Abstract

Lake Victoria has experienced changes that include introduction of alien species, over exploitation of fish, eutrophication and climate change. This review is a scenario of nitrogen cycle acceleration resulting in retention above the total inflow and the potential effect of climate on the N cycle. Excess nitrogen is attributed to nitrogen fixation, algal proliferation and decomposition. The nitrogen transformation like ammonia conversion to nitrate is enhanced over horizontal distance at higher temperature during dry season. Nitrogen (N) concentration in the vertical profile is related to climate variability of water temperature, lake water movement and differences in nitrogen loads from the catchment. Despite all, the effect of eddy currents or heat transfer caused by solar radiation on nitrogen processes is unknown. However, annual cycle of vertical oxygen distribution caused by stratification seems to provide potential condition for nitrous oxide production throughout the lake as compared to nitrogen gas. Therefore, understanding the relationships between organisms’ diversity and community structure particularly of autotrophic and heterotrophic nitrogen bacteria, and their ecosystem functions in the entire freshwater lake is important for nitrogen budget. Due to scarcity of information, it is not possible to ascertain projection of climate influence on N dynamics in the Lake Victoria ecosystem. The ultimate suggestions on mitigation measures are to enforce policies that reduce both point and non-point sources of N into the lake and maintain riparian forests and wetlands.

Key words: Climate-effects, freshwater, Lake Victoria, nitrogen-ecotoxicology.