ABSTRACT:

The deep-sea floor is at present believed to harbor extremely diverse benthic communities, biodiversity within the deep-sea meiobenthos being particularly pronounced. In the Interoceanmetal Benthic Impact Experiment (10M BIE) test site located in the eastern Pacific's Clarion-Clipperton Fracture Zone (CCFZ) at the depth of about 4300 m, genus-level diversity of meiobenthic nematodes and harpacticoid copepods, the meiofauna dominants, was examined immediately before and immediately after (July 1995), as well as 22 months after (May 1997) the experimental disturbance performed to simulate environmental effects of polymetallic nodule collecting. During the second sampling series, the sediment showed a substantial enrichment with freshly deposited phytodetritus. We examined changes in various diversity measures of the two taxocoenes. The results of diversity analyses showed a nematode and harpacticoid taxocoene generic diversities to respond differently to the perturbations in the 10M BIE test site's sedimentary environment. The harpacticoid diversity seemed to have been affected by the disturbance as such, the anthropogenic component of the disturbance proving quite important. The nematodes showed a clear shift in the community structure visible in the 1997 sampling series, the number of genera being reduced and two genera (Desmoscolex and Pareudesmoscolex) gaining immensely in quantitative importance. This temporal shift obscured any effect that might have been produced by the man-made disturbance, quite moderate in extent in itself, and is taken as evidence of a response to the episode of organic enrichment caused by phytodetritus sedimentation.

INTRODUCTION

Diversity, a concept encompassing both the number of species (and/or of higher taxonomic units) and the partitioning of individuals between those units (Hill, 1973), is an important attribute of communities and ecosystems and rellects phenomena affecting them on various temporal and spatial scales (Angel, 1996). Diversity is also recognized as being closely linked to the functioning of ecosystems (Cardinale et al., 2000).

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