Time trend of Butyl- and Phenyl-Tin contamination in organisms of the Lagoon of Venice (1999–2003)

In the period 1999-2003 a monitoring study on the accumulation of organotin compounds in edible organisms in the Lagoon of Venice was conducted. Butyl and Phenyl derivatives were determined in pooled samples of Mytilus galloprovincialis and Tapes spp. with the aims of assessing organotin contamination in the Lagoon of Venice in the period just preceding their ban in Europe, monitoring the concentrations in organisms with a high commercial use, evaluating a potential hazard for human health due to seafood and identifying the possible contamination sources. Sampling stations (up to 20) were distributed around the Lagoon and particularly concentrated in the area close to the town of Chioggia. Significantly higher (analysis of variance (ANOVA), p < 0.05) tributyltin (TBT) concentrations were found in mussels (from 38 +/- 8 to 6,666 +/- 1,333 microg kg(-1) d.w., as TBT(+)), than in clams (from 6 +/- 1 to 2,256 +/- 451 microg kg(-1) d.w., as TBT(+)). During the 3 years of the survey no increase in average concentrations of the butyltin compounds (tributyltin (TBT) + dibutyltin (DBT) + monobutyltin (MBT)) was observed (ANOVA, p > 0.05) in either species. Furthermore, by analyzing the entire data set, it is evident that most stations show analogous concentrations in the 3 years for both species, whereas few have anomalously higher concentrations. If organotin concentrations in specimens from some sites are compared with the Tolerable Average Residue Level, a possible risk for human health must be considered.     

Inter- and Intra-Annual Chemical Variability During the ice-Free Season in Lakes with Different Flushing Rates and Acid Deposition Histories

Quantifying chemical variability in different lake types is important for the assessment of both chemical and biological responses to environmental change. For monitoring programs that emphasize a large number of lakes at the expense of frequent samples, high variability may influence how representative single samples are of the average conditions of individual lakes. Intensive temporal data from long-term research sites provide a unique opportunity to assess chemical variability in lakes with different characteristics. We compared the intra- and inter-annual variability of four acidification related variables (Gran alkalinity, pH, sulphate concentration, and total base cation concentration) in four lakes with different flushing rates and acid deposition histories. Variability was highest in lakes with high flushing rates and was not influenced by historic acid deposition in our study lakes. This has implications for the amount of effort required in monitoring programs. Lakes with high flushing rates will require more frequent sampling intervals than lakes with low flushing rates. Consideration of specific lake types should be included in the design of monitoring programs.     

Multiscale Spatial and Small-Scale Temporal Variation in the Composition of Riverine Fish Communities

We studied the multiscale (sites, river reaches and rivers) and short-term temporal (monthly) variability in a freshwater fish assemblage. We found that small-scale spatial variation and short-term temporal variability significantly influenced fish community structure in the Macquarie and Namoi Rivers. However, larger scale spatial differences between rivers were the largest source of variation in the data. The interaction between temporal change and spatial variation in fish community structure, whilst statistically significant, was smaller than the variation between rivers. This suggests that although the fish communities within each river changed between sampling occasions, the underlying differences between rivers were maintained. In contrast, the strongest interaction between temporal and spatial effects occurred at the smallest spatial scale, at the level of individual sites. This means whilst the composition of the fish assemblage at a given site may fluctuate, the magnitude of these changes is unlikely to affect larger scale differences between reaches within rivers or between rivers. These results suggest that sampling at any time within a single season will be sufficient to show spatial differences that occur over large spatial scales, such as comparisons between rivers or between biogeographical regions.     

