Dis­solved oxy­gen lev­els low in Ch­e­sa­peake Bay


Spe­cial from the Star Democrat

— A pro­longed heat wave could be be­hind low dis­solved oxy­gen lev­els in the Ch­e­sa­peake Bay in late July, ac­cord­ing to the Mary­land Depart­ment of Nat­u­ral Re­sources.

Each year be­tween June and Septem­ber, DNR com­putes data col­lected on the Bay’s dis­solved oxy­gen.

Oys­ters, crabs, striped bass and other crea­tures in the Bay need dis­solved oxy­gen in the water to sur­vive. Lit­tle to no oxy­gen in the water is called hy­poxia, of­ten re­ferred to as “dead zones.”

Hy­poxic ar­eas are caused by ex­cess nu­tri­ent pol­lu­tion, pri­mar­ily from hu­man ac­tiv­ity like agri­cul­ture and waste­water. The nu­tri­ent pol­lu­tion feeds al­gae blooms, and when the al­gae dies it set­tles to the bot­tom and ab­sorbs the oxy­gen in the water, said Bruce Michael, di­rec­tor of re­source as­sess­ment ser­vice at DNR, in a July in­ter­view.

The sum­mer started off pos­i­tive. Late June dis­solved oxy­gen lev­els were the sec­ond best in the Ch­e­sa­peake Bay since since 1985. But by late July, dis­solved oxy­gen lev­els were the sev­enth worst since 1985, ac­cord­ing


to DNR. How­ever, of­fi­cials in July did ex­pect the dead zone to get larger as the sum­mer con­tin­ued.

Ac­cord­ing to DNR’s data on dis­solved oxy­gen con­di­tions in Mary­land’s por­tion of the main­stem of the Bay, the hy­poxic zone in late June was .42 cu­bic miles.

In the late July pe­riod, the hy­poxic zone was ap­prox­i­mately 1.65 cu­bic miles, which is greater than the late July 1985-2015 av­er­age of 1.29 cu­bic miles, ac­cord­ing to DNR. Hy­poxia ex­tended south of the Patux­ent and Po­tomac rivers, DNR stated.

“A pro­longed heat wave likely ex­ac­er­bated low oxy­gen con­di­tions, as warmer waters hold and mix less oxy­gen,” DNR stated. “A lack of sig­nif­i­cant winds also pre­vented sur­face oxy­gen from mix­ing to bot­tom waters.”

In the be­gin­ning of June, sci­en­tists from the Univer­sity of Mary­land Cen­ter for En­vi­ron­men­tal Sci­ence, National Oceanic and At­mo­spheric Ad­min­is­tra­tion, U.S. Ge­o­log­i­cal Sur­vey and the Univer­sity of Michi­gan re­leased pre­dic­tions for this sum­mer’s Bay dead zone. They es­ti­mated that the dead zone will be ei­ther av­er­age or slightly smaller com­pared to pre­vi­ous sum­mers.

Newspapers in English

Newspapers from USA

© PressReader. All rights reserved.