[T]he David Folger slowly churns its way west in a straight line across Lake Champlain. A quarter of a mile from the shore, ship’s captain Rich Furbish reverses course and transects the lake again.
This goes on for more than 12 hours, as Middlebury professor Tom Manley guides student Perri Silverheart through a project involving sub-sediment mapping of the lake bed.
Manley says information gathered as part of the project could aid current efforts to bolster the lake’s water quality.
Manley said the lake’s hydrology is understood today to an unprecedented degree, but said it’s important to put that understanding to the proper use, in order to ensure management decisions are based on accurate science.
Furbish, who’s captained vessels on Lake Champlain for the past 50 years, said he’s encouraged that management decisions take into account the level of science they currently do.
“There used to be three types of people who cared about Lake Champlain,” he said. “Fishermen, water skiers and a few sailors.”
These days, he said, “it’s remarkable how far we’ve come in raising the consciousness of people in this state – both states – of the value of this lake. That wasn’t always the case. I think we’re in a great place, as far as consciousness, awareness and concern.”
Manley says he’d rather see more awareness.
Although members of the public seem to understand that the lake needs some form of support, scientists have grown frustrated that political will seems more oriented toward management than research. This could lead to unintended consequences, he said.
Take Missisquoi Bay, for example. It’s one of the areas identified as having the worst water quality of any on the lake. The reason is in one sense obvious, Manley said.
Farmland and forests drain large amounts of phosphorus into a shallow bay, where warm water and plentiful nutrients allow algae to flourish.
The “flushing rate” of a waterbody has an important effect on algae growth, he said. Slow-moving water offers a more hospitable climate for the organisms, he said.
He compares Missisquoi Bay’s hydrology with that of a bathtub filled and drained by two separate hoses.
The bay was once free-flowing, he said – imagine a bathtub filled and drained by similarly-sized, unoccluded hoses — but in the late 1800s Vermonters built a causeway across one of its ends.
“All of a sudden, your hose got very small, so you can fill up Missisquoi Bay, but you can’t drain it very rapidly,” he said.
Many believe such causeways artificially obstruct currents that could flush areas like Missisquoi Bay, Manley said. The state hired a firm several years ago to study the matter, however, and their models showed that wasn’t the case, he said.
Research since that time has shown Missisquoi Bay to contain water currents that weren’t previously guessed at. No current mathematically-based model incorporates this information into calculations that would show the effects of removing Missisquoi Bay’s and other nearby causeways.
A model like this must exist in order to make informed decisions on how best to manage the lake, Manley said.
“There’s this general misconception that, if you spend five or six years researching, say, they dynamics of Lake Champlain, that you’ve got it all covered, that there’s nothing more to learn, and it’s all management,” he said. “In reality, as you learn more and more about the lake, you learn you know less and less about how it actually operates.”
This doesn’t need to be the case, he said. The Great Lakes have a mathematical model that produces reliable results, but it’s the product of years of funding and research that Lake Champlain currently lacks.
Without something comparable, Manley said, any dramatic measures affecting Missisquoi Bay’s hydrology are probably premature.
“There is a significant and valid public concern that these causeways are modifying the circulation patterns of that particular waterbody,” Manley said of the bay. “A lot of people would like to see these causeways removed, so the open circulation patterns can start moving again.
However, he said, “right now … we don’t have enough information to know what would happen.
“There could be this domino effect that could occur that no one’s foreseen, that a properly calibrated numerical model could have provided us,” he said.
For the first time, researchers now possess enough information to calibrate such a model for water flowing in and out of Missisquoi Bay.
Manley said a promising research proposal could be funded soon that would incorporate this data into the type of model he says is needed to make needed management decisions.
For the time being, Manley didn’t express great confidence in the models used by the EPA to depict current conditions.
If it’s an accurate model, it may serve its purpose, he said. With the limited information currently available to scientists, it’s hard to say whether that’s the case, he said.
Despite the lack of models predicting future hydrological behavior, much is known about the lake’s current conditions.
Researchers know, for instance, that algae blooms were particularly bad last summer.
