Zooplankton Community Grazing Rates in Some Lakes and a Reservoir in Ethiopia
No Thumbnail Available
Date
1994-06
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Addis Ababa University
Abstract
Zooplankton community grazing rate as % of algae grazed per day was
determined in five lakes and one public water-supply reservoir from March, 1993 to October,
1993_ Physical and chemical measurements (Temperature, Secchi depth, alkalin~y, salin~y etc_)
were taken at the same time. Radio-labelling and change in chlorophyll A (chl.a.) methods
were used. Zooplankton commun~y grazing rates ranging from 0-95% day'l were obtained. In
size fractionated community grazing always, the larger size zooplankters showed higher
%G.day'1. Increase in ambient density of zooplankton resulted in increased %G.day'l in ali
cases except for Lake Bishoftu in which the reverse took place. Two regression models relating
%G.day-l to temperature (Temp.). mean zooplankton biomass (SO), total zooplankton biomass
(ZB), large size zooplankton biomass (UB) and total chlorophyll a (chl.a.) were tested.
Backward deletion procedure resulted in three models which explained 27 - 64% of the total
variation in %G.day'l. In both the regression models and the correlation matrices, chl.a.
concentration was negatively related to %G.day'1. In the later case, temperature was negatively
related to %G.day'l and ali types of zooplankton biomass. The regression coefficients were not
significant at 5% significant level. Grazing results are compared with other works in temperate
and tropical regions and discussed.
Description
Keywords
Biology