Effects of chronic metal exposure and sediment organic matter on digestive absorption efficiency of cadmium by the deposit‐feeding polychaete Capitella species I

Abstract

Organic matter such as humic acid and bacterial slime exopolymer are common in estuarine and coastal sediments, where they are ingested by animals that process particulate detritus. Both humic acid (HA; refractory) and exopolymer (EPS; easily digestible) bind metals and therefore might represent a source of particulate‐bound metals to deposit‐feeding organisms. This study examined how cadmium preexposure (3 and 30 μg Cd/g dry wt. sed.), gut passage time (GPT), and quality and quantity of the organic coating on sediment particles interact to determine cadmium absorption efficiency (Cd‐AE) in Capitella sp. I. Pulse‐chase experiments using 109Cd and 51Cr were used to determine Cd‐AE in individual worms. Worms were given a pulse of carbon‐cleaned, HA‐coated or EPS‐coated sediment particles. The third treatment was divided into three EPS concentrations (high, medium, and low). A 5‐d preexposure to cadmium did not affect the egestion rates during either the preexposure period or the chase phase. Worms given a pulse of carbon‐cleaned particles exhibited higher egestion rates during the chase phase than worms given a pulse of organic‐coated particles, and no differences were seen in egestion rate between worms exposed to HA‐ and high‐EPS‐coated particles. Egestion rates decreased with increasing EPS concentration. The presence of refractory organic material decreased the absorption efficiency of cadmium from sediment relative to Cd‐AE from carbon‐cleaned sediment but not relative to Cd‐AE from sediment coated with a high concentration of EPS. The Cd‐AE increased linearly with increasing exopolymer coating on sediment particles. Overall, Cd‐AE increased with increasing gut passage time in worms that were not preexposed, although Cd‐AE from HA‐coated particles was independent of gut passage time. Preexposure to cadmium reversed the relationship between gut passage time and cadmium absorption efficiency. Thus, the implications are that sedimentary organic matter and worm physiology might be especially important in controlling metal bioavailability in deposit‐feeding organisms and should be considered in sediment quality approaches.

Uptake and Efflux of Cd and Zn by the Green Mussel Perna viridis after Metal Preexposure

“…Selck et al (9) reported that Cd AE increased with increasing gut passage time in Capitella sp., but this pattern was reversed in worms following preexposure to Cd. Data presented herein suggest that preexposure to elevated Cd or Zn does affect metal AE, in particular, those of Cd following Cd exposure.…”

“…These studies did not consider metal uptake via the dietary route. Selck et al (9) investigated the effects of chronic metal exposure on the Cd assimilation efficiency by a depositfeeding polychaete Capitella. Cd assimilation efficiency was positively related to gut passage time in unexposed worms, but this pattern was reversed following Cd exposure.…”

Microbial Extracellular Polymeric Substances (EPSs) in Ocean Systems

“…When animals ingest the matrix, coincidentally during their feeding on sediments, cells or flocs, they will consume the sorbed metals and organics as well. EPS have been shown to be an efficient trophic-transfer vehicle for sorbed metals in amphipods (Schlekat et al, 1998, 1999, 2000; Selck et al, 1999), and organic compounds such as pesticides, although most of the latter work has even been conducted in freshwater systems (Widenfalk et al, 2008; Lundqvist et al, 2010, 2012). …”

<b>Organochlorine residues in tissues of marine fauna along the coast of Kenya-Mombasa Island</b>

“…Organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) are biologically stable compounds that are hydrophobic and fat-soluble and therefore accumulate in aquatic biota at concentrations that exhibit ecotoxicological effects [2,3]. Moreover, bacterial communities have been shown to bioconcentrate OCPs [4] and extracellular polymeric substances (EPS) that are secreted by the microorganisms in aquatic habitats act as a vector for contaminant uptake into aquatic food webs [5,6]. The increasing usage of these hazardous manmade chemicals has become a matter of great concern.…”