Sources and bioavailability of polynuclear aromatic hydrocarbons in Galveston Bay, Texas

Oyster and sediment samples collected from six sites in Galveston Bay from 1986 to 1998 were analyzed for polynuclear aromatic hydrocarbons (PAHs). Total concentrations of parent PAHs in oysters ranged from 20 ng g⁻¹ at one site to 9,242 ng g⁻¹ at another and varied randomly with no clear trend over the 13 year period at any site. Concentrations of alkylated PAHs, which are indications of petroleum contamination, varied from 20 to 80,000 ng g⁻¹ in oysters and were in higher abundance than the parent PAHs, indicating that one source of the PAH contaminants in Galveston Bay was petroleum and petroleum products. Four to six ring parent PAHs, which are indicative of combustion source , were higher than those of 2–3 ring parent PAHs, suggesting incomplete combustion generated PAHs was another source of PAHs into Galveston Bay. Concentrations of parent PAHs in sediments ranged from 57 to 670 ng g⁻¹ and were much lower than those in oysters. Sediments from one site had a high PAH concentration of 5,800 ng g⁻¹. Comparison of the compositions and concentrations of PAHs between sediment and oysters suggests that oysters preferentially bioaccumulate four to six ring PAHs. PAH composition in sediments suggests that the sources of PAH pollution in Galveston Bay were predominantly pyrogenic, while petroleum related PAHs were secondary contributions into the Bay.     

Galveston Bay: Temporal changes in the concentrations of trace organic contaminants in national status and trends oysters (1986–1994)

The temporal distributions for six classes of trace organic contaminants (chlordanes, DDTs, dieldrin, PAHs, PCBs, and butyltins) in oysters from six Galveston Bay sites from National Oceanic and Atmospheric Administration’s National Status and Trends (NS&T) Mussel Watch Program are compared with other NS&T sites from the Gulf of Mexico as well as all NS&T sites of the United States (East Coast, West Coast, and Gulf of Mexico). Decreases in the median for the Gulf-wide concentration of chlordanes, dieldrin, and butyltins occurred during 1986–1994. The Gulfwide median concentrations of DDTs, PAHs, and PCBs exhibited a strong cyclic distribution with time. For Galveston Bay oysters, “high” concentration is defined as the concentration greater than the median plus one standard deviation for all Gulf of Mexico sites. The percentage of sites having high concentrations during 1986–1994 for Galveston Bay oysters are 49% for dieldrin, 45% for butyltins, 40% for chlordanes, 38% for PCBs, 30% for PAHs, and 21% for DDTs. For PCBs, 43% of Galveston Bay oyster samples analyzed over the first 9 yr have concentrations high enough for potential biological effects to be observed in oysters. The percentages in other agents were chlordanes (22%), butyltins (22%), dieldrin (5%), and PAHs (4%). National Academy of Science-proposed regulatory limits for oysters were exceeded in only 2% of Galveston Bay samples for DDTs and 1% for PCBs. All other contaminants were below proposed NAS limits.     

Delivery of Trace Metals (Al,Fe, Mn,V, Co,Ni, Cu,Cd, Ag,Pb) from the Trinity River Watershed Towards the Ocean

The Trinity River (Texas, USA) contains in its watershed 23 different reservoir lakes, the largest one being Lake Livingston situated in the lower Trinity River watershed and two potentially polluting metroplexes, Dallas and Houston. In order to determine fluxes of nutrients and trace metals to Galveston Bay, a survey that included 24 discreet samples collected over a year and at various stages of discharge was carried out during 2000–2001. Geochemical (i.e., sorption by Fe oxyhydroxides), biological (i.e., seasonal uptake by sinking algae in Lake Livingston), and hydrological (i.e., dilution effects by increasing flow rates) controls were found to be mainly responsible for variations in dissolved trace metal concentrations rather than pollution sources. The Trinity River loads of suspended sediments and pollutant trace metals entering Galveston Bay at Anahuac were <20% of those reaching Lake Livingston, and only a few percent of the total upstream trace metal load is entering the Gulf of Mexico. Thus, during the transit through the 23 man-made lakes and an estuary, >96% of the pollutant trace metal load is lost to sediments.     

