Effects of contaminated sediments on particle size selection by the polychaete Capitella sp I

Capitellid polychaetes are generally considered opportunistic species, char acteristic of organically enriched and disturbed habitats. The feeding beha vior of capitellids dramatically affects physical properties of sediments b y repackaging sediment particles into large fecal pellets that persist for years. Particle size selection by Capitella sp. I was quantified using two approaches. Organic-rich sediments from four locations subjected to varying degrees of anthropogenic disturbance were used in the first approach. Sedi ment contamination, measured as the concentrations of selected polycyclic a romatic hydrocarbons (PAHs) varied from 0.08 to 31 ppm. The median size of mineral particle ingested was approximate to 4 mu m for all sediments. Worm s selectively ingested the smallest particles in the most contaminated sedi ment. Because of potential ambiguity in obtaining accurate measurements of in situ particle sizes of natural sediments, a second experiment used glass beads as tracers added to natural sediment. Treatments consisted of phenan threne added at six concentrations, from 0.07 to 13 ppm. Worms preferential ly fed on small beads (most preferred particle size 17 +/- 4 mu m) in all t reatments, and selection was unaffected by phenanthrene concentrations. Sel ective feeding on the finest sediment particles and their incorporation int o long-lived fecal pellets may affect the persistence of organic contaminan ts in sediments. (C) 1999 Elsevier Science BN. All rights reserved.