diplodon chilensis patagonicus shells: a XANES study

X-ray absorption near-edge spectroscopy (XANES) at the Mn K-edge was used to investigate the environment of Mn in situ within the growth increments of the long-lived freshwater bivalve species Diplodon chilensis patagonicus. Single XANES spectra and Mn Kalpha fluorescence distributions were acquired at submillimetre resolution (up to 100 microm x 50 microm), at Mn concentrations below the weight percent range (100-1000 microg g(-1)) in a high Ca matrix. The position and intensity of the pre-edge feature in the shell spectrum resembles best that of the Mn(II)-bearing reference compounds, suggesting that this is the oxidation state of Mn in the bivalve shells. By comparison with the XANES spectra of selected standard compounds, hypotheses about Mn speciation in the shell are also reported. In particular, different factors, such as provenance, ontogenetic age, variable Mn-concentrations or seasonal shell deposition seem not to influence the speciation of the metal in this bivalve species.

Sublethal toxicant effects with dynamic energy budget theory: application to mussel outplants

We investigate the effectiveness of a sublethal toxic effect model embedded in Dynamic Energy Budget (DEB) theory for the analysis of field data. We analyze the performance of two species of mussels, Mytilus galloprovincialis and M. californianus, near a diffuser discharging produced water in the Southern California Bight, California. Produced water is a byproduct of oil production consisting of fossil water together with compounds added during the extraction process, and generally contains highly elevated levels of pollutants relative to sea water. Produced water negatively affects the production of somatic and reproductive biomass in both mussel species; we show that these negative effects can be quantified with our DEB-based modeling framework through the estimation of toxic effect scaling parameters. Our analyses reveal that the toxic impact of produced water on growth and reproduction of M. californianus is substantially higher than for M. galloprovincialis. Projections of the expected lifetime production of gonad biomass indicate that the environmental impact of produced water can be as large as 100%, whereas short-term assessment without the use of DEB theory projects a maximum effect of only 30%.

Sublethal toxicant effects with dynamic energy budget theory: model formulation

We develop and test a general modeling framework to describe the sublethal effects of pollutants by adding toxicity modules to an established dynamic energy budget (DEB) model. The DEB model describes the rates of energy acquisition and expenditure by individual organisms; the toxicity modules describe how toxicants affect these rates by changing the value of one or more DEB parameters, notably the parameters quantifying the rates of feeding and maintenance. We investigate four toxicity modules that assume: (1) effects on feeding only; (2) effects on maintenance only; (3) effects on feeding and maintenance with similar values for the toxicity parameters; and (4) effects on feeding and maintenance with different values for the toxicity parameters. We test the toxicity modules by fitting each to published data on feeding, respiration, growth and reproduction. Among the pollutants tested are metals (mercury and copper) and various organic compounds (chlorophenols, toluene, polycyclic aromatic hydrocarbons, tetradifon and pyridine); organisms include mussels, oysters, earthworms, water fleas and zebrafish. In most cases, the data sets could be adequately described with any of the toxicity modules, and no single module gave superior fits to all data sets. We therefore propose that for many applications, it is reasonable to use the most general and parameter sparse module, i.e. module 3 that assumes similar effects on feeding and maintenance, as a default. For one example (water fleas), we use parameter estimates to calculate the impact of food availability and toxicant levels on the long term population growth rate.

[Effects of starvation and refeeding in winter on the growth, survival, and biochemical composition of different size Ruditapes philippinarum]

From December 2007 to April 2008, a laboratory experiment was conducted to study the effects of various starvation periods followed by the same refeeding period on the growth, survival, and biochemical composition of different size Ruditapes philippinarum at water temperature 3.0 degrees C-4.2 degrees C, salinity 25-27, and pH 7.90-8.16. No significant differences in the growth characteristics of R. philippinarum at low temperatures were observed among different size groups. The tolerance to starvation increased with increasing size, while the survival rate decreased with increasing starvation period, point-of-no return (PNR50) was not observed during the study period. For the larger size group (7 mm), the body moisture and lipid concentrations generally decreased with increasing starvation period. During starvation, the body protein content increased initially as a result of lipid being utilized for energy, but decreased thereafter when the lipid was depleting. Ash content remained unchanged during the study period, and was not affected by starvation or refeeding.

