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Spatial variation in abundance and diversity of the smaller surface and near-surface eelgrass-associated intertidal macrobenthos within a warm-temperate estuarine bay in the Garden Route National Park, RSA

Authors

  • R. S. K. Barnes

    Corresponding author
    1. Knysna Field Laboratory (Department of Zoology and Entomology, Rhodes University), Knysna 6570, RSA & Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, UK
    • Knysna Field Laboratory (Department of Zoology and Entomology, Rhodes University), Knysna 6570, RSA & Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, UK
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Abstract

  • 1.Smaller members (<10 mm) of the sediment-surface macrobenthos of Nanozostera capensis meadows across 9 km2 of the marine Outer Basin of the Knysna estuarine bay (Garden Route National Park, Western Cape, South Africa) were investigated at a series of 24 stations.
  • 2.Ordination (nMDS) disclosed the existence of five clusters of stations related to degree of exposure. Relatively sheltered stations were dominated by two endemic species of deposit-feeding microgastropod, and they supported significantly higher macrobenthic densities but lower species diversity and less evenness than relatively exposed stations. The latter were dominated by polychaetes and also possessed more suspension feeders, equivalent to more open seagrass beds in other latitudes. Species richness per station, however, was relatively constant across the whole basin.
  • 3.The smaller benthic macrofauna, totalling 82 species, was found to include several animals (<5 mm) hitherto unknown from the region, including one gastropod genus (Cornirostra) not previously known from Africa.
  • 4.Species were patchily distributed across all scales from 1 m to >1 km, but variance partitioning showed components of total variance to decrease with increasing spatial scale: sample (46.5%), station (30.0%), site (23.5%).
  • 5.These findings are discussed in relation to conservation site selection in rich but faunistically heterogeneous seagrass beds that are impacted by bait collection or other human disturbance. Copyright © 2010 John Wiley & Sons, Ltd.
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