Dual Tracer Studies of the Assimilation of an Organic Contaminant from Sediments by Deposit Feeding Oligochaetes

Abstract

The assimilation of [14C]2,4,5,2′,4′,5′-hexachlorobiphenyl (HCBP) from Lake Michigan sediments by oligochaete worms was determined in laboratory microcosms using dual tracer techniques. Particle size selective feeding by oligochaetes makes single tracer calculations of assimilation from bulk feces subject to errors resulting from the changing distribution coefficients of adsorbed constituents as a function of particle size. 51Cr3+ adsorbed to sediments passes through the guts of worms without being assimilated and serves as a conservative tracer of ingestion. Assimilation efficiencies for HCBP decreased from 36 to 15% over the initial 10 d of active feeding and was inversely related to average defecation rate which increased from 0.05 to 0.25 mg sediment∙mg worm−1∙h−1 over the same period. In combination with measured defecation rates, assimilation efficiencies were used to estimate HCBP uptake rates of 3.9–8.1 pmol∙mg worm−1∙h−1. Assimilation efficiencies appear to be dependent upon gut clearing times which are a function of both gut volume and feeding rate and which are estimated to vary from <1 to >5 h.

Bioavailability of pyrene to the deposit-feeding polychaete Arenicola marina: importance of sediment versus water uptake routes

“…Besides changing the partitioning of PAHs in the sediment matrix, organic matter also changes the rate of processes offering potential uptake routes (sediment ingestion, assimilation and irrigation) for infauna (Taghorn & Jumars 1984, Klump et al 1987. Several studies indicate that sediment ingestion is an important route for bioaccumulation of highly hydrophobic contaminants (Weston 1990, Meador et al 1995, Leppänen & Kukkonen 1998, whereas smaller and more water-soluble PAHs probably are taken up from porewater.…”

“…Infaunal deposit-feeding species ingest large amounts of sediment, and exposure may be more dependent on feeding rate and assimilation efficiency than on water concentration. Both feeding rate and assimilation of organic contaminants are affected by environmental factors such as food quality and sediment type as well as the contaminant concentration in the sediment (Taghorn & Jumars 1984, Klump et al 1987, Mayer et al 1996. If bioaccumulation in infauna is controlled mainly by ingestion, irrigation and other physiological processes, the use of EPT in risk assessment may be misleading.…”

Chemical and biological availability of sediment‐sorbed hydrophobic organic contaminants

“…Contaminant assimilation efficiencies determined through short-term laboratory exposures for deposit-feeding invertebrates are relatively high. For example, hexachlorobiphenyl assimilation efficiencies of 16.1 to 46.4% have been reported for oligochaetes [2]; fluoranthene assimilation efficiencies of 56 and 22.4 to 46.0% have been measured for Capitella sp. I [7] and for hydrobia [8], respectively.…”

Sediment Extraction Using Deposit-Feeder Gut Fluids: A Potential Rapid Tool for Assessing Biaccumulation Potential of Sediment-Associated Contaminants

“…) in which solubilization was measured with A. brasiliensis gut fluid and absorption efficiency was measured using the 14 C: 51 Cr dual tracer technique (Klump et al 1987) with the confamilial polychaete Abarenicola paciflca. In these experiments, solubilization of five PAHs (28 to 47 percent) by A. brasiliensis fluid consistently overestimated absorption efficiency in A. pacifica (4 to 24 percent, Figure 6), suggesting incomplete digestive absorption of solubilized contaminants.…”