This Sentinel 2 satellite photo of Chautauqua Lake shows abundant algal growth in the southern basin and a much clearer northern basin. (image courtesy Jill Singer)

Did you know that there is a war underway each summer in our lakes for nutrients and light? This war is between plants and algae! Like a football game, each side has many players who excel with differing abilities to use various nutrients and light. In this war, if the plants are winning, the lake has clearer, healthier waters. If the algae are winning, the lake has green or blue-green turbid water. Having moderate amounts of both plants and algae as the base of a lake’s food web is ideal for healthy abundant fisheries.

Chautauqua Lake is a naturally fertile and biologically productive lake with high concentrations of the critical nutrient phosphorus. According to the 2023 CSLAP report, the north basin, which is much deeper than the south basin, had a mean total phosphorus concentration of 0.03 mg/Liter, while the south basin had a mean concentration of 0.0526 mg/L. According to the Total Maximum Daily Load (TMDL) for Phosphorus (P) in Chautauqua Lake report (2012), both basins violate the New York State’s guidance value for total phosphorus: 0.020 mg/L. This 2023 value for the mean concentration in the south basin is more than double the desired level for enjoyable lake conditions. Human activities over decades have made this lake more fertile.

Shallow lakes can exist in alternative stable states: a clear-water state that typically supports abundant submerged vegetation and provides high quality wildlife habitat or a turbid-water state with frequent algal blooms, poor habitat, and few plants (Vitense, K. et al, 2019). Stable clear-water lakes generally support abundant fisheries and support recreational uses, but plants may impede uses to some degree. Stable turbid lakes generally suffer from degraded gamefish populations and frequent harmful algae blooms which make the water unfit for swimming. As a result, lakeshore property values are harmed by a lake tipping to the turbid state.

The south basin of Chautauqua Lake, with its excess phosphorus levels, highly developed watershed, and very shallow waters is in the range for a “bistable lake,” meaning that at many times the algae are winning the battle and sometimes the plants are winning the battle. This basin is susceptible to tipping into a stable turbid-state lake, with frequent harmful algae blooms shading out vital aquatic vegetation, resulting in the loss of abundant fisheries. Our valued fisheries depend upon healthy plant communities for reproduction, shelter, and food that plants provide for fish prey species. If algae blooms shade the south basin and the “narrows” make them devoid of most plants for three or more years, we will likely see a decline in our valuable fisheries as well as declining lakefront property values.

Could the south basin tip into a stable turbid-water state? In the 2019 Racine-Johnson Aquatic Ecologists plant and insect survey report, they wrote that the south basin was likely devoid of submerged aquatic plants from July through September, as a result of town- and village-sponsored herbicide treatments, exhibiting characteristics of a turbid state. During their plant survey, the inventory team noted the observation of “one of the thickest cyanobacteria scums we had observed on the water from Bemus Bay south to Burtis Bay.” They concluded that the herbicide treatments which eliminated the plant communities and were associated with extensive algal blooms, “… were detrimental to the lake community.” The authors noted, “Our late summer/early fall plant survey findings came as a shock and should alarm the stakeholders of Chautauqua Lake.”

Lake scientists know that, in overly fertile lakes, if too many plants are killed, removed, or eaten by fish, algae will take advantage of phosphorus not used by the plants and will grow abundantly. Vitense et al (2021) note that increases in populations of bottom feeding fish, such as carp and bullheads, and other perturbations can drive transitions to a turbid state. Vitense et al suggest that “encouraging the expansion of submerged aquatic plant cover substantially reduces the probability a clear lake will transition” [to a turbid state].

As a lake property owner, boater, and fisherman, I hope that scientists, community leaders, and consultants will heed this research and: 1) choose to maintain healthy, nutrient-absorbing aquatic plant communities by avoiding management practices that kill or remove significant parts of the plant community in our lake, 2) adopt new laws, and 3) employ conservation and management actions to effectively control phosphorus loading from the watershed and internal sources. Let’s work to push the south basin of the lake to have cleaner, clearer waters and away from the tipping point of becoming a stable turbid-state lake!

Chautauqua Watershed Conservancy is a nationally accredited land trust working to preserve and enhance the water quality, scenic beauty and ecological health of the lands and waters of the Chautauqua region. For more information, visit chautauquawatershed.org.