Slight Improvements Seen in Bay Health During Summer 2006
“Typical” conditions still not enough for a balanced, healthy Bay ecosystem
November 2006 -- The Bay is doing slightly better than it was last year, according to data gathered this summer by scientists with the Bay program. Observations were generally in line with the “typical” conditions Bay scientists forecast in May for bay grasses, dissolved oxygen and harmful algal blooms.
However, conditions must move from “typical” to “vastly improved” for a balanced, healthy Bay ecosystem, according to Carlton Haywood, chair of the Bay Program's Monitoring and Analysis Subcommittee and director of program operations for the Interstate Commission on the Potomac River Basin.
Three key measures of Bay health showed varying improvements during the 2006 summer months compared to a year ago.
- Summer dissolved oxygen levels, an essential measure of water quality for nearly all Bay species, were somewhat better in 2006 than during the same period last year. However, the levels were still typical of the generally poor water quality that affects the Chesapeake every summer.
- Vital underwater bay grasses may be showing signs of improvement in some areas, but important beds in the lower Bay have not fully recovered from major losses in late summer 2005.
- Conditions were mixed for the extent and duration of harmful algal blooms that regularly hit Potomac River waters.
Spring 2006 weather conditions were considered extreme, with lower than average rainfall from mid-February to mid-May. The region was then deluged at the end of June with rainfall amounts nearing the 100-year-flood mark in some areas. Conditions were fairly average for the rest of the summer, until the remnants of Hurricane Ernesto washed into the area in August.
“Summer conditions are determined largely by the pollutant load washed into the Bay by rain in the preceding winter and spring,” according to Haywood. “The health of the Bay in the critical summer season will improve as we take action in the fall to reduce the level of pollutants in the watershed. Planting winter cover crops that stop pollutants from washing into local rivers with spring rains is just one of many practical actions we can take that will have a positive impact on the Chesapeake.”
Scientists and researchers from the University of Maryland, the Virginia Institute of Marine Science and the Maryland Department of Natural Resources worked with colleagues from federal and other state agencies to develop the forecast and monitor conditions throughout the summer.
The forecast, compared with actual observations, is highlighted below.
Dissolved Oxygen
Forecast: The average anoxic volume would be 1.08 km3, ranking in the middle range of the past 20 years.
Actual: The 2006 forecast was exceptionally accurate. On average, the amount of anoxia in the Bay's mainstem this summer was 0.93 km3, or 1.79 percent. This figure is a significant improvement from 2005, which was the fifth worst summer on record. In fact, 2006 ranks as the seventh best year for dissolved oxygen compared to the past 21 years.
Underwater Bay Grasses
Forecast : Slight increases in the northern Bay and lower Potomac River, along with a partial recovery of eelgrass in Tangier Sound.
Actual: The beds in the northern Bay may have increased more than expected, while growth in the Potomac River was mixed. In Tangier Sound, grasses may have experienced some recovery. Final bay grass survey results will be available in early 2007, enabling scientists to make a conclusive assessment of the forecast.
Harmful Algal Blooms
Forecast: A moderately high likelihood of a bloom in the tidal Potomac River that would begin in early summer and last one to two months.
Actual: A harmful algal bloom occurred in late summer as opposed to early summer. The bloom lasted 1.5 months and reached 26 miles from the onset, measured at Blossom Point on July 26. The remnants of Hurricane Ernesto ended its growth.