SOME ENVIRONMENTAL ASPECTS OF OPEN WATER ALGAL CULTIVATION - ZANZIBAR, TANZANIA

In recent years the open-water cultivation of the red algae, Eucheuma spinosum has become a large-scale activity within much of the coastal zone around the island df Zanzibar and in areas along the Tanzanian co ast. This commercial venture provides a good deal of foreign exchange and has brought about a considerable change in the economy and social structure of many coastal villages. To assess the environmental effect s of Eucheuma spinosum farming, the present study investigated the pop ulation dynamics of benthic meiofauna, the primary and bacterial produ ction in the associated water column and benthos, and the flux of nutr ients between the benthos and water column in farm areas and nonfarmed control areas. The results indicate that the farming has no discernib le effects on water-column microbial production, but has a clear effec t on both benthic microbial processes and meiofauna populations. It is not entirely clear, however, which particular aspect of the algal far ming is responsible for the observed changes, but it is thought that m echanical alteration of the sediment surface and possible enhancement of local benthic fish grazing may play a role.