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1.
The Pacific oyster Crassostrea gigas was introduced in Europe for commercial purposes in the mid 1960s. It was initially thought that low winter temperatures would restrain this species' reproduction and settlement; however, its present distribution in areas where no introduction has taken place suggests that natural invasion and expansion has occurred. Along the European coast, wild populations of Pacific oysters are already found from northern Germany to southern Portugal. Whether C. gigas will continue to further expand through northern waters will depend on its physiological performance. In this study, the performance of wild oyster populations has been studied in terms of growth and reproduction at three stations: La Rochelle (France; 46°N), Yerseke (Oosterschelde estuary, The Netherlands, 51°N), and Texel (Wadden Sea estuary, The Netherlands, 53°N). The French population had the lowest somatic-shell mass ratio and an increase in maximum shell length, somatic and gonadal mass was observed from France to the Netherlands. In addition, mean oocyte diameter decreased significantly from south to north. The combination of increasing gonadal mass and decreasing oocyte volume suggests an increasing reproductive output in terms of egg numbers from France to The Netherlands. Differences in temperature between locations will at least be partly responsible for the observed patterns; however, other environmental factors (such as food availability, predation pressure, sediment type and/or seston concentration) cannot be excluded. Since smaller eggs (oocytes) are thought to have a longer development time, the environmental conditions along the Dutch coast may result in increased larval dispersal and possibly in further population expansion.  相似文献   

2.
In this work, we analysed the latitudinal trends in the nursery habitat colonization processes of the European flounder (Platichthys flesus). This was accomplished by estimating the duration of the pelagic and metamorphic stages, as well as the duration of the spawning period, in several nursery areas across its geographical distribution range in the European Atlantic Coast: Mondego estuary (Portugal), Vilaine estuary (France), Slack estuary (France), Wadden Sea (Netherlands) and the Sørfjord (Norway). All juvenile flounders were captured with beam trawls in June/July 2010, and otolith microstructure was used to determine the duration of each stage by means of daily growth increments. The pelagic and metamorphic stages were longer at the middle of the distribution range, and lasted in total up to two months after hatching. The spawning period occurred between mid-January and early-July over the species' distribution range, with a time lapse of nearly two months between the Mondego estuary and the Sørfjord, as a consequence of warmer water temperature earlier in the season in southern areas. In general, total length of the captured fish showed a latitudinal cline between the northernmost and southernmost sampling sites, with higher values at the middle of the distribution range. The results also suggested the existence of a countergradient growth compensation mechanism in the northernmost populations. Apart from temperature, which sets the general metabolic pace of organisms, differences between sites were also related with local features, such as the extension of the continental platform and adaptations to transport and retention mechanisms.  相似文献   

3.
The feeding ecology, growth and spatial–temporal abundance and distribution of Pomatoschistus microps (Krøyer, 1838) and Pomatoschistus minutus (Pallas, 1770) were studied between June 2003 and June 2004, based on beam trawl surveys and macrobenthic samples conducted in the Mondego estuary, Portugal. Polychaetes, molluscs and amphipods were the most important items in the diet of P. microps, while for P. minutus the dominant preys were polychaetes, mysids and decapods. Pomatoschistus microps' recruitment lasted for six months and was composed of three new cohorts per year. Pomatoschistus minutus had an uncommon long reproductive season, from April to November, and population segregation was found, corresponding to the two reproductive peaks. Populations of both species were composed mainly of 0-group individuals with sand gobies presenting a more extended life span. In the Mondego estuary, inter- and intra-specific spatial segregation occurred between the two species and between the 0+ and 1+ age groups of P. microps.  相似文献   

4.
Cerastoderma edule and Mya arenaria are two common bivalve species in European waters. Longevity and maximum size are much greater in the latter species. Because comparison of species life-history strategies states that a long life span (i.e. high annual survival) generally goes with lower fecundity, we hypothesise that reproductive output would be lower in M. arenaria than in C. edule. In the present paper, we studied the reproductive strategies of these two species in an intertidal and a subtidal area of the western Dutch Wadden Sea, by following seasonal changes in absolute and relative weights of somatic and gonadal tissues in these bivalves. Starting of spawning was similar in the two species, around May, except for intertidal M. arenaria, which initiated spawning in August. Individual energy investment in reproduction was similar for the two species but, unlike M. arenaria, C. edule spawned completely, releasing all energy of gonadal mass in the form of gametes. Mya arenaria used the gonad not only for reproduction but also for storage. In the intertidal area, we found a trade-off between longevity and reproduction, i.e. maximum reproductive output (expressed as a proportion of body mass) was higher in C. edule than in M. arenaria. However, since body size is larger and life span longer in M. arenaria than in C. edule, mean lifetime reproductive output per individual must be higher in the first than in the latter. Based on the differences in reproductive strategies of these two species, we hypothesise that the negative effects of warming climate on bivalve population dynamics in the Wadden Sea will be stronger in C. edule than in M. arenaria.  相似文献   

