Basis for the protection and management of tropical lakes

Management of lakes for the protection of water quality, aquatic life and other uses must be approached somewhat differently in the tropics from how it is approached at temperate latitudes. More than half of all tropical lakes are accounted for by natural river lakes or reservoirs. Therefore, degradation of water quality in rivers will have direct negative effects on the majority of lakes in the tropics. Also, regulation of rivers, which is one result of river impoundment, is a potential cause of damage to river lakes. Tropical lakes are more sensitive than temperate lakes to increases in nutrient supply and show higher proportionate changes in water quality and biotic communities in response to eutrophication. Tropical lakes are especially prone to loss of deep‐water oxygen, and in order to maintain ecological stasis therefore require more stringent regulation of organic and nutrient loading than temperate lakes. Nutrient containment must be more strongly oriented toward nitrogen, the most probable limiting nutrient in tropical lakes, than has been the case at temperate latitudes. However, phosphorus control is also important. Nitrogen management may be more feasible in the tropics because of high temperature, which is one of the critical conditions for efficient denitrification. Planktonic and benthic communities of the tropics bear a close resemblance, both in composition and diversity, to those of temperate latitudes; there is no parallel to the latitudinal gradient in biodiversity that is characteristic of terrestrial ecosystems. Foci of biodiversity, which require special attention, include the endemic species of ancient lakes and the diverse fish communities of very large rivers. The latter are an especially valuable untapped economic resource, but face severe impairment due to hydrological regulation and pollution of rivers. Effective management programs for tropical lakes will focus on interception of nutrients, protection of aquatic habitats from invasive species, and minimization of hydrological changes in rivers to which lakes are connected. In the absence of protective management, tropical lakes will decline greatly in their utility for water supply, production of commercially useful species, and recreation.