Cultural Oligotrophication: Causes and Consequences for Fisheries Resources

Research on the impacts and processes of eutrophication has dominated limnological research for several decades, and it is only recently that implications of nutrient removal and declining ecosystem production (oligotrophication) on fisheries and food chains have been reported. To many persons, oligotrophication is synonymous with “clean”water and aesthetic improvements, but to others, it often implies an unproductive and declining fisheries resource. In this article we use a phosphorus (P) mass‐balance approach to provide a historic perspective for the ongoing oligotrophication of highland terrestrial and aquatic ecosystems and the concurrent eutrophication of lowland, coastal ecosystems. Because mined sources of P for fertilizer production are declining and costs are likely to increase substantially within the next century, we opine that it is time to reconsider the ways we manage our nutrient resources. We should recommence all means of recycling P, and consider ways to reintroduce recycled nutrients in a balanced N:P ratio to some aquatic ecosystems, in a carefully controlled and ecologically sensitive way to restore sufficient fisheries production levels. If we continue to mismanage P sources and ignore the importance of nutrient balances for the maintenance of productive fisheries, then choices soon will have to be made between having aesthetically clear freshwaters but unproductive fisheries, or productive fisheries in “greener” lakes and streams.