MEIOBENTHOS DISTRIBUTION PATTERN IN THE TROPICAL EAST ATLANTIC - INDICATION FOR FRACTIONATED SEDIMENTATION OF ORGANIC-MATTER TO THE SEA-FLOOR

To test the extent to which sea surface productivity governs the distr ibution pattern of benthic organisms, meiobenthic standing stocks were investigated on the shelf, continental margin and the adjacent abyssa l plains off the western African coast between Guinea (10 degrees N) a nd Angola (18 degrees S). The area of investigation is characterized b y gradients in surface productivity due to spatially and seasonally va rying coastal upwelling. Reflecting the dependency of deep-sea organis ms on organic matter input from the euphotic zone, similar gradients o ught to be expected within the benthos. Meiofaunal abundances and biom asses (including Foraminifera) from a total of 57 stations along 13 tr ansects across the continental margin showed a fairly close correlatio n with sediment-bound chloroplastic pigment concentrations, indicating the sedimentation of particulate organic matter from phytoplankton pr oduction. However, certain discrepancies in faunal and pi,ament distri bution patterns were found in regions apart from the centres of enhanc ed primary productivity, i.e. apart from the upwelling centres: wherea s pigment concentrations in the sediments were still comparably high, meiofaunal numbers in those peripheral areas were generally lower. It is suggested that smaller/lighter phytodetritial matter, transported o ver long distances by subsurface currents and exposed to ongoing micro bial degradation during its passage, probably does not have the same e nergy content as the relatively fast-sinking, larger phytodetritus agg regates (''marine snow''), which are found in centres of enhanced prim ary productivity and support extensive benthic stocks. Thus, meiobenth ic abundances in relation to sediment-bound pigment concentrations on the western African continental margin may indicate fractionated sedim entation of organic matter to the sea floor.