[Effects of sea water temperature and salinity on the growth and survival of juvenile Meretrix meretrix Linnaeus]

A laboratory test was conducted to study the effects of different sea water temperature (17 grads) and salinity (19 grads) on the growth and survival of juvenile Meretrix meretrix. The suitable and optimum sea water salinities for the survival of juvenile M. meretrix were 6.5-39.5 and 9.0-31.0, and those for the juvenile growth were 7.3-38.7 and 15.0-23.0, respectively. The suitable sea water temperature for the survival of the juveniles was 4.0 degrees C-36.1 degrees C; the suitable temperature for the growth was 7.0 degrees C-35.4 degrees C, more suitable temperature was 17 degrees C-33.5 degrees C, and the optimum growth temperature was 24 degrees C-27 degrees C. Juvenile M. meretrix had stronger adaptability to high sea water temperature and low sea water salinity.

Toxicity of lead, cadmium and mercury on embryogenesis, survival, growth and metamorphosis of Meretrix meretrix larvae

In order to assess the toxicity of heavy metals on the early development of Meretrix meretrix, the effects of mercury (Hg), cadmium (Cd) and lead (Pb) on embryogenesis, survival, growth and metamorphosis of larvae were investigated. The EC(50) for embryogenesis was 5.4 microg l(-1) for Hg, 1014 microg l(-1) for Cd and 297 microg l(-1) for Pb, respectively. The 96 h LC(50) for D-shaped larvae was 14.0 microg l(-1) for Hg, 68 microg l(-1) for Cd and 353 microg l(-1) for Pb, respectively. Growth was significantly retarded at 18.5 microg l(-1) (0.1 microM) for Hg, 104 microg l(-1) (1 microM) for Cd and 197 microg l(-1) (1 microM) for Pb, respectively. The EC(50) for metamorphosis, similar to 48 h LC(50), was higher than 96 h LC(50). Our results indicate that the early development of M. meretrix is highly sensitive to heavy metals and can be used as a test organism for ecotoxicology bioassays in temperate and subtropical regions.

[Growth and mortality of the mollusk Pteria sterna in wild banks of Southern Baja California, Mexico]

The Gulf of California nacre shell Pteria sterna is an important marine resource in Mexico, and the main species for "half" and round pearl production in the American continent. Wild spat can only be extracted legally for research or culture activities. This study calculates growth and mortality parameters for wild stocks in the eastern coast of Southern Baja California. Height's data (353 dorso-ventral measurements) were taken from 1997 to 1999 at Santa Rosalia, Mulegé and Loreto Bay coast. The maximum length was estimated at 130.35 mm (124.22-136.48 mm, p>0.95). The length frequency data were set in a "virtual year". Seasonal von Bertalanffy growth parameters were calculated in the ELEFAN I routine, the values are: L(infinity) = 156.02 mm, k = 0.48 year(-1), t0 = -0.216 years, C = 0.43, WP = 0.73. and t(s) = 0.5. The growth performance index was phi' = 4.068. The total mortality was calculated from length-converted catch curve Z = 3.34 year(-1). The length-weight relationship was fixed for the equation W = 0.000756 * L(i)(2.7075) (r2 = 0.90, n = 233). The growth parameters values in experimental repopulation conditions are quite different, in contrast with the growth estimated in wild stocks oysters. The value of total mortality is similar to the estimations for Pinctada fucata populations from the Red Sea and P. radiata from the Mediterranean Sea.

Effects of copper on development and survival rate of Paphia malabarica Chemnitz larvae under low saline condition

Venerid clam, Paphia malabarica Chemnitz, is the commercially exploited species distributed exclusively in Vembanad Lake and Ashtamudi estuary, along the south west coast of India. In this study, the survival rate and development of P. malabarica larvae were studied for 3 days in ambient salinity (33), copper (2.5 microg Cu2+ l(-1)), reduced salinities (25 and 20) and a combination of copper in low salinities. No significant differences were found in larval development between treatments. The survival rates decreased considerably with low salinities although the combination of copper and low salinity gave synergistic effects. The reduced survival in low salinities would limit population growth of this species in estuarine areas experiencing low salinities and also explains the absence of larval settlement on habitats close to harbors or river mouths.

