EASTON — The Chesapeake Bay’s underwater grasses have seen another year of growth, according to a survey released last month, by the Chesapeake Bay Program.
Brooke Landry, a biologist in the Resource Assessment Service with the Department of Natural Resources, said the total Bay underwater grass coverage reached 76,000 acres in the summer of 2014, a 27 percent increase from 2013. Despite the increase, that is only 41 percent of the 185,000-acre long-term restoration goal.
Underwater grasses provide habitat for marine life, like crabs and young fish, and offer food to small invertebrates and migratory waterfowl. The grasses also absorb excess nutrients in the water, trap suspended sediment and slow wave action and shoreline erosion.
“I feel pretty confident in saying that based on my own field observations and purely anecdotal accounts from other Maryland citizens, the numbers will be up again this year (2015),” Landry said.
The Chesapeake Bay’s submerged aquatic vegetation, or underwater grasses, are analyzed each year by the Virginia Institute of Marine Sciences. The Chesapeake Bay Program and others then use that data as an indicator of Bay health.
The survey found that the 27 percent increase in 2014 from 2013 levels was largely due to the expansion of widgeon grass in the mid-Bay.
Widgeon grasses have a broad salinity tolerance, Landry said, which is why they’re thriving in the both the less salty and more salty portions of the Bay. However, widgeon grasses have a tendency to “explode onto the scene where you might not have seen it for years or even decades before,” but “it has also been known to disappear unexpectedly,” she said.
The Susquehanna Flats in the upper Bay continues to have the largest grass bed, according to the survey.
The Susquehanna Flats’ grass beds took a big hit after hurricanes Lee and Irene in 2011, said Bob Orth, a professor of marine sciences and coordinator of the submerged aquatic vegetation survey at the Virginia Institute of Marine Sciences. Those grass beds, however, still haven’t reached their levels seen prior to hurricanes Lee and Irene, Orth said.
“But, the fact that they persisted and we continue to see an increase is pretty impressive,” he said, later adding that the Susquehanna Flats is one of the only two grass beds that can be seen from satellite.
In 2014, eelgrass in the lower Bay continued its recovery, but 2015 isn’t turning out as well for the lower Bay’s eelgrass, Orth said. Eelgrass is a species that requires cooler temperatures, Orth said, pointing to the warming of the Bay and hot summers as factors that could be causing the decline this year.
Orth said that, while working on the 2015 survey this year, they’re seeing underwater grasses in areas of the Bay where it historically hasn’t been mapped before — mostly in the middle part of the Bay from the “boom or bust” species of widgeon grasses.
Widgeon grass has become the only underwater grass species in the mid-Bay, where back in the 1960s there were probably four or five species, Orth said. These types of monoculture fluctuations are happening all over the world with widgeon grass, he said, naming North Carolina specifically, which is seeing the same type of widgeon grass expansion.
But diversity of grasses is important, Landry said.
She said that when water quality shifts, different species handle it differently. So in the the mid-Bay, where there is only widgeon grass, if it would happen to disappear for any given water quality reason, it could leave the mid-Bay barren of underwater grasses, Landry said.
If there are multiple species in the area, and one dies off, there’s a better chance that the entire bed will survive because the other species might do better under the water quality conditions. A diverse grass bed also is better for habitat, as “different critters use different grass beds” for varying reasons.
Landry stressed the importance of continuing Bay cleanup and improving water quality, in regard to keeping the Bay’s grasses healthy and expanding.
Landry said there’s a good chance that the goal of 185,000 acres of submerged aquatic vegetation in the Bay can be reached, “if we continue efforts to cut pollution that runs into the Bay.”
“Underwater grasses need light to grow, just like any other plant, so we have to make sure the water gets cleaner and clearer so that when those underwater grass seeds float into your stream or river and settle, they have the conditions necessary to sprout, grow and reproduce,” Landry said.