EASTON — The Chesapeake Bay’s waters received one of the best scores of the last few decades, according to a report card released Tuesday, May 17, by the University of Maryland Center for Environmental Science.
Overall health of the Bay improved in 2015, scoring a C, or 53 percent, according to the report.
Scientists are crediting a number of factors to the improved score, including moderate weather, sewage treatment upgrades, use of winter cover crops by farmers and reductions in atmospheric nitrogen deposition.
No overall scores for regions of the Bay were lower than last year, according to the report.
But, out of all the regions, the Choptank River’s health improved the most, due to increases in underwater grasses and an improved benthic community — clams, oysters, mussels and worms.
The mid-stem of the Bay had the highest water clarity of all the regions, but also had the worst score for dissolved oxygen — mostly in its deep segments — which the Bay’s organisms need to survive.
Increased water clarity can lead to resurgences of aquatic grasses, which significantly improved in 2010 and are one of the most important habitats in the Bay region, providing a home for species like blue crabs and striped bass.
Baywide, though, water clarity was considered poor, but still an improvement from last year.
“Almost all Chesapeake Bay tributaries exhibited a gradient in water clarity, with murkier water in the mid to upper reaches and clearer waters in the lower reaches,” the report reads. “The Bay’s mainstem exhibited a similar pattern, with murkier water in the Upper Bay and clearer water in the Mid and
Lower Bay regions.”
Bill Dennison, vice president for science applications at the University of Maryland Center for Environmental Science, said improvements are expected after a drought year, because nutrients aren’t being washed into the Bay as much.
“However, in 2015 stream flow was below normal, but nowhere near the drought conditions in 1992 and 2002,” Dennison said. “Thus, the high score for 2015 indicates that we’re making progress reducing what’s coming off the land.”
Excess nutrients, like nitrogen and phosphorus, can runoff into the Bay’s waterways and fuel algae growth blooms, resulting in poor water quality and and can lead to reduced dissolved oxygen levels. Algae blooms can also block sunlight from getting to the Bay’s underwater grasses.
While nitrogen levels improved Bay-wide, the Choptank and Upper Eastern Shore rivers scored among the worst for total nitrogen. Tributaries across the Bay had higher concentrations of nitrogen in their upper reaches and lower concentrations in the lower regions, and the mainstem of the Bay exhibited a similar pattern.
“Higher concentrations of nitrogen in the mid to upper reaches of the tributaries can, in part, be attributed to runoff of excess nitrogen from fertilizers, power plants, and factories getting into creeks, streams, rivers, and groundwater that then feed into the Bay,” the report reads.
One score Bay-wide declined — total phosphorus. The mid-Bay and Choptank River scored the second and third highest respectively for phosphorus, though. Phosphorus concentration trends in the water were similar to nitrogen, according to the report.
Officials on Tuesday were pleased with the results, which have been trending up the past few years, and credit the improvements to the Bay region’s efforts to reduce pollution are working.
“We should take the opportunity to celebrate these results,” said Nick DiPasquale, director of the federal Chesapeake Bay Program.
“But we should also recognize that the long term success of our work to restore water quality and the health of this vitally important ecosystem will depend on stepping up and sustaining our efforts over the long-term to reduce nutrient and sediment pollution discharges to streams and rivers throughout the watershed,” he said.
People can see the report card at chesapeakebayreportcard.org.