The results of the 2013 Cazenovia Lake aquatic plant survey show that the invasive species Eurasian watermilfoil more than doubled in the number of locations where it was found from 2012 to 2013, and one-third of all the milfoil in the lake were medium to dense in abundance.
These results, coming after a year of no chemical treatments of the lake to combat Eurasian watermilfoil, contributes to the town board’s intention to continue actively addressing the issue of lake health and treatment during 2014, said Town Supervisor Bill Zupan.
The town will look to take a “holistic approach” to the work, which will include not only further chemical treatment of the lake, but also weed harvesting, benthic mats, possible biological solutions (introducing animals such as moths and weevils into the lake to eat the milfoil) and a continued focus on rainwater run-off mitigation, Zupan said. The town also has a phosphorous study of the lake ongoing, in conjunction with SUNY ESF, which is investigating the sources of the lake’s high phosphorous levels.
The town also will submit to the state Department of Environmental Conservation a suggested figure of 259 acres of the lake to be treated for Eurasian milfoil, “and we’ll see how many of those will be chemically treated,” Zupan said.
The 2013 aquatic plant survey of Cazenovia Lake was undertaken in September and October by Robert Johnson, of Racine-Johnson Aquatic Ecologists, who has been doing the Cazenovia Lake surveys since 2009. He used the “rake toss” method — tossing a rake head into the water and cataloguing the aquatic plants that are pulled out — to determine plant species presence, location and an estimate of species abundance, as well as to “describe and evaluate the impact of the 2009, 2010 and 2012 herbicide treatments to the lake with triclopyr (Renovate®) to control the growth of Myriophyllum spicatum (Eurasian watermilfoil),” according to the report.
The Cazenovia Town Board approved the survey — and its $8,000 price tag — last September to help the board members decide whether or not a chemical treatment program for the lake would be warranted in 2014.
The town previously treated the lake with Renovate (triclopyr) in 2009, 2010 and 2012 in an effort to bring the invasive species Eurasian water milfoil under control. No chemical treatment was applied to the lake last year due to the cost and the shortened timetable to submit permit applications to the state Department of Environmental Conservation.
The conduct the 2013 survey, Johnson sampled and recorded plant species presence and abundance at the same 304 locations previously sampled in 2010, 2011 and 2012, and also an additional four new locations in Carpenter’s Pond, the report said.
According to the report, Johnson and his team collected samples with a dual-headed rake and assigned an overall plant abundance estimate to the amount on the rake. They classified and recorded the entire rake sample as “dense (D)” — more than an armful and difficult to get into the boat; “medium (M)” — an arm full; “sparse (S)” — two hands full; “trace (T)” — a small handful or less; or “zero (O)” — a bare rake. The field crew then separated each sample to individual species, analyzed the separations by recording the species identification and a percentage estimate of each species on site.
The major findings of the report are that the Eurasian watermilfoil was “reduced significantly” in 2009 and 2010, increased in 2011, reduced again in 2012 but then increased again in 2013 from 123 locations in the lake in 2012 to 255 locations in 2013. Of those 255 locations, 33 percent had watermilfoil that was medium or dense in abundance, the report stated.
The 2009, 2010 and 2012 lake treatments with triclopyr “continue to show no significant negative effect on an overwhelming number of non-target plant species,” although the species white water lily and northern watermilfoil did decrease, although that was expected, the report stated. The species coontail, elodea, eel grass and benthic filamentous algae were found in abundance in the target survey areas, and the species flat-stemmed pondweed “increased significantly,” the report stated.
“The very positive high native plant species numbers (richness) present in Cazenovia Lake continue to constitute a very diverse aquatic pant (macrophyte) community providing stability that should slow invasion by non-native species,” the report stated.
The full report can be read on the town’s website at townofcazenovia.org, under the “Caz Lake Restoration” tab.
Jason Emerson is editor of the Cazenovia Republican. He can be reached at [email protected].
