Dead zones, or areas of little to no dissolved oxygen, form when nutrient-fueled algae blooms die. As bacteria help these blooms decompose, they suck up oxygen from the surrounding waters. The resulting hypoxic or anoxic conditions can suffocate marine life.
The Chesapeake Bay Program tracks dissolved oxygen as an indicator of water quality and Bay health.
The latest NOAA-funded forecast from researchers at the University of Maryland Center for Environmental Science (UMCES) and the University of Michigan predicts an average summer hypoxic zone of 1.108 cubic miles, lower than last year’s mid-summer hypoxic zone of 1.45 cubic miles.
This predicted improvement should result from the lower than average nutrient loads that entered the Bay this spring. According to the U.S. Geological Survey (USGS), 36,600 metric tons of nutrients entered the estuary from the Potomac and Susquehanna rivers, which is 30 percent lower than average.
The Bay’s dead zones are measured at regular intervals each year by the Maryland Department of Natural Resources (DNR) and the Virginia Department of Environmental Quality. While the final dead zone measurement will not take place until October, DNR biologists measured better than average dissolved oxygen on its June monitoring cruise, confirming the dead zone forecast.
To track the health of the Chesapeake Bay, researchers across the watershed watch so-called “indicator species” for clues about water quality. Bay grasses—sensitive to pollution but quick to respond to water quality improvements—are one such indicator, and are monitored each year by the U.S. Fish and Wildlife Service (USFWS).
Bay grasses, also known as submerged aquatic vegetation or SAV, provide critical habitat and food for wildlife, add oxygen to the water, absorb nutrients, trap sediment and reduce erosion.
During the months of May, July and September, biologists like Chris Guy, who works with USFWS, visit randomly selected sample sites throughout the Bay. Occasionally accompanied by volunteers, their mission is to track the ebb and flow of underwater grass beds in order to gauge the health of the Bay.
Once a sampling site is reached, researchers use a refractometer to determine the salinity of the water. Different bay grass species prefer different salinity levels, and this measurement gives biologists a hint as to what kind of grasses they should expect to find.
Biologists measure water clarity by submerging a black and white Secchi disk until it is no longer visible, at which point it is pulled up and the waterline is measured. Clear water is important to the health of bay grasses. Because they need sunlight to survive, submerged aquatic vegetation is typically not found in water deeper than five feet.
Once the salinity and turbidity are measured, a rake is tossed into the water and allowed to sink to the bottom.
As the rake grips the bottom and the boat moves forward, the line attaching the rake to the boat becomes taught. The thrower hauls it back on board, records the grass species that are found and rates the abundance level on a scale of one to four. A one indicates an empty rake, while a four means that at least 70 percent of the rake is full of grass.
Hundreds of sampling trips allow scientists to amass a set of data that can be used to measure grass abundance across the Bay. Over the past 30 years, this number has fluctuated with changes in weather and water quality. In 2012, bay grasses experienced a 21 percent decline, from just over 63,000 acres in 2011 to just over 48,000 in 2012. The Chesapeake Bay Program and its partners hope to restore 185,000 acres of underwater grasses to the Bay, which would approach historic twentieth century averages and bring a dramatic improvement to the entire Bay ecosystem.
View more photos on the Chesapeake Bay Program Flickr page.
Photos by Steve Droter
Former Maryland State Senator Bernie Fowler saw his sneakers through 34 inches of water at the 26th annual Patuxent River Wade-In on June 9. This marks a one-inch drop from last year’s “sneaker index,” which is what Fowler has come to call the deepest point at which he can still see his shoes as he wades into the water.
Fowler holds the wade-in each year to bring attention to the polluted waters of the Patuxent River and the Chesapeake Bay. This year marked the fourth wade-in to be held at Jefferson Patterson Park and Museum, after decades on Broomes Island.
In the 1950s, Fowler could wade into the Patuxent up to his chest and still see fish, shellfish and underwater grasses. But as nutrient and sediment pollution are pushed into the river, algae blooms and suspended silt block sunlight from reaching the river bottom and degrade water clarity. The 1950s sneaker index of 63 inches now serves as the benchmark for a restored Patuxent River.
Fowler’s infamous white sneakers were retired before this year’s wade-in, but will be preserved for permanent display at the Calvert Marine Museum.
View more photos on the Chesapeake Bay Program Flickr page.
Baltimore Harbor scored a C- on its latest water quality report card, marking a modest improvement from the previous year’s failing grade. According to the Waterfront Partnership of Baltimore and Blue Water Baltimore, who released the Healthy Harbor Report Card earlier this month, the Harbor met water quality standards 40 percent of the time in 2012.
Image courtesy Affordable Memories Photography of Fredericksburg/Flickr
While the spring of 2012 brought an algae bloom, a fish kill and a sewage spill to the Harbor, the summer saw little rainfall and a drop in the amount of polluted runoff being pushed off of streets and into the urban waterway.
The nonprofits behind the release of the report card hope to make the Harbor swimmable and fishable by 2020, and have embarked on a number of environmental initiatives to achieve this goal. More than 50 floating wetlands continue to capture stormwater runoff, absorb excess nutrients and provide habitat to water-filtering invertebrates after being installed along the Harbor’s shoreline. And students from five Baltimore City public schools have formed Green Teams to boost local awareness about the region’s persistent trash problem.
Learn more about the Healthy Harbor Report Card.