Water quality in US estuaries set to decline further as population rises

The US National Ocean Service (NOS) report shows that, since 1970, nutrient-related water quality problems have become worse in 48 of the 139 estuaries studied while in 14 estuaries conditions have improved. Alarmingly, scientists predict that conditions will become even worse in 86 estuaries by the year 2020 as population growth and development in the coastal zone increases. Conditions are predicted to improve in only eight estuaries. According to NOAA scientists, these results highlight the need for a strong national response to this pervasive problem (see related story).

The report, National Estuarine Eutrophication Assessment: Effects of Nutrient Enrichment in the Nation’s Estuaries, provides an overview of the scale, scope and characteristics of nutrient associated problems affecting US coastal water bodies.

To complete the study, NOAA compiled information over a seven year period about water quality parameters associated with nutrient enrichment and eutrophication for 138 estuaries and the Mississippi River Plume. Problem conditions range from excessive algal blooms to low levels of dissolved oxygen, losses of submerged aquatic vegetation and occurrences of nuisance and toxic algal blooms.

Of the systems studied, 44 have significant problem conditions, and 40 have moderate problems. According to the report, these problem conditions are not isolated. Although they occur in estuaries along all coasts, the Gulf of Mexico and mid Atlantic regions have the greatest percentage of estuaries with high-level problems.

These conditions have been shown by other studies to alter the uses of the estuaries, at times closing shell fishing beds, causing human health risks, destroying habitat for fisheries, and leading to loss of tourism.

The study, carried out by the NOS for the National Oceanic and Atmospheric Administration (NOAA), indicates that for the majority of estuaries with significant problems, human related nutrient inputs are an important influence on development of those problems. However, many of these estuaries are also naturally sensitive to nutrient inputs.

“These results can be used to more effectively focus management of this problem and, specifically, to develop a national response strategy,” says NOAA scientist Dr. Suzanne Bricker, lead author of the report. For example, the priority for estuaries in serious condition should be reduction of nutrients, Bricker says. For those in less serious condition, but which are located in areas where coastal population growth puts them at high risk, the priority should be on monitoring and prevention of future degradation.