Multidisciplinary assessment of pollution at three sites in Long Island Sound

Winter flounder (Pseudopleuronectes americanus) were sampled from three sites located near Norwalk, New Haven, and Niantic, Connecticut, in Long Island Sound during February 1987, to evaluate the degree of chemical contamination and to determine possible effects of contaminant exposure. At each site, sediment and infaunal invertebrates were also collected and analyzed for trace metals and organic chemicals. Specimens of liver and kidney from winter flounder were examined for histopathological conditions, including the presence of macrophage aggregates in liver tissue. Liver samples were also analyzed for DNA damage (i.e., the formation of adducts between DNA and chemical contaminants). Blood samples were collected and analyzed for erythrocyte micronuclei. The sampling site near New Haven was determined to be the most affected site, from the standpoints of greater chemical contamination and possible effects on winter flounder. Concentrations of aromatic hydrocarbons (AHs) and polychlorinated biphenyls (PCBs) were highest in sediment from this site, and the highest prevalences of the histopathological changes and DNA alterations were also found in the livers of winter flounder from this site. No differences in the concentrations of contaminants in fish or in frequencies of erythrocyte micronuclei in fish blood were found between sites. None of the sites sampled had contaminant levels or prevalences of lesions as high as previously found at other East Coast locations (e.g., Boston Harbor, Massachusetts, Raritan Bay, New York). Overall, our results indicate moderate levels of pollution at two of the urban sites in Long Island Sound and provide a framework for expanded studies to better define the extent and impact of chemical pollution in Long Island Sound.     

Contributions of coastal and watershed energy sources to secondary production in a Northeastern Pacific Estuary

We examined the relationship between variation in origin of organic matter and benthic secondary production in a shallow, macrotidal estuary on the United States Pacific Northwest coast, Willapa Bay, Washington. Spatial variation in energy sources and benthic productivity were investigated at both local (vertical height and cross-bank components) and regional (sites within the bay) scales. We determined the stable carbon isotope ratios of oysters (Crassostrea gigas) to evaluate marine versus terrestrial energy sources, compared growth rates of oysters, and made time series measurements of physical variablest at estuarine channel and intertidal stations. The stable carbon isotope ratios of oysters ranged from ?22‰ in inner portions of the estuary to ?18‰ near the mouth and oysters grown on the substrate surface were enriched in δ¹³C relative to those grown in the water column. These patterns are consistent with terrigenous inputs away from the estuary mouth and benthic microalgae in the diets of on-bottom oysters. The highest oyster growth was found at an inner estuary site where riverine inputs are relatively high and coincided, with high ammonium in the water column. However, for most sites in Willapa Bay, oyster growth actually declined away from the estuary mouth. Reducing the time available for feeding by transplanting oysters higher in the intertidal zone had significant negative effects on growth(e.g., a reduction of 27–35% over 0.5 m). Despite the fact that oysters grown on-bottom had access to different resources than those in the water column, their growth was slower at amy given tidal elevation, which may be due to on-bottom competition with other suspension feeders, boundary layer effects, or interference from turbidity. In a practical sense, oyster growers have been adjusting to allochthonous energetic support of food webs in Willapa Bay for more than a century, because they have traditionally moved oysters from southern parts of the bay where recruitment is relatively high to beds where market-size oysters can be grown closer to the mouth. This study provides mechanistic support for these practices and suggests that climatic events on a variety of temporal scales (Pacific Decadal Oscillation, upwelling events) could have economic consequences for aquaculture.     

Spatial distribution and source of heavy metals in reclaimed lands of Homebush Bay: The venue of the 2000 Olympic Games,Sydney, New South Wales

