Determining ecologically acceptable nutrient loads to natural wetlands for water quality improvement

Natural wetlands often function as nutrient sinks, reducing nutrient inputs into lakes and streams. P loading from anthropogenic sources has significantly affected many natural wetlands. This paper describes a method to determine an acceptable P load to natural wetlands based on ecological principles. This approach can be used to determine how much P can be assimilated without diminishing species diversity and, thereby, sets a limit for cultural eutrophication of natural wetlands. The basis for determining an acceptable load is management of risk to species diversity by determination of the maximum area of a wetland that can be put at risk while preserving biodiversity of the overall wetland system. Two cases are distinguished: 1) simple-stress, where growth of the affected area immediately increases risks for species loss, and 2) subsidy-stress, where growth of the affected area first benefits then diminishes net species diversity.