Continuous high-frequency monitoring of estuarine water quality as a decision support tool: a Dublin Port case study

High-frequency, continuous monitoring using in situ sensors offers a comprehensive and improved insight into the temporal and spatial variability of any water body. In this paper, we describe a 7-month exploratory monitoring programme in Dublin Port, demonstrating the value of high-frequency data in enhancing knowledge of processes, informing discrete sampling, and ultimately increasing the efficiency of port and environmental management. Kruskal–Wallis and Mann–Whitney tests were used to show that shipping operating in Dublin Port has a small–medium effect on turbidity readings collected by in situ sensors. Turbidity events are largely related to vessel activity in Dublin Port, caused by re-suspension of sediments by vessel propulsion systems. The magnitudes of such events are strongly related to water level and tidal state at vessel arrival times. Crucially, measurements of Escherichia coli and enterococci contamination from discrete samples taken at key periods related to detected turbidity events were up to nine times higher after vessel arrival than prior to disturbance. Daily in situ turbidity patterns revealed time-dependent water quality “hot spots” during a 24-h period. We demonstrate conclusively that if representative environmental assessment of water quality is to be performed at such sites, sampling times, informed by continous monitoring data, should take into account these daily variations. This work outlines the potential of sensor technologies and continuous monitoring, to act as a decision support tool in both environmental and port management.     

Results from the NOAA National Status and Trends Program on distribution and effects of chemical contamination in the coastal and estuarine United States

The NOAA National Status and Trends (NS&T) Program has been monitoring chemical contamination in fish livers, and surface sediments since 1984 and in molluscan tissue and sediments since 1986. Data from fine-grained sediment at 175 sites are used to describe the spatial distribution of contamination throughout the coastal and estuarine United States. Highest levels are generally found in, and considered representative of, urban areas. It should be noted, however, that these levels are not as high as have been found near discharge pipes or in isolated industrial areas through other monitoring efforts. Dramatic biological responses, such as liver tumors in fish or apparently toxic contaminant levels in sediment, are found infrequently. Subtle biological changes, especially those that affect reproductive ability, are being sought. Data from three annual collections of mollusks have been used to identify early signals of temporal trends in contamination at NS&T sites.     

Trace metal concentrations in suspended particles, sediments and clams (Ruditapes philippinarum) from Jiaozhou Bay of China

Suspended particulate matter (SPM), sediments and clams were collected at three sites in Jiaozhou Bay to assess the magnitude of trace metal pollution in the area. Metal concentrations in SPM (Cu: 40.11-203; Zn: 118-447; Pb: 50.1-132; Cd: 0.55-4.39; Cr: 147.6-288; Mn: 762-1670 microg/g), sediments (Cu: 17.64-34.26; Zn: 80.79-110; Pb: 24.57-49.59; Cd: 0.099-0.324; Cr: 41.6-88.1; Mn: 343-520 microg/g) and bivalves (Cu: 6.41-19.76; Zn: 35.5-85.5; Pb: 0.31-1.01; Cd: 0.51-0.67; Mn: 27.45-67.6 microg/g) are comparable to those reported for other moderately polluted world environments. SPM showed a less clear pattern. Metal concentrations in sediments displayed a clear geographical trend with values increasing with proximity to major urban centers. The clams (on dry weight) showed a complex pattern due to the variability introduced by age-related factors. Cd showed an apparent reverse industrial trend with higher concentrations in clams collected at distant stations. Zn, Pb and Mn showed no clear geographical pattern, whereas Cu increased in the clams collected in the most industrialized area. In addition, the bioaccumulation factors (BAF) were calculated. The result indicated that the studied Ruditapes philippinarum in Jiaozhou Bay possessed different bioaccumulation capacities for Cd, Zn, Cu, Pb and Mn, and Cd, Zn had a relatively high assimilation of those metals from sediment particles. A significant relationship with clam age was observed for Zn (positive) and Cu (negative) suggesting different physiological requirements for both metals with age. Trace metal concentrations measured in the tissue of the investigated clam were in the range considered safe by the WHO for human use.     

