What do we know about the sources of nutrients fueling algae blooms and plant growth in Chautauqua Lake?
The deeper glacial till soils of our region contain an abundance of phosphorus, which makes the sediments and waters in our lakes naturally more fertile and able to support more algae and aquatic plant growth. Human activities (especially since European settlers arrived) have cleared forests, conducted intensive animal and crop agriculture, and developed roads, parking lots, buildings, and lawns which have accelerated the deposition of nutrient-laden soils, animal wastes, crop fertilizers, and human sewage into Chautauqua Lake. Nutrients, sediments, metals, synthetic organic chemicals, and other pollutants are also delivered to our watersheds and lakes by wind and precipitation.
The shallower southern basin of Chautauqua Lake has an average depth of about 11 feet, while the northern basin has an average depth of about 33 feet. The northern basin has much more water volume than the southern basin. Wind, wave, and boat action easily resuspend sediments, causing turbid conditions much more frequently in the southern basin. It also makes it easier for water to mix and not stratify due to water temperatures in the southern basin. Nutrients in the lake’s water generally become more concentrated in the shallower basin and toward Celoron. More developed suburban and urban land uses in general deliver more pollutants to the lake than the more heavily forested rural areas, and since the lake is quite shallow, lake plant and algae conditions are consistently more problematic in Lakewood east to Celoron. Once the nutrient phosphorus gets in the lake, a significant portion of the annual load reaching the lake stays in the lake. Lake plants and algae containing phosphorus die and decay. Some of that phosphorus is released to the water column, and some accumulates in the sediments.
Phosphorus is most often the nutrient element limiting algae and plant growth in Chautauqua Lake, with nitrogen sometimes limiting as well. These nutrients come primarily from runoff from the watershed and secondarily from precipitation and wind deposition of soil and leaf materials. Phosphorus can be in a dissolved form very readily available for absorption and use by algae and plants, in organic form as part of plant and animal materials, or tightly bound to soil particles. The 2012 Total Maximum Daily Load for Phosphorus in Chautauqua Lake report estimated that 25% of the phosphorus load to the northern basin of the lake was from internal loading released from sediments and that 55% of the load to the southern basin was from internal loading.
Researchers from the Jefferson Project, SUNY-Fredonia, and Bowling Green State University are using multiple sampling and monitoring approaches over several years with the intent to better understand the watershed nutrient loading and internal nutrient loading to the lake and the lake stratification, weather, and wind conditions as they relate to what triggers problematic harmful algae blooms. The completion of tertiary wastewater treatment plants in Mayville and Chautauqua have substantially reduced human sources of annual phosphorus loading to the entire lake over the last 10 years. Installing public sewers along more of the lake is also reducing human nutrient loading to the lake.
Preliminary data indicate that heavy rainfall storm events with heavy phosphorus pulses to the lake, hot and calm weather, and strong summer lake water temperature stratification setting up oxygen-deficient conditions in deep waters promoting the release of phosphorus from sediments followed by strong wind water mixing events, can all be factors in making phosphorus abundant and available for harmful algae blooms. In addition, the deep northern basin may react differently to these factors than the shallow southern basin. Warmer waters from climate change may enhance lake stratification and accelerate the release of phosphorus from sediments.
We know that excessive nutrient and sediment loading from poorly managed agricultural practices, wastewater treatment systems, and urban land uses all load the lake with nutrients that fuel plant and algae growth and that phosphorus loading to the lake is cumulative. The more we substantially reduce the amount of nutrients and sediments reaching the lake today, the better the conditions will be in the lake tomorrow!
by John Jablonski III, CWC Executive Director