A large part of the Sydney 2000 Olympic Site at Homebush Bay was reclaimed over several decades using an estimated 9 Mt of domestic, commercial and industrial waste. Past activities, such as reclamation of wetlands, land clearing, shoreline remodelling and industrial practices, have caused an adverse environmental impact on the Homebush Bay site. Core samples (n = 4513) collected from the reclaimed lands of Homebush Bay show that, prior to remediation, soil contaminated by heavy metals (Cr, Cu, Pb, Zn) may have posed a threat to groundwater in the area. Mean Pb concentrations from the three land types at the Olympic site range from 65 to 374 μg/g in reclaimed areas, 78–167 μg/g in landfill areas and 44–52 μg/g in non‐infilled areas, respectively. Heavy‐metal concentrations in soils from non‐infilled areas indicate that these parts of the site were uncontaminated. The distribution of heavy metals in soil samples revealed a close association between elevated concentrations and the presence of fill materials at the site. Metal concentrations were frequently above Australian and New Zealand Guidelines for Fresh and Marine Water Quality. The Olympic Coordination Authority's remediation strategy to clean up the Homebush Bay site included consolidating contaminated waste into landscaped hills, which were capped with impermeable clay and thermal destruction of scheduled waste on site. The primary aims of the current study were to provide a scientific foundation for the remediation/rehabilitation of natural systems, and to make a contribution to the Olympic Coordination Authority's Development Plan and Environmental Management System for the site.     

Organic and organometallic compounds in estuarine sediments from the Gulf of Mexico (1993–1994)

Sediment samples from 281 estuarine sites in the Gulf of Mexico were collected in 1993–1994 and analyzed for several classes of organic and organometallic compounds as part of the Environmental Monitoring and Assessment Program of the United States Environmental Protection Agency. Polynuclear aromatic hydrocarbons (PAHs) were the contaminant class found most frequently and in the highest concentrations; the sum of 24 congeners (ΣPAHs) ranged from <5 ng g^?1 to 15.500 ng g^?1 (dry wt basis). A low percentage of samples (3.9%) exceeded 2000 ng g^?1 ΣPAHs, and only six samples (2.1%) exceeded 4000 ng g^?1, a level above which adverse biological effects may be expected to occur. Less than 4% of sediments exceeded 20 ng g^?1 for the sum of 20 polychlorinated biphenyls (ΣPCBs) and only four samples (1.4%) exceeded 20 ng g^?1 for the sum of several organochlorine pesticides (ΣOCPs). A sample from Freeport Harbor, Texas, contained 4230 ng g^?1 ΣPAHs, 322 ng g^?1 ΣPCBs, and 49.6 ng g^?1 ΣOCPs. Tributyltin exceeded 100 ng g^?1 in only four samples, all of which were from stations in Corpus Christi Bay or Galveston Bay in Texas. The detection of a suite of organophosphate pesticides was very rare and did not exceed 15 ng g^?1. Sediments from the tidally influenced section of the Mississippi River in Louisiana contained low to moderate levels of all classes of organic compounds. The most contaminated sites were in urban estuaries (e.g., Corpus Christi, Galveston, and Pensacola (Florida bays), underscoring the need to concentrate future monitoring and assessment efforts at the regional and local level.     

Contrasting Growth Patterns of Suspension-Feeding Molluscs (Mercenaria mercenaria, Crassostrea virginica, Argopecten irradians, and Crepidula fornicata) Across a Eutrophication Gradient in the Peconic Estuary, NY, USA

While many coastal ecosystems previously supported dense meadows of seagrass and dense stocks of bivalves, the impacts of overfishing, eutrophication, harmful algal blooms, and habitat loss have contributed to the decline of these important resources. Anthropogenic nutrient loading and subsequent eutrophication has been identified by some researchers as a primary driver of these losses, but others have described potential positive effects of eutrophication on some estuarine resources. The Peconic Estuary, Long Island, NY, USA, offers a naturally occurring nutrient-loading gradient from eutrophic tidal creeks in its western reaches to mesotrophic bays in the eastern region. Over 2 years, we conducted an experiment across this gradient to examine the effects of eutrophication on the growth of estuarine species, including juvenile bivalves (northern quahogs (Mercenaria mercenaria), eastern oysters, (Crassostrea virginica), and bay scallops (Argopecten irradians)) and slipper limpet (Crepidula fornicata). Water quality and phytoplankton community biomass and composition were concurrently monitored at each site, and the effects of these variables on the growth of estuarine species were analyzed with multiple regression model. Eutrophication seemed to impact shellfish through changes in the quality of food and not the quantity since the growth rates of shellfish were more often correlated with densities of specific cell types or quality of seston rather than bulk measures of phytoplankton and organic seston. Northern quahogs and eastern oysters grew maximally within eutrophic locales, and their growth was positively correlated with high densities of autotrophic nanoflagellates and centric diatoms in these regions (p?<?0.001). The growth rates of northern quahogs were also positively correlated with relative water motion, suggesting an important role for tidal currents in delivering seston to suspension feeders. Bay scallops and slipper limpets were negatively impacted by eutrophication, growing at the slowest rate at the most eutrophic sites. Furthermore, bay scallop growth was negatively correlated with densities of dinoflagellates, which were more abundant at the most eutrophic site (p?<?0.001). These results suggest that nutrient loading can have significant but complex effects on suspension-feeding molluscs with select species (e.g., oysters and clams) benefiting from eutrophication and other species performing poorly (e.g., scallops and slipper limpets). Future management approaches that seek to restore bivalve populations will need to account for the differential effects of nutrient loading as managers target species and regions to be restored.     

