Phytoplankton community relationship to environmental variables in three Kenyan Rift Valley saline-alkaline lakes

Abstract

Temporal changes in total alkalinity, ionic composition and nutrient concentrations were studied in the saline, alkaline endorheic Kenyan Rift Valley Lakes Bogoria, Nakuru and Elmentaita to understand the association of these variables with phytoplankton community structure. In total, 24 taxa were found, with L. Bogoria having the fewest species. Although the cyanobacterium Arthrospira fusiformis dominated the phytoplankton biomass, especially in L. Bogoria, other groups came into play especially during high water levels in L. Nakuru and L. Elmentaita. Cluster analysis based on species biomass resulted in four groups, characterised by 13 indicator taxa. Most of the variation in these groups appeared to be associated with hydrological stability and perhaps biological factors rather than water chemistry, which only explained 44% of the variance in taxa composition on the first four axes derived from redundancy analysis. Species numbers decreased with elevated conductivity and water temperature. Synechocystis sp. occurrence coincided with phosphorus, water temperature and conductivity increase, whereas the distributions of Arthrospira fusiformis and Arthrospira platensis were mainly influenced by both light attenuation and elevated nitrate concentrations. Increases in silica and ammonium and declines in conductivity, total phosphorus and water temperature enhanced diatom abundances. Not only do the results of the present study indicate the unexpectedly high variability of phytoplankton community composition and water chemistry in these three alkaline tropical lakes, but also the data assist our understanding of the factors influencing flamingo populations on these lakes, which are significant conservation reserves and tourist attractions.

Unique picoeukaryotic algal community under multiple environmental stress conditions in a shallow, alkaline pan

“…However, the maximum abundance of that PPP community was two orders of magnitude smaller than the values presented here ). Other saline lakes at various locations around the globe can similarly be favourable habitats for photoautotrophic picoplankton blooms (Fanjing et al 2009;Wu et al 2009;Krienitz et al 2012), although some lakes have been found to be dominated also by other taxa above the pico size range (García et al 1997;Harper et al 2003;Schagerl and Oduor 2008). In several East African soda lakes picoeukaryote abundances can exceed 3 million cells ml -1 (Krienitz et al 2012),…”

A detailed time series assessment of the diet of Lesser Flamingos: further explanation for their itinerant behaviour

“…This highly sought after food resource has been observed to undergo significant changes in its biomass over time. Ballot et al (2004) observed changing dominance between A. fusiformis (hereinafter referred to as, Arthrospira) and Anabaenopsis abijatae Kebede & Willén in some saline lakes, which have been attributed to their response to the changing environmental stress expressed as fluctuations in physical and chemical variables (Schagerl & Oduor, 2008). Since Lesser Flamingos are specialised consumers of Arthrospira, such changes in biomass and quality are bound to affect the population of these birds in these soda lakes and in some cases, may also contribute to the sporadic mass mortalities observed at times.…”

Algal communities of Kenyan soda lakes with a special focus on Arthrospira fusiformis

“…KrieniTz et al 2003;BalloT et al 2005;Schagerl & oDuor 2008;KrieniTz & KoTuT 2010;Kaggwa et al 2012), where temporal trends have often indicated periodic dominance and absence of certain taxa especially at extreme salinity. Apart from the predominant Arthrospira, also other cyanobacteria occur in these lakes.…”