Limnologist Sets Record Straight
ST. MARYS — A limnologist who has been tasked with overseeing the alum applications at Grand Lake St. Marys the previous two years says comments attributed to him in a Columbus Dispatch article indicating the applications did not work were misinterpreted.
Dr. Harry Gibbons, of Tetra Tech, countered the article, which included comments attributed to him that he made during a presentation at a forum in Columbus last month. The article indicated this year’s alum application was likely ruined because high winds stirred phosphorus-rich sediment from the bottom of the lake.
“I was addressing an audience of ecologists and limnologists and it was a technical talk where I compared several lakes,” Gibbons said during a teleconference with local media on Thursday. “It wasn’t just Grand Lake St. Marys — it was other lakes. I was getting at there are things that are different at smaller lakes that you have to consider when managing the phosphorus in larger lakes.”
As part of that discussion, the topic turned toward the impact of wind on internal cycling as it related to phosphorus. Gibbons used Grand Lake St. Marys as an example because it is a shallow lake.
Gibbons then touched upon the alum treatments in 2011 and 2012 at the lake. He noted the 2011 application was a partial treatment with a scaled down dosage. The 2012 treatment included the same number of acres but included a slightly stronger dose.
“Even that 4,900 acres hasn’t received 100 percent of the dose, but we are up to 30 percent of the dose required to treat the whole lake,” Gibbons said, noting he presented data that 2011 application reduced phosphorus in the lake. “I pointed out in 2012, we had a higher wind energy — approximately three times — so the internal cycling was induced by wind and the resuspension of sediments was higher in 2012 than in 2011, and that we hadn’t completed our model yet to be able to define for 2012 how much phosphorus came in from the watershed and when it came in, how much phosphorus came in from sediments and when that came in and how much phosphorus was not coming in from the sediments because of the 2012 alum treatment.”
Scientists with Tetra Tech are still in the process of compiling all the data as part of the 2012 application. A finished study is not expected to be completed until the end of the year.
“In that talk, I said we have to work on our analysis before we can say how effective 2012 was,” Gibbons said. “But we know we had more internal cycling from the untreated areas so it’s not going to appear on face value as easy to define. But we will be able to quantify that and define that. That was misinterpreted as 2012 wasn’t effective. That’s not true, it was effective, we just don’t know the quantified results until we finish our analysis.”
Gibbons said local residents should not jump to the conclusion that the alum applications are not working. In fact, Gibbons noted the alum is a key piece in the puzzle to healing Grand Lake St. Marys.
“It’s an incremental step toward reducing that internal load that is the fuel for the summertime blooms,” Gibbons said. “And we have seen in both years some phosphorus tied up and removed from the biological availability. So we have made progress and demonstrated that we can move forward in managing the lake. It’s not the silver bullet. The watershed has to be managed.”
Locally, Grand Lake St. Marys Restoration Commission Manager Milt Miller said the group is taking an active approach toward cleaning up the lake and restoring its water quality.
“Clearly it’s a partnership and we are well aware of the internal load in our lake bottom,” Miller said. “We have a focus on the dredging effort ... Just recently we received a nationwide permit from the Army Corps to re-establish some wetlands using the lake-bottom silt as the soil base.”
To build the wetlands, the dredging operations at the lake will be ramped up.
“We will have a 90-acre site representing 770,000 cubic yards that will come out of the lake,” Miller said. “The alum, plus the dredging effort and the re-establishment of wetlands are key to getting the internal loading out.”
Gibbons estimated a 100 percent saturation of alum covering 100 percent of the lake would cost $20 million to $30 million. Miller said a decision to go forward with a third alum application is not expected until state officials can review Gibbons’ report.
“There is no magic bullet — it’s a jigsaw puzzle,” Miller said.
“In the mean time, locally, in cooperation with the state, can’t let anytime pass us by. So we are working on the wetlands, the dredging, rough fish removal and all those other pieces that will add up to a whole puzzle at the end. Alum is not the silver bullet, alum was embraced because it represented a short-term solution to get our economy back, hoping that the alum would buy us time to work in the watershed.”
This year’s drought also may impact the alum application. Gibbons said with less water in the lake, the phosphorus levels from internal cycling could have become more concentrated. However, Gibbons said the alum still should have been successful in removing phosphorus.
“When we look at this year’s data, we see the microcystin was going up, the alum treatment occurred and the microcystin and the blue-green concentrations and phosphorus all dipped,” Gibbons said. “It took until June until they recovered ... We see from data that we saw those impacts. I’m very confident we saw a positive impact.”
With all that’s going on in the watershed and inside Grand Lake St. Marys, Miller said he is confident the lake will be restored.
“We went from a bloom year in which the lake was effectively closed to usage to the last two years, where we had the best fishing season we had in recent history,” Miller said.
“We tend to battle the memory of people who remember the horrible pictures of two-and-a-half years ago. We have visitors coming to our lake now saying this isn’t like anything we imagine. Our message is the lake is still open, it’s still usable, it’s breathtaking and please come back.”