The impact of global warming on cichlids reproduction in the lake

As a result of the global warmingduring the past century, there’s a rise of 0.9 degreesCelsius in the upper 100 meters water level of the lake. This results in a sharp density gradient between the upper water layer and the deep water layer. Nutrient regeneration rate decreases and the vertical penetration of oxygen in the deeper layerreduced. LakeTanganyika is anoxic (no oxygen), for almost all its depth (from 100 meters and down), thus further reduction of the concentration of dissolved oxygen in deep water is critical to the existing biotic.

At a depth of 100 meters and lower, nutrients rise up through the vertical mixing that occurs mainly due to the southeastern trade winds, which weakened following the warming of the area. This Vertical mixing rising up these nutrients with it and is the main reason for primary production in the upper water level of the lake. As a result of nutrient depletion, the amount of zooplankton is significantly decreased. There has been a serious impact on the food chain at the upper water leveldue to starvation of  zooplanktivorous fish. Phytoplankton biomass which was measured in 2000 was lower by 70% compared to the biomass measured in 1975. Phytoplankton composition changed when cyanobacteria turn and become dominates the earth’s warming continues.

There are several implications for global warming- juvenile and zooplanktivorous fish suffer from starvation resulting in extensive mortality than in previous years. Also, due to rising water temperature, the reproductive period of cichlids that require a specific range of temperatures to breed narrows down. As a resultthese species abundancy shrinking which also affects negatively on the aquatic food chain.


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