One month after the state issued a public health advisory for a harmful algal bloom in Logan County, the cyanobacteria covering Briggs Lake is nearly gone.
The Kentucky Energy and Environment Cabinet has been monitoring the harmful algal bloom – which was originally discovered as the Kentucky Division of Water was conducting ambient sampling in Briggs Lake on Sept. 22 – through satellite imagery.
“In the latest image, it appears to have cleared up throughout the majority of the lake, with a small portion still visible. We expect to resample it this week or next to reassess the advisory,” cabinet spokesperson Robin Hartman said in an email.
Blue-green algae, which is actually cyanobacteria, is common in Kentucky waterways. In 2016, the U.S. Geological Survey and Army Corps of Engineers partnered to study Nolin River Lake. They found high concentrations of nitrogen, phosphorous, chlorophyll and pheophytin at high levels in an adjacent riverine site to the lake, which had blue-green algae as the almost exclusive source of phytoplankton.
“All of our reservoirs in Kentucky are dominated by cyanobacteria in the phytoplankton community,” said Jade Young, a water quality biologist and limnologist for the USACE Louisville District.
When the Kentucky Division of Water sampled Briggs Lake last month, there were colonies of cyanobacteria visible across the entire lake. The thickest part of the bloom was on the northeast side, according to Hartman.
Algal blooms occur naturally with a combination of sunlight, warm weather, low-turbidity water and the presence of nutrients. But an excess of nutrients from agricultural runoff, stormwater runoff, wastewater, fossil fuel use, fertilizers, detergents or pet waste can cause harmful algal blooms, according to the Environmental Protection Agency.
In this situation, September’s statewide drought and extreme heat contributed to the bloom, according to Young, who described harmful algal blooms as a “new contaminant, relatively speaking.”
Harmful algal blooms produce toxins called microcystins, which pose significant health risks to people, pets and wildlife. State officials said ingested water might increase the risk of skin irritation and gastrointestinal symptoms such as stomach pain, nausea, vomiting and diarrhea.
As a safety precaution, USACE recommends avoiding waterways with visible algae and routinely washing life jackets and water equipment, Young said.
“We recommend avoiding contact with any visible algae,” Young said.
Bloom conditions can change rapidly. To view current advisories, visit the state’s Harmful Algal Bloom viewer at watermaps.ky.gov/HABs.
On Friday, the state’s recreational public health advisories for the harmful algal bloom in Briggs Lake and along parts of the Ohio River remained active.
From 1972 to 1975, the Environmental Protection Agency sampled major reservoirs impacted directly or indirectly by municipal sewage treatment plant discharge through the National Eutrophication Survey. (Eutrophication is when an excessive plant growth sucks up the oxygen in a body of water.)
Now, the EPA selects a random sample of lakes across the U.S. every five years for its National Lakes Assessments.
In 2016, the EPA released the findings from the 2012 sampling: 40 percent of lakes had excessive levels of total phosphorus and 35 percent had excessive levels of total nitrogen – both of which can contribute to algal blooms, low oxygen levels and harm to aquatic life. Microcystins were detected in 39 percent of the 1,038 lake sampled, but concentrations rarely (less than one percent) reached the moderate or high levels of concern established by the World Health Organization.
Nearly a third of the lakes had degraded benthic macroinvertebrate communities and about a fifth had degraded zooplankton communities.
The assessment analyses linked the biological condition of lakes with phosphorus pollution, in particular.