Abstract:
A study was conducted with an objective of determine the spatial and temporal distribution, abundance and
diversity of plankton along a salinity gradient in the Lakes Naivasha and Oloiden. The phytoplankton and some physico
chemical parameters were sampled monthly for one year (August, 2020 to July, 2021). Identification and counting of
phytoplankton were done under a compound microscope and the diversity was studied using indices. Salinity was higher
in Lake Oloiden sites and it was associated negatively with the phytoplankton abundance. Thirty-two species were
identified and they belonged to the families: Bacillariophycea, Chlorophycea, Dinophycea, Euglenophycea, Cyanophycea
and Rhodophycea. The most abundant families were Bacillariophycea and Cyanophycea (Lake Naivasha), and
Chlorophycea and Dinophycea (Lake Oloiden). The diversity index was low: 0.97 and 0.67 for Oseria and Oloiden (ST1,
ST2) respectively. The Margalef’s index was highest for Oseria (4.62) and lowest for Oloiden ST1 and ST2 (2.86). The
dominance index (D) was highest in Korongo (0.16) and lowest in Oloiden ST1 (0.1) while Korongo had the lowest
evenness (0.77) and Oseria’s was the highest (0.86). The species richness decreased with an increase in salinity. The
phytoplankton diversity was low in the lakes and it could be attributed to the salinity. Further research should be done
along the salinity gradient since conditions may change and, thus the phytoplankton diversity.
