Ch­e­sa­peake Bay grasses are re­bound­ing

Dorchester Star - - REGIONAL -

CAMBRIDGE — A key in­di­ca­tor of the health of the Ch­e­sa­peake Bay is prompt­ing op­ti­mism from area re­searchers.

Since Septem­ber 2017, un­der­wa­ter grasses be­gan ap­pear­ing near the Univer­sity of Mary­land Cen­ter for En­vi­ron­men­tal Science (UMCES) Ch­e­sa­peake Bi­o­log­i­cal Lab­o­ra­tory in south­ern Mar yland.

Their come­back af­ter 45 years sig­nals a ma­jor pos­i­tive shift in the health of the Ch­e­sa­peake Bay, ac­cord­ing to a state­ment from UMCES.

“The Ch­e­sa­peake Bay has turned the cor­ner,” Peter Good­win, president of UMCES, said. “In fact, it’s one of the large ecosys­tems in the world that has prob­a­bly made the most progress.”

Since 1925, UMCES’s Ch­e­sa­peake Bi­o­log­i­cal Lab­o­ra­tory has oc­cu­pied the penin­sula in Solomons, where the Patux­ent River flows into the Ch­e­sa­peake Bay. The grasses haven’t been seen there since 1972.

“We’re very glad to re­port the largest resurgence of (Bay) aquatic grasses, due to man­age­ment ac­tions, ever recorded,” Bill Den­ni­son said. He is vice president for science ap­pli­ca­tions at UMCES.

Ac­cord­ing to a new study co-au­thored by Den­ni­son, the resurgence of grasses here — and sim­i­lar re­cent come­backs seen through­out the es­tu­ary in re­cent years — are the di­rect re­sult of decades of ef­forts to re­duce nu­tri­ent pol­lu­tion in the Ch­e­sa­peake Bay.

An anal­y­sis of more than 30 years of data shows that sus­tained man­age­ment ac­tions over the past two decades have reduced nu­tri­ent pol­lu­tion in the Ch­e­sa­peake by 23 per­cent since 1984 and have led to a resurgence of eco­log­i­cally and eco­nom­i­cally im­por­tant aquatic grasses.

Un­der­wa­ter grasses, also known as sub­merged aquatic veg­e­ta­tion (SAV), have re­gained 17,000 hectares to achieve the high­est cover in al­most half a cen­tury. A hectare equals 100 acres.

“What emerged from that anal­y­sis is that this nu­tri­ent diet is start­ing to pay real div­i­dends in the resurgence of grasses around the Bay,” Den­ni­son said. “We’re been call­ing these grasses our coastal ca­naries, the things that are most sen­si­tive to wa­ter qual­ity degra­da­tion, and the things we have to watch as long-term in­di­ca­tors of these wa­ter qual­ity sit­u­a­tions.”

Aquatic grasses are known as a sen­tinel species, an in­di­ca­tor of broader eco­log­i­cal func­tion or an early warn­ing of eco­log­i­cal im­pair­ment.

They are im­por­tant eco­log­i­cally, pro­vid­ing habi­tat for baby crabs and other crea­tures while pro­tect­ing shore­lines and sta­bi­liz­ing sed­i­ments so that ero­sion is min­i­mized. They are also im­por­tant eco­nom­i­cally since they are home for com­mer­cial species such as blue crab, sil­ver perch, and striped bass.

Since 1950, the hu­man pop­u­la­tion around the Ch­e­sa­peake Bay has dou­bled, lead­ing to changes in land use and adding to the sub­stan­tial nu­tri­ent and sed­i­ment runoff from both ur­ban and agri­cul­tural lands.

In­creas­ing nu­tri­ent in­puts fu­eled al­gal growth in the wa­ter that pre­vented light from reach­ing the Bay grasses, which grow along the bot­tom. These con­di­tions also fa­vored the growth of al­gae that grow on the leaves of the bay grasses them­selves, fur­ther shad­ing them from light. Tens of thou­sands of hectares of SAV were lost, the largest de­cline doc­u­mented in more than 400 years.

Re­searchers from 10 in­sti­tu­tions across the coun­try an­a­lyzed 30 years of data to pre­dict the im­pacts of peo­ple liv­ing near the Bay on sub­merged aquatic veg­e­ta­tion, an eco­log­i­cally and eco­nom­i­cally vi­able habi­tat.

