Potential harmful algal bloom spotted in New Melones near Camp Nine bridge

The state has identified a potential harmful algal bloom at New Melones Reservoir downstream of the log jam and Camp Nine bridge in Calaveras County.

A potential harmful algal bloom (HAB) has been identified at New Melones Reservoir downstream of the log jam and Camp Nine bridge in Calaveras County.

Algae appears naturally every summer in lakes and reservoirs across the country, but one species of a group of organisms known as cyanobacteria (blue-green algae) produces toxic compounds called cyanotoxins that can present health hazards when in abundance, per a July 20 public service announcement from the California State Water Boards and the local health departments in Calaveras and Tuolumne counties. The “California State Water Boards” consist of the State Water Resources Control Board and the nine Regional Water Quality Control Boards.

Greener water and cyanobacteria at New Melones were observed via a state-operated satellite tool that provides data to help prioritize where field sampling should be conducted and when to reach out to local health and water body managers.

Exposure to blue-green algae can result in rashes or other skin irritation, allergy-like reactions, runny nose or sore throat.

If blue-green algae is ingested in large amounts, symptoms could include sharp severe stomach aches, diarrhea and vomiting, liver damage, numb limbs, tingling fingers and toes, and dizziness.

Young children and dogs are at higher risk to cyanotoxin exposure since they’re more likely to drink water while wading and swimming, often stay in longer than adults, and have a smaller body size than adults.

Blue-green algae has been described as “pea soup or spilled paint on the surface and can also produce a swampy odor when the cells break down.”

“Bloom awareness” signs have been posted at New Melones, and “We encourage visitors to all water bodies to practice healthy water habits at all times,” the announcement states.

New Melones Lake park manager Cynthia Davenport said the area is mostly used by fisherman.

“At New Melones, we are watching the satellite data and communicating with the Bureau of Reclamation and County Environmental Health,” California Freshwater Harmful Algal Blooms Program Lead Keith Bouma-Gregson, Ph.D. told the Enterprise in an email Monday. “If the bloom intensifies, we will be collecting samples and updating any advisory levels based on cyanotoxin concentrations.”

Such is the protocol for any harmful algal bloom (HAB) identified in water bodies in Calaveras County.

This is the first HAB identified in Calaveras County this year, based on the state HAB Incident Reports Map.

New public reports of a bloom would initiate a multi-agency investigation, Bouma-Gregson said.

Reports of these blooms have steadily increased across the state from 91 in 2016 to 241 reports in 2019, according to a State Water Boards Frequently Asked Questions sheet.

They’re caused, in part, by increased inputs of nutrients like nitrogen and phosphorus from fertilizers and human or animal waste.

Additionally, low flows; stagnant water; increased intensity and duration of sunlight; and sustained high temperatures facilitate ideal conditions for cyanobacteria. Research suggests rising temperatures and changing precipitation patterns caused by climate change have catalyzed cyanobacteria growth.

It’s unknown whether there’s been an increase in frequency of blooms in the Sierra foothills, due to a lack of comprehensive monitoring data, Bouma-Gregson said.

To report a suspicious bloom, or an animal illness or human illness potentially related to a bloom, call (916) 341-5357 or call toll free: 1 (844) 729-6466 or email CyanoHAB.Reports@waterboards.ca.gov.

Residents can also call the Calaveras County Environmental Health Department at 754-6399 or the Tuolumne County Environmental Health Department at 533-5990 to report a bloom.

For more information about harmful algal blooms, visit the following pages:



Davis graduated from UC Santa Cruz with a degree in Environmental Studies. He covers environmental issues, agriculture, fire and local government. Davis spends his free time playing guitar and hiking with his dog, Penny.

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