Macrozoobenthos diversity in an oxygen minimum zone off northern Namibia |
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Authors: | Michael Lothar Zettler Ralf Bochert Falk Pollehne |
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Institution: | (1) Present address: Department of Biology, Leibniz Institute for Baltic Sea Research (IOW), Seestr. 15, 18119 Warnemuende, Germany |
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Abstract: | A benthological survey in the Benguela upwelling area off northern Namibia (located at 17.3°S and water depth ranging between
26 and 117 m) showed the concentration of dissolved oxygen and the accumulation of organic-rich sediments to control macrozoobenthic
community patterns. In contrast to highly biodiverse nearshore areas with well-structured shell deposits of the brachiopod
Discinisca tenuis (Sowerby 1847), the benthic community in the oxygen minimum zone (OMZ) decreased strongly in species numbers. Nevertheless,
a well-established community ranging from 13 to 31 species persisted. Species densities (300–3,350 ind m−2) and biomass (4–109 g afdw/m2) were surprisingly high for areas with near bottom oxygen concentrations from 0.06 to 0.88 ml l−1. In contrast to OMZ’s of other upwelling areas, where the benthic macrofauna is generally dominated by small-bodied polychaetes,
off Namibia larger key organisms like the bivalve Nuculana bicuspidata (Gould 1845) and the snail Nassarius vinctus (Marrett 1877) accounted for a large proportion of the macrozoobenthos >1 mm. This is supposed to have a distinct effect
on the functional properties of the sediments.
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