You are here:
Effects of Hypoxia on Animal Burrow Construction and Consequent Effects on Sediment Redox Profiles
Citation:
WEISSBERGER, E. J., L. L. COIRO, AND E. W. DAVEY. Effects of Hypoxia on Animal Burrow Construction and Consequent Effects on Sediment Redox Profiles. JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY. Elsevier Science Ltd, New York, NY, 371:60-67, (2009).
Impact/Purpose:
The purpose of this research was to determine the effects of mild hypoxia on the burrowing behavior of common estuarine species. The results of a laboratory experiment indicate that amphipods and clams burrow to shallower depths under hypoxic conditions compared with normoxic conditions, dissolved oxygen concentration alone can affect the depth to which oxygen penetrates the sediment, and burrowing infauna can increase the depth to which oxygen penetrates the sediment, but not to the same degree as they would under normoxic conditions. This is the first study to examine these phenomena in a causal, rather than correlative, framework.
Description:
Previous studies investigating the effects of hypoxia on benthic infauna and consequent effects on sediment chemistry provide only correlative results from the field. In order to establish causation and isolate effects of hypoxia on individual species, we conducted a laboratory experiment to investigate the effects of mild hypoxia on the burrowing behavior of three marine species (the hard clam Mercenaria mercenaria, the polychaete worm Neanthes virens, and the amphipod Leptocheirus plumulosus) and consequent effects on sediment redox profiles. Animals were introduced into defaunated sediment and allowed to burrow for four months at mildly hypoxic (2 mg l-1) and normoxic (7 mg l-1) dissolved oxygen levels. Sediment redox profiles were taken at varying temporal intervals for the duration of the experiment. At the end of the experiment, the sediment was imaged using computer-aided tomography to quantify burrow volume and location. For all species, burrow volume remained constant over DO treatments, but amphipod and clam burrows were shallower in hypoxic treatments compared with normoxic treatments. Redox profile discontinuity (RPD) depth was shallower in hypoxic treatments compared with normoxic treatments for experiments without animals, indicating that water column oxygen concentration alone influences diffusion of oxygen into the sediment. Clams and worms, but not amphipods, increased the RPD depth relative to no-animal controls in both hypoxic and normoxic treatments, but the effect was greater in normoxic conditions. These results suggest that although hypoxia can reduce burrowing depth, infauna can still increase the depth to which oxygen penetrates the sediment, but not to the same degree as they would under normoxic conditions.