Are You Fertilizing The Lake?

By John Jablonski III, CWC Executive Director

Is lawn fertilization contributing to Chautauqua Lake’s algae blooms?  Chautauqua Lake has experienced seasonal algae blooms for decades.  It has always been a relatively fertile lake, with abundant plant and algae contributing to very productive panfish, smallmouth and largemouth bass, and muskellunge fisheries.  Our lake has suffered from more prolonged harmful algae blooms in recent summers.  Changes in the lake community after its invasion by zebra mussels, global warming and possibly other contributing factors have caused blue-green algae (cyanobacteria) blooms to be documented at various locations in the lake resulting in beach closures and advisories against swimming more often.  Cyanobacteria sometimes produce toxins that can be poisonous to pets and humans.  Blooms with the toxins present are called “harmful algae blooms” or HABs for short.

What does it take to produce a bloom?  The cyanobacteria need to be present with warm water, sunshine and nutrients – especially phosphorus (P) and nitrogen (N) – in order to grow and reproduce rapidly, thus creating a bloom.  In freshwater lakes, phosphorus is a main driver of algae blooms. New York State prohibits the sale of lawn fertilizers containing phosphorus for routine lawn fertilization.  One can purchase lawn “starter” fertilizer containing P to help germinate recently seeded lawns.  Phosphorus is naturally abundant in most soils in our region.  P comes from treated wastewater, runoff from fertilized crop fields and pastures and as part of soil eroded from yards, fields, stream banks, and construction sites.  It falls from the sky as a pollutant in precipitation.  Nitrogen is different.  Many species of cyanobacteria can get their nitrogen directly from nitrogen gas dissolved in lake water.  Our atmosphere is 78% nitrogen.  Many cyanobacteria need abundant phosphorus to grow but don’t need nitrogen in the “fixed” form of ammonia or nitrate to grow.  However, nitrogen in the form of ammonia, urea or nitrates  is much more efficiently used than gaseous nitrogen.  Recent research on Chautauqua Lake by SUNY-Fredonia researcher Jennifer Phillips Russo, working with Courtney Wigdahl-Perry, Ph.D., indicates that the growth of cyanobacteria implicated in “blue green algae” blooms in Chautauqua Lake, may be promoted by fixed nitrogen in the form of ammonia or nitrate.  In Russo’s experiments, cyanobacteria growth accelerated with when abundant phosphorus and these nitrogen compounds are present.  This is affirmed by similar findings for Microcystis for Lake Erie.  The SUNY-Fredonia Benchmark Chautauqua Lake Studies had also indicated that algae abundance was limited by available nitrogen compounds in the 1970s.  Other research has found that the abundant cyanobacteria in the Lake is of the species that need nitrogen in the water in a form other than the gaseous form in order to grow abundantly to form blooms.

Where does “fixed” nitrogen come from?  Soil organisms can obtain nitrogen in the air and use it to form nitrogen compounds more readily available for plants and algae.  It comes from animal and plant wastes.  It comes from human wastes.  It comes from fertilizers spread to grow crops and lawns across our watersheds.  

Wastewater treatment plants on Chautauqua Lake have limits on the amount of nitrogen compounds that can be released to the lake.  Nitrates from animal wastes, fertilizers and septic systems are soluble and can pass through the soil into the nearest water body or into well water.  Many farms in our region are implementing agricultural environmental management plans to reduce loss of nutrients from cropland to waterways. Turf grass, such as Kentucky blue grass in lawns, needs annual applications of nitrogen fertilizer to be healthy in a lawn.  Other species need less nitrogen.  Fertilizing lakefront and watershed lawns in the summer may directly contribute to feeding harmful algae blooms in our lakes.  Just because the product says “phosphate-free” doesn’t mean it won’t fertilize lake algae and plants.

If you choose to fertilize your lawn.  To avoid fertilizing lake algae and plants, follow the recommendations in the Cornell Lawn Care Without Pesticides publication that, for most low maintenance lawns, a fall application of nitrogen fertilizer is best (between Halloween and Thanksgiving).  Following this recommendation will make it least likely that the nitrogen in the fertilizer will wash into the nearest waterway and into the lake where it can fuel nuisance algae blooms during the summer season. You can access the entire Lawn Care Without Pesticides document for more detailed lawn care information at  

The Conservancy invites all landowners and landscapers to “get on board” to starve the algae and save our lakes by carefully managing healthy landscapes for healthy waters! Contact the CWC for assistance with landscaping your yard or grounds to improve its benefits for clean water and wildlife habitat.

CWC will be holding its annual meeting at 5 PM Saturday, July 20th at Webb’s with Dr. Rebecca Schneider, Department of Natural Resources, Cornell University, presenting on the impacts of global warming on our waters and the role of land trusts in addressing those impacts. The public is invited to attend.  For more information, visit or, or call 664-2166.

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