Polycyclic aromatic hydrocarbons (PAHs) in surface sediments from the Bizerte Lagoon,Tunisia: levels,sources, and toxicological significance

To assess the status of polycyclic aromatic hydrocarbon (PAH) contamination in sediments from the Bizerte Lagoon (northern Tunisia), 18 surface sediment samples were collected in March 2011 and analyzed for 14 US Environmental Protection Agency priority PAHs by high-performance liquid chromatography. The total concentrations of the 14 PAHs (ΣPAHs) ranged from 16.9 to 394.1 ng g^?1 dry weight (dw) with a mean concentration of 85.5 ng g^?1 dw. Compared with other lagoons, coasts, and bays in the world, the concentrations of PAHs in surface sediments of the Bizerte Lagoon are low to moderate. The PAHs’ composition pattern was dominated by the presence of four-ring PAHs (45.8 %) followed by five-ring (26.8 %) and three-ring PAHs (12.7 %). The PAH source analysis suggested that the main origin of PAHs in the sediments of the lagoon was mainly from pyrolytic sources. According to the numerical effect-based sediment quality guidelines of the USA, the levels of PAHs in the Bizerte Lagoon should not exert adverse biological effects. The total benzo[a]pyrene toxicity equivalent values calculated for the samples varied from 3.1 to 53.7 ng g^?1 dw with an average of 10.6 ng g^?1 dw.     

Characteristics of petroleum hydrocarbons in surficial sediments from the Songhuajiang River (China): spatial and temporal trends

This paper presents the spatial and temporal characteristics of petroleum hydrocarbons (PH) in surficial sediments from the Songhuajiang River using the method of petroleum chemical fingerprinting. Twenty-four surface sediment samples were collected at 17 sites along the river from upstream to downstream in flood season (August 2005) and icebound season (December 2005) and were analyzed for PH including n-alkanes (C(16)-C(33)), isoprenoid alkanes (pristane and phytane), and unresolved complex mixture (UCM). The concentration of PH varied from 22.64 to 91.45 μg g(?-1) dry sediment. n-alkanes with a carbon number from 16 to 33 were detected in all samples, and the UCM was the dominant composition for PH. The variability of the PH concentration was mostly influenced by external conditions, such as seasonal change and industrial area position, as well as internal sediment physicochemical properties, such as organic carbon and grain size. The concentration of hydrocarbons is higher in flood season than in icebound season and is higher upstream than downstream. The diagnostic ratios of specific hydrocarbons showed that the PH pollution comes from a combination of biogenic and petrogenic sources, and petrogenic input is dominant in icebound season relative to flood season. It also indicates that there is a clear terrigenous input of n-alkanes in flood season. Principal components analysis was used to study the composition and characteristics of PH in Songhuajiang River sediments and to assess the spatial and temporal distribution of their natural and anthropogenic sources.     

Characterizing spatial structure of sediment E. coli populations to inform sampling design

Escherichia coli can persist in streambed sediments and influence water quality monitoring programs through their resuspension into overlying waters. This study examined the spatial patterns in E. coli concentration and population structure within streambed morphological features during baseflow and following stormflow to inform sampling strategies for representative characterization of E. coli populations within a stream reach. E. coli concentrations in bed sediments were significantly different (p?=?0.002) among monitoring sites during baseflow, and significant interactive effects (p?=?0.002) occurred among monitoring sites and morphological features following stormflow. Least absolute shrinkage and selection operator (LASSO) regression revealed that water velocity and effective particle size (D ₁₀) explained E. coli concentration during baseflow, whereas sediment organic carbon, water velocity and median particle diameter (D ₅₀) were important explanatory variables following stormflow. Principle Coordinate Analysis illustrated the site-scale differences in sediment E. coli populations between disconnected stream segments. Also, E. coli populations were similar among depositional features within a reach, but differed in relation to high velocity features (e.g., riffles). Canonical correspondence analysis resolved that E. coli population structure was primarily explained by spatial (26.9–31.7 %) over environmental variables (9.2–13.1 %). Spatial autocorrelation existed among monitoring sites and morphological features for both sampling events, and gradients in mean particle diameter and water velocity influenced E. coli population structure for the baseflow and stormflow sampling events, respectively. Representative characterization of streambed E. coli requires sampling of depositional and high velocity environments to accommodate strain selectivity among these features owing to sediment and water velocity heterogeneity.     

