PRIMARY PRODUCTION BY PHYTOPLANKTON ALONG THE KENYAN COAST DURING THESE MONSOON AND NOVEMBER INTERMONSOON 1992, AND THE OCCURRENCE OF TRICHODESMIUM

Phytoplanktonic primary production was measured during the SE monsoon in June-July and during the intermonsoon period in November-December 1 992. Primary production was highest on the northernmost transect durin g the SE monsoon, whereas during the intermonsoon it was highest on th e southernmost transect. In general primary production was higher duri ng the intermonsoon, and highest productivity was measured along the s outhern coast of Kenya. The more stable hydrodynamical conditions duri ng the intermonsoon period promoted the occurrence of the nitrogen-fix ing cyanobacterium Trichodesmium, primarily at the shallower stations. Nitrogen fixation assays suggested that this cyanobacterium was respo nsible for most of the new production. Comparison between net primary productivity, bacterial productivity and benthic respiration suggests that rates of primary production should be higher than measured, imply ing that primary production can be as high as that in tropical upwelli ng systems, despite the fact that a regular and well-developed upwelli ng period does not always seem to occur. (C) 1997 Elsevier Science Ltd .