In August, the aerial view of the Rappahannock River at the mouth of the Chesapeake Bay was tainted by swaths of dark reddish-brown that looked similar to the wavy bands oil makes when in it’s in water.
But the darkness in the river wasn’t a substance. It was a vast area of living organisms.
On August 17, Virginia Institute of Marine Science (VIMS) confirmed a visible algal bloom in the Rappahannock River near Tappahannock. On the 31st, VIMS confirmed another algal bloom farther down the river between Urbanna and Saluda.
The photo above, taken off the coast of Windmill Point, at the mouth of the Chesapeake Bay is believed to be part of the August 31st algal bloom, according to scientists at the Chesapeake Bay Foundation (CBF).
Algal blooms risks
It’s normal to find algae in any aquatic setting, but in certain conditions algae can grow excessively and become a harmful algae bloom (HAB), sometimes called a red tide.
Algal blooms are common in the Chesapeake Bay and waters throughout Virginia, but that doesn’t mean they’re harmless or a matter to be taken lightly. There are a number of potential risks associated with algal blooms.
One of the major problems is that algal blooms can lead to dead zones, explained Joe Wood, senior scientist and resident expert on algal blooms for CBF.
When the algal blooms die, that dead material sinks to the bottom of the water, rots, and sucks all of the oxygen out of the water, creating a dead zone where aquatic plants and animals can’t survive. This happens in the bay and its tributaries, said Wood.
Dead zones could have major implications for the Northern Neck since some of the areas biggest resources are the fisheries—crabs, oysters, striped bass, and menhaden. Those are a local draw and an important part of the local economy, said Kenny Fletcher, CBF’s Virginia communications coordinator.
Both of the algal blooms confirmed in the Rappahannock River in August were Prorocentrum minimum. “This species can cause oxygen depletion in the water … and can lead to fish kills and shellfish mortalities,” said VDH in its notices about the blooms.
The second major problem with HABs is that some algae are noxious and can produce toxins, such as neurotoxins, that affect human and animal health.
Determining whether the bloom exists is one thing but characterizing what’s there is also a big part of it. Because there are thousands of different species of algae, explained Wood. Fortunately, the algae that caused the blooms in the Rappahannock in August “is not known to produce a toxin harmful to people,” according to VDH.
But in cases where the algal bloom is a human health threat, authorities will announce a recreational closure for the affected water, which communicates to the public that the water isn’t safe for their use, noted Wood. And that could also have serious implications locally.
“The other big part of the Northern Neck’s economy is tourism. People want to come there because of the beautiful waters, and if there is a warning put out by the health department to not go out swimming or to not spend time on the water because of harmful algal blooms, that’s something that people take to heart,” said Fletcher.
Addressing pollution that causes HABs
“We may be used to a state where harmful algal blooms and dead zones are a part of life. They happen every year in parts of the waters that surround the Northern Neck, or at least most years,” Fletcher said.
And it may seem like the region is evading the consequences, but the Rappahannock River and the waters around the Northern Neck aren’t the resources they could be. They aren’t as healthy and strong as they would be if we were able to address some of the pollution problems that are exacerbating the harmful algal blooms and the dead zones, he added.
There are three main areas of focus with regard to the pollution that encourages HABS. One is wastewater from sewage treatment plants. That’s an area we’ve made major progress on in the last 15 years, he said. And that’s largely because about $1 billion has been spent in Virginia upgrading wastewater treatment plants, which immediately cut nutrients to the Bay.
Stormwater runoff from impervious surfaces, such as roads, and from our homes is a second big source of pollution. Wood encouraged giving some thought to how much fertilizer we put on lawns and the other things stormwater interacts with before it runs off our property.
But the third and largest source of pollution is agriculture, according to CBF.
“Addressing agricultural pollution is a major thing that needs to happen,” said Wood. “And there’s no better option for doing that than forested buffers. Having trees at the edges of our streams and rivers intercepts as much pollution as you can hope for. That’s the best practice that we have.”
However, it’s not the only tactic that’s encouraged. Livestock fencing to keep cows out of streams is a big one. There’s also managing the amount of nutrients applied to crops and having a sustainable level of fertilizer application.
“There’s a variety of tools that can be used. But managing those sources is the biggest step that’s needed to address these bloom issues,” said Wood.
“We’ve made some progress in the ag and stormwater sectors as well. But not nearly as much as we hoped to,” said Wood. Goals were set for 2025, and we definitely need acceleration to hit the targets states have committed to because we’re not necessarily on track to hit those goals,” he added.
Right now, a lot of the money from the state budget is going toward practices upstream from the Northern Neck, such as the upper Rappahannock River watershed west of Fredericksburg and even as far away as the Shenandoah River. Soil and water conservation offices and agriculture extension offices are doing outreach to farmers, and the Chesapeake Bay Foundation has people on the ground in Shenandoah meeting with farmers and landowners.
People in this region shouldn’t dismiss those efforts as being relevant only to the areas where they are occurring. “What happens in the Shenandoah River flows into the Potomac and eventually affects places on the Northern Neck. So even when the emphasis on the practices are 100 miles away, they’re still improving the waters that sur-
round the Northern Neck,” said Fletcher.
Factoring in climate change
In addition to pollution, we have climate change to wrestle with. But we can exercise more control over one of those problems than the other, Wood explained.
“Both are contributing factors. So, if we don’t do anything about nutrients [entering the water] and we have climate change issues, both of those are going to be exacerbating the problem and we’re going to be in a real mess, from a nutrient perspective.”
Additionally, many of the practices encouraged to protect the waters from pollution do double-duty by also addressing climate change. Wood pointed to forested buffers as a prime example. Planting trees sequesters carbon, he said.
A seasonal break
Algal blooms have a seasonal nature. Like many plants, algae are most prolific when it’s hot, “so late summer,” said Wood. There are spring and fall blooms, but in the winter time, things kind of shut down biologically, he added.
Both of the August algal blooms in the Rappahannock River are now deemed “prior events,” and with the weather change, it’s safe to assume the blooms are no longer active, noted Fletcher.
If algal blooms will return to the Rappahannock River with next year’s heat and how severe they may be is a looming question.
Knowing when algal blooms are going to happen is virtually impossible to predict. But usually when we have a really wet year, we have a really bad dead zone because more pollution gets carried to the Bay, said Wood.