Toxic algae warning rises to ‘danger’ level at Fresno-area lake. ‘Stay out of the water’
A warning about toxic algae at Hensley Lake in Madera County was recently elevated from a “caution” to a “danger” advisory by the California State Water Resources Control Board.
“STAY OUT OF THE WATER,” an entry about Hensley Lake, updated Friday, reads on a map of harmful algal blooms around California, maintained by the State Water Board. “Do not touch scum in the water or shore. Do NOT let pets go in the water, drink the water, or eat scum on the shore. Do not eat shellfish from this waterbody.”
The danger advisory is for a location on the east side of the lake. The west side remains under a caution advisory, two tiers below the state’s most severe “danger” warning for toxic algae.
The danger area is described as being around Hensley Lake’s Buck Ridge boat launch, the east floating dock.
Concentrations of microcystin, a toxin produced by cyanobacteria, were found to be 148 micrograms per liter in that area – far above the threshold of over 20, when levels are deemed high enough for a danger advisory, the Central Valley Regional Water Quality Control Board told Madera County.
That was from an Aug. 9 sampling of scum. A dead fish was also near where the sample was collected, officials reported.
Dexter Marr, deputy director of the Madera County Environmental Health Division, said warning signs have been updated from “caution” to “danger” on the east side by the U.S. Army Corps of Engineers, which maintains Hensley Lake.
Marr said a social media post about the algae, shared by the Madera County Department of Public Health on Saturday, should have been the danger flier, not the caution one that was posted on its Facebook page. The caution poster says, “You can swim in this water, but stay away from algae and scum in the water” while the elevated danger image states, “Stay out of the water until further notice. Do not touch scum in the water or on shore.”
The State Water Boards’ caution advisory for Hensley Lake’s western floating dock adds, “Do NOT let pets go in the water, drink the water, or eat scum on the shore.”
Algal bloom monitoring at Hensley Lake has been ongoing. Marr wasn’t sure on Wednesday what the next steps are for testing or possible treatments there.
Hensley Lake is the only Madera County location Marr is aware of with the highest “danger” level advisory for harmful algae. Eastman Lake, along with Beasore and Willow creeks, are other Madera County locations on the state’s harmful algal blooms map, which relies on voluntary reporting that’s then reviewed by the State Water Board. There are dozens of harmful algal blooms recorded throughout the central San Joaquin Valley and California.
Algae considered in Mariposa family death investigation
The state’s algal bloom listing for Hensley Lake was updated three days after a Mariposa family was mysteriously found dead along a Sierra National Forest trail in Mariposa County.
Mariposa County Sheriff Jeremy Briese said toxic algae is among things being considered in the case with “no smoking gun” clues. The sheriff’s office didn’t release new updates about that investigation on Wednesday. Toxicology results are pending.
The Mariposa family was found dead a couple miles from the south fork of the Merced River, Briese said, which has a known harmful algal bloom.
More samples were collected from that location last week by officials. The State Water Board expects to have results from those tests within two weeks. There is currently a “caution” advisory from the state for the algal bloom in that area.
The California Department of Public Health reported that while animals have been poisoned from algae, “no known human fatalities have been documented from recreational or drinking water exposure to cyanobacterial toxins” that can be found in algae. Not all algae is harmful, but some species can produce toxins (poisons).
This story was originally published August 26, 2021 at 7:45 AM.
