A review of phytoplankton dynamics in tropical African lakes

Abstract

This paper provides a synthesis of current knowledge on phytoplankton production, seasonality, and stratification in tropical African lakes and considers the effects of nutrient enrichment and the potential impacts of climate warming on phytoplankton production and composition. Tropical African lakes are especially sensitive to climate warming as they experience wide fluctuations in the thermocline over a narrow range of high water temperatures. Recent climate warming has reduced phytoplankton biomass and production in the lakes. A decline in the production of palatable chlorophytes and an increase in cyanobacteria has led to reduced zooplankton production and a consequent decline in fish stocks, all of which can be associated with the elevated water temperatures. This indicates that even moderate climate warming may destabilise phytoplankton dynamics in tropical African lakes, thereby reducing water quality and food resources for planktivorous fish, with consequent negative impacts on human livelihoods.

Zooplankton Communities in the Shallow Lake Guiers (Senegal, West Africa)

“…In the African tropical zone, this is supported by increasing evidence of algal blooms, regularly reported in various freshwater ecosystems (PAGANO and SAINT-JEAN, 1988;OCHUMBA and KIBAARA, 1989;COGELS et al, 1993;NDEBELE-MURISA et al, 2010). In Senegal, recent studies in the lower Senegal River area confirm that eutrophication of the main freshwater ecosystems are causing changes in the composition of plankton communities (e.g., BOUVY et al, 2006;KÂ et al, 2006;CHAMPALBERT et al, 2007).…”

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

“…Conversely in the tropics, the key driving force appears to be the dry and wet seasons, which influence the chemical dynamics of the water column and ultimately their biota (SonDergaarD et al 1990;nDeBele-muriSa et al 2010). Schagerl & oDuor (2008) found out that the variation in phytoplankton groups was associated with hydrological stability rather than water chemistry, which only explained 44% of the variance in taxa composition.…”

Responses to a warming trend and “El Niño” events in a tropical lake in western Mexico

“…In general, global warming is causing more superficial thermoclines, longer and more stable stratification periods and reduced vertical mixing which leads to more intense deep-water oxygen depletion, higher nutrient limitation and changes in phytoplankton succession (Shimoda et al 2011;Winder et al 2009). These changes can favor smaller, less palatable phytoplankton species, ultimately lowering fish populations and therefore affecting local economies (Catalan et al 2013;Ndebele Murisa et al 2010). During ''El Niño'' years (warm ENSO phase) all these changes can be further aggravated (Katz et al 2011;Shimoda et al 2011).…”