Experimental confirmation of multiple community states in a marine ecosystem

Small changes in environmental conditions can unexpectedly tip an ecosystem from one community type to another, and these often irreversible shifts have been observed in semi-arid grasslands, freshwater lakes and ponds, coral reefs, and kelp forests. A commonly accepted explanation is that these ecosystems contain multiple stable points, but experimental tests confirming multiple stable states have proven elusive. Here we present a novel approach and show that mussel beds and rockweed stands are multiple stable states on intertidal shores in the Gulf of Maine, USA. Using broad-scale observational data and long-term data from experimental clearings, we show that the removal of rockweed by winter ice scour can tip persistent rockweed stands to mussel beds. The observational data were analyzed with Anderson's discriminant analysis of principal coordinates, which provided an objective function to separate mussel beds from rockweed stands. The function was then applied to 55 experimental plots, which had been established in rockweed stands in 1996. Based on 2005 data, all uncleared controls and all but one of the small clearings were classified as rockweed stands; 37% of the large clearings were classified as mussel beds. Our results address the establishment of mussels versus rockweeds and complement rather than refute the current paradigm that mussel beds and rockweed stands, once established, are maintained by site-specific differences in strong consumer control.

In situ potential use of metallothionein as a biomarker of cadmium contamination in Ruditapes decussatus

Cadmium (Cd) and metallothionein (MT) concentrations were analysed in the gills and digestive gland of clams Ruditapes decussatus collected from two sites of the Gulf of Gabès (Tunisia) which differ by their degree of pollution. The effect of biotic (maturity stages, protein, sex and body mass) and abiotic factors (temperature, salinity, site and season) on Cd and MT concentrations showed that in the reference site "Bordj d'Ungha" physiological changes caused by gamete development and maturity contributed more to changes in MT concentrations than the bioavailable Cd concentrations; whereas, in the contaminated site "El Hofra", MT induction responded to raised Cd bioavailabilities rather than to physiological changes. With a view to using MTs as metal exposure biomarker in monitoring program, our results show that the analysis in the digestive gland seem to be more relevant than in gills, and that males appear as the most promising candidates compared to females in the determination of this biomarker.

Environmental levels of atrazine decrease spatial aggregation in the freshwater mussel, Elliptio complanata

The commonly used herbicide atrazine (ATR), may cause estrogen-like alterations and, like other xenoestrogens, may alter behavior. Here effects on animal aggregation were tested in freshwater mussels exposed short-term to ecologically relevant ATR concentrations between 1.5 and 150microg/L. The aggregation index (AI), the fraction of mussels in the most densely populated tank section, was evaluated and showed higher AI at later times in both 6- and 72-h trials (p<0.001). After 72h, there was also less aggregation in estradiol- and mid-ATR-treated animals, 26% and 24% less than control, respectively (p<0.04). These data suggest that freshwater mussels tend to aggregate, that 72-h exposure to ecologically relevant ATR concentrations decreases aggregation, and that estradiol exposure has a similar effect. Given that bivalve aggregation may be related to reproduction, the results suggest that low concentrations of ATR may have ecological consequences on animal populations in this species.

Bivalves as indicators of environmental variation and potential anthropogenic impacts in the southern Barents Sea

Identifying patterns and drivers of natural variability in populations is necessary to gauge potential effects of climatic change and the expected increases in commercial activities in the Arctic on communities and ecosystems. We analyzed growth rates and shell geochemistry of the circumpolar Greenland smooth cockle, Serripes groenlandicus, from the southern Barents Sea over almost 70 years between 1882 and 1968. The datasets were calibrated via annually-deposited growth lines, and growth, stable isotope (delta(18)O, delta(13)C), and trace elemental (Mg, Sr, Ba, Mn) patterns were linked to environmental variations on weekly to decadal scales. Standardized growth indices revealed an oscillatory growth pattern with a multi-year periodicity, which was inversely related to the North Atlantic Oscillation Index (NAO), and positively related to local river discharge. Up to 60% of the annual variability in Ba/Ca could be explained by variations in river discharge at the site closest to the rivers, but the relationship disappeared at a more distant location. Patterns of delta(18)O, delta(13)C, and Sr/Ca together provide evidence that bivalve growth ceases at elevated temperatures during the fall and recommences at the coldest temperatures in the early spring, with the implication that food, rather than temperature, is the primary driver of bivalve growth. The multi-proxy approach of combining the annually integrated information from the growth results and higher resolution geochemical results yielded a robust interpretation of biophysical coupling in the region over temporal and spatial scales. We thus demonstrate that sclerochronological proxies can be useful retrospective analytical tools for establishing a baseline of ecosystem variability in assessing potential combined impacts of climatic change and increasing commercial activities on Arctic communities.

