Effects of periodic environmental hypoxia on predation of a tethered polychaete, Glycera americana: Implications for trophic dynamics

Abstract

Hypoxia and anoxia have significant deleterious ecological effects on living resources throughout many estuarine and marine ecosystems worldwide. Brief periods of low oxygen have the potential to facilitate transfer of benthic production to higher trophic levels as many benthic infaunal species have shallower sediment depth distributions during hypoxic events. In August-September 1994, a time-lapse camera equipped with a water quality datalogger was used to document in situ exploitation of a tethered prey organism (Glycera americana Leidy) by mobile fish and crustacean predators during alternating normoxia-hypoxia cycles in the York River, Virginia, USA. Based on photographic and diver observations, this hypoxia-induced benthic-pelagic transfer of production is more likely to occur when environmental dissolved oxygen concentrations rise above an apparent threshold between 1 and 2 ml l-1. When oxygen concentrations dechne below approximately 1.5 ml l-1 (30% O2 saturation), the response of the predator to increased prey availability is abruptly interrupted. There is no energy gain by the predator until oxygen concentrations rise above this critical threshold level. It is suggested that predators return to affected areas and resume feeding activity before stressed infauna are able to return to normal positions in the sediment.