THE EFFECT OF EXPERIMENTALLY INCREASED NEAR-BOTTOM FLOW ON METAZOAN MEIOFAUNA AT A DEEP-SEA SITE, WITH COMPARISON DATA ON MACROFAUNA

It has been argued that strong near-bottom hows affect macrofauna and meiofauna in the deep sea, but the evidence comes largely from studies that compared sites separated geographically by hundreds to thousands of kilometers and in depth by hundreds of meters. In this paper, the results of the first experimental investigation of the effects of stro ng near-bottom flow on deep-sea metazoan meiofauna are presented. At a site (32 degrees 27.581' N, 127 degrees 47.839' W) at 583 m depth on the Fieberling Guyot summit plain, the submersible Alvin emplaced weir s designed to increase the near-bottom flow locally. After 6.5 weeks, sediments in the weirs and unmanipulated locations in the vicinity wer e sampled. The abundances of nematodes, harpacticoid copepods, ostraco ds, and kinorhynchs, considered collectively and as individual taxa, w ere significantly lower in the weir samples than in the background sam ples. Parallel responses were observed in total macrofaunal and mollus k abundances. Proportional declines in kinorhynchs and mollusks were o bserved as well. These results suggest that strong near-bottom flow ca n reduce the abundance of meiofauna and macrofauna in the deep sea and alter assemblage composition. (C) 1998 Elsevier Science Ltd. All righ ts reserved.