Lake eutrophication: Control of phytoplankton overgrowth and invasive aquatic weeds

Abstract

This brief review describes the major causes of lake cultural eutrophication and assesses different strategies applied to control or reduce the negative consequences of this eutrophication. Excessive nutrient inputs, particularly from agricultural lands through non-point source runoff, are among the main causes of cultural eutrophication on a global scale. Reducing nutrient inputs from agricultural lands through management of lake catchment areas, therefore, is an integral part of any effort to control lake eutrophication. Nutrient enrichment results in algal blooms and creates favourable condition for the invasion of a lake by alien aquatic weeds, making this invaluable freshwater resource unsuitable for many purposes, including drinking, agricultural and industrial water resources, fishing, transportation and recreational purposes. A major part of this review addresses attempts made to address the negative impacts of eutrophication by restoring water quality. Several research outputs discussing bottom-up and top-down control mechanisms were utilized for the present review. Much emphasis has been given in the literature regarding the use of biomanipulation as a promising and sustainable solution for controlling eutrophication. Biomanipulation tools used to control cyanobacteria and algal bloom have involved zooplanktivorous fish removal, piscivorous fish stocking, daphnia stocking, benthivorous fish removal, planktivorous fish stocking and mussel stocking. Further, some insect and fungal species have been used as biological control agents in an effort to control invasive aquatic weeds in tropical lakes. Although this review is limited in its analysis and explanation of the drawbacks associated with each described biomanipulation method, it can be deduced that biomanipulation generally exhibits considerable potential for controlling or reducing phytoplankton overgrowth and aquatic weed invasions, assuming it is also integrated with strategies to control external nutrient loadings to lakes.