Effects of suspended, diesel-contaminated sediment on feeding rate in the darter goby, Gobionellus boleosoma (Teleostei: Gobiidae)

Abstract

The darter goby, Gobionellus boleosoma, a bottom-feeding gobiid fish, was used as a meiofaunal predator in laboratory experiments designed to determine the effect of suspended diesel-contaminated sediment on feeding rate. Estuarine sediments are sinks for hydrophobic contaminants, and contaminant exposure from suspended sediment seems likely in estuarine mudflats. The darter goby is a small estuarine fish that lives in shallow mudflats surrounding Spartina alterniflora marshes, feeding primarily on meio- and small macrofauna. We first showed that darter gobies are effective feeders on suspended meiobenthic copepods and that this feeding was not affected by suspended sediment loads as high as 2000 mg l −1. Harpacticoid copepods then were offered as ad libitum prey to gobies after exposure to either contaminated or non-contaminated sediments via a single turbidity event 24 h prior to feeding. Based on gut content analysis, goby standard length influenced feeding rate as larger gobies ingested more meiobenthic copepods in the 1-h experiment. Diesel-fuel contamination reduced feeding rate by 50–100% in all but the lowest dosage examined; ANCOVA (with length as a co-variate) indicated that feeding rate after exposure to suspended sediments above 200 mg PAH kg dry sediment −1 was significantly reduced relative to uncontaminated controls. No feeding occurred at 687 mg PAH kg dry sediment −1 (the greatest concentration tested). The proportion of non-feeding fishes increased with increasing levels of contamination, and an additional experiment suggested that the source of contamination was associated with direct contact with contaminated sediment rather than exposure to water previously associated with contaminated sediment.