Clams, deposit-feeding

Copper concentrations in sediment interstitial pore waters correlate positively with concentrations of dissolved copper in the overlying water column and are now used to predict the toxicity of test sediments to freshwater amphipods (Ankley et al. 1993). Sediment-bound copper is available to deposit-feeding clams, especially from relatively uncontaminated anoxic sediments of low pH (Bryan and Langston 1992). The bioavailability of copper from marine sediments, as judged by increased copper in sediment interstitial waters, is altered by increased acid volatile sulfide (AYS)... 

Extractable concentrations of sediment-bound zinc were positively correlated with zinc concentrations in deposit feeding clams (Luoma and Bryan 1979). Availability of sediment zinc to bivalve molluscs was higher at increased sediment concentrations of amorphous inorganic oxides or humic substances, and lower at increased concentrations of organic carbon and ammonium acetate-soluble manganese. Zinc uptake by euryhaline organisms was enhanced at low water salinity (Luoma and Bryan 1979). 

The bioavailability of selenium to a benthic deposit-feeding bivalve, Macoma balthica from particulate and dissolved phases was determined from AE data. The selenium concentration in the animals collected from San Francisco Bay was very close to that predicted by a model based on the laboratory AE studies of radiolabelled selenium from both particulate and solute sources. Uptake was found to be largely derived from particulate material [93]. The selenium occurs as selenite in the dissolved phase, and is taken up linearly with concentration. However, the particle-associated selenium as organoselenium and even elemental selenium is accumulated at much higher levels. The efficiency of uptake from the sediment of particulate radiolabelled selenium was 22%. This contrasts with an absorption efficiency of ca. 86% of organoselenium when this was fed as diatoms - the major food source of the clam. The experiments demonstrated the importance of particles in the uptake of pollutants and their transfer through the food web to molluscs, but the mode of assimilation was not discussed. 

Luoma SN, Jenne EA. 1977. The availability of sediment-bound cobalt, silver and zinc to a deposit-feeding clam. In Drucker H, Wilding RE, eds. Biological implications of metals in the environment. Springfield, VA National Technical Information Service. 

The affect of physicochemical form on uptake from solids has been more carefully studied where sediments are the source of food to animals. When deposit-feeding clams -were fed various types of sedimentary substrates (oxides of iron and manganese organic detritus inorganic and biogenic carbonates) labelled with Cd, Co and Zn, uptake of the nuclides varied... 

Luoma, S. N. and Jenne, E. A. Factors affecting the availability of sediment-bound cadium to the deposit-feeding estuarine clam Macoma balthica, p. 283-291 in Cushing, C. E., ed., "Radioecology and Energy Resources," Ecol. Soc. 

The rates of uptake k within a species under constant conditions have been shown to vary by only a factor of 2 or 3 for PAHs of widely varying hydrophobicity (Bender et al. 1988, Landrum 1988) however, the uptake transfer coefficients (similar to k for naphthalene (0.011 hr ) and chrysene (0.0015 hr" ) differed by 7.5 times in a deposit-feeding clam Macoma balthica) (Foster et al. 1987). This uptake coefficient was determined for animals exposed to sediment-associated PAHs hence, some of the difference may be caused by reduced bioavailability of the more hydrophobic PAHs. 

We have examined the BAFiocS for PAHs, which are hypothesized to be the same for each PAH, from another study (Meador et al. 1995) and have found an interesting pattern of PAH accumulation. The BAF,ocS for R, abronius exhibited the same pattern as that found by Varanasi et al. (1985) for this species, but a different pattern was found for the depositfeeding polychaete (Armandia brevis) (Fig. 16) which is more similar to that shown for the deposit-feeding clam (M. nasuta) (Varanasi et al. 1985). The differences observed are likely the result of feeding mode. Because the amphipods in the study by Meador et al. (1995) were assumed to have inadequate dietary input, they probably received most of their tissue burden of both LPAHs and HPAHs through water uptake hence, the BAF,oc would not be an appropriate measure of bioaccumulation. It has been proposed by Meador et al. (1995) that both deposit feeders and nondeposit... 

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