State of the Coastal Environment: Eutrophic Conditions in Estuarine Waters

摘要

High expressions of eutrophic conditions are exhibited in 44 estuaries of the coterminous United States, representing approximately 40% of the national estuarine surface area. An additional 40 estuaries exhibit moderate conditions. When considered together, the estuaries with moderate to high eutrophic conditions represent approximately 65% of the nation's estuarine surface area. High conditions, determined by assessing the extent of primary and secondary symptoms of eutrophication, occur in estuaries along all coasts, but are most prevalent in estuaries along the Gulf of Mexico and Middle Atlantic coasts. A high level of human influence is associated with 36 of the 44 estuaries with high eutrophic conditions. While high levels of primary symptoms, such as elevated levels of chlorophyll a, are strong indicators of the onset of eutrophication, secondary symptoms such as depleted dissolved oxygen, indicate more serious or highly developed eutrophication. Moderate to high expressions of at least one of the secondary symptoms are exhibited in 82 estuaries, representing 67% of the estuarine surface area studied.