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Journal of Experimental Marine Biology and Ecology 242 1999 41–57
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Effects of contaminated sediments on particle size selection by the polychaete Capitella sp. I
Ching-Yi Horng, Gary L. Taghon
Rutgers University , Institute of Marine and Coastal Sciences, 71 Dudley Road, New Brunswick,
NJ 08901-8521, USA
Received 4 January 1999; received in revised form 28 May 1999; accepted 28 June 1999
Abstract
Capitellid polychaetes are generally considered opportunistic species, characteristic of or- ganically enriched and disturbed habitats. The feeding behavior of capitellids dramatically affects
physical properties of sediments by 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. Sediment contamination, measured as the con-
centrations of selected polycyclic aromatic hydrocarbons PAHs varied from 0.08 to 31 ppm. The median size of mineral particle ingested was ¯ 4 mm for all sediments. Worms selectively
ingested the smallest particles in the most contaminated sediment. 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 phenanthrene added at six concentrations, from 0.07 to 13 ppm. Worms preferentially fed on small
beads most preferred particle size 1764 mm in all treatments, and selection was unaffected by phenanthrene concentrations. Selective feeding on the finest sediment particles and their
incorporation into long-lived fecal pellets may affect the persistence of organic contaminants in sediments.
1999 Elsevier Science B.V. All rights reserved.
Keywords : Capitella; Particle selection; PAHs
1. Introduction
Important insights concerning the effects of benthic deposit-feeding macrofauna on
Corresponding author. Tel.: 11-732-932-6555 ext. 547; fax: 11-732-932-8578. E-mail address
: taghonahab.rutgers.edu G.L. Taghon 0022-0981 99 – see front matter
1999 Elsevier Science B.V. All rights reserved.
P I I : S 0 0 2 2 - 0 9 8 1 9 9 0 0 0 9 3 - 3
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.-Y. Horng, G.L. Taghon J. Exp. Mar. Biol. Ecol. 242 1999 41 –57
sediment-bound organic contaminants can be gained by quantifying selection by the organism for different particle types. Contaminants associated with preferred particles
will have a higher probability of being ingested, packaged into fecal material, and kept in the bioturbated zone of the sediment column e.g. Jumars et al., 1981. Once
contaminants are ingested by the deposit-feeder, they may be metabolized by the animal itself McElroy, 1985; McElroy et al., 1990 or by bacteria present in the hind-gut of the
animal Plante et al., 1990. Particle-bound contaminants can also be passed out of the gut and incorporated in fecal pellets. The feces of invertebrates can be sites of elevated
microbial activity Hargrave, 1976; higher organic contents of feces relative to ambient sediment, resulting from selective feeding, is one possible cause.
Selective feeding has been documented in a wide variety of deposit feeders. Despite considerable variations among taxa in feeding mode and feeding appendages, deposit
feeders generally preferentially ingest smaller, low-density particles for review, see Taghon, 1989, although exceptions exist e.g. Whitlatch and Weinberg, 1982. Further
studies have shown that surface properties of particles, such as roughness and presence of an organic coating, strongly influence particle selection in species that use tentacles to
collect particles Self and Jumars, 1978, 1988; Jumars et al., 1982; Taghon, 1982. The effects of particle-bound contaminants on particle selection are unexplored. Con-
centrations of organic contaminants such as polycyclic aromatic hydrocarbons PAHs and polychlorinated biphenyls PCBs are often much greater in smaller size and
´ low-density fractions of sediments Prahl and Carpenter, 1983; Pierard et al., 1996;
Horng, 1998. Hence, knowledge of the selectivity of deposit feeders for different types of particles is important in predicting the long-term fate of contaminants in the marine
environment.
The impact of fecal pellet production by polychaetes of the genus Capitella could be especially significant for the fate of organic contaminants. Capitella capitata, originally
believed to be a single species, is now known to consist of a complex of species that differ in life history characteristics Grassle and Grassle, 1976. Members of the
Capitella sibling species complex are often the dominant inhabitants of organically enriched sediments and have been used as an indicator of heavily polluted environments
Grassle and Grassle, 1974; Pearson and Rosenberg, 1978. Capitella sp. I is the most opportunistic of the sibling species belonging to this complex Grassle and Grassle,
1976. Capitellids repackage fine sediment particles into large, robust pellets. High abundances of Capitella spp. are found in organic-rich sediments around ocean outfalls
on the Palos Verdes Shelf in southern California Stull et al., 1986a,b. These sediments also contain high concentrations of DDT and PCBs Lee et al., 1996. Drake 1996
reported that up to half of the silt and clay fractions , 63 mm of the effluent-affected sediment is incorporated into large 63–500 mm fecal pellets, probably produced by
capitellid polychaetes. DDT concentrations have a bimodal distribution, with a peak in the mud fraction and a peak associated with the sand-sized fecal pellets. Gallagher and
Keay 1998 found that the most contaminated sediments in Boston Harbor contain several species of Capitella, including species I. They estimated that the ‘half-life’ of
capitellid fecal pellets is from 5 to 33 years. This is several orders of magnitude longer than the time it takes fecal pellets made by other species of deposit feeders to break
down Taghon et al., 1984.
C .-Y. Horng, G.L. Taghon J. Exp. Mar. Biol. Ecol. 242 1999 41 –57
43
There have been numerous studies of the effects of sediment chemical composition on the feeding and growth rates and reproductive output of Capitella spp. Tenore, 1977;
´ Gremare et al., 1988; Marsh et al., 1989; Forbes and Lopez, 1990; Tsutsumi et al., 1990;
Bridges et al., 1994. Only one previous study has quantitatively evaluated particle selectivity by Capitella spp., and that study used uncontaminated sediments Self and
Jumars, 1988. In this study, we used two different approaches to examine the influence of contaminants on particle selection by Capitella sp. I. The first approach tested
whether particle selection on natural sediments varied with the degree of contamination. Organically enriched sediments from four different collection sites were used. Particle
selection was examined by comparing the particle size distributions in fecal pellets with those in the sediments. This approach provided information about the sizes of mineral
particles being ingested from natural sediments. From the perspective of testing particle selection, however, this method is relatively insensitive with respect to small particles,
due to the very great abundance of small particles in natural sediments. The second approach was to determine the effect of a single PAH on particle selection. Phenan-
threne-spiked sediments were used for this selection experiment. Glass beads were used as a tracer to evaluate size selection, because they offer the advantage of testing
preference for different particle sizes with equal sensitivity Self and Jumars, 1988.
2. Materials and methods
