For those fortunate enough to spend an afternoon paddling, swimming or fishing on Cazenovia Lake, particularly in a good year and on a great weekend, there are few reasons to ask any questions. Just enjoy. But for the residents of the lake, for those managing the lake, for these visitors and those who live and breathe the lake, this simple but disarming question is often asked but rarely answered: Why?
Why do weeds keep coming back? Why do we need to keep managing them? Why does the lake suffer from harmful algal blooms? Why didn’t they come this year? Why do we care about road salt and nutrients?
For those concerned about harmful algal blooms, or HABs, the answer to “Why?” has always been nutrients. The simple equation, nutrients = algae, has long been the first rule in lake ecology and the forever mantra of lake management. So, controlling nutrients meant controlling algae.
But, in 2015, low-nutrient Canandaigua Lake exhibited a widespread bloom at the north end of the lake. It was assumed that this was due to local, temporary, isolated nutrient sources; or perhaps an anomaly, attributed at various times to the weather, or bad luck, or something else the likes of which wouldn’t be seen again.
And this seemed right, or at least right enough, until Skaneateles Lake exhibited toxic blooms this past September. The same Skaneateles Lake described in rarefied breathiness as the best lake in the world, and the same Skaneateles Lake with nutrient levels 3 times lower than in Cazenovia Lake and other lakes thought to be vaguely “susceptible” to blooms. And at the same time when Cazenovia Lake was far from green.
Maybe we don’t know “Why?” Perhaps the letter “Y” represents not the end but the beginning in “Why” — just one part of the question, but one affording great insights into the “Why?”
For, perhaps there are many paths to HABs — and for some lakes, the other arm of the Y — the path unrelated to nutrients, but broadly summarized as “other stuff” — may be the more important path to HABs and therefore the path to a “Y” not.
In Cazenovia Lake, weed control means reducing Eurasian watermilfoil, one of the many invasive plants in New York referred to as AIS, or aquatic invasive species. For lake communities seeking to reduce problems with AIS, management means controlling the introduction of the plant once AIS already in the lake are reduced, whether using chemicals or some other tool. And weed control has been effective at reducing Eurasian watermilfoil in the lake.
So why do some lakes never have a problem with invasive weeds, even when AIS are introduced, and why do the plants persist in the lake, even when they are knocked down?
In this case, the Y of weed management also leads managers down two paths — preventing more plants (or new AIS) from entering the lake, but also trying to stop the “other stuff” — those things that make AIS grow so weedy. Sediment. Nutrients. But maybe also salt. And maybe some things harder to manage, like fish or weevils or other stuff we haven’t yet figured out.
So, what is a manager or concerned citizen to do? Lake management is complicated. And messy. And more than one person or agency can handle. The why can’t be reduced to simple equations: HABs = nutrients, AIS = introduction.
Managing HABs and AIS in Cazenovia Lake means learning more about the Y, about the other stuff. It involves using all of the tools in the toolbox. But it mostly means working together — lake residents, government officials, professionals, citizen scientists — to ask Why? and to explore Y.
There are many opportunities to get involved. Come to the Cazenovia Lake Summit on Nov. 18 to learn more about what is happening at the lake, and more about what you can do.
Scott Kishbaugh P.E., is chief of the Lake Monitoring and Assessment Section, Bureau of Water Assessment and Management, NYSDEC Division of Water.