Spawning, development, and the duration of larval life in a deep-sea cold-seep mussel

We describe culturing techniques and development for the cold-seep mussel "Bathymodiolus" childressi, the only deep-sea bivalve for which development has been detailed. Spawning was induced in mature mussels by injection of 2 mmol l(-1) serotonin into the anterior adductor muscle. The mean egg diameter is 69.15 +/- 2.36 microm (+/-S.D.; n = 50) and eggs are negatively buoyant. Cleavages are spiral and at 7-8 degrees C occur at a rate of one per 3-9 h through hatching, with free-swimming blastulae hatching by 40 h and shells beginning to develop by day 12. When temperature was raised to 12-14 degrees C after hatching, larvae developed to D-shell veligers by day 8 without being fed. Egg size and larval shell morphology indicate that "B." childressi has a planktotrophic larva, but we did not observe feeding in culture. Wide distribution of this species throughout the Gulf of Mexico and amphi-Atlantic distributions of closely related congeners suggest that larvae may spend extended periods in the plankton. Duration of larval life was estimated for "B." childressi by comparing calculated settlement times to known spawning seasons. These estimates suggest variability in the larval duration, with individuals spending more than a year in the plankton.

The link between operational efficiency and environmental impacts. A joint application of Life Cycle Assessment and Data Envelopment Analysis

Life Cycle Assessment (LCA) allows the estimation of the environmental impacts of a process or product. Those environmental impacts depend on the efficiency with which operations are carried out. In the case that LCA data are available for multiple similar installations, their respective operational performances can be benchmarked and links between operational efficiency and environmental impacts can be established. In this paper, this possibility is illustrated with a case study on LCA of mussel cultivation in rafts. For each site (raft) both its inputs consumption and mussel production are known. A separate LCA of each site has been performed and its corresponding environmental impacts have been estimated. Using Data Envelopment Analysis (DEA) on the input/output data allows computing the relative efficiency of each mussel raft and setting appropriate efficiency targets. The DEA targets represent virtual cultivation sites, which consume less input and/or produce more output. The performance of an LCA study for each of these virtual cultivation sites and the comparison between their environmental impacts are used to estimate the environmental impacts consequences of operational inefficiencies. This direct link can help to convince the managers and operators of the cultivation sites of the double dividend of reducing inputs consumption and achieve operational efficiency: lower costs and lower environmental impacts.

Effects of the antifouling compound, Irgarol 1051, on a simulated estuarine salt marsh ecosystem

Toxicity effects of the antifouling compound, Irgarol 1051, were examined using a simulated estuarine salt marsh ecosystem. The 35 day mesocosm exposure incorporated tidal flux and contained seawater, sediments, marsh grass, and estuarine biota. Irgarol (10.0 microg/l) caused a significant reduction in phytoplankton biomass and primary productivity. HPLC pigment analysis indicated significant effects of irgarol on both phytoplankton and periphyton community composition, with decreased concentrations of pigments representative of diatom species. There was also a significant decrease in dissolved oxygen levels in the 10.0 microg/l irgarol treatment. Growth of the hard shell clam was significantly reduced in the 1.0 and 10.0 microg/l irgarol treatments. The effects observed occurred at irgarol concentrations greater than those typically measured in the environment. Prolonged exposure, the accumulation of irgarol in sediments, plant, or animal tissues, and the interaction of irgarol with other chemicals in the environment; however, could increase risk.

