Use of the euryhaline bivalve Potamocorbula amurensis as a biosentinel species to assess trace metal contamination in San Francisco Bay

Abstract

Potamocorbula amurensis was assessed as a biosentinel species in San Francisco Bay, California, USA. Uptake of metal in both the laboratory and field showed that P. amurensis was sufficiently responsive to Ag. Cd, Cr, Ni and V to detect environmental differences in exposure. It was less suitable as an indicator of Cu and Zn contamination. Concentration factors for P. amurensis were: Ag, 386000; Cd, 50200; Cr. 36600; Cu, 12200; Ni, 5200; and Zn, 115500. Samples were collected from 6 stations throughout the bay at near-monthly intervals from January 1991 to March 1992. Variability within a collection was influenced by gut content and animal size. Other sources of variability were time Icoefficient of variation (CV) = 10 to 21 %l, small-scale spatial variability (within 3 km, CV = 10 to 25%), and large-scale spatial variability (CV = 3.3 to 12.4%). Depuration for 48 h was necessary to mitigate bias from gut content. Precision was improved by analyzing large numbers of indiv~duals (60 to 120) separated into several (5 to 14) composites at each collection and by determining, from regression, the mean and variance for samples with significant correlations between metal concentration and shell length. Repeated monthly sampling increased the accuracy of long-term site characterizations. Temporal variability was small because of drought. The grand means of the concentratlons of Ag, Cd, Cr, Ni, and V in the tissues of P. amurensis at each station for the 15 mo period revealed persistent contamination from industrialized Suisun Bay to the mouth of San Francisco Bay. Demonstration of responsiveness, precision and accuracy should be a prerequisite for the optimal use of biosentinels.

Historical trends of metals in the sediments of San Francisco Bay, California

“…Ultramafics can contain as much as 2000 kg/g Ni and Cr, and greywackes > 150 kg/g V (Taylor and McLennan, 1985). Inputs of Cr, Ni and V from oil refineries and a steel mill in San Pablo and Suisun Bays (Gunther et al, 1987;Luoma et al, 1990;Brown and Luoma, 1995;Abu-Saba and Flegel, 1995) do not appear to affect sediment concentrations of these metals. Perhaps the oxidation states of locally discharged Cr and V is not conducive to adsorption to particle surfaces (Abu-Saba and Flegel, 1995); or the high natural baseline might confound detection of industrial influences.…”

“…Salinities less than 1 can occur during the highest river flows; low flow salinities are typically 17 to 24 in northern San Pablo Bay. Previous studies have documented enriched concentrations of Cr, Ni, V, Cu and Cd in water and bivalves in Suisun and northern San Pablo Bay as a result of a variety of industrial discharges (Flegal et aI., '1991;Abu-Saba and Flegel, 1995;Brown and Luoma, 1995).…”

Influence of microalgal biomass on absorption efficiency of Cd, Cr, and Zn by two bivalves from San Francisco Bay

“…P. amurensis is an invader species to SFB from eastern Asia and became an abundant benthic bivalve in the bay after 1986 (Carlton et al 1990). This euryhaline filter-feeding clam has a very rapid filtration rate (Werner and Hollibaugh 1993) and a rapid gut passage time (-24 h) (Decho and Luoma 1991), and is found in a variety of substrates in both the intertidal and subtidal zone of the bay (Brown and Luoma 1995).…”

Selenium fractionation and cycling in the intertidal zone of the Carquinez Strait. Annual report, October 1, 1995--December 31,1996

“…Recently, the clam Potamcorbula amurensis, an invader species from eastern Asia, was found to accumulate high levels of Se and other trace elements (Brown and Luoma, 1995). This may be due to the species high feeding rate and efficiency in bioaccumulating Se (Luoma et al, 1996), and is probably not indicative of higher Se levels in the clam's food source (phytoplankton).…”