What factors determine trace metal contamination in Lake Tonga (Algeria)?

A study of trace metal (TM) contamination was conducted at Lake Tonga (Algeria), a site surrounded by several indirect contamination point sources such as an abandoned mine and steelworks. Studying two sampling sites over four seasons, we were able to depict the spatial and temporal variability of TM contamination in the lake. Among the seven TM examined (Pb, Cd, Fe, Zn, Ni, Cu, and Cr), only Fe, Pb, and Cd showed concentrations significantly higher than the site’s geological background. The contamination index (sediment concentration/background concentration) calculated for these three TM (Cd = 1.9?±?1.6, Fe = 6.8?±?1.8, and Pb = 3.3?±?2.6) clearly indicated anthropogenic contamination. Sediment TM contamination differed both between sampling sites and seasons despite environmental variables (e.g., oxygen and pH) being similar, thus suggesting different TM contamination sources. Fe contamination was high at the two sampling sites and over all studied seasons, possibly indicating general lake-scale Fe contamination, probably related to atmospheric deposition of steelworks emissions both on the lake and within the watershed. Lake tributaries were further suspected of channeling Fe contamination from the watershed into the lake. On the other hand, the sampling site close to the outlet was especially rich in Cd and Pb typically reflecting contamination by mine wastes. The indirect connection between the abandoned mine and the lake indicates that runoff of mine leachates through groundwater was likely a candidate in explaining the specificity of the TM contamination in this part of the lake. This study provides insights for management of TM contamination by addressing both spatial and temporal variability within the lake as well as differences in contamination sources.     

Effective Long-term Ecological Monitoring Using Spatially and Temporally Nested Sampling

Effective environmental management requires documentation of ecosystem status and changes to that status. Without long-term data, short-term natural variability can mask chronic and/or cumulative impacts, often until critical levels are reached. However, a trade-off generally occurs between sampling in space and time. This study analyses a spatially and temporally nested long-term (12 years) monitoring programme conducted on benthic macrofauna in a large harbour. Sampling was carried out at six sites for 5.5 years, after which only two sites were sampled for the next 5 years. After this period, all six sites were sampled for another 2 years. While ecology is frequently thought of being highly variable, this design was able to detect trends, and cycles, in abundance, with only around 10% of species at each site exhibiting unpredictable temporal variability. Sites exhibiting similar trends in the abundance of a species over the 12.5-year period were generally spatially contiguous, and the spatial scale of change could be assessed. Continuous sampling at two sites identified whether changes in unsampled sites were related to long-term cycles. Moreover, this sampling provided a long-term background of temporal fluctuations against which to assess the ecological significance of observed changes.     

New evidences in the complexity of contamination of the lagoon of Venice: polybrominated diphenyl ethers (PBDEs) pollution

This study presents the first evaluation of the current pollution by polybrominated diphenyl ethers (PBDEs) of surface sediments from the Lagoon of Venice. We focused the research on tri-to hepta-BDEs, the main components of penta- and octa-mixtures, which are considered to be the most toxic for the biocoenosis. The results pointed out a quite homogeneous contamination of this keystone European transitional environment, with ∑ ₁₃PBDEs values ra nging from 0.39 to 6.78 ng/g dry weight; these values reflect low to moderate pollution levels, which is in conformity to other coastal European ecosystems. The average PBDE profile of the lagoon sediments follows this decreasing trend of congeners: BDE-47>BDE-99> >BDE-190>BDE-28>BDE-153>BDE-154>BDE-138, BDE-183, and BDE-17, which is similar to the worldwide distribution pattern. BDE-47 and BDE-99 revealed a recent use of a penta-BDE mixture, while the presence of hepta-BDEs (BDE-183 and BDE-190) in all of the sites can indicate the actual use of a deca-BDE formulation, because these congeners are considered to be debrominated byproducts of BDE-209 degradation.     