Influence of the salinity adjustment methods, salts and brine, on the toxicity of wastewater samples to mussel embryos

One of the main problems of the Whole Effluent Toxicity is related to the use of bioindicator species representative of the target environment. Most wastewater discharges are of fresh water, so their salinity has to be adjusted when they are discharged to transitional and marine coastal waters, in order to perform toxicity bioassays with reliable organisms. At the moment, there is no optimum technique to allow sample salinity to be adjusted and no specific information regarding salinity adjustment when bivalves are being considered for toxicity test performance. This paper provides information on the potential use of different methods to adjust the salinity of hotel/domestic wastewater samples with different brands of natural and synthetic Dry Salts (DS) and HyperSaline Brine (HSB) for use in the embryo larval development bioassay with the mussel Mytilus galloprovincialis. HyperSaline Brine derived from reconstructed artificial seawater proved to be more viable for wastewater salinity adjustment than DS.

Axinopsida serricata shell encrustation: a potential indicator of organic enrichment conditions in sediments in the southern Strait of Georgia, British Columbia, Canada

We evaluate the potential of the geographic and within-sediment distribution patterns of rust-coloured shell encrustations on an abundant subtidal bivalve, Axinopsida serricata (Carpenter, 1864) as geochemical indicators of organic enrichment from marine municipal outfalls. The progressive development of shell encrustation over the life of the animals is suggested by heavier encrustations on large shells compared to smaller shells regardless of the geochemical conditions of the habitat. Heavy encrustations decline in an exponential manner at sediment acid volatile sulphide (AVS) levels>7 micromol/g. Analyses show that the reddish shell encrustations are from an amorphous iron oxide or hydroxy-oxide likely micro-biologically mediated; the oxides appear to be embedded within the inner matrix of an organic layer, with a chemically distinct outer layer. A schematic model is proposed which shows how enrichment of labile organic carbon around outfalls affects the availability of dissolved iron in sediments and leads to less extensive encrustations on bivalve shells. Predominantly sandy sediments with low organic loading have much less potential for iron oxide deposition than silty sediments due to greater oxygen penetration into the surface sediment. Shell encrustation appears to be relatively persistent and indicative of long-term conditions, regardless of spatial and temporal fluctuations in sediment geochemistry. With more research on development over the life-cycle of the animal, the pattern of A. serricata shell encrustation has the potential to rapidly provide a map of cumulative labile organic loading and oxygen penetration of sediments around municipal outfalls on the west coast of North America where this species is common. However, caution must be used in interpreting results, since background sediment characteristics (substrate type, bottom currents and sediment transport) can affect encrustation patterns.

A micro-dilution method for detecting oxytetracycline-resistant bacteria in marine sediments from salmon and mussel aquaculture sites and an urbanized harbour in Atlantic Canada

A micro-dilution technique with changes in optical density (OD) used to measure bacterial growth over 72 h in culture media containing 0, 5, 10, 20, 40, 80 and 160 microg OTC (oxytetracycline)ml(-1) was applied to determine growth inhibition (GI) in mixed bacterial strains cultured from samples of marine sediments and salmon feed pellets. Growth of control cultures (Aeromonas salmonicida) was inhibited at all OTC concentrations. Some feed pellet samples and under-cage sediments from salmon aquaculture sites in the Bay of Fundy showed GI up to > or = 160 microg OTCml(-1). Lower values (40 to 80 microg OTC ml(-1)) occurred in subsurface (5-18 cm) sediments, > 100 m from salmon pens and adjacent to sewage outfalls in Halifax Harbour. GI values < 20 microg OTC ml(-1) in sediment from reference locations in Halifax Harbour and mussel aquaculture sites are considered to reflect natural background levels for OTC resistance.

Does Manila clam cultivation affect habitats of the engineer species Lanice conchilega (Pallas, 1766)?

The major French site of Manila clam Ruditapes philippinarum (Adams and Reeves, 1850) cultivation is located in the Chausey Archipelago where the associated practices are highly mechanized: every steps of production are made with tractor-driven machinery. The Manila clam concessions are concentrated on Lanice conchilega (Pallas, 1766) bioherms, which are known to increase alpha-diversity and to locally modify sediment dynamics. This study focus on the impacts of Manila clam cultivation on (i) the natural populations of L. conchilega and on (ii) the structure of the associated benthic assemblages during the different steps of the farming production cycle. We found that the L. conchilega populations are significantly affected within the concessions where their total abundances drastically decrease, their spatial patterns are modified and the associated benthic assemblages are significantly altered. Our results are discussed in a context of a sustainable management of the Manila clam cultivation in coastal areas.

