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The meiofauna:macrofauna ratio across the continental slope of the Goban Spur (north-east Atlantic)

Published online by Cambridge University Press:  04 April 2001

Els Flach
Affiliation:
Centre for Estuarine and Coastal Ecology, Netherlands Institute of Ecology (NIOO-CEMO), PO Box 140, 4400 AC Yerseke, The Netherlands
Jan Vanaverbeke
Affiliation:
University of Gent, Department of Biology, K.L. Ledeganckstraat 35, B-9000 Gent, Belgium
Carlo Heip
Affiliation:
Centre for Estuarine and Coastal Ecology, Netherlands Institute of Ecology (NIOO-CEMO), PO Box 140, 4400 AC Yerseke, The Netherlands
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Abstract

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Meio- and macrofauna density and biomass were estimated at the OMEX-transect across the continental slope of the Goban Spur at water depths ranging from 208 to 4460 m in the north-east Atlantic. A linear increase in the ratio between meio- and macrofauna densities with increasing water depth was found. At the continental shelf meiofauna densities were ∼50 times higher than macrofauna densities, whereas in the abyss meiofauna densities were more than 1000 times higher. This change in ratio was due to a significant decrease in macrofauna densities with increasing water depth, whereas the meiofauna densities stayed more or less at the same level. The ratio in biomass between meio- and macrofauna showed a dip at ∼1000 m. At this depth macrofauna biomass was ∼55 times higher than meiofauna biomass, whereas at ∼4500 m macrofauna biomass was only about three times higher. Macrofauna biomass was high at ∼1000 m, due to the high mean individual weight of the macrofauna, whereas meiofauna biomass and mean individual weight were low at this depth.

Meiofauna consisted of ∼90% nematodes. Within the macrofaunal fraction (>0.5 mm) a linear increase in the ratio between nematodes and macrofauna sensu stricto with depth was found. At the deepest station ∼20% of the macrofaunal fraction were nematodes, at the shallowest station only ∼2%. Thus, large nematodes became relatively more important with increasing water depth. Within the macrofauna a decrease in the abundance of filter- and surface deposit-feeders relative to the subsurface deposit-feeders with increasing water depth was observed, which may be related to a change in food input. As no decrease in mean individual weight with increasing water depth within either group could be observed, the change in meio:macrofauna ratios along the OMEX-transect merely reflects a change in taxonomic (functional) composition, rather than a change in size.

Type
Research Article
Copyright
© 1999 Marine Biological Association of the United Kingdom