Development of the Coastal Intensive Site Network (CISNET)

The U.S. Environmental Protection Agency (EPA), National Oceanic and Atmospheric Administration (NOAA), and National Aeronautics and Space Administration (NASA) have formed a partnership to establish pilot sites for the development of a network known as the Coastal Intensive Site Network (CISNet). CISNet is composed of intensive, long-term monitoring and research sites around the U.S. marine and Great Lakes coasts. In this partnership, EPA and NOAA are funding research and monitoring programs at pilot sites that utilize ecological indicators and investigate the ecological effects of environmental stressors. NASA is funding research aimed at developing a remote sensing capability that will augment or enhance in situresearch and monitoring programs selected by EPA and NOAA. CISNet has three objectives: 1) to develop a sound scientific basis for understanding ecological responses to anthropogenic stresses in coastal environments, including the interaction of exposure, environment/climate, and biological/ecological factors in the response, and the spatial and temporal nature of these interactions, 2) to demonstrate the value of developing data from selected sites intensively monitored to examine the relationships between changes in environmental stressors, including anthropogenic and natural stresses, and ecological response, and 3) to provide intensively monitored sites for development and evaluation of indicators of change in coastal systems.     

Assessment of the Quality Characteristics of Two Lakes (Koronia and Volvi) of N. Greece

Quality parameters from 17 sampling stations from Lake Koronia and 18 from Lake Volvi were determined during sampling period of one year. Physicochemical parameters (pH, conductivity, DO) did not show remarkable differences neither between sampling sites nor between sampling periods. Nutrient concentrations (nitrogen and phosphorus compounds) were higher in lake Koronia than in Volvi showing relatively small temporal and spatial variations. As far as heavy metals in sediments, lake Koronia is considerably more polluted than Volvi lake especially with the metals Fe, Mn, Zn, Pb and Cd. The mean total concentrations of metals in lake Koronia decrease in the order Mn > Zn > Cr > Pb > Cu > Fe > Cd. The mean total concentrations of metals in lake Volvi decrease in the order Mn > Zn > Cr > Cu > Pb > Fe $>$ Cd.     

The New Bedford Harbor Superfund site long-term monitoring program (1993–2009)

New Bedford Harbor (NBH), located in southeastern Massachusetts, was designated as a marine Superfund site in 1983 due to sediment contamination by polychlorinated biphenyls (PCBs). Based on risks to human health and the environment, the first two phases of the site cleanup involved dredging PCB-contaminated sediments from the harbor. Therefore, a long-term monitoring program (LTM) was developed to measure spatial and temporal chemical and biological changes in sediment, water, and biota to assess the effects and effectiveness of the remedial activities. A systematic, probabilistic sampling design was used to select sediment sampling stations. This unbiased design allowed the three segments of the harbor to be compared spatially and temporally to quantify changes resulting from dredging the contaminated sediments. Sediment was collected at each station, and chemical (e.g., PCBs and metals), physical (e.g., grain size), and biological (e.g., benthic community) measurements were conducted on all samples. This paper describes the overall NBH-LTM approach and the results from the five rounds of sample collections. There is a decreasing spatial gradient in sediment PCB concentrations from the northern boundary (upper harbor) to the southern boundary (outer harbor) of the site. Along this same transect, there is an increase in biological condition (e.g., benthic community diversity). Temporally, the contaminant and biological gradients have been maintained since the 1993 baseline collection; however, since the onset of full-scale remediation, PCB concentrations have decreased throughout the site, and one of the benthic community indices has shown significant improvement in the lower and outer harbor areas.     

