BACTERIOPLANKTON ABUNDANCE AND PRODUCTION AND NANOZOOPLANKTON ABUNDANCE IN KENYAN COASTAL WATERS (WESTERN INDIAN-OCEAN)

Bacterial abundance, [H-3]thymidine incorporation rate and heterotroph ic nanoflagellate abundance were measured in the water column along tr ansects perpendicular to the Kenyan coast (western Indian Ocean) durin g June-July (SE monsoon) and November-December (intermonsoon) 1992. Ba cterial abundance was low (less than 6 x 10(5) cells ml(-1)). Bacteria l production estimated from thymidine incorporation rate at near-coast al stations was higher during the intermonsoon period. Production esti mates decreased with depth and distance from the coast. Growth rates o f bacteria and heterotrophic nanoflagellate abundance were higher duri ng the intermonsoon, indicating a higher turnover than during the SE m onsoon. Grazing rates by nanoflagellates, based on their abundance, we re estimated to be 100% or more of bacterial production. Bacteria prob ably supply only part of the nanoflagellate carbon demand. Bacterial p roduction (BP) was high compared with primary production (PP), with av erage BPnet/PPnet ratios of much greater than 100% and 34% during the SE monsoon and intermonsoon, respectively. Compared with open oceanic regions, both BP and PP in Kenyan coastal waters are low. We conclude that BP is not directly coupled to PP and that recycled carbon, e.g. v ia grazing, is an important source for bacterial growth. (C) 1997 Else vier Science Ltd.