Deep dive shows damaged Chesapeake Bay can heal
By TAMARA DIETRICH
Mar. 31, 2018
CHESAPEAKE, Va. (AP) — For the last few years, experts have touted annual progress in restoring underwater grasses to the Chesapeake Bay, and credited that progress to ongoing efforts to curb nutrients in the vast watershed.
Now, environmental scientists say they've documented the most prolonged and robust recovery of such submerged meadows in the world. And they say it's not just a victory for the Chesapeake, but a road map for other damaged estuaries.
Their analysis of 30 years of data shows that sustained anti-pollution efforts have reduced nitrogen levels in the bay by 23 percent and phosphorus by 8 percent, and spurred the biggest resurgence in underwater grasses along thousands of miles of coastline in nearly half a century.
"We like to say if we can do it in the Chesapeake Bay, we can do it anywhere," said Jonathan Lefcheck of the Bigelow Laboratory for Ocean Sciences in East Boothbay, Maine.
Lefcheck is formerly with the Virginia Institute of Marine Science in Gloucester Point and lead author on a paper about the study that appeared recently in the "Proceedings of the National Academy of Sciences."
The research effort brought together more than a dozen experts in various fields from several institutions so they could synthesize or "pull new insights out of existing data," said co-author Bill Dennison of the University of Maryland Center for Environmental Science.
The scientists partnered with the Chesapeake Bay Program and for a year and a half analyzed annual surveys of submerged aquatic vegetation (SAV) and water-quality data sets going back to 1984, focusing on the nutrients cascading into the watershed and their impact on underwater grasses.
It's considered the longest such timeline of an estuarine marine system on the planet, because the Chesapeake is so well-studied.
They mapped every kind of underwater grass across the entire bay, some 16 species in all, from its freshwater upper region to its brackish mouth in Hampton Roads.
"And we've shown what we suspected all along," said Lefcheck, "which is that nutrients are the key here."
In 2016, the bay supported nearly 100,000 acres of SAVs; numbers for 2017 are expected to surpass that.
Dennison calls their findings a good news story for those "fatigued with repeated bad environmental news."
"My sense is that we are hungry for inspiration, like this story, that we can reverse some of the environmental degradation that has taken place," Dennison said in a recent blog post.
The findings are also a nod to bay jurisdictions that have been working for several years now to reduce nutrient runoff, said Robert "J.J." Orth, another co-author who heads up the sea-grass monitoring and restoration program at VIMS.
"We want managers to know that they're doing a good job, that their efforts are paying off, because it's a tough road," said Orth. "It's hard to explain to people what an oxygen molecule is, but if you can have tangible evidence that these underwater grasses are doing better because of the efforts to reduce nutrients, it makes a difference."
The sheer diversity of SAV species they found also bodes well for the future, researchers said, because it means the grass beds are more resilient to hurricanes, intense rain events and other weather disturbances.
Diverse beds also tend to produce more cover and hardier habitat for other creatures and organisms, said Lefcheck, much like coral reefs or terrestrial forests.
The Chesapeake is the largest estuary in North America, its 64,000-square-mile watershed stretching over portions of six states and the District of Columbia.
By the 1970s, the bay had become so badly polluted that its SAVs were dying off. It wasn't alone. According to Dennison, one study conducted 10 years ago found that the world was losing a soccer field-size bed of sea grass every 30 minutes since 1980.
This was a worrisome trend — marine scientists call underwater grasses the "coastal canaries" in the coal mine, because, as the grasses go, so goes the waterway.
In 1984, Virginia and other bay states united with federal agencies and conservation and academic groups to form the Chesapeake Bay Program to try to save the bay. Their efforts faltered until 2010, when the U.S. Environmental Protection Agency put bay jurisdictions on a pollution diet, restricting their Total Maximum Daily Loads of nitrogen, phosphorus and sediment to the watershed.
Nutrients such as nitrogen and phosphorus fuel massive algae blooms that decay and cause oxygen-deprived dead zones in the bay that kill fish and plants. Sediment silts over bottom habitat and reduces water clarity, which prevents light from reaching submerged vegetation. Without light, the grasses die.
Most nitrogen enters the watershed — and, ultimately, the bay — through farm runoff and wastewater discharges, so management efforts have focused largely on upgrading treatment plants and encouraging best-management practices among farmers.
Since cleanup began in 1984, underwater grasses in the bay have increased four-fold. This, even as the population in the watershed has doubled to 18 million people.
Twice now, President Donald Trump has tried to slash funds for the bay program or cut it entirely. Both times, Congress, which broadly supports the cleanup work, has fully restored the program's $73 million federal budget, most of which is given to bay states and localities for anti-pollution measures. Congress passed its latest omnibus spending bill on March 23 that funds the government through September and again fully funds the program.
"This is a time, now that we know that positive things are definitely happening, that you don't just pull out," said Orth. "It's not one of these 'mission accomplished' — it's a mission that really has to be maintained."
Other researchers who partnered in the study are from the Maryland Department of Natural Resources and the Center for Ocean Health, the Smithsonian Environmental Research Center, St. Mary's College of Maryland, the U.S. Geological Survey, the National Socio-Environmental Synthesis Center, Texas A&M University-Corpus Christi and the EPA. VIMS is affiliated with the College of William and Mary in Williamsburg.