Heavy metals in the Derwent Estuary

Analyses of the concentrations of Cd, Cr, Co, Cu, Fe, Pb, Mn, Hg, Ni, and Zn in filtered waters, suspended particulates, sediments, shellfish, fish, airborne particulates, and sewage have confirmed work of other investigators showing that the Derwent Estuary is heavily contaminated, particularly withmercury, cadmium, lead, andzinc, and have added further information regarding the distribution of each metal. Apparently most of the contamination originated from the earlier operation of a zinc refining plant. A study of shellfish growing in variously contaminated regions found that more than 20 species could be listed in order of their respective abilities to accumulate each heavy metal. For example, the mussel (Mytilus edulis) was found to be a good indicator of cadmium and mercury contamination, but less valuable as an indicator of zinc. The surf barnacle, (Catophragmus polymerus) was found to be one of the most sensitive biological indicators of cadmium contamination. An indication of the steps by which a waste metal is eventually accumulated at high and even toxic concentrations in seafoods, may be seen from a comparison of the relative concentrations of cadmium, lead, mercury, and zinc found in mussels, sediments, suspended particulates, and filtered waters. The high concentrations recorded for metals include: 1,100 μg/g Hg, 10,000 μg/g Zn, and 862 μg/g Cd in dried sediments; 1,500 μg/g Cd in airborne dust fallout; 200 μg/g Cd and 100,000 μg/g Zn in dried oysters; and 16 μg/l Hg, 15 μg/l Cd and 1,500 μg/l Zn in filtered waters.     

Experimental Effects of the Grass Shrimp, Palaemonetes pugio, on Hard-Substrate Communities in Chesapeake Bay and an Adjacent Coastal Bay, USA

With increased shoreline hardening and development, it is important to understand the ecological processes occurring in these and adjacent coastal habitats. A common species found associated with these hard-substrate habitats in Chesapeake Bay is the grass shrimp, Palaemonetes pugio. Caging experiments were conducted from June to August 2010 to examine the effects of shrimp on the recruitment and development of hard-substrate communities. Experiments were conducted at two low-salinity sites within Chesapeake Bay and one high-salinity site in an adjacent coastal bay in Virginia. The addition of grass shrimp reduced recruitment of polychaetes and scyphistomae of the sea nettle, Chrysaora quinquecirrha, and increased recruitment of encrusting bryozoans and the oyster, Crassostrea virginica. After 12?weeks, sea nettles at one low-salinity site, dominated predator-exclusion treatments. At the high-salinity site, oysters dominated when shrimp were present. Although it is unclear whether the results of short-term caging studies can be applied across larger temporal and spatial scales, the significant effects of grass shrimp on two important Chesapeake Bay species suggests that increases in hard-substrate habitat could have broader impacts within this and other systems.     

Chemical contaminant exposure and effects in four fish species from Tampa Bay,Florida