5.
The seasonal occurrence and reproductive strategy of the nemertean Tetrastemma fozensis, which inhabits the mantle cavity of the bivalve Scrobicularia plana, was studied through the analysis of the temporal diversity of a T. fozensis population. Bimonthly sampling was carried out from February 2001 to January 2002 at mudflats of Villaviciosa estuary (Asturias, Northern Spain). Nemerteans were found throughout the study period, but variations in their abundance were detected, with a maximum during winter months and a minimum during summer months. Moreover, variations in mean size of nemerteans were found, with maximal sizes at the end of the spring and the beginning of the summer and minimum size at early autumn. The annual variations in population parameters (decrease in abundance and complete disappearance of large individuals in summer) suggest that T. fozensis has a distinct reproductive season and a semelparous reproductive strategy.  相似文献   

6.
0-Group sole, Solea solea (Linnaeus, 1758) were sampled in four nursery grounds: two on the Northern French coast and two on the Portuguese coast. Juvenile sole were collected at the Vilaine estuary (Northern Bay of Biscay) in 1992, in the Authie estuary (Eastern English Channel) in 1997, and in the Douro and Tagus estuary (Northern and central Portugal, respectively) in 2005. Left lapilli otoliths were used to estimate age and investigate variability in growth rates and hatch dates. In the French study areas nursery colonisation ended in early June in the Vilaine estuary and in late June in the Authie estuary. In the Portuguese estuaries nursery colonisation ended in May in the Douro estuary and in late June in the Tagus estuary. Growth rates were higher in the Portuguese estuaries, 0.767 mm d−1 in the Tagus estuary and 0.903 mm d−1 in the Douro estuary. In the French nurseries, growth rates were estimated to be 0.473 mm d−1 in the Villaine estuary and 0.460 mm d−1 in the Authie estuary. Data on growth rates from other studies shows that growth rates are higher at lower latitudes, probably due to higher water temperature. Spawning took place between early January and early April in the Villaine estuary's coastal area in 1992. In 1997, in the Authie estuary spawning started in late January and ended in early April. On the Douro estuary's adjacent coast spawning started in mid-January and ended in late March, in 2005, while on the Tagus estuary's adjacent coast spawning started in mid-February and ended in mid-April, in the same year. Literature analysis of the spawning period of sole along a latitudinal gradient ranging from 38°N to 55°N in the Northeast Atlantic indicated that there is a latitudinal trend, in that spawning starts sooner at lower latitudes. Results support that local conditions, particularly hydrodynamics, may overrule general latitudinal trends.  相似文献   

7.
We present an ecophysiological model of the bivalve Cerastoderma edule that simulates individual growth and reproduction under ambient conditions in temperature and food availability in the Oosterschelde estuary, SW Netherlands. The model contains feedback loops in the uptake and metabolism of food and in the partitioning of carbon to the internal state variables: somatic tissue, storage, organic shell matrix and gametes.The model was calibrated for 24 parameters, based on random distributions of parameter values. This procedure includes an estimate of confidence intervals of the output variables. The simulated growth of shell length and animal wet and dry weight reflected the observed values of growth in the field for the period 1993 – 1997. The model is a tool for the integration of ecophysiological knowledge of this species and also for carrying-capacity studies of shellfish culture and for environmental management of populations in estuarine and coastal areas.  相似文献   

