Climate Change and Coastal Eutrophication

Author(s): Rabalais, N.

The world’s climate has changed and human activities will continue to contribute to the acceleration of greenhouse gases and temperature rise. The major drivers of these changes are increased temperature, altered hydrological cycles and shifts in wind patterns that might alter coastal currents. Increasing temperatures alone have the potential to strengthen pycnoclines in estuarine and coastal waters, but lower surface salinity (e.g., from increased freshwater runoff) would be more of a factor in stratifying the water column. The combination of increased nutrient loads (from human activities) and increased freshwater discharge (from GCC) will aggravate the already high loads of nutrients from the Mississippi River to the northern Gulf of Mexico, strengthen stratification (all other factors remaining the same), and worsen the hypoxia situation. Reduced precipitation, on the other hand, would lower the amount of nutrients and water reaching the coastal zone and, perhaps, lead to oligotrophication and reduced fisheries productivity, or perhaps alleviate hypoxia. The increase or decrease in flow (whichever occurs), flux of nutrients and water temperature are likely to have important, but as yet not clearly identifiable, influences on hypoxia. In anticipation of the negative effects of global change, nutrient loadings to coastal waters need to be reduced now, so that further water quality degradation is prevented.

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