Indicators of Coastal Water Quality
The flow of nutrients into coastal waters from land-based sources has seen a worldwide increase over the last decades. The resulting change in water quality has many potential impacts on coastal and marine ecosystems. Phosphorus and nitrogen contribute to enhanced algae growth, and subsequent decomposition reduces oxygen availability to benthic sea creatures like fish, shell fish, and crustaceans. Changes to nutrient loadings can also change the phytoplankton species composition and diversity. In extreme cases, eutrophication can lead to hypoxia—oxygen-depleted “dead zones”—and harmful algal blooms.
Measuring chlorophyll concentrations as an indicator of algae biomass may provide one tool to assess coastal water quality and its change over time. Here, we used chlorophyll-a concentrations derived from NASA's Sea-viewing Wide Field-of-view Sensor (SeaWiFS) to analyze trends over a ten year period (1998–2007). We attempted to identify near-coastal areas with improving, declining, and stable chlorophyll concentrations that can provide guidance for decision making in the context of environmental management.