Expansion of alien gammarids in the Vistula Lagoon and the Vistula Delta (Poland)

Amphipod crustaceans belong to the most successful invaders of aquatic environments. The work provides information concerning the spatial and temporal scales of expansion of four alien gammarid amphipods (three of them of Ponto-Caspian and one of North American origin): Pontogammarus robustoides (G.O. Sars, 1894), Obesogammarus crassus (G.O. Sars, 1894), Dikerogammarus haemobaphes (Eichwald, 1841), and Gammarus tigrinus Sexton, 1939 in the Vistula Lagoon (VL) and the Vistula Delta (VD) in 2008–2010. The mean abundance of these gammarids in nearshore zones was 382 ind?m^?2 in VL and 89 ind?m^?2 in VD. Their mean biomasses were likewise greater in VL (0.91 g?m^?2) than in VD (0.49 g?m^?2). G. tigrinus was the most dominant species in both nearshore zones of VL and VD and attained the highest frequency in these areas. The study gives evidence of total extinction of native gammarid species.     

Iron, cadmium, and chromium in seagrass (Thalassia testudinum) from a coastal nature reserve in karstic Yucatán

The management of protected areas in karstic regions is a challenge because flooded cave systems form there and provide underground hydrological conducts that may link different zones. As a consequence, affectations to the protected areas can possibly occur as a consequence of human activities in remote areas and may therefore pass undetected. Thus, the monitoring of possible contaminants in these regions is becoming imperative. In this work, we analyze the concentration of essential (iron) and non-essential metals (cadmium and chromium) in the seagrass Thalassia testudinum that grows in Yalahau Lagoon, located in a near-to-pristine protected area of the Yucatán Peninsula, close to the rapidly developing touristic belt of the Mexican Caribbean. Salinity and silicate patterns show that Yalahau is an evaporation lagoon, where groundwater discharge is important. High iron (>400 μg/g), cadmium (>4 μg/g), and chromium (≈1 μg/g) concentrations were found in the area of highest groundwater input of the lagoon. High levels (5.1 μg/g) were also found near the town dump. In the rest of the sampling sites, metal concentrations remained near to background levels as estimated from other works. Temporal changes of concentrations in the seagrass tissues show also a local input and an input from the groundwater that could provoke an environmental problem in the Yalahau Lagoon in the near future.     

Assessment of trace elements in the shell layers and soft tissues of the pearl oyster Pinctada radiata using multivariate analyses: a potential proxy for temporal and spatial variations of trace elements

Concentrations of trace elements (Cd, Cu, Ni, Pb, V, and Zn) were determined in the soft tissues (adductor muscle and gills) of the pearl oyster Pinctada radiata and surficial sediments from two sampling sites located in the northern part of the Persian Gulf by Graphite Furnace Atomic Absorption Spectrophotometer (GFAAS). Moreover, the levels of Li, Mg, Al, Mn, Fe, Cu, Sr, Ba, Pb, and Zn were measured in two shell layers (prismatic and nacreous) using Laser Ablation Inductively Coupled Plasma Mass Spectrometer (LA-ICP-MS). There were significant differences between the sampling sites with regard to mean concentrations of Cu, Mn, and Al in the prismatic layers of the shells. But in terms of the soft tissues, only in the case of Ni accumulation in the muscle significant differences between the sites could be observed. No significant differences could be found between the sites from the elements concentrations in the sediments point of view. The levels of Cd, Cu, Ni, and Zn in the gills were markedly higher than those in the muscle. Concentrations of Mn, Mg, Li, and Cu in the prismatic layer were significantly higher than in the nacreous but the reverse case could be found for Sr. The patterns of metal occurrence in the selected tissues, shell layers, and sediments exhibited the following descending order: Zn, Ni?>?Cd, Cu?>?V, and Pb and Zn, Ni, Cd?>?Cu, V, and Pb for muscle and gills, respectively; Zn?>?Cu, Ni, Pb, Cd, and V for sediments; Mg?>?Sr, Mn, Li, Al, Fe, Ba, Cu, Pb, and Zn for the prismatic layer; and Sr, Mg?>?Mn, Al, Fe, Li, Ba, Cu, Pb, and Zn for the nacreous layer. In most cases, the temporal variations of the elements levels in the prismatic layer were clearer than those in the nacreous layer (especially for Li, Mg, Mn, Pb, and Fe). Comparison of the gained data from this study with the other relevant researches shows that in most cases the levels of the elements in this investigation either fell within the range for other world areas or were lower. Generally, it can be concluded that the shell (especially prismatic layer) of P. radiata can be considered as a suitable proxy for temporal and spatial variations of the trace elements (and probably some environmental parameters) in the study area.     

