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

Abstract

The bioavailability to clams (Potamocorbula amurensis and Macoma balthica) of Cd, Cr, and Zn from suspended particulate material (SPM) collected during a phytoplankton bloom was compared to bioavailability from SPM dominated by resuspended sediments. Bioavailability was also compared among mudflat sediments amended with different levels of living benthic microalgae. Bioavailability was defined by absorption efficiencies determined using pulse-chase protocols, modified for studying natural particle assemblages. The partitioning of Cd and Zn to particles (&) increased as the microalgae biomass (Chl a) increased in the particle assemblages; partitioning of Cr was less affected by the algal biomass. The clams fed particle assemblages enriched with microalgae absorbed Cd and Zn with significantly greater efficiency than did the clams fed algae-poor particles. This was partially explained by the greater occurrence of Cd and Zn in the cytosolic fraction of the particle assemblages that were microalgae enriched, as well as by the efficient absorption of cytosolic material by the clams. Among metals, Zn was most efficiently absorbed by both clams, and Cr the least. M. balthica absorbed Zn more efficiently from all types of food particles (39-82%) than did P. amurensis (13-50%). P. amureasis absorbed Cd with greater efficiency from the bloom SPM (44-48%) than did M. balthica (13-21%), but the two clams absorbed Cd similarly from benthic microalgae (26 51%). The addition of microalgae to complex natural particle assemblages clearly affected the bioavailability of associated metals, so studies using sediments (or suspended particulate material) that do not include a realistic living food component could underestimate metal bioavailability from particle ingestion.

Uptake and loss kinetics of Cd, Cr and Zn in the bivalves Potamocorbula amurensis and Macoma balthica:effects of size and salinity

“…Both Cr (111) and Cr (VI) were used to simulate the exposure of clams in natural estuarine conditions in which Cr in particulate phase is dominated by Cr (111) and in dissolved phase by Cr (VI) (Abu-Saba & Flegal 1995). Feeding cultures of Cr-labeled bacterial cells to clams was necessary to achieve enough radioactivity in the clam tissue, since Cr from bacterial cells is highly available by Macoma balthica and Potamocorbula amurensis (Decho & Luoma 1994, 19961, while Cr from most other food sources is much less bioavailable (Lee & Luoma 1998). Both cultures were incubated for 4 d on a 1ight:dark cycle (14 h L:10 h D) in an 18°C incubation chamber.…”

“…The gut residence time is -24 h for P. amurensis and 72 to 96 h for M. balthica (Decho & Luoma 1991). The substantial loss of Cr during the first 4 d was the result of low assimilation of this metal compared to Cd and Zn (Lee & Luoma 1998). …”

“…We restrict the present study to physiological influx of dissolved metals and loss kinetics. Influx from food is addressed in a separate paper (Lee & Luoma 1998).…”

“…In North SFB, Cd, Cr, and Ni levels in P. amurensis decreased with an increase in salinity. The biological and geochemical processes responsible for the differences in metal bioaccumulation patterns among metals and between 2 species are largely unknown (Decho & Luoma 1991, Lee & Luoma 1998.…”

Influence of reactive sulfide (AVS) and supplementary food on Ag, Cd and Zn bioaccumulation in the marine polychaete Neanthes arenaceodentata

“…Metals in sediments can be concentrated by benthic organisms and may have adverse effects at elevated levels (Long et al 1995, Hornberger et al 2000. The geochemical nature of the metal-sediment association and the relative distribution of metals between porewater and sediments could have considerable influence on the eventual fate and bioavailabililty of metals to aquatic organisms (Luoma & Bryan 1982, Di Toro et al 1990, Lee & Luoma 1998. Transfer of metals from sediments to benthic organisms may also be affected by biological attributes of animals such as feeding behaviors, life habits, reproductive cycles, growth, and size (Cain & Luoma 1990, Arifin & Bendall-Young 1997, Warren et al 1998, B. G. Lee et al 2000a) Studies (e.g., Morse et al 1987, Di Toro et al 1990 have recognized reactive sulfides (AVS, acid volatile sulfide) in sediments as a major factor controlling porewater metal chemistry.…”