Search

The aim of this study was to evaluate the use of metal concentrations in clam organs to monitor metal contamination in coastal sediments. The concentrations of Cd, Cr, Cu, Hg, Ni, Pb, V, and Zn were measured in the kidneys, gonads, mantles, gills, digestive gland, and hearts of the infaunal clam Amiantis umbonella collected from a contaminated site near desalination and power plant discharges, and a reference site in Kuwait Bay. Metal concentrations in sediment and sediment pore water were also measured at the collection sites of individual clams at the contaminated site. The concentrations of all metals in all organs (except Zn in the digestive gland) were significantly higher in clams from the contaminated site than from the reference site. Metal concentrations in several organs in A. umbonella from the contaminated site were correlated with those in the sediments and pore waters to which they were exposed. However, fresh weights of gonads, gills, and mantles were significantly lower in clams from the contaminated site compared to the reference site, indicating that the observed elevated concentrations of metals in the organs of clams from the contaminated site largely reflect lower organ weights, rather than higher metal loads, and that these organs in A. umbonella and perhaps other clams are not appropriate for use as biomonitors of metal contamination. Metal concentrations in clam kidneys showed a wide dynamic range with respect to environmental contamination and kidney weight was not variable. Therefore, metal concentrations in clam kidneys provide a reliable biomonitor of contaminant metals in coastal marine sediments.

Wet deposition of total phosphorus has been measured as part of the New Jersey Atmospheric Deposition Network (NJADN). Precipitation samples were collected in 1999—2001, using automated wet-only precipitation collectors at four sites in New Jersey, representing different land-use regimes. Total phosphorus volume-weighted mean concentrations (VWM) and the wet depositional fluxes were estimated on seasonal and annual timescales. VWM concentrations (± standard error) of total phosphorus ranged from 4.1 ± 0.80 to 15 ± 8.8 μg L-1 at all sites and were of similar magnitude across the region. The wet deposition flux estimates ranged from 3.9 to 14 mg m-2 y-1. VWM concentrations and fluxes were similar to those measured at other locations in the eastern United States.

The factors controlling the accumulation of mercury in fish are poorly understood. The oft invoked lipid solubility of MMHg is an inadequate explanation because inorganic Hg complexes, which are not bioaccumulated, are as lipid soluble as their MMHg analogs and, unlike other hydrophobic compounds, MMHg in fish resides in protein rather than fat tissue. We show that passive uptake of the lipophilic complexes (primarily HgCl2 and CH3HgCl) results in high concentrations of both inorganic and MMHg in phytoplankton. However, differences in partitioning within phytoplankton cells between inorganic mercury — which is principally membrane bound — and MMHg — which accumulates in the cytoplasm — lead to a greater assimilation of MMHg during Zooplankton grazing. Most of the discrimination between inorganic and MMHg thus occurs during trophic transfer while the major enrichment factor is between water and phytoplankton. As a result, MMHg concentrations in fish are ultimately determined by water chemistry which controls MMHg speciation and uptake at the base of the food chain.