8.
The macrobenthic production of an estuarine system was evaluated over a 14-year study period in a seagrass bed and in a sandflat. Over this period, the estuary suffered severe eutrophication and extreme weather events with important impacts on the community, impairing system functioning and ultimately the goods and services provided by the estuary (decline in the seagrass bed, decreased community production and/or a boost in the production by opportunist species, such as Hydrobia ulvae). Following the anthropogenic impacts, management measures were introduced which allowed a gradual recovery of the seagrass bed and a new macrobenthic community structure manifested by production increases of slow-growing species, such as Scrobicularia plana and Hediste diversicolor. There was a gradual re-orientation of energy into population biomass instead of population density but this was not translated into higher community production, mainly due to the decreased production of opportunist species (H. ulvae and several polychaetes). Several weather extreme events occurred during this post-mitigation phase - floods, heatwaves and droughts, all of which had negative impacts on macrobenthic dynamics and production. The heatwaves led to the greatest decreases in macrobenthic production, mainly due to S. plana perhaps associated with its physiological intolerance of higher temperatures. The prolonged drought that followed the heatwaves maintained low levels of production by S. plana and H. ulvae. With climate change, the frequency and intensity of extreme weather events are likely to increase worldwide so that the recovery of impacted/disturbed systems from impacts such as eutrophication may be seriously affected by these additional stressors, compromising attempts to improve the ecological quality of estuarine ecosystems.  相似文献   

9.
A survey within the French National Programme of Ecotoxicology was carried out in 2002, 2003 and 2004 to study the response of Nereis diversicolor populations (Polychaeta, Nereididae) to the impact of pollution in the Authie estuary (non-contaminated site) and in the Seine estuary (contaminated site). In the period studied, the density varied from 672 ind. m−2 to 3584 ind. m−2 in the Authie estuary and from 80 ind. m−2 to 920 ind. m−2 in the Seine estuary. Biomass varied from 3.94 g m−2 (dry weight) in February 2004 to 38.0 g m−2 in August 2003 in the Authie estuary and from 3.4 g m−2 in February 2002 to 0.6 g m−2 in February 2004 in the Seine estuary. Density and biomass of the populations of N. diversicolor were consistently lower in the Seine estuary than in the Authie estuary. Size frequency histograms permit the analysis of the cohorts as well as the elaboration of the growth curves. For the individuals from the Authie estuary, the relation between dry weight (DW) and length L3 (prostomium, peristomium and chaetiger 1) was DW = 4.2205 L32.9832. For those from the Seine estuary, the relation between dry weight and L3 was DW = 0.4697e1.7209L3. The individuals of N. diversicolor should belong to eight cohorts in Authie estuary (two cohorts each year) instead of six cohorts for those from the Seine estuary. These differences can be attributed to the effect of pollution on the population of N. diversicolor.  相似文献   

10.
The annual total and organic mercury bioaccumulation pattern of Scrobicularia plana and Hediste diversicolor was assessed to evaluate the potential mercury transfer from contaminated sediments to estuarine food webs. S. plana was found to accumulate more total and organic mercury than H. diversicolor, up to 0.79 mg kg−1 and 0.15 mg kg−1 (wet weight) respectively, with a maximum annual uptake of 0.21 mg kg−1 y−1, while for methylmercury the annual accumulation was similar between species and never exceeded 0.045 mg kg−1 y−1. The higher organic mercury fraction in H. diversicolor is related to the omnivorous diet of this species. Both species increase methylmercury exposure by burrowing activities and uptake in anoxic, methylmercury rich sediment layers. Integration with the annual biological production of each species revealed mercury incorporation rates that reached 28 μg m−2 y−1, and to extract as much as 11.5 g Hg y−1 (of which 95% associated with S. plana) in the 0.4 km2 of the most contaminated area, that can be transferred to higher trophic levels. S. plana is therefore an essential vector in the mercury biomagnification processes, through uptake from contaminated sediments and, by predation, to transfer it to economically important and exploited estuarine species.  相似文献   

