The Chickahominy Report

The east­ern oys­ter formed mas­sive reefs that used to fil­ter the waters of the Chesa­peake Bay. (Vir­ginia Depart­ment of Envi­ron­men­tal Quality)

MECHANICSVILLE, Va. — In a dire assess­ment of the state of the Earth­’s shell­fish reefs, The Nature Con­ser­van­cy announced last week that oys­ter reefs such as those that were once com­mon in the Chesa­peake Bay are the most threat­ened marine habi­tats in the world.

The report, Shell­fish Reefs at Risk, was unveiled at the Inter­na­tion­al Marine Con­ser­va­tion Con­gress in Wash­ing­ton, D.C., on Thurs­day. The report found that that 85 per­cent of the world’s oys­ter reefs have been lost, and in some regions the loss of oys­ter reef habi­tat approach­es 99 percent.

The destruc­tion of the east­ern oys­ter (Cras­sostrea vir­gini­ca) pop­u­la­tion in the Bay has been noth­ing short of cat­a­stroph­ic. In an often cit­ed study, Roger Newell in 1988 esti­mat­ed that oys­ter stocks in the Bay declined from 190 mil­lion kilo­grams (400 mil­lion pounds) when intense har­vest­ing began in the late 1800s to 1.9 mil­lion kilo­grams (4 mil­lion pounds) in the 1980s. Oys­ter stocks have decline fur­ther since.

The pri­ma­ry cause for these loss­es include over­har­vest­ing, sed­i­men­ta­tion, pol­lu­tion, and the rel­a­tive­ly recent arrival of two dis­eases — Der­mo and MSX — that dev­as­tat­ed the remain­ing Chesa­peake Bay oys­ter population.

The destruc­tion of oys­ter reefs, as well as those formed by oth­er bivalves, such as clams and mus­sels, have had cat­a­stroph­ic con­se­quences in terms of degra­da­tion and loss of ecosys­tem ser­vices that these reef sys­tems pro­vide. Oys­ters, as fil­ter feed­ers, can remove a con­sid­er­able amount of sed­i­ment and nutri­ents from the water col­umn. Pri­or to 1870, the oys­ters could fil­ter the entire vol­ume of the Bay in 3 to 6 days. It takes the remain­ing oys­ters near­ly a year to do the same.

The increas­ing con­cen­tra­tions of nutri­ents fuel the growth of phy­to­plank­ton, and that, plus the increased sed­i­men­ta­tion from runoff into the Bay, reduces clar­i­ty of the water, which in turn reduces the light avail­able for the growth of sea grass­es. Sea grass beds are anoth­er habi­tat that plays vital roles in many impor­tant Bay organ­isms. The increased phy­to­plank­ton can also con­sume all the avail­able oxy­gen in the water col­umn, which cre­ates dead zones — places where ani­mals, such as fish and shell­fish, can­not survive.

Oys­ter reefs form hard sub­strates nec­es­sary for the set­tling and estab­lish­ment of young oys­ters, but oth­er organ­isms as well, includ­ing mus­sels and bar­na­cles. The struc­ture and poten­tial food avail­abil­i­ty on an oys­ter reef attracts eco­nom­i­cal­ly impor­tant species, such as blue crab, croak­er, sea trout and striped bass.

Despite recog­ni­tion of the impor­tance of a healthy Chesa­peake to the cul­ture, econ­o­my, and envi­ron­ment of the Mid-Atlantic region, poli­cies to turn con­di­tions around have gen­er­al­ly been inef­fec­tive or inad­e­quate. Nev­er­the­less, The Nature Con­ser­van­cy report does men­tion some rea­sons for hope. Recent research has shown it is pos­si­ble to restore some of the Bay’s oys­ter reefs. Giv­en prop­er pro­tec­tions, the restored oys­ters can devel­op resis­tance to the dis­eases that near­ly wiped out what remained of the Chesa­peake’s over­stressed oys­ters the past four decades. Like­wise, respon­si­ble aqua­cul­ture offers eco­nom­ic ben­e­fits while simul­ta­ne­ous­ly eas­ing har­vest pres­sure from wild oys­ter pop­u­la­tions and nat­ur­al reefs.

The Chesa­peake may nev­er return to the con­di­tion that John Smith wit­nessed in his 17th cen­tu­ry explo­rations. Nev­er­the­less — while much of the respon­si­bil­i­ty to save the Bay rests on those who live and work through­out its water­shed — restora­tion of oys­ter reefs will fix many of the prob­lems we have created.

— David M. Lawrence