Many parts of Chautauqua Lake experienced both heavy extended algae blooms and dense plant growth this past summer, especially in the northern basin of the lake, which made it difficult, unpleasant or impossible to use the lake in some neighborhoods in late summer.
Plants, algae,and cyanobacteria (commonly and formerly called blue-green algae) need nutrients, sunlight and appropriate temperatures for growth. Phosphorus is the nutrient that most commonly limits plant and algae growth in freshwater lakes. Nitrogen, in forms available to these organisms, can also be a limiting factor. Cyanobacteria, some of which potentially produce chemicals toxic to animals and humans, can get their nitrogen from gaseous nitrogen dissolved in lake water. So what happened in the 2011 growing season to produce the plant and algae conditions that were experienced of Chautauqua Lake?
First, we know that there had to be plenty of nutrients available for both plants and algae to simultaneously flourish. Where does that come from? The most significant sources of nutrients come from crop lands and pastures, wastewater treatment plants, lawns, rooftops, driveways, streets and parking lots, road ditches, excavated or barren soils, stream banks, pet wastes, precipitation and septic systems. For Chautauqua Lake, you can see this information in the Chautauqua Lake Watershed Management Plan Executive Summary on page 10. This report can be found on the Planning Chautauqua website at www.planningchautauqua.com/watershed/chautlake_mgmt_plan.htm.
A combination of nutrients and weather contributed to the abundant outbreaks of plant growth and algae blooms in Chautauqua Lake this summer.
Photo by Scott Alperin
Last spring, the Chautauqua watershed experienced some intense storms, which are suspected of washing extra nutrients from the watershed into the lake, exceeding the watershed's natural filtration systems' abilities to hold back these nutrients. This extraordinarily large load of ''non-point source'' nutrients hit as the lake temperatures were rising. After these storms, we had long periods of sunny weather, warming up this ''soup.'' So the lake possibly had more nutrients than usual and then sunnier, warmer weather than usual, delivering more sun energy for photosynthesis at higher water temperatures than normal, accelerating the growth of the plants, green filamentous algae (cotton candy-like growth attached to rooted plants, docks, rocks, etc.), free-floating algae and cyanobacteria (''blue-green algae''). As the summer went on, precipitation became infrequent, and the level of the lake dropped, bringing the lake surface to the plants in many places. In addition, the Chautauqua Lake Association, which has historically mechanically harvested Chautauqua Lake plants, has had its state and county government funding significantly cut over the last two years, which greatly reduced the acreage of plants it could harvest in 2011.
So, what does this mean for the future conditions and management of the lake? According to climate models and meteorological data, our region of New York state is already experiencing the impacts of human-induced climate change, with more intense precipitation events and air and water temperatures warming faster on average during the spring and summer. Also, the number of days with ice cover on the lakes in the northern United States has measurably declined since the 1950s. We can anticipate our lakes losing their ice cover sooner and warming faster each spring, with more intense storms exacerbating soil erosion and carrying more nutrients and sediments into our water bodies. We can anticipate plants and algae growing faster, as temperatures reach thresholds for growth sooner each spring.
So what can we do about this? That will be addressed next Sunday in Part II.
The Chautauqua Watershed Conservancy presently has its 2011-12 membership drive underway and is seeking donations to conserve the Wells Bay Lakeshore Forest. To support these efforts or for more information on CWC's preventive watershed efforts, visit our website at www.chautauquawatershed.org, or call 664-2166.