Rivers in Crisis
Talbot County Creekwatchers, a volunteer organization of over 60 members, has monitored the tributaries of Talbot County for water quality since 1999, assessing the Upper Choptank, Tred Avon, Miles, and Wye Rivers, and Broad, Harris, Island, and La Trappe Creeks. The United States Geological Survey (USGS) has been testing water quality on the Choptank River near Greensboro since 1965, and the EPA Chesapeake Bay Program and MD DNR have measured water quality near the Choptank River Bridge since 1984. Dr. Thomas Fisher, University of Maryland environmental biologist working at Horn Point Laboratory, has analyzed and published summaries of these data. The results of these important efforts reveal a dramatic, frightening, and steady decline in water quality:
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Water Clarity: Very Poor and Continues to Decline
Turbidity testing measures the ability of light to pass through water. Excess turbidity, or poor water clarity, indicates that light cannot penetrate deeply enough below the surface to support growth of underwater grasses. Light should be able to penetrate at least six feet in a healthy estuary. Over 90% of recent measurements show poor water clarity.
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Nitrogen Pollution: Over Four Times Acceptable Levels
Excess nitrogen promotes excessive algae growth, which turns water cloudy and dark. Algae decomposes when it dies, sucking oxygen out of the water and creating dead zones. Certain forms of algae are toxic to fish and humans. The amount of nitrogen flowing into the Choptank was twice as high in 2005 as it was in 1985.
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Phosphorus Pollution: Over Two Times Acceptable Levels
Phosphorus binds to sediment and leads to excess nutrient enrichment of our rivers. As with nitrogen, this causes unhealthy algae growth, poor water clarity, and oxygen-dead zones, a process called eutrophication.
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Oxygen Levels: Inadequate Oxygen Levels Common
Dissolved oxygen is essential to all aquatic life. As a result of the above-described problems, over the past decade there has been a consistent decline in oxygen content in our tributaries. We are nearing a crisis where the rivers we cherish may no longer support aquatic life. In 1985 the Choptank supported 3,561 acres of underwater grasses - key habitat for crabs, small fish, and worms. In 2006 the river had just 1,092 acres, about a 70% loss.
Resources:
Following are three graphs and a published paper prepared by Dr. Fisher. The nitrate2008 and totalP2008 graphic show data on water chemistry at the USGS monitoring station near Greensboro MD. Both graphics show consistent increases in total p and nitrate (the dominant form of total N in non-tidal streams) over the last few decades. These graphs both indicate declining water quality, as N (in the form of nitrate) and P are both major causes of algal blooms downstream. The third graphic (chla_DO_vs_year2008) is EPA Chesapeake Bay Program data for station ET5.2 at the Choptank River bridge (Rt. 50). This graphic shows consistent increases in annual average values of chlorophyll a (the universal algal pigment indicative of algal biomass) and consistent decreases in dissolved oxygen in summer bottom waters (June-August) over the last few decades. These are the classic symptoms of eutrophication of aquatic systems. Projections of these trends into the next few years predict increasing algal blooms and crab, oyster, and fish kills due to lack of oxygen in bottom waters at this station.