Algae persistent this year
This year has offered conditions especially conducive to blue-green algae, Lake Champlain Committee staff scientist Mike Winslow said.
“We’re still seeing blooms in St. Alban’s Bay, and particularly in eastern Missisquoi Bay,” he said last month. “It seems to be tapering a bit, but it’s definitely still out there in those northeastern bays.”
The north end of Lake Carmi, and Lake Iroquois as well, have seen algae recently proliferate, Winslow said.
Algae continued later into the fall this year than it commonly has in the past, he said.
A couple of factors have made 2015 particularly conducive to algae growth in the lake, he said.
“It’s probably tied to spring rainfall,” Winslow said, noting especially heavy rainfall that took place in June. These rains washed nutrients such as phosphorus from fields, forests and roads, and into the lake.
Warm weather late into the fall “is absolutely a factor” contributing to algae growth, Winslow said, in that the lake’s temperature has risen along with that of the air.
“Water temperature is a threshold thing – once it exceeds a certain temperature, [algae] can bloom and thrive,” he said. “We’ve passed that threshold. What I suspect, with the high temperatures, is that blooms will persist longer, into the fall.”
And as Vermonters embark on an ambitious task of improving Lake Champlain’s water quality, they should understand that the problem of algae blooms will continue for years, University of Vermont’s Patrick Professor for Watershed Science and Planning Dr. William Bowden said.
“I am very concerned that in a year or two years or three years, people are going to say, ‘Oh my gosh, look at all the money we’ve spent, and we’re still getting algae blooms,’” Bowden said.
“It has taken us 200 years to get ourselves into the fix we find ourselves in with Lake Champlain … and it’s going to take perseverance, and it’s going to take a lot of money, and it’s going to take a lot of effort and time to get the lake back to a level where it’s acceptable to us,” he said.
One 40,000th of a paper clip
What’s acceptable in the lake are exceedingly small amounts of phosphorus, Bowden said.
Pollution limits that the EPA seeks to put in place in Missisquoi Bay would bring phosphorus levels down to an average of .025 milligrams per liter. The main body of the lake should contain .010 milligrams per liter, the same EPA document states.
To put that in perspective, Bowden refers to the mass of a paper clip. That’s about one gram, he said.
A liter is roughly a quart, or two pints, or a little over four cups. A milligram per liter equates to about one thousandth of a paper clip of material dissolved into a quart of water.
The phosphorus concentration sought in Missisquoi Bay, then, equals the mass of 1/40,000 of a paper clip, dissolved into roughly a quart of water.
Today’s phosphorus levels in the lake still consist of miniscule quantities – Missisquoi Bay’s phosphorus levels are only somewhat over twice the amount the EPA considers acceptable.
“Algae living in the lake really need very little of this phosphorus to make a lot of biomass, of chlorophyll,” Bowden said. “That is the problem.”
Algae require this phosphorus in the water because it’s the only one of the three critical elements constituent to life that the organisms can’t pull from the air, Bowden said.
Those critical elements are carbon, nitrogen and phosphorus.
“All animate forms require these elements in more or less the same proportions – those portions being “a lot of carbon, a little less nitrogen, and even less phosphorus,” he said.
The dose makes the poison
This ratio is important, Bowden said.
Living organisms have “no trouble whatsoever” in acquiring carbon, he said. Plants pull it from the air, and animals get it from plants.
For most creatures, the challenge lies in obtaining sufficient nitrogen and phosphorus. Fertilizers typically contain both, to overcome this difficulty in plants.
Blue-green algae, however, possess a special enzyme that allows them to pull nitrogen from the air.
“That gives them a competitive advantage,” Bowden said.
That advantage allows blue-green algae in the presence of phosphorus to grow beyond the constraints that other, competing, organisms would impose on them in a balanced ecosystem.
“If you give them a little bit of phosphorus … they can make as much biomass as they want,” Bowden said.
“The amount of dry [phosphorus] mass dissolved in the water is infinitesimally small, but enough to support these large algal blooms,” he said. “That’s what makes it so difficult to manage – just a little bit … can wreak havoc under the right circumstances.”