Concentrations of selected anthropogenic chemical contaminants and levels of pollution-related biological effects were measured during three consecutive years (1990–1992) in hardhead catfish (Arius felis), Gulf killifish (Fundulus grandis), longnose killifish (F. majalis), and red drum (Scieaenops ocellatus) from 12 subtidal and intertidal sites in Tampa Bay and nearby Sarasota Bay. Each species was collected from at least four sites. Compared to nonindustrialized sites, concentrations of PCBs, DDTs, and alpha-chlordane in liver, and of fluorescent aromatic compounds in bile, were highest in fish from sites in or near Hillsborough Bay, the most industrialized portion of Tampa Bay. The results of analyses for two biochemical markers of contaminant-induced effects in fish, hepatic cytochrome P4501A activities and levels of hepatic DNA adducts, also showed the highest levels to be in all four fish species from sites in the vicinity of Hillsborough Bay. Liver lesions, considered to be pollution-associated in several other bottom-feeding fish species, were found in hardhead catfish and longnose killifish, exclusively from sites in Hillsborough Bay. Overall, concentrations of selected contaminants and their derivatives in the four target fish species generally reflected concentrations of these contaminants found in sediment. The biochemical and histopathological responses demonstrated that chemical contaminant concentrations in the vicinity of Hillsborough Bay are sufficiently high to cause adverse effects in indigenous fish species. The results, collectively, showed that the extent of contaminant exposure and biological effects in fish from sites in Tampa Bay were low to moderate compared to more urbanized coastal sites of the United States. *** DIRECT SUPPORT *** A01BY073 00009     

A comparison of early juvenile red drum densities among various habitat types in Galveston Bay, Texas

Seagrass meadows are often cited as important nursery areas for newly settled red drum even though many estuaries, such as Galveston Bay, Texas, support large numbers of red drum and have limited seagrass cover, suggesting the use of alternate nursery areas. We examined patterns of habitat use for newly settled red drum at six sampling areas in Galveston Bay; two areas had seagrass beds and four areas had no seagrass. We measured densities in different habitat types using epibenthic sleds and enclosure samplers. Peak recruitment of young red drum to the estuary occurred during September through December. Highest densities of new settlers were found in seagrass meadows (primarilyHalodule wrightii), but when seagrass was absent, the highest densities of red drum occurred along theSpartina alterniflora marsh edge interface. Densities were relatively low on nonvegetated bottom away from the marsh edge. We also examined density patterns in other habitat types at selected sampling areas and found no red drum within marsh vegetation away from the marsh edge interface (5 and 10 m into the marsh interior). Oyster reefCrassostrea virginica was sampled using lift nets, and we found no red drum using this habitat, although adjacent seagrass and marsh interface habitats were used. Even though red drum densities in marsh edge were low relative to seagrass, the large areal extent of marshes in the bay complex probably makes marsh edge the most important nursery habitat for red drum in Galveston Bay.     

Metal accumulation in surface salt marsh sediments of the Bay of Fundy,Canada

We measured the amount of arsenic, chromium, copper, lead, nickel, vanadium, and zinc accumulated over a five-year period from 1997 to 2002 in surface sediments of seven salt marshes along the New Brunswick coast of the Bay of Fundy, Canada. Study sites extended from outer to inner Bay, spanning a gradient in tidal range (6–12 m) and mean sediment deposition rate (0.27–1.76 cm yr⁻¹). In each study site, metal concentrations were measured in low and high marsh areas. Concentrations of chromium, nickel, and zinc appear to be within their natural range, while arsenic, lead, and vanadium are enriched in some sites. Calculated sediment metal loadings rates showed variability among marsh sites that closely followed sediment deposition patterns, suggesting sediment deposition rate is the driving factor of short-term metal accumulation in Fundy marshes. The value of salt marshes as a sink for metals may be enhanced by high sedimentation rates.     

Kepone®: Toxicity and bioaccumulation in blue crabs

Two long-term studies were conducted to determine toxicity, uptake and depuration of Kepone in blue crabs (Callinectes sapidus). In the first, Kepone was administered to crabs in seawater (0.03 or 0.3 μg Kepone/I) or food (eastern oyster,Crassostrea virginica, containing 0.25 μg/g Kepone). Uptake of Kepone in 28 days was primarily through the contaminated oysters. When these crabs were held in Kepone-free seawater and fed Kepone-free oysters for 28 days, no loss of the insecticide was evident. There were adverse effects on molting and survival in crabs fed oysters that contained 0.25 μg/g Kepone. A second study was conducted to determine: (1) the depuration of Kepone over a 90-day period in blue crabs fed oysters from the James River, Virginia (containing 0.15 μg/g Kepone); and (2) the effects of Kepone on molting and survival of blue crabs fed James River oysters or laboratory-contaminated oysters that contained 0.15 or 1.9 μg/g Kepone. Crabs fed Kepone-contaminated oysters followed by a diet of Kepone-free oysters for 90 days had detectable concentrations of the insecticide in tissues. Also, blue crabs that ate oysters containing Kepone in concentrations similar to those found in oysters from the James River, died or molted less frequently than crabs fed Kepone-free oysters meats.     