11.
The Lima estuary (NW Portugal) is at the end of an international watershed, whose potential role as a spawning and nursery habitat for local fish populations has not been previously examined. To address this knowledge gap, fortnightly plankton surveys were conducted between April 2002 and April 2004. A total of 12,903 larvae, belonging to 20 families and 50 taxa were collected, with a mean abundance of 8 individuals per 100 m3. Gobiidae was the most abundant family comprising 71% of the total catch, followed by Clupeidae with 12% of the total. The top six abundant taxa (Pomatoschistus spp., Sardina pilchardus, Ammodytes tobianus, unidentified Clupeidae, Symphodus melops and Solea senegalensis) represented 91% of the total catch. Fish larvae showed a seasonal trend with abundances increasing during spring and summer. Diversity was generally low (H′ = 0.65) with high dominance of very few taxa. Near the ocean, the larval fish assemblage was more diverse due to the presence of marine species. In the lower estuary Channel zone, abundance was lower than in the two upstream salt marsh zones (North and South zones) and no statistical differences in abundance or diversity values were found within the latter zones. ANOSIM results demonstrated seasonal differences in the species composition, mainly during the second winter period which was typified by a pelagic species A. tobianus. The community in the Channel zone was more diverse in comparison with the other zones, which were highly dominated by the most abundant species. The spatial and temporal trends of the most abundant species were typical for Iberian estuaries, with the exception of the low abundance of anchovy larvae and the unusually high numbers and frequency of S. pilchardus, usually mentioned as accidental in estuarine systems. Overall results suggest that the Lima estuary larval fish assemblage has a strong seasonality and affinity to the salt marsh zones. It seems that spawning seasonality controlled the presence of temporary estuarine residents, while environmental aspects controlled the general abundance trend of the resident species.  相似文献   

12.
An experimental study on Phragmites australis leaf litter decomposition was conducted in the estuarine environment, Ria de Aveiro, Western Portugal, using the leaf-bag technique, with fine- (1 mm) and coarse-mesh (5 mm) bags. The leaf bags were placed in the field sites at day 0, covering a complete salinity gradient, and replicates were collected over time, at days 3 (leaching), 7, 15, 30 and 60. The biomass loss through the leaching phase, about 20% of the initial leaf mass, was independent of both the salinity and the bag mesh size. The biomass decay pattern along the salinity gradient varied through time and presented strong similarities between the two mesh sizes, with the remaining biomass always lower in the 5 mm mesh-size bags. At days 7 and 15, the lowest remaining biomass was observed at the head of the estuary, the preferential distribution area of P. australis. At day 30, the remaining biomass was higher in the marine area and diminished under a direct relationship with salinity, reaching the lowest value in the freshwater environment, with values ranging from 66% to 44% of the initial weight in 5 mm bags, and from 79% to 51% in 1 mm bags. The largest heterogeneity in the remaining biomass among the study areas positioned along the salinity gradient was found close to days 30 (5 mm) and 40 (1 mm). The overall results indicate that the relationship between leaf decay rate and salinity depends on the decay time considered (k15, k30 or k60) and, for the later stages (k60), also on the leaf-bag mesh size. This implies that the use of leaf litter decay rates as a functional indicator in transitional waters will need to take into consideration the factor location in the salinity gradient and leaf litter stage at which the decay rate is determined. The differences between the decay rates with the mesh size acted mainly at the level of the absolute k value and not at the level of the pattern along the salinity gradient. Even so, the data obtained at the mouth of the estuary, in the area closest to a fully marine environment, indicated that after the initial biomass loss through leaching, P. australis decayed either very slowly, in the 5 mm, or not at all, in the 1 mm mesh bags.  相似文献   

13.
Stable carbon and nitrogen isotopes were used to assess site fidelity of Solea solea and Solea senegalensis juveniles, to investigate food web interactions and to determine the dominant nutrient pathways in two nursery areas in the Tagus estuary, Portugal. Samples of water from the main sources and from the nursery areas and respective saltmarsh creeks were collected for isotope analysis, as well as sediment, benthic microalgae, saltmarsh halophytes, S. solea, S. senegalensis and its main prey, Nereis diversicolor, Scrobicularia plana and Corophium spp. While site fidelity was high in 0-group juveniles, it was lower for 1-group juveniles, possibly due to an increase in mobility and energy demands with increasing size. Analysis of the food web revealed a complex net of relations. Particulate organic matter from the freshwater sources, from each nursery's waters and saltmarsh creeks presented similar isotopic composition. Sediment isotopic composition and saltmarsh halophytes also did not differentiate the two areas. All components of the food web from the benthic microalgae upwards were isotopically different between the nursery areas. These components were always more enriched in δ13C and δ15N at the lower nursery area than at the nursery located upstream, appearing as if there were two parallel trophic chains with little trophic interaction between each other. A mixture of carbon and nitrogen sources is probably being incorporated into the food web. The lower nursery area is more dependent upon an isotopically enriched energy pathway, composed of marine particulate organic matter, marine benthic microalgae and detritus of the C4 saltmarsh halophyte Spartina maritima. The two nursery areas present a different level of dependence upon the freshwater and marine energy pathways, due to hydrological features, which should be taken into account for S. solea and S. senegalensis fisheries and habitat management.  相似文献   

