The abundance, biomass and composition of planktonic ciliates were studied
in two Great Lakes of Africa, Malawi and Victoria, between June, 1997, and June,
1999, to investigate their role in the food webs of these lakes. Oligotrichs
(Strombidium, Strobilidium and Halteria) were the most abundant group of
ciliates in both lakes. Other important ciliates in terms of abundance and/or
biomass included heterotrichs, peritrichs, haptorids, and peniculids. Mean ciliate
abundance was 1.5 ciliates·mL-1 and 20.1 ciliates·mL-1
in Lakes Malawi and Victoria, respectively. Ciliate biomass ranged from 0.03 to
7.82 µg C·L-1 (mean
1.8 ± 0.7 µg C·L-1)
in Lake Malawi and ranged from 24.2 to 61.82 µg C·L-1
(mean 36 µg C·L-1) in Lake Victoria. Ciliate abundance and biomass
were higher at offshore than inshore stations of both lakes despite that
chlorophyll exhibited the opposite trend. Both lakes demonstrated vertical and
temporal variation in their ciliate communities as well. Herbivores were an
important feeding guild in both lakes, while mixotrophs and bacterivores were
also important in Lakes Malawi and Victoria, respectively.