Environmental impacts of heavy metals (Co, Cu, Pb, Zn) in surficial sediments of estuary in Daliao River and Yingkou Bay (northeast China): concentration level and chemical fraction

Heavy metal pollution in the surficial sediments derived from the estuary in Daliao River and Yingkou Bay is investigated to assess environmental quality, pollution level, bioavailability and toxicity. The ranges of Pb, Co, Zn and Cu concentrations in the surficial sediments are: 16.57–39.18, 3.61–16.02, 16.53–39.18, 2.77–43.80 mg/kg. Results of the geoaccumulation index (I _geo) show that the pollution levels of four metals are in the “unpolluted” class except for Pb in 15 sampling sites. The pollution level of the study area assessed by pollution load index (PLI) shows that except for the moderately polluted region of sites 1, 2, 3, 8, 12 and 13, other sites belong to unpolluted state. The sequence of pollution extent of different heavy metals is: Pb > Zn > Co > Cu. At all sampling sites, the grades of potential ecological risk of Co, Cu, Pb and Zn are “light”. The order of potential ecological risk is: Pb > Co > Cu > Zn. Sequential extraction of the metals indicates that the states of Pb, Cu, Co and Zn in the sediment are relatively stable at most sites of the estuary in Daliao River and Yingkou Bay, which means that there is a low source of pollution arriving in this area. While only at several sites, Co, Pb and Zn are labile, which are considered as anthropogenically originated.     

Positive Relationship between Freshwater Inflow and Oyster Abundance in Galveston Bay,Texas

Analysis of fisheries-independent data for Galveston Bay, Texas, USA, since 1985 shows eastern oysters (Crassostrea virginica) frequently demonstrate increased abundance of market-sized oysters 1 to 2 years after years with increased freshwater inflow and decreased salinity. These analyses are compared to Turner’s (Estuaries and Coasts 29:345–352, 2006) study using 3-year running averages of oyster commercial harvest since 1950 in Galveston Bay. Turner’s results indicated an inverse relationship between freshwater inflow and commercial harvest with low harvest during years of high inflow and increased harvest during low flow years. Oyster populations may experience mass mortalities during extended periods of high inflow when low salinities are sustained. Conversely, oyster populations may be decimated during prolonged episodes of low flow when conditions favor oyster predators, parasites, and diseases with higher salinity optima. Turner’s (Estuaries and Coasts 29:345–352, 2006) analysis was motivated by a proposed project in a basin with abundant freshwater where the goal of the project was to substantially increase freshwater flow to the estuary in order to increase oyster harvest. We have the opposite concern that oysters will be harmed by projects that reduce flow, increase salinity, and increase the duration of higher salinity periods in a basin with increasing demand for limited freshwater. Turner’s study and our analysis reflect different aspects of the complex, important relationships between freshwater inflow, salinity, and oysters.     

The distribution of heavy metals in the hard clam,Mercenaria mercenaria,in the lower Chesapeake Bay region

Populations of the hard clam,Mercenaria mercenaria, were sampled at thirty sites in the lower Chesapeake Bay region in 1972 and 1973. Subsamples were taken for analysis for the trace metals cadmium, copper and zinc. Emphasis was placed on samples from the York and James rivers, two very productive and commercially utilized clam grounds. The levels of metals determined were comparable to those reported from other regions except Southampton Water in the United Kingdom. Differences in levels between the York and James rivers were statistically significant (P<0.001) which indicates that the James River probably suffers from contamination by these metals. One metal, copper, varied significantly with the age of the organism whereas the other two, cadmium and zinc, varied with salinity. InMercenaria the salinity of the sampling site must be considered before cadmium and zinc data can be interpreted. A standard action-level to denote pollution from copper would be adequate in this species.     

