THE POTENTIAL TROPHIC SIGNIFICANCE OF <i>CALLIANASSA MAJOR</i> FECAL PELLETS1

Abstract

The trophic significance of the fecal pellets of Callianassa major was investigated by measuring 1) the rates at which fecal material was produced, 2) its organic carbon and nitrogen content, and 3) its ingestion by other animals. Our results indicate that 456 ± 118 fecal pellets are produced per burrow per day and from 175 ± 46 to 2,600 ± 670 pellets m −2 day −1 , depending on population density, and that an entire C. major population occupying an area of about 200,000 m 2 produces about 280 × 10 6 pellets/day. The carbon and nitrogen contents of the pellets were 3 and 0.3% of their dry weight. Aging the pellets had no effect on their carbon content but halved the nitrogen content in 48 hr. Ingestion experiments indicated that fecal pellets were eaten by hermit crabs, probably by blue crabs, and possibly by several other beach inhabitants. The results were used to calculate the rate at which organic carbon is made available in fecal pellets, and this rate was compared to production rate measurements for local primary producers. The potential quantitative significance of fecal pellets as a food source is discussed.