Macrofaunal involvement in the sublittoral decay of kelp debris: the detritivore community and species interactions |
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| Authors: | AP Bedford PG Moore |
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| Institution: | University Marine Biological Station, Millport, Isle of Cumbrae, Scotland |
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| Abstract: | The fauna associated with sea-bed accumulations of decomposing Laminaria saccharina has been studied by year-round SCUBA diving at two sites in the Clyde Sea area. Seasonal changes in density of 64 species are reported. In the autumn, large quantities of kelp are detached by storms. This weed carries with it to the sea bed a large part of its normal fauna. Additional species settle onto the weed from the plankton whilst others migrate onto it from the surrounding sea bed. Peak densities of associated species were recorded in autumn. Litter bag experiments in situ showed that, except during the summer, weed is lost from sea-bed accumulations at a faster rate when macrofaunal animals are excluded. The macrofauna therefore inhibits decomposition. The relative importance of interactive cropping by three macrodetritivores, Psammechinus miliaris (Echinodermata), Platynereis dumerilii (Polychaeta) and Gammarus locusta (Amphipoda) was studied by in situ containment of different species combinations. The presence of Gammarus with Psammechinus resulted in less weed being lost than when Psammechinus was isolated. This is because Gammarus selectively crops rotting weed, retarding frond disintegration by microbes. Platynereis retards microbial colonization of frond tissues ruptured during its feeding by repeated cropping of the same region. Weed would decompose very rapidly were it not for macrofaunal cropping. Macroalgal decay thus differs profoundly from that of vascular plants. |
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| Keywords: | macrofauna kelp detritivores sublittoral zones Scotland coast |
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