14.
A nocturnal demersal nekton assemblage was sampled fortnightly for two years at five sites in the Labu estuary using a 3 m beam trawl with a 3·2 cm mesh net. Forty-eight species were caught, totalling 31 458 individuals with the five most abundant species comprising over 95% of the catch. Using multiple regression techniques with Fourier transformations, the mean number of species, S, the mean abundance, N, and mean weight, W, were found to conform to a regular annual cycle with maxima in April and May. Seven of the 11 most abundant species demonstrated regular annual cycles of abundance. S, N and W were greatest in the wider, middle sites and lowest in a shallow, stagnant side branch of the estuary. Catch weights and abundances were significantly correlated with physical data.Salinity and temperature values in the estuary exhibited an annual cycle with maxima occurring in February/March. The annual thermal variation of surface water outside the estuary followed a similar cycle. The salinity at the mouth of the Markham River is lowest during January/February, which corresponds with the rainy season in the Markham River catchment. Significant annual variation existed between years in estuarine bottom salinity and salinity values in Labu Bay.Several species exhibited a greater variation in abundance and mass between years than within years. This supports the hypothesis that in the tropics between-year variation in coastal marine biotic communities is greater than within-year variation.  相似文献   

15.
The Lusitanian toadfish, Halobatrachus didactylus (Bloch and Schneider, 1801), is a subtropical sound-producing marine teleost that inhabits estuaries and other brackish water ecosystems in its northern distribution area. The relative isolation of populations within estuaries may cause important modifications in the bio-ecology of this species. The males of this species present two morphotypes which are more accurately distinguishable during the reproductive season. In the Tagus estuary population, the two types of reproductive males were present: type I, the “characteristic” morphotype, and type II, the alternative morphotype. The opportunistic males had more developed testis while type I males had more developed accessory glands. Type I males presented more developed swimbladders and larger body size and live longer than type II males. On the contrary, type II males grew faster and matured earlier. The feeding habits of the two male morphotypes were similar during the reproductive season but differences were found between reproductive specimens and non-reproductive specimens. The diet of reproductive specimens was mainly composed of benthic prey in contrast to predominance of nectobenthic prey in the diet of non-reproductive specimens. The females of H. didactylus generally had an intermediate pattern between the two male morphotypes. The percentage of type II males tended to be higher in denser areas of the estuary. In comparison with populations from different size ecosystems, smaller ecosystems revealed important modifications on the bio-ecology of the species due to the increased competition for nesting sites and mating partners, favouring alternative male tactics.  相似文献   

16.
《Journal of Sea Research》1999,41(3):203-212
Bivalve eggs generally contain large amounts of lipids which, in comparison with proteins and carbohydrates, have high energy contents and are thus costly in energetic terms. As lipid contents vary between species, comparisons of reproductive investments should not only include numbers and sizes of eggs, but also their energy content. We estimated the investment in egg material of mature females of the Baltic tellin Macoma balthica (L.) in terms of both mass and energy content. All mass below a minimum body mass (below which no eggs are produced) was defined as structural mass. This threshold amounts to a body mass index (BMI) of 5.6 (ash-free dry mass per cubic shell length in mg cm−3). More than half (55%) of the mass above the structural mass was invested in egg material and 45% in extra somatic tissue and tissue for production and storage of gametes. This means that the amount of eggs spawned ranged from 0 (at BMI = 5.6 mg cm−3) to 33% of the total ash-free dry mass (at a high BMI value of 14 mg cm−3). Eggs contained a relatively large amount of lipids, about 30% of their ash-free dry mass, whereas non-egg material contained only about 7% lipids. Eggs of two other bivalves in the Wadden Sea, the cockle Cerastoderma edule and the mussel Mytilus edulis, were smaller and contained only about 11% and 20% lipids, respectively. Energy content of M. balthica eggs amounted to ∼0.006 J, in the other two species to ∼0.002 J. The function of the more expensive eggs in M. balthica may be related to its early spawning in spring, causing slower larval development until first feeding.  相似文献   

