Deep-Sea Research I 45 (1998) 625 —638 The effect of experimentally increased near-bottom flow on metazoan meiofauna at a deep-sea site, with comparison data on macrofauna David Thistle,* Lisa A. Levin  Department of Oceanography, Florida State University, Tallahassee, FL 32306-4320, U.S.A.  Marine Life Research Group, Scripps Institution of Oceanography, La Jolla, CA 92093-0218, U.S.A. Received 10 January 1997; accepted 9 July 1997 Abstract It has been argued that strong near-bottom flows affect macrofauna and meiofauna in the deep sea, but the evidence comes largely from studies that compared sites separated geographi- cally 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 strong near-bottom flow on deep-sea metazoan meiofauna are presented. At a site (32° 27.581 N, 127° 47.839 W) at 583 m depth on the Fieberling Guyot summit plain, the submersible Alvin emplaced weirs designed to increase the near-bottom flow locally. After 6.5 weeks, sediments in the weirs and unmanipu- lated locations in the vicinity were sampled. The abundances of nematodes, harpacticoid copepods, ostracods, and kinorhynchs, considered collectively and as individual taxa, were significantly lower in the weir samples than in the background samples. Parallel responses were observed in total macrofaunal and mollusk abundances. Proportional declines in kinorhynchs and mollusks were observed as well. These results suggest that strong near-bottom flow can reduce the abundance of meiofauna and macrofauna in the deep sea and alter assemblage composition.  1998 Elsevier Science Ltd. All rights reserved. Keywords: Meiofauna; Nematoda; Harpacticoida; Ostracoda; Kinorhyncha; Seamount; Deep sea; Disturbance; Macrofauna * Corresponding author. Fax: 001 850 644 2581; e-mail: dthistle@garnet.acns.fsu.edu. 0967-0637/98/$19.00  1998 Elsevier Science Ltd. All rights reserved. PII: S 0 9 6 7 - 0 6 3 7 ( 9 7 ) 0 0 1 0 1 - 5