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

Abstract

Seasonal variations of zooplankton communities and their interactions with phytoplankton and environmental parameters were studied over a twelve-month period in Lake Guiers (Senegal, West Africa). Zooplankton was most abundant during the warm and rainy season corresponding to the flood event (July to October) with peaks for rotifers and cyclopoid copepods in July-August and September-October, respectively. Filamentous cyanobacteria were the dominant phytoplankton during the warm season (August to November), while diatoms were dominant during the cool season (December to April). Temperature increase and river flooding both played an important role in these successions, favoring intense development of cyanobacteria and cyclopoid copepods. Trophic interactions also seem to be an important factor in structuring of the plankton community. Overall, the plankton composition displayed a trend toward a eutrophication state. Our study confirms the existence of seasonality in zooplankton communities and the importance of using biological indicators such as phyto-and zooplankton to monitor water quality, in particular in tropical freshwater ecosystems. IntroductionIn freshwater ecosystems, zooplankton abundance and diversity vary along with limnological conditions and trophic status (CHAPMAN et al., 1985;PINTO-COELHO et al., 2005). Among other various factors, zooplankton development can be limited by environmental conditions and the quantity, quality and availability of food (GULATI et al., 1992). Nutrients may also be a determining factor behind changes in abundance, composition and dynamics of phytoplankton and zooplankton communities (CASÉ et al., 2008;MARISTELA et al., * Corresponding author 406 S. KÂ et al.

Benthic‐pelagic coupling drives non‐seasonal zooplankton blooms and restructures energy flows in shallow tropical lakes

“…Comparative investigations of temperate and tropical population dynamics have demonstrated a significant increase of intra-annual variation in primary production rates with latitude (Melack 1979), but did not reveal systematic differences in annual variation of phytoplankton biomass (Kalff and Watson 1986). Consequently, the seasonality and the drivers of observed temporal fluctuations in the tropics became a focal point of research (Melack 1988;Masundire 1994;Ka et al 2011).…”