Bioavailability of sedimentary metals from a contaminated bay

Abstract

Sediments are considered the sink for metals in aquatic environments because of their strong metal-binding capacity, but they are a potential source for metal ingestion by marine benthic animals as well. Sediment contamination is now a major environmental problem in many countries, including China. This study examines the bioavailability to a marine suspension-feeder (the clam Mactra veneriformis) and a deposit-feeder (the peanut worm Sipunculus nudus) of sediment-bound Cd, Cr and Zn along a gradient of metal contamination. To this end, metal assimilation efficiency and metal extraction by gut juice were quantified and compared. Metal concentrations in sediments collected from 4 sites were 5.40 to 43.7 mg Cd kg Metal assimilation by the clams was independent of the metal concentration in the sediment. In the deposit-feeding sipunculid, the bioavailability of sediment-bound Cd increased with increasing contamination of the sediment, as a result of the increasing partitioning of Cd into the easily exchangeable phase, and decreasing partitioning into the reducible phase. Cd assimilation also increased with increasing total organic carbon content in the sediments.The Cd assimilation efficiency was directly correlated to Cd extraction by gut juices collected in vitro from the peanut worm. No such relationship was found for Cr and Zn. Geochemical and biological controls on metal bioavailability therefore differ between the metals and with the extent of sediment contamination. The limitation of the radiotracer technique to quantify metal assimilation efficiency by marine benthic invertebrates from sediments should be recognized when it is used to predict metal concentrations in target animals.KEY WORDS: Metal · Bioavailability · Contamination · Sediment · Sipuncula · ClamsResale or republication not permitted without written consent of the publisher

Heavy Metal Contents in Tissues of Dominant Species of the Benthos and in Bottom Sediments of Zolotoi Rog Bay, Sea of Japan

“…Experimental data and kinetic modeling have shown that the passage of sediment through the digestive tract determines heavy metal accumulation by deposit-feeding polychaetes and sipunculans [22,31,32]. Comparison of the trace element composition of organisms from polluted and relatively clean areas has revealed a relation between metal storage by infauna and the environmental concentrations of metals.…”

Alteration of organic matter during infaunal polychaete gut passage and links to sediment organic geochemistry. Part I: Amino acids

“…Chen and Mayer, 1999;Ahrens et al, 2001a). Further, several studies suggest that animal taxon and physiology are important controls on faunal feeding and digestive processes (Mayer et al, 1996;Wang et al, 2002). Different taxa have been shown to ingest different particle sizes, and to assimilate compounds from different food sources with varying efficiency .…”

Bioaccumulation of Heavy Metals in the Volta Clam, Galatea Paradoxa (Born, 1778) in Relation to Their Geoaccumulation in Benthic Sediments of the Volta Estuary, Ghana

“…This, possibly, explains the absence of any significant spatial variations in metal concentrations between the two sampling sites. The results possibly suggest that the levels of contamination of these metals do not exceed the clam's capacity of regulation (Wang et al 2002).…”