Biomass and Production of the major zooplankton in Lake Kuriftu, Ethiopia
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Date
2009-07
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Addis Ababa University
Abstract
Studies on the biomass and production of the dominant zooplankton were done in Lake Kuriftu
from August, 2008 to May, 2009. The cyclopoid copepod (Thermocyclops consimilis)
constituted 71% in abundance in Lake Kuriftu, but cladocerans and rotifers are also present
almost in equal proportions. Brachionus calyciflorus (12%) was the second dominant species
next to T. consimilis. T. consimilis was raised in the laboratory to obtain life history
information (duration of embryonic and post-embryonic development) at 20 and 25.90C, and
fed mixed algal food enhanced with F/2 culture medium. Laboratory data on the duration of
development and biomass, together with population abundance data obtained in the field, were
used to estimate the biomass and production of this species in Lake Kuriftu. The mean biomass
and production of T. consimilis, attained during the study period, were 23.8 mg dry weight
(DW) m-3 and 0.78 mg DW m-3day-1, respectively with daily and annual P:B ratio 0.033and
13.10, respectively. The dry mass of B. calyciflorus was determined from its biovolume by
approximating the nearest geometric formula. Dry weight and recruitment of new individuals
were used to calculate the production of B. calyciflorus. The mean biomass and production of
this species were 629.66 μg DW m-3 and 180.38 μg DW m-3 day-1, respectively with daily and
annual P:B ratio 0.29 and 21.31, respectively. Zooplankton production rates were low
compared to values reported in the literature for the same or other species of equivalent sized
copepods, from both tropical and subtropical regions.
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Biology