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Zooplankton community structure of Lake Turkana, Kenya
Malala, J.O. (2000). Zooplankton community structure of Lake Turkana, Kenya. MSc Thesis. VUB: Brussel. 96 pp.
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| Beschikbaar in | Auteur |
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Documenttype: Doctoraat/Thesis/Eindwerk
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| Abstract |
Zooplankton distribution and abundance in Lake Turkana was studied during the flooding of the river Omo between August and October 1999 at three sites in the western (Ferguson's Gulf), central (near Central Island) and eastern (Allia Bay /Sibiloi National Park) sectors of the lake. The aim was to provide information on the community structure and diversity at the study sites along an inshore-offshore direction. All samples were subsurface, collected using a 50 µm mesh width net with a mouth diameter of 12.5 cm towed at a constant speed (5 ms-1) behind a boat. Standard enviromnental variables such as temperature, Secchi depth, conductivity , pH and dissolved oxygen were concurrently measured. Particulate Organic Carbon and phytoplankton chlorophyll a were also determined for all stations. When subjected to multivariate statistics, Canonical Correspondence Analysis (CCA) clustered all stations into those located in the Ferguson's Gulf and those in the rest of the study area. Results for environmental variables show higher concentration of dissolved oxygen, conductivity, chlorophyll a, and Particulate Organic Carbon (POC) in areas located within the Ferguson's Gulf compared to areas located within the rest of the study area. Zooplankton community analysis using TWINSPAN also showed the inner Ferguson's Gulf as a distinct community separate from the rest of the lake. Zooplankton taxa were dominated by the Cyclopoid copepodites and their nauplii, with nauplii accounting for over 80% numerical abundance in most gulf stations. Calanoid copepod, Cladocera, Rotifera, and Protozoa were ubiquitous. A Monte Carlo permutation test (p < 0.05) showed that the distribution of the taxa was mainly affected in a decreasing order by environmental variables such as temperature, Secchi depth, conductivity , and Particulate Organic Carbon. High carbon to chlorophyll a ratio suggested that the source of particulate matter might be allochthonous, mainly from the submerged decaying vegetation that once occupied the dry Ferguson's Gulf and Allia Bay areas, before the recent flooding caused by the El Nino rains. Diversity results show the Ferguson's Gulf to be the least diverse community while stations influenced by the open lake waters but located in the Allia Bay/Sibiloi National Park the most diverse. The potential influence of temperature, Secchi depth, conductivity, and Particulate Organic Carbon on the zooplankton community in these two areas is discussed. |
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