Those circumstances are part of the reason different parts of the lake are more prone to algal blooms than others, he said.
Certainly, phosphorus concentrations alone are an important contributor to this phenomenon, Bowden said.
In places like Missisquoi Bay and St. Alban’s Bay are found sizeable rivers laden with phosphorus from heavy agricultural use in their watersheds, he said. Those rivers “are dumping directly into these confined embayments … so the concentrations are quite high,” he said.
But these bays’ topography plays an important role aside from constricting phosphorus-rich river flows within a relatively small area, he said.
These bays also act as incubators, Bowden said, offering plenty of light and warmth as a function of their shallow floors.
As in a greenhouse, the abundant light and warmth allows prolific plant growth, but within a circumscribed space.
Blue-green algae are present throughout the lake, Bowden said, typically in concentrations low enough not to cause problems.
“But when we create the right conditions … and then give them lots of phosphorus, these guys are able to grow very rapidly,” he said. “They out-compete the other algae … and as a consequence, they explode, and get to the point you can actually see them.”
Algae whose chlorophyll has visibly colored the water green is considered to have bloomed, Bowden said.
Such blooms frequently enough indicate neurotoxins that they’re best to avoid, Bowden said. This is true even though the association between blue-green algae’s toxicity and its coloration isn’t well established.
“The trouble – and really this is at the forefront of science – is that there’s not a good correlation between the strength of the greenness we see out there and the presence of toxins,” he said.
Despite the larger and long-term implications of phosphorus pollution, it’s important to recognize that water conditions immediately adverse to humans are often both local and acute, Winslow said.
Algae blooms commonly occur in certain areas, such as in Missisquoi Bay and St. Alban’s Bay. They can nevertheless disperse within hours, Winslow said.
The latter case is true for E. coli, the other common cause of beach closures in Lake Champlain, said Frank Spaulding, parks project coordinator at the Vermont Department of Forests, Parks and Recreation.
Cyanobacteria and E. coli are the two waterborne organisms for which Spaulding’s department regularly tests.
Their presence infrequently closes beaches at state parks, he said.
Under Spaulding’s direction, the Department of Forests, Parks and Recreation tests water at 42 sites throughout the state all summer, and unacceptably high test results have led to only 16 closures during that period. Except for a single incident in Alburg, test results at each of those beaches returned to acceptable levels within a day.
The Alburg Dunes site returned high results for E. coli twice in succession, Spaulding said, and remains on alert pending further results.
As is often true for blue-green algae, high concentrations tend to be fleeting events, and nearly always confined to specific locations, he said.
“You can’t take results beyond where the sample was taken,” Spaulding said.
As is also the case with cyanobacteria, high E. coli concentrations in the water aren’t always a threat to human health, he said.
The bacteria is instead an indicator that other pathogens may be present, Winslow said.
“E. coli in and of itself isn’t necessarily dangerous, but it resides in the intestines of both humans and other animals, and its presence indicates that some waste has been in the water,” Winslow said. “As E. coli levels increase, the chance of getting sick will increase as well.”
Geese are sometimes posited as the source of such wastes, Spaulding said, but it’s generally unknown where any particular concentration of the bacteria originated.
The water’s fine
Once an area returns to normal levels of E. coli (Spaulding said these levels in Vermont lakes – typically single- or double-digit quantities of bacteria cells in a liter of water – “are phenomenal”) or blue-green algae, the water is safe to swim in, he said.
Winslow agreed. Come next summer, there’s no reason not to get in.
“Try to avoid green, scummy messes,” he said, but in the main body of the lake, “there’s nothing hidden that’s going to cause you to be sick.”
This is true as a rule for Vermont’s state park beaches, Spaulding said.
“What we have is beach areas that by and large, and pretty universally, have clean water,” he said. “There’s no reason to believe there’s anything wrong with swimming at a Vermont state park. If you don’t go in the water, enjoy looking at it, and enjoy what Vermont has to offer.”
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