17.
The influence of prolonged mouth closure on the population dynamics of the caridian shrimp, Palaemon peringueyi and the estuarine isopod, Exosphaeroma hylocoetes, in the littoral zone of temporarily open/closed Kasouga Estuary located on the south-eastern coastline of southern Africa was assessed monthly over the period October 2007 to September 2008. Prolonged mouth closure of the estuary contributed to hypersaline conditions (psu > 35) prevailing throughout the estuary for the last four months of the study. The high salinities coincided with a decrease in the areal extent (up to 80%) of the submerged macrophytes, mainly Ruppia maritima, within the littoral zone of the estuary. Total abundance and biomass values of the shrimp and isopod over the period of investigation ranged from 0 to 14.6 ind m−2, from 0 to 13.3 mg dwt m−2, from 12 to 1540 ind m−2 and from 0.1 to 2.16 mg dwt m−2, respectively. Maximum values of both the shrimp and isopod were recorded in the upper reaches of the estuary in close association with R. maritima. Over the course of the investigation, both the abundance and biomass values of the shrimp decreased significantly (P < 0.05 in both cases) which could be related to reduced habitat availability, R. maritima, that acts as a refuge against fish predation. Additionally, the decrease in abundance and biomass values could be attributed to reduced recruitment opportunities for the shrimp and the cessation of reproduction in the estuarine isopod. The establishment of a link to the marine environment following an overtopping event in September 2008 contributed to a decrease in salinity within the system although no recruitment of either the isopod or shrimp was recorded.  相似文献   

18.
Assessments of temporal variation in stable carbon and nitrogen ratios were used to examine seasonal trends of the water column and benthic food webs in the Mondego estuary (Portugal). There was a marked seasonality in weather and water column conditions, including nutrient supply and chlorophyll concentrations. In spite of the pronounced environmental changes, we found little evidence of seasonal variation in δ13C and δ15N of producers and consumers in the Mondego estuary, with a few notable exceptions. Nitrogen isotope ratios in macrophytes (Zostera noltii, Ulva sp., Enteromorpha sp., and Gracilaria sp.), and in two grazers (Idotea chelipes and Lekanesphaera levii) increased during late summer, with the highest δ15N values being measured in July, during a period of elevated temperatures and drought, which may have favored high rates of denitrification and heavier δ15N values. The results suggest that stable-isotope values from macrophytes and selected grazers are useful as tracers of seasonal changes in nitrogen inputs into estuaries, and that those of consumers reflect other factors beyond seasonal variations in N and C sources.  相似文献   

19.
《Journal of Sea Research》2010,63(4):295-298
The American razor clam Ensis americanus is a marine bivalve indigenous from the American coast that was introduced in Europe in the late 1970s and has managed to build up strong populations along the European coast. In the present paper, we studied energy investment into soma and gonads by following the seasonality in growth and reproduction of this species in a subtidal area of the western Dutch Wadden Sea. Body and somatic mass indices showed a seasonal pattern with maximal values in August and minimal in April. Gonadal mass index showed the opposite trend with highest values in April. Spawning started in April/May and a second, but weaker, spawning event apparently occurred in August/September. Gonadosomatic ratio values were very low. Just before the spawning period, only 2.5% of the body mass of E. americanus consisted of gonads.  相似文献   

20.
Due to the lack of knowledge regarding annual bioaccumulation rates in estuarine and marine fauna, the main aim of this work was to study the annual mercury bioaccumulation in the well-documented bivalve species Scrobicularia plana along a human induced mercury gradient in the Ria de Aveiro coastal lagoon (Portugal) and in a nearby, non-polluted system (Mondego estuary), parallel to the risks associated with its consumption by humans.Minimum total mercury concentration was as low as 0.019 mg kg−1 (wwt) in 4+ year old organisms in the reference site, where a significant negative correlation (p < 0.05) was found between total mercury concentrations and size, resulting in negative bioaccumulation rates (detoxification). On the other hand, values reached 1.8 mg kg−1 (wwt) in 3+ year old bivalves from the most contaminated area, where a strong positive correlation with size was found (p < 0.01) and annual bioaccumulation rates were as high as 0.25 mg kg−1 yr−1. Annual bioaccumulation rates were highly correlated with suspended particulate matter mercury concentrations. Even though the levels of organic mercury contents increased parallel to the contamination gradient, at each sampling station, no increment was found with age, which corresponded to a decrease in organic mercury percentage with age.In terms of ecological management and public health, the ratio of 0.01 consistently found between Scrobicularia plana annual mercury accumulation rates and SPM mercury levels for most sites may permit to roughly estimate S. plana contamination of commercial sized individuals (>2.5 cm) and, if verified and confirmed in other systems, be used as a simple management tool.  相似文献   

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