Trace metals and dissolved organic carbon in an estuary with restricted river flow and a brown tide bloom

This study was designed to establish the distributions of trace metals (Cd, Co, Cu, Ni, Pb, and Zn), dissolved organic carbon (DOC), and inorganic nutrients (PO₄ and H₄SiO₄) in the water column of the small, relatively pristine Peconic River estuary. We were also able to examine the effects of a harmful microalgal bloom, known as the brown tide, which occurred in the area during our study. Because river inflow to the Peconic estuary is restricted by a small dam at the head of the estuary, direct evaluation of the relative importance of riverine inputs on estuarine metal distributions was possible. The simultaneous analyses of geochemical carrier metals (Al, Fe, and Mn), an indicator of sewage (Ag), and other ancillary parameters (e.g., suspended particulate matter, dissolved O₂, chlorophylla) were used to describe the major processes controlling metal concentrations in the dissolved phase. The trace metal distributions indicated two distinct biogeochemical regimes within the estuary: an anthropogenically perturbed region with high metal levels (e.g., Ag, 165 pM; Cu, 51 nM; Zn, 57 nM) at the head (Flanders Bay), and a larger outer region with relatively low metal concentrations. The very similar distributions of some metals (e.g., Mn, Ni) in the Peconic estuary compared to those in estuaries having much higher river flow demonstrated the dominant role of internal processes (e.g., diagenetic remobilization) in controlling these metal patterns. An inverse relationship between dissolved Fe and DOC with cell counts of the brown tide microalgaeAureococcus anophagefferens in our field study suggested a close association with the bloom, although a similar relationship was observed between dissolved Al and brown tide cell counts, implying that removal of Fe could be due to particle scavenging rather than biological uptake.     

Temporal and spatial variations of trace metal concentrations in oysters from the Patuxent River, Maryland

Concentrations of copper (Cu), silver (Ag), and cadmium (Cd) in eastern oysters (Crassostrea virginica) from the upper Patuxent River estuary analyzed since 1986 (Cd since 1991) were high relative to concentrations in other sites in the United States analyzed by the National Oceanic and Atmospheric Administration National Status and Trends program. Patuxent River oysters had above average concentrations of Ag and Cu, and unusually high concentrations of Cd. Metal concentrations were highest in summer, a period in which oyster meat condition index was relatively low. Copper values were highest in 1986–1987, likely elevated by erosion from Cu-Ni alloy condensers at a local power plant. Silver and Cd values exhibited more year-to-year variation. A number of factors were examined as candidates to explain the interannual differences, including river flow, salinity, and oyster condition, but none was able to explain the high and low years. Samples collected in spring and late summer of 1996 at a number of oyster bars located along the length of the Patuxent River showed that concentrations of all three metals increased with distance up-river. For Cd, the upstream increase was linear with distance, while for Ag and Cu, there was a secondary maximum near river km 16. A close correlation was observed between Ag and Cu for individuals at each site, with a poorer correlation between Cd and either Ag or Cu.     

Heavy metal concentrations in sediments and in mussels from Argentinean coastal environments,South America

Among environmental contaminants, heavy metals are currently considered to be some of the most toxic ones present worldwide due to their harmful effects on organisms and ability to bioaccumulate in aquatic systems. In this work, the concentration of heavy metals (Cd, Cu, Pb, Zn, Ni and Cr) in Brachidontes rodriguezii and in the fine sediments of several coastal sites at the southwest of Buenos Aires Province, Argentina is analyzed. The Bahía Blanca Estuary and Pehuen-Có beach are located in a highly complex oceanographic and ecological regional system, which creates the basis of one of the most valuable Argentinean habitats for fishing commercial species. An assessment, which involved analyzing distribution pattern of trace metals, comparative studies with sediment and ecological quality guidelines; and a sequential and integrated index analyses approach (containing Metal Pollution Index, Biosediment Accumulation Factor, Geo-accumulation Index (Igeo), Pollution Load Index and the mean Probable Effect Level quotients), was followed to estimate enrichment and risks of heavy metals in the sediments and in the mussels from these study areas. The results showed higher concentrations of some heavy metals (e.g., Cd, Cr and Ni) in mussels collected at Pehuen-Có, while no spatial differences in sediments were observed. According to the international environmental regulations, mean values of trace metals in mussels allowed to place both sites between “unpolluted and moderately polluted” and between the “low and medium category” of pollution. Furthermore, the mean concentrations found were within the detected ranges in other coastal sites worldwide.