Munkes, Britta (2001) Nährstoffeinträge in Korallenriffe. (Diploma thesis), Christian-Albrechts-Universität zu Kiel, Kiel, Germany, 39 pp.

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Abstract

The aim of this study was to assess the role of zooplanktivorous fish in the import of extrinsic organic matter to a fringing coral reef in the Golf of Aqaba, Red Sea. A six-week survey was carried out along a cross-reef section in the coral reserve in front of the Aqaba Marine Science Station, Jordan, between and 2000. Belt transects showed high abundances of zooplanktivorous fish near the shelf break, dominated by small swarmforming serranids and pomacentrids, mostly Pseudanthias spp. and Neopomacentrus miryae. Fish numbers declined towards the shallower and sandier inshore areas near the reef crest, alongside with a shift in the zooplanktivore community. Loose aggregations of Pomacentrus trichourus dominated over the shallow fore-reef, scattered Pseudanthias squamipinnis near the reef crest. Very dense schools of silversides (Atherinomorus spp.) hovered near the reef crest in the early part of the investigation, but disappeared thereafter. Cross-shore distributions of zooplankton collected with a push net showed marked depletions of the larger size classes coinciding with highest abundances (2 ind. m-2) of fish near the shelf break, along with maximum rates of feeding (19 bites min-1), egestion (0.15 g C m-2*12h-1) and excretion (315 μ,moles m-2 d-1 ). Ammonia dominated total inorganic nitrogen, particularly near the shallower reef areas, suggesting rapid remineralization of the settled organic material. A weak onshore flow ( app. 1.0 cm s-1) prevailed throughout the investigation, suggesting a net import of oceanic zooplankton into the coral reef of 0.6 g C m-2 d-1. Remineralization of this extrinsic material may fuel 15% of the net community production of this high latitude reef. High concentrations of large zooplankton near the reef crest are probably due to aggregation in a downwelling cell, supporting the so-called Type II-enrichment hypothesis.

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