ABSTRACT: The meiofauna of hydrothermal deep-sea sediments in the North Fiji Basin (NE Pacific) was investigated. Nematodes were the dominant taxon. The structure of the hydrothermal nematode communities from the Fiji Basin is compared with (1) the communities from adjacent oxic deep-sea sediments, (2) other hydrothermal vent areas and (3) shallow reduced environments such as cold seeps and subsurface anoxic sediments of eutrophic bottoms. Although the genus composition of the hydrothermal area and the biodiversity on a generic or functional-morphological level did not deviate greatly from the control areas, we found differences at the species level and in the size spectra and the species diversity. None of the species found in the hydrothermal sediments occurred in the surrounding areas. The size spectra of the vent communities was shifted towards larger nematodes, and species diversity was much lower in the hydrothermal area. The similarity in nematode genus composition between hydrothermal sites and control areas stands in contrast with the presence of a specialized endemic hydrothermal macrofauna. The absence of a planktonic life stage, in combination with small size, makes it more difficult for nematode species to migrate between isolated hydrothermal patches.

KEY WORDS: Nematodes · Hydrothermal vents · Community analysis · Colonization

Published in MEPS Vol. 157 (1997) on October 16
ISSN: 0171-8630. Copyright © Inter-Research, Oldendorf/Luhe, 1997