Assessing Eutrophication Potential of a Freshwater Lake by Relating Its Bioproductivity and Biodiversity: A Case Study of Lake Wilson on Central Oahu, Hawaii

Algal bloom in a freshwater lake is a rapid increase of aquatic plants, which disrupts the ecological balance and its potential for beneficial uses. This problem has been managed by relating the trophic levels of a lake with nutrient loading. This traditional management approach is less than satisfactory as it neglects considering the intricate relationship between nutrient loading and the algal community. As a result, it often fails to detect an imminent algal bloom and fails to formulate and implement timely remedial measures. The advancement of modern molecular biosciences has provided an opportunity to improve this traditional approach. In this study, field and laboratory experiments on lake bioproductivity and biodiversity were conducted in Lake Wilson on central Oahu, Hawaii. Bioproductivity or algal productivity was evaluated in terms of the rate of chlorophyll growth in the lake water, and the biodiversity or genetic biodiversity was evaluated by using the method of denaturing gradient gel electrophoresis of the algae species and the Shannon index. Research results indicated that eukaryote communities in Lake Wilson were more diverse under the mesotrophic state of algal productivity than those under the oligotrophic and eutrophic states. Therefore, the reduction of the biodiversity of a mesotrophic lake can be used in water quality management as a warning sign of an imminent algal bloom