The influence of developmental stages and protective additives on cryopreservation of surf clam (Spisula sachalinensis) larvae

This study was performed to find out the optimal larval stage and the most desirable protective additives for cryopreservation of surf clam, Spisula sachalinensis larvae. The survival rates of frozen-thawed larvae increased with post developmental stage. The highest value of 96.1 +/- 1.0% was achieved using umbo stage larva as developmental stage and 0.2 M sucrose as protective additive.

[Bioremediation potential of Apostichopus japonicus (Selenka) in coastal bivalve suspension aquaculture system]

Suspension aquaculture of filter-feeding bivalves can produce large amount of faeces and pseudofaeces (biodeposits) that may impact aquaculture environment, while deposit-feeding sea cucumbers may effectively utilize such particulate wastes and act as a scavenger in mariculture system. In this paper, the ingestion, growth, and excretion of deposit-feeder Apostichopus japonicus were investigated in situ seasonally to evaluate its bioremediation potential of a suspension aquaculture system of filter-feeding bivalves. The results showed that A. japonicus could grow well in newly designed culture nets, with its maximum specific growth rate being 0.34% d(-1). The A. japonicus could effectively use the biodeposits generated by co-cultured bivalves, and the ingestion rate at 21.2 degrees C in summer, 19.2 degrees C in autumn, and 7.7 degrees C in winter was 0.1746, 0.0989, and 0.0050 g g(-1) d(-1), respectively. A. japonicus could promote the regeneration of nutriens in biodeposits via the excretion of considerable amount of dissolved N and P, and the excretion also showed obvious seasonal fluctuation. The extrapolation based on the in situ investigation results showed that when co-cultivated with bivalves in lantern nets, A. japonicus would ingest 4.5-159.6 kg hm(-2) d(-1) of dry biodeposits and excrete 1,382.5-3,678.1 mmol hm(-2) d(-1) of NH4(+)-N and 74.6-335.7 mmol hm(-2) d(-1) of PO4(3-)-P, indicating that the deposit-feeding A. japonicus had a great bioremediation capability in suspension aquaculture systems. The integrated model of deposit-feeding A. japonicus and filter-feeding bivalve could not only benefit the economy, but also sustain the environment.

Effect of sewage discharge in Spisula subtruncata (da Costa 1778) populations

Sewage discharge is a common source of pollution in coastal marine waters. Several municipal treatment plants dump treated water in medium to fine sand Spisula subtruncata communities. This bivalve is generally considered a major food source for demersal fishes, and it is important as a dominant species in structuring the macrobenthic community during the spring and summer months. We sampled within five locations affected by sewage discharge along the Castellon coast (northwest Mediterranean Sea) where S. subtruncata (da Costa 1778) is a common bivalve. Van Veen grab samples were obtained for the study of the bivalve population and to characterize the sediment. The sewage discharges studied affect Spisula populations. In the stations near the outfalls, the abundance and the average size of S. subtruncata decreased. However, this effect did not correlate with sediment characteristics, such as granulometry or pH.

Declining populations of freshwater pearl mussels (Margaritifera margaritifera) are burdened with heavy metals and DDT/DDE

Many aquatic mollusks, such as the freshwater pearl mussel (Margaritifera margaritifera), are in decline throughout Europe. The reasons are largely unknown; factors that have been suggested to contribute are river bed compaction due to agricultural practices, eutrophication, or pollutants of various natures. Brittle shells of recently deceased pearl mussels from northern Bavaria with weak calcium incrustations point to the possibility that calcium metabolism is affected. It is known that certain persistent organic pollutants and some heavy metals may induce calcium deficiency in wildlife. Elevated levels of the organochlorine insecticide DDT and its metabolite DDE, as well as of cadmium and some other heavy metals, have been found in pearl mussels. Both classes of environmental pollutants are known to potentially interfere with calcium homeostasis.