Testing Bantam Lake for potentially harmful cyanobacteria

A cyanobacteria, phormidium (cluster of rods, center), and a zooplankton, Bosmina longirostris (bottom)

     With help from the Northeast Cyanobacteria Monitoring Program, we are reviewing the species composition of the "blue-green algae" in Bantam Lake and other water bodies on the property.  We frequently use the University of New Hampshire's Center for Freshwater Biology for identifying the so-called "Dirty Dozen" species of cyanobacteria, as well as phytoplankton and zooplankton.  Our observations are reported to the Cyanoscope iNaturalist.
     Cyanobacteria are naturally occurring photosynthetic organisms that live within the top ten feet of surface water.  While these organisms are usually harmless and nearly omnipresent, high concentrations of them known as blooms concentrate the toxins they releases.  When this happens, they can cause harm to fish, aquatic plants, and amphibians, as well as terrestrial animals who swim or drink water in which there's been a bloom.  Blooms can be caused by a shift in the nutrient levels in water, like an increase in nitrogen caused by fertilizer runoff.  Blooms usually occur in warm weather.
      The Dirty Dozen are the twelve most commonly observed species of cyanobacteria in New England.  We've sampled water from Beaver Pond, Bantam River, and Litchfield Town Beach, and will sample from several other locations on Bantam Lake.  So far, we've found nine of the twelve.  They are not present in large enough quantities to be harmful, and some, like phormidium, can be indicators of clean water when in normal quantities.  By sampling at Bantam Lake, we are hoping to better understand the community of cyanobacteria present in the lake.  Shifts in the species present could tell us more about water quality and hopefully warn us before a bloom occurs.