Scientists: Bay may contribute more to global warming
Methane concentration higher than expected
Methane buildup in the Chesapeake Bay alone, if released, is equal to current methane estimates for all the estuaries in the world combined, according to a study released by University of Maryland Center for Environmental Science.
The research report, “Methane concentrations increase in bottom waters during summertime anoxia in the highly eutrophic estuary, Chesapeake Bay, U.S.A.,” explores the role of methane emissions during dead zone and storm events and how the Chesapeake Bay could contribute more to global warming than previously believed.
“Methane influx is a consequence of eutrophication that hasn’t been focused on in the Chesapeake Bay,” said study author Laura Lapham, a professor at UMCES Chesapeake Biological Lab, in an interview.
Methane, a colorless, odorless, naturally occurring flammable gas, is normally under control in estuaries like the Chesapeake Bay. Methane is also a greenhouse gas that traps heat in the earth’s atmosphere, caus- ing global warming.
Eutrophication is the excessive amounts of nutrients, such as phosphorus and nitrogen often from runoff, that cause plant and animal life to die due to the lack of oxygen. Oxygen depletion is also know as anoxia. According to the study, the Chesapeake Bay is overwhelmed with nutrients that cause pollution leading to low oxygen concentrations and methane emissions.
Lapham and a team of researchers studied the water at the bottom of the Chesapeake Bay over the course of a summer in 2013, setting up instruments perched above the mud that would track any signs of methane being released into the water, according to a UMCES release.
During April, methane concentrations were low when bottom waters were fully oxygenated and increased as dissolved oxygen was depleted. Methane concentrations peaked in mid-July, which could be attributed to the disturbance of sediments. Concentrations decreased in early August and then returned to background levels when normal oxygen conditions returned in late September.
“The natural consumption process controls methane,” reported Lapham. “The majority is consumed before being released into the atmosphere.” However, she acknowledges there is the possibility that storms could come through and churn up the water, releasing the methane, warned Lapham.
To address the problem of methane buildup in the water and to minimize methane emissions into the atmosphere, Lapham suggests decreasing the amount of nutrients going into the bay.
Maryland, Pennsylvania and Virginia are already engaged in many efforts underway to restore the bay, to include the upgrading of wastewater treatment plants and the reducing of pollution runoff from stormwater and agriculture, shared Maryland Direc- tor of the Chesapeake Bay Commission Bevin Ann Buchheister in an interview.
“The bay restoration effort, and all the pollution reduction practices watershed states are implementing for wastewater, stormwater and agriculture, are aimed at eliminating those very dead zones that could contribute methane to the atmosphere, so we need to continue and accelerate our efforts,” said Buchheister. “With this new information, we can also view our restoration efforts as serving a dual purpose: restoration of the bay and decreasing our contribution to climate change.”