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MICROBIAL CONTROL OF LIVE/DEAD ZOOPLANKTON RATIO IN SEVASTOPOL BAY

Vladimir S. Mukhanov, Daria Litvinyuk

Abstract


To explain higher fraction of live zooplankton in heavily polluted and eutrophic Sevastopol Bay comparing with cleaner adjacent waters, a hypothesis has been proposed and tested experimentally that more intensive bacteria-driven decomposition of dead organisms in the bay reduced their pool and, as a result, increased the live-to-dead zooplankton ratio. In the experiment, a heat-killed batch culture of the copepod Calanipeda aquaedulcis was used as a substrate for decomposition by natural microbial communities from the waters of different pollution status. Bacterioplankton abundance and in situ decomposition rate of copepod carcasses were shown to be about 3-fold higher in the bay (1.3 × 106 cells ml-1 and 0.13 day-1, respectively) while an approximation of zooplankton non-predatory mortality rates gave equal values for both the sites (about 0.046 day-1). These findings call for revising the ways of interpreting the results of zooplankton viability assays in their relation to water pollution status.   


Keywords


zooplankton; viability; mortality; copepod; carcasses; decomposition; microbial hotspots; Sevastopol bay.

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