Spatial and temporal distribution and diversity of zooplankton along a salinity gradient between the Lake Naivasha and the Lake Oloiden | The Eldoret National Polytechnic

Date

2023-07-07

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Eldoret National Polytechnic

Abstract

There has been an increase in the water level in the Lake Naivasha (fresh water) which led toits merging with Lake Oloiden (saline). This was due to the increase in rainfall: associatedwith climate change. This may have an impact on the zooplankton community (biodiversity)due to the salinity gradient that resulted. A study was conducted to investigate the spatial andtemporal distribution and diversity of zooplankton along a salinity gradient between the LakeNaivasha and the Lake Oloiden. The salinity was measured insitu using a YSIMultiparameter meter and zooplankton were sampled twice by towing a zooplankton net witha flow meter for 10 minutes (monthly, per site for one year). The zooplankton were identifiedand analyzed under a compound microscope (×100). The species diversity, evenness andspecies richness index were computed. The salinity was higher in Oloiden ST1 and ST2 ascompared to the rest of the sites while the correlation showed a slight positive associationbetween salinity and zooplankton numbers. A total of 17 species were identified and theybelonged to the following families: Branchionidae, Lecanidae, Trichocercidae, Sisidae,Daphnidae and Cyclopoidae. The density (Ind/l) was highest for daphnidae, cyclopoidae andsisidae; however, Lake Oloiden had a lower density as compared to the rest of the sites. Thediversity index was low; H’= 0.87 for Oloiden ST2 and H’=0.64 for Crescent. Speciesrichness (d) was highest (2.84) for Oloiden ST2 and lowest in Crescent (1.24). Speciesevenness was highest in Crescent (0.83) and lowest in Oseria (0.71). The diversity index,evenness and Margalef’s index was higher in Lake Oloiden as compared to Lake Naivasha.The salinity gradient had an impact on the distribution and diversity of zooplankton; speciesdiversity, evenness and species richness increased with increase in salinity.

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