Last week, Biomonitoring Coordinator Adrianna Hirtler traveled around Cayuga Lake to collect samples of phytoplankton including cyanobacteria for analysis at CSI’s certified water testing lab. The ongoing survey is helping CSI build a better understanding of Cayuga Lake’s natural cyanobacteria populations, the photosynthesizing bacteria that form harmful algal blooms.
During the survey, Adrianna traveled to eight locations around the lake. At each location, except for Cayuga Lake State Park where too much ice was still present, she collected both a grab sample of lake water, and a sample of lake water concentrated roughly 5,000 fold using a plankton net. Back at the lab each sample was analyzed under a compound microscope to identify which types of cyanobacteria and other phytoplankton were present. This survey was conducted as part of the Cayuga Lake Phytoplankton Project, an effort by CSI to survey cyanobacteria density and toxin production in Cayuga Lake during non-bloom conditions. The project began with an initial survey in April of 2019. A survey of phytoplankton was then conducted every two weeks from late July until November, providing “snapshots” of non-bloom phytoplankton and cyanobacteria populations before, during, and after the summer months when harmful algal blooms are usually observed. Preliminary results suggest that the cyanobacteria genus Microcystis is present in the lake, and can produce microcystin toxin, during non-bloom conditions. These observations were highlighted in our recent newsletter, the Fall 2019 Water Bulletin, which is available under the Outreach and Education tab on our website. They imply a simple relationship, i.e., the more Microcystis, the more microcystin toxin.
This week, there were no obvious signs of cyanobacteria in any of the seven grab samples. Sparse colonies of cyanobacteria were observed in the concentrated plankton net samples collected from three of the seven locations: the shoreline of Union Springs, the boat launch at Mud Lock Canal Park at the northern outlet of the lake, and at Dean’s Cove Boat Launch. The colonies of cyanobacteria observed in these samples were far more sparse than anything that resembes a bloom of cyanobacteria, i.e., a harmful algal bloom.
A few colonies of the cyanobacteria Microcystis observed in a sample of highly concentrated lake water collected on February 25, 2020.
As summer approaches we will be tracking how the non-bloom populations of cyanobacteria and other phytoplankton may change. With our dedicated volunteer partners around the lake, CSI will also continue to monitor and report any blooms that may occur.