Is the HEBBLE isopod fauna hydrodynamically modified? A second test

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Abstract

Several times per year, the High Energy Benthic Boundary Layer Experiment (HEBBLE) site (4820 m depth, 40°27′N 62°20′W) experiences benthic storms during which near-bottom flows can erode millimeters of sediment. Thistle and Wilson (Deep-Sea Research, 34 1987, 73–87) predicted that isopods that inhabited the surface of the sediment would be relatively rare at the HEBBLE site compared to those at quiescent deep-sea sites. They tested this prediction by comparing the composition of the HEBBLE isopod fauna to that of a quiescent site and found a significant difference in the predicted direction. Although this result was encouraging, the strength of their inference was limited because only one site from each type of environment had been compared. We performed a second test of Thistle and Wilson's hypothesis by comparing the composition of the isopod fauna from two additional physically quiescent locations (4500 m depth, 14°40′N 125°26′W, and 4800 m depth, 12°57′N 128°19.5′W) to that of the HEBBLE site. Those isopods that are thought to be exposed to the erosion caused by storms occurred in a significantly greater proportion of the samples at the quiescent sites than at the HEBBLE site, a result consistent with Thistle and Wilson's hypothesis.