This story was reported and written by VPM News.
The Chesapeake Bay’s “canary in the coalmine” got a little healthier in 2023.
The Virginia Institute of Marine Science released its 2023 Submerged Aquatic Vegetation report in July, revealing that SAV expanded for the third year running to nearly 83,000 acres.
SAV refers to rooted underwater plants like grasses — not algae or seaweed. They are known to have a range of ecosystem benefits, from reducing sedimentation to providing habitat for Bay critters.
“What we're seeing right now is … recovery,” said Chris Patrick, director of the SAV Restoration and Monitoring Program at VIMS.
From 2016-2018, Bay grass acreage was at a high point across 40 years of monitoring; it covered more than 100,000 acres of Bay and river floors. But in 2019, Patrick’s first year in charge of VIMS, that changed dramatically.
“It was just a bad year,” Patrick said. “It was the worst we've ever seen in all the years we've been monitoring.”
Widgeon grass — a species that Patrick said reproduces prolifically, but is vulnerable to nutrient pollution — has taken up more space in the middle Bay than in the past. In 2018, Virginia experienced a historically rainy year, which swept more sediment and nutrients into the water than the widgeon grass could handle.
It “just folded up,” Patrick said.
In a year, SAV coverage decreased by 40,000 acres .
Four years later
Now, widgeon grass is re-establishing itself in the middle Bay, and other species are taking root — sometimes in places they haven’t been seen before.
Patrick said eelgrass is growing deeper underwater than it has in years.
“The only way they can do that is if they're getting enough light to survive,” he said.
To Patrick, that’s a sign that efforts to reduce sedimentation in the Bay are having noticeable effects. That’s good for eelgrass because it’s sensitive to temperature, preferring to live in cooler waters.
“In the early 2000s, eelgrass was starting to get really squeezed in the lower Bay,” Patrick said. “It was getting pushed up into the shallows by poor water quality, and then it was getting hammered by these hot summers.”
With multiple record-breaking global average temperatures this summer — and more likely in coming years as temperatures continue to rise — reducing sun-stifling sediment is key to giving SAV species, like eelgrass, space to grow.
Sediment naturally enters the water when land, streambanks, shorelines and coasts are eroded by flowing water and rain.
Human activities have increased the amount of sediment flowing into the Bay: Vegetation has been removed from some banks, where it previously slowed runoff and held sediment in place. Other shorelines have been entirely hardened with concrete or other materials, increasing runoff and making water cloudier.
Although SAV expanded this year, Patrick said the grasses face pressure from growing human populations around the Bay and its tributaries.
To mitigate that impact, local, state and federal governments will likely have to keep spending big on wastewater treatment system upgrades, stormwater management and agricultural best-management practices . Richmond is working to address its storm- and wastewater woes, calling on state legislators to give big money to reduce nutrient pollution from sewage overflows .
“It’s kind of a moving target,” Patrick said. “And then, we’ve got climate change to deal with.”
That means more hot days like the ones we’ve been having this spring and summer. Climatologists also say tropical storms and hurricanes, along with short and heavy rainstorms, are becoming more common in our area. Virginia is expected to receive heavy rains later this week from the remnants of Tropical Storm Debby , which made landfall in Florida on Monday.
Some sections of the Bay survey area didn’t fare well.
In the oligohaline, or “slightly salty,” segment of the Bay, bay grass acreage was half of what it was the previous year. Patrick said those declines were localized, and didn’t have a major impact on the system as a whole in this survey. In a press release, the Chesapeake Bay Foundation attributed the losses to sedimentation and algae blooms .
VIMS will release the 40th edition of the SAV survey next year; it’s the longest-running report of its kind on the planet, according to Patrick.
Patrick’s team of staff, grad students and postdoctoral researchers have about 12,000 kilometers of shoreline to cover in their survey — “You could fly to Egypt and back,” he said. So, most monitoring work is done from above with aerial and satellite imagery.
The localities that joined the Chesapeake Bay Watershed Agreement have a target of 130,000 acres of SAV by 2025, en route to an eventual goal of 185,000 acres. None are on track to meet cleanup goals by the deadline.
Copyright 2024 VPM
