Marine Eutrophication Review

The results of three different approaches are used to investigate relationships between nitrogen availability and phytoplankton primary production and abundance in coastal ecosystems. The three approaches are controlled experiments in marine enclosures, history of changes in coastal ecosystems, and cross-system comparisons. Most systems can be expected to have increased primary production with increased nitrogen loadings or long-term average concentration. Nitrogen availability alone is not a very precise predictor of phytoplankton production or abundance. The magnitude of the change in phytoplankton production or abundance found for most systems is typically in the range of 1.4 to 3 times for a doubling in nitrogen loading or concentration. However, there are coastal ecosystems which have not followed the general relationships found. Until the characteristics which sets those systems apart from other systems can be identified, there is no guarantee that any individual system will have the typical response.