Trace metal concentrations in suspended particles, sediments and clams (Ruditapes philippinarum) from Jiaozhou Bay of China

Suspended particulate matter (SPM), sediments and clams were collected at three sites in Jiaozhou Bay to assess the magnitude of trace metal pollution in the area. Metal concentrations in SPM (Cu: 40.11–203; Zn: 118–447; Pb: 50.1–132; Cd: 0.55–4.39; Cr: 147.6–288; Mn: 762−1670 μg/g), sediments (Cu: 17.64–34.26; Zn: 80.79–110; Pb: 24.57–49.59; Cd: 0.099–0.324; Cr: 41.6–88.1; Mn: 343−520μg/g) and bivalves (Cu: 6.41–19.76; Zn: 35.5–85.5; Pb: 0.31–1.01; Cd: 0.51–0.67; Mn: 27.45−67.6 μg/g) are comparable to those reported for other moderately polluted world environments. SPM showed a less clear pattern. Metal concentrations in sediments displayed a clear geographical trend with values increasing with proximity to major urban centers. The clams (on dry weight) showed a complex pattern due to the variability introduced by age-related factors. Cd showed an apparent reverse industrial trend with higher concentrations in clams collected at distant stations. Zn, Pb and Mn showed no clear geographical pattern, whereas Cu increased in the clams collected in the most industrialized area. In addition, the bioaccumulation factors (BAF) were calculated. The result indicated that the studied Ruditapes philippinarum in Jiaozhou Bay possessed different bioaccumulation capacities for Cd, Zn, Cu, Pb and Mn, and Cd, Zn had a relatively high assimilation of those metals from sediment particles. A significant relationship with clam age was observed for Zn (positive) and Cu (negative) suggesting different physiological requirements for both metals with age. Trace metal concentrations measured in the tissue of the investigated clam were in the range considered safe by the WHO for human use.     

Mesozooplankton assemblages and their relationship with environmental variables: a study case in a disturbed bay (Beagle Channel,Argentina)

This study focused on the seasonal and spatial analysis of the mesozooplankton community in a human-impacted subantarctic bay in Argentina and aimed to detect assemblages associated with environmental variability. Mesozooplankton samples and environmental data were obtained in the Ushuaia Bay (UB) seasonally, from August 2004 to June 2005, and spatially, from coastal (more polluted), middle (less influenced) and open sea water (free polluted) sampling stations. Remarkable seasonal changes on the mesozooplankton community were observed. Nitrogenated nutrients, chlorophyll a, salinity and temperature were the prevailing environmental conditions likely associated with the different mesozooplankton assemblages found in the bay. The copepods Eurytemora americana, Acartia tonsa, Podon leuckarti and Nematoda were particularly observed on the northwest coast of the bay, characterized by the highest level of urban pollution, eutrophicated by sewage and freshwater inputs from the Encerrada Bay which is connected to it. The stations situated in the northeast area, mostly influenced by freshwater input from rivers and glacier melting, showed low mesozooplankton abundances and an important contribution of adventitious plankton. The copepods Ctenocalanus citer, Clausocalanus brevipes and Drepanopus forcipatus were mostly observed at the stations located near the Beagle Channel, characterized by open sea and free polluted waters. Our findings suggest that the variations observed in the mesozooplankton assemblages in the UB seem to be modulated by environmental variables associated with the anthropogenic influence, clearly detected on the coast of the bay. Certain opportunistic species such as A. tonsa and E. americana could be postulated as potential bioindicators of water quality in subantarctic coastal ecosystems.