OLCOTT – Federal scientists are trying to get to the bottom of what’s happening at the bottom of Lake Ontario.
Divers from the U.S. Environmental Protection Agency on Monday focused on the waters between Olcott and Wilson, scooping up samples of water that included algae and invasive mussels.
They collected samples about 10 feet deep.
They took more 20 feet down, and also 30 feet and 60 feet beneath the surface for laboratory analysis.
Algae is native to the lake, but excessive amounts can disrupt boating, swimming, fishing and other recreational activities, scientists said.
“In general, what we’ve been finding is the two shallower stations have had significantly more cladophora [algae] growth than the deeper two,” said Alan Humphrey, a unit dive officer for the EPA’s Environmental Response Team. “Recreationally, it’s become a real nuisance for boaters and for swimmers. There may be a nutrient impact.”
The scientists' work on board the EPA’s environmental research vessel Lake Guardian is part of a summerlong survey of what’s happening in Lake Ontario. The 180-foot watercraft spends every summer on one of the five Great Lakes – rotating among them. The vessel arrived at Lake Ontario in June and will remain into the fall. The crew assists the EPA’s Great Lakes National Program Office in monitoring and reporting on the Great Lakes ecosystem.
As part of the binational effort by the United States and Canada, scientists analyze nutrients flowing into Lake Ontario. Both countries want a targeted balance of nutrients low enough to keep algal growth in check and high enough to support the lake’s ecosystem.
“In order to answer that question, we have to understand what’s driving the benthic algal growth on Lake Ontario,” said Fred Luckey, an EPA environmental scientist.
Surveys like this have been done by Environment and Climate Change Canada, but are being done for the first time on the U.S. side of the Great Lakes.
Scientists theorize a combination of factors, including the colonization of the lake by invasive zebra and quagga mussels and nutrient runoff into the lake, could contribute to proliferation of nuisance cladophora in near-shore areas.
It’s possible, they said, that the mussels’ ability to clear the water allows for more sunlight to penetrate the water at greater depths. That, along with increases in phosphorus and other nutrients from shoreline septic sewer systems, wastewater overflows and agricultural runoff, could feed the algae growth.
Besides the locations off of Niagara County, surveys also are being done farther east – near Irondequoit and Sackett’s Harbor.
The U.S. Geological Survey and the U.S. Fish & Wildlife Service are assisting the EPA.
"The key to understanding this is modeling," Luckey said. "You can't really understand this unless you have real-live data to model."
Divers Scott Grossman and Brad White jumped overboard Monday morning from an EPA single-engine, 30-foot dive pontoon boat – a companion vessel to the Lake Guardian – into 70-degree water.
The divers wore full SCUBA outfits and carried bright orange zipper sacks filled with empty, marked jumbo zip-close bags and three squares fashioned out of thin PVC piping.
About halfway down to a 20-foot depth, the divers dropped the plastic squares and let them sink to the lake bottom. That marked the roughly one square meter total area from where they’d collect their algae and mussel samples. The samples were placed into the large plastic bags.
It's something the EPA divers have repeated monthly since May, and will do again in September.
Cladophora typically grows larger as summer wears on. The algae there could be an inch thick or more, or scattered.
On Monday, it was the latter.
“It was as we’d expect at this location. There was a lot of rock with some zebra mussels and with some limited growth of cladophora at the location,” Grossman said.
White added: “I only noticed one tuft of 5 to 10 mussels on it. That’s what it sort of felt like. It was hard to see at that point.”
Grossman and White completed a habitat assessment and recorded the estimated percents of live and dead cladophora and the coverage at the site.
It’s a site they’ve been to in May, June and July – and will visit again next month.
At this particular depth, the men also recovered a special cylindrical device anchored to the lake bottom.
The unit – called a multiparameter sonde – is about the length of a baseball bat and includes sensors. Every hour it's in the water, it logs water temperature, chlorophyll, dissolved oxygen, connectivity, turbidity, phosphorus and light penetration. Besides the one near Olcott, there are others at Irondequoit and Sackett’s Harbor at the 20 foot depth.
After resurfacing about 20 minutes later, the divers relay the device to EPA water quality samplers Neal Johansen and Emily Nering, who are waiting on a nearby EPA watercraft.
“We need to recover the instrument so they can download data,” Humphrey said.
A USB cable attaches the sensors to a computer operated by Nering and Johansen, who download the data. They also clean and recalibrate the sensors before returning the unit to its spot on the lake bottom. Then, the process will be repeated for the final time in September.
“They’re going to do some predictive modeling with the data,” Nering said.
There’s extreme variability in seasonal cladophora blooms in Lake Ontario from one year to the next.
It’s too early to know for sure what feeds them, but scientists have some ideas.
Most of them involve phosphorus, sunlight and water clarity.
The chief suspects: invasive zebra and quagga mussels.
The mussels hitchhiked their way into the Great Lakes from Russia aboard freighters in the 1980s.
Since then, they’ve made the water look clearer. But, it doesn’t mean the lakes – including Lake Ontario – are healthier.
“In spite of the fact they’re tiny little guys on the bottom, they’ve affected this entire ecosystem,” said Richard Henry, a Fish and Wildlife Service biologist. “They’re not just an invasive species. They’ve become a keystone species.”
The species has dismantled the natural order in Lake Ontario, biologists said.
Consider this: The mussels have sucked so much phytoplankton out of the lake over the years that perch, lake trout and whitefish populations have nose-dived.
“It’s very difficult for their fry to survive and they’re going to have a hard time coming back,” Johansen said.
What’s more, although the mussels also feast on algae like cladophora, once the algae grows past a certain point and attaches strand after strand to itself, it grows uncontrolled. The mussels can’t eat it.
Are nutrients helping fuel that growth?
That’s part of what scientists hope to learn from the data they’re gathering from the lake bottom now.
“The overall purpose of this is to find the relationship between cladophora and zebra mussels and dissolved phosphorus,” Johansen said. “It’s a three-pronged question we’re trying to get our hands around.”