The effect of food concentration, body size, and environmental oxygen tension on the growth of the deposit‐feeding polycheate, Capitella species 1

This study investigates the separate and interactive effects of food concentration, environmental oxygen level, and body size on the growth rates of Capitella species 1 individuals. Reduction of environmental pO2 or food concentration decreased the volume‐specific growth rates of both large (>1.3 mm3; >1.6 mg wet wt, WW) and small (<1.0 mm3; <1.1 mg WW) worms. Within the high‐food treatments a reduction in environmental pO2 from ∼130 to 35 mm of Hg decreased the growth rates of worms by up to 36% d− 1. Growth of large worms decreased in response to reductions in either pO2 or food concentration. The growth rates of small worms decreased significantly only in response to reductions in environmental pO2 levels. Reductions in either food concentration or environmental oxygen level alone decreased the growth of large worms to the same extent as a concomitant decrease in both. When worms were fed 100% natural sediment, a reduction in average O2 tension from 38 to 21 mm of Hg decreased the growth of large worms from 2% d−1 to −25% d−1. The growth rates of small individuals were unaffected (−4 to −3% d−1). We predict that under conditions of near‐bottom hypoxia or food limitation (e.g. complete pelletization of ingestible sediment) populations of Capitella sp. 1 will experience size‐dependent growth with large animals (>1.6 mg WW) experiencing the greatest decline in growth rate.