by Catherine Krikstan
August 03, 2012
Nutrient and sediment levels at a number of Chesapeake Bay monitoring sites have improved since 1985, according to a report released by the U.S. Geological Survey (USGS). These improvements in long-term trends indicate pollution-reduction efforts are working.
By measuring nutrient and sediment trends and by tracking changes in water clarity, underwater grasses and other indicators of river and Bay health, the USGS and Chesapeake Bay Program partners can make a more accurate assessment of changes in our waters. This kind of on-the-water monitoring is an integral part of ensuring Bay states and the District of Columbia are meeting "pollution diet" goals.
Excess nutrients and sediment can harm fish, shellfish and underwater grasses. Nitrogen and phosphorous fuel the growth of algae blooms that later rob water of the oxygen that aquatic species need to survive; sediment clouds the water, blocking the sunlight that plants need to grow. But a number of practices, from upgrading wastewater treatment plants to reducing agricultural, urban and suburban runoff, can stop or slow nutrients and sediment from entering the Bay.
According to the USGS report, one-third of monitoring sites have shown improvement in sediment concentrations since 1985. Within the same time period, two-thirds of these sites have shown improvement in nitrogen concentrations and almost all have shown improvement in phosphorous concentrations. However, in the past decade, the majority of sites surveyed showed no significant change in nitrogen or phosphorous levels, and only a handful showed improvement in sediment trends.
This doesn't mean that pollution-reduction efforts have been in vain. Long-term trends show us that pollution-reduction efforts do have an impact; findings from the last 10 years illustrate the lag time that can exist between restoration efforts and firm evidence of restoration success.
While upgrades to wastewater treatment plants, for instance, can yield relatively quick results, the effects of consistent reduced fertilizer on farms or suburban lawns may not be visible for years.
"While we see long-term improvements in many areas of the Bay watershed, there is a lag time between implementing water-quality practices and seeing the full benefit in rivers," said USGS scientist Scott Phillips. "Which is one reason why scientists see less improvement over the past 10 years."
"Long-term trends indicate that pollution-reduction efforts are improvement water-quality conditions in many areas of the watershed," Phillips said. "However, nutrients, sediment and contaminants will need to be further reduced to achieve a healthier Bay."
Learn more about Monitoring the Chesapeake Bay Watershed.