Grand Lake officials provide season recap
CELINA — Advisory signs at Windy Point Beach were down this year for 15 weeks announced Grand Lake St. Marys State Park Manager Dave Faler Saturday morning at the monthly meeting for the Lake Improvement Association.
“When you think of that, it’s been over 10 years since we could remove those signs,” said Faler.
Some algae like planktothrix are active in the lake currently, but overall, the lake’s water quality this summer was as good as it’s been in the last 10 years.
West Beach and East Beach saw 13 weeks with no red advisory sings.
“Out of the entire swimming season from Memorial Day to Labor Day, that’s only two weeks that we had red signs on those beaches,” said Faler. “It’s been a great, great year.”
Dr. Stephen Jacquemin, associate professor of biology at Wright State University – Lake Campus, was on hand to describe the changes that the lake saw this year.
“It’s been unique. There’s been some comparisons to a little over a decade ago,” said Jacquemin.
He said that the lake began with no algae when the ice came off in early spring.
He mentioned how there was low external loading in the spring which paved the way for good early summer water quality and then internal loading helped blue-green algae levels spike.
“Within a week, we saw that huge uptick. That coincided with some temperature changes in the water that coincided with some nutrient cycling changes,” said Jacquemin. “All
of a sudden there was a lot of nutrients that were available when the temperature went up. A lot of that has to do with what’s bound in the sediment. We talk about external versus internal load — you see what happens when you turn off the external load. You get incredible water clarity, incredible water quality. You also see what happens with the internal load. That’s not something we can necessarily turn off over night. That’s going to take years and years of concerted management practices to sort of remove and draw down that internal load.”
He explained that once the water temperature reached a critical point, diatoms began falling off.
“They didn’t necessarily fall off because they got out-competed by the blue-greens, they fell off because that’s one of the things that just happens when you get water temperature upticks,” said Jacquemin. “Those diatoms don’t tend to hang around as much.”
Microcystins then took over which formed turquoise, almost copper sulfate green and blue colors along the margins, according to Jacquemin.
“We know that some of those color changes are a stress response,” he said.
When the microcystin left, it paved the way for aphanizomenon, a type of cyanobacteria that inhabits freshwater lakes and can cause dense blooms.
“Once the microcystin left, nearly overnight, things turned on a dime and the microcystin monoculture in some areas turned into a near monoculture of aphanizomenon. This was the one that looked like tiny, little grass clippings were sort of floating there,” said Jacquemin.
Planktothrix then came next.
“Almost overnight, it [aphanizomenon] subsided and paved the way for planktothrix. The shifting and the changing of the guards of these different species of algae is a complicated relationship between what’s there and what’s available from a nutrient cycling perspective. We know this because we can watch them, you can see them,” said Jacquemin.
Currently, the lake has an “almost” 100% monoculture of planktothrix, said Jacquemin.
“What we have right now is kind of back to normal. I don’t have a crystal ball so I can’t tell for sure but I would be surprised if we see any more shifts,” he said. “This is planktothrix and it’s going to be here until the ice is on. What happens next spring will be contingent on that external load pattern.”
LIA President Keith Westrick was happy with the water quality this year, but said it won’t allow lake officials to put their guards down.
“Regardless if we have three more years in a row just like this one, we still keep working on those treatment trains and we still keep addressing the issues that caused it,” said Westrick. “We can celebrate but we also don’t say, ‘Mission accomplished, it’s done.’ We continue to work all the time.”