The study used aerial sur­veys from 1984 to 2015, mon­i­tor­ing data, his­tor­i­cal in­for­ma­tion on land use and fer­til­izer ap­pli­ca­tion and water­shed model es­ti­mates for the loads of nu­tri­ents and sed­i­ments from land runoff and point sources such as waste­water treat­ment plants.

The study con­firmed that nu­tri­ents play a dom­i­nant role in re­duc­ing SAV cover.

Long-term nu­tri­ent trends show that wa­ter col­umn ni­tro­gen con­cen­tra­tions have de­clined on av­er­age by 23 per­cent, and phos­pho­rus con­cen­tra­tions by eight per­cent since 1984, the big­gest re­duc­tions oc­cur­ring in the mid-1990s.

De­clin­ing nu­tri­ent lev­els co­in­cided with a 316 per­cent, or four­fold, in­crease in SAV cover dur­ing the same pe­riod, from 7,878 hectares in 1984 to 24,874 hectares in 2015, based on aerial sur­veys.

“Con­cern for the over­all health and econ­omy of the Bay led to un­par­al­leled co­op­er­a­tion among fed­eral, state, lo­cal and sci­en­tific agen­cies whose joint ef­forts iden­ti­fied nu­tri­ent pol­lu­tion and sub­se­quent loss of SAV as the two most crit­i­cal is­sues fac­ing Ch­e­sa­peake Bay,” ac­cord­ing to a UMCES state­ment.

These agen­cies in­sti­tuted mea­sures to re­duce nu­tri­ent in­puts as well as longterm mon­i­tor­ing pro­grams to gauge their ef­fec­tive­ness, es­tab­lished the Ch­e­sa­peake Bay as one of the few places on Earth where com­pre­hen­sive long-term data ex­ist to link im­pacts and eco­log­i­cal restora­tion at broad scales, ac­cord­ing to UMCES.

“This come­back of un­der­wa­ter grasses reaf­firms that gov­ern­ment and stake­hold­ers can come to­gether to set goals and im­ple­ment man­age­ment ac­tions to make an im­pact on a large and com­plex coastal ecosys­tem,” Good­win said. “These are sen­si­tive in­di­ca­tors of the health of Ch­e­sa­peake Bay, and it is im­por­tant that these suc­cess­ful man­age­ment strate­gies are con­tin­ued.”

The study, “Long-term nu­tri­ent re­duc­tions lead to the un­pre­de­cented re­cov­ery of a tem­per­ate coastal re­gion” was pub­lished in the March 5 Pro­ceed­ings of the Na­tional Academy of Sciences by re­searchers from the Bigelow Lab­o­ra­tory for En­vi­ron­men­tal Science, Vir­ginia In­sti­tute of Ma­rine Science, Univer­sity of Mary­land Cen­ter for En­vi­ron­men­tal Science, En­vi­ron­men­tal Pro­tec­tion Agency Ch­e­sa­peake Bay Pro­gram, U.S. Ge­o­log­i­cal Sur­vey, Na­tional So­cioEn­vi­ron­men­tal Syn­the­sis Cen­ter, St. Mary’s College of Mary­land, Smith­so­nian En­vi­ron­men­tal Re­search Cen­ter, Mary­land Depart­ment of Nat­u­ral Re­sources, and Texas A&M Univer­sity Cor­pus Christi.

“UMCES leads the way to­ward bet­ter man­age­ment of Mary­land’s nat­u­ral re­sources and the pro­tec­tion and restora­tion of the Ch­e­sa­peake Bay,” ac­cord­ing to www.umces.edu. “From a net­work of lab­o­ra­to­ries lo­cated across the state, UMCES sci­en­tists pro­vide sound ad­vice to help state and na­tional lead­ers man­age the en­vi­ron­ment, and pre­pare fu­ture sci­en­tists to meet the global chal­lenges of the 21st cen­tury.”

PHOTO COUR­TESY MD DNR

Sub­merged aquatic grasses are mak­ing a come­back in the Ch­e­sa­peake Bay, ac­cord­ing to re­searchers at the Univer­sity of Mary­land Cen­ter for En­vi­ron­men­tal Science.

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