Benthic algae mats are typically attached to riverbeds or lakebeds, but pieces of the mats can detach and float on the surface of the waterbody or wash ashore

VANCOUVER – Clark County residents and dog owners who recreate in the Columbia River and along its shorelines should be on the lookout for a newly reported type of harmful algae that caused the death of a dog in October.

Benthic algae mats are typically attached to riverbeds or lakebeds, but pieces of the mats can detach and float on the surface of the waterbody or wash ashore. The algae mats can contain toxins that can make people and pets sick and can be fatal to pets.

Clark County Public Health first learned about the presence of benthic algae mats in Clark County when a dog died after eating algae along the shoreline of an island in the Columbia River in October. Testing of the dog’s stomach contents and samples of algae collected from the site by Public Health staff indicated cyanotoxin poisoning as the cause of the dog’s death. After identifying the cause of the dog’s death, Public Health posted educational signs about benthic algae mats at marinas and boat launches on the Columbia River.

Earlier this week, Public Health received a report of possible benthic algae mat material along the Columbia River shoreline at Cottonwood Beach in Washougal. Public Health staff visited Cottonwood Beach and found algae that appears similar to the algae that caused the dog’s death in October.

Public Health has not received any reports of illness linked to algae exposure at Cottonwood Beach, and it’s unclear whether the algae found at Cottonwood Beach contains toxins that could be harmful to people and pets.

As a precaution, Public Health has posted educational signs about benthic algae mats at Cottonwood Beach. And Public Health is urging residents to check for potentially harmful algae anytime they are recreating in and along the Columbia River and other waterbodies this summer.

Benthic algae mats can grow in fast- and slow-moving water and do not impact water clarity. People should check the shorelines of water bodies for clumps or blobs of algae that may be bright or dark green, yellow, brown, orange or red. The algae can be slimy, gelatinous or slippery, and it may have a foul odor.

If algae mat material is present, people and pets should avoid contact with the algae and the water. Dogs and children are particularly susceptible to the effects of toxins from algae. Do not let children touch or put algae in their mouths, and do not let dogs eat the algae or drink from water where algae are present.

Residents should also check local water bodies for blooms of harmful algae (planktonic algae blooms). These algae blooms are more familiar to Clark County residents, as they often grow and produce toxins that result in advisories at local lakes, such as Vancouver Lake and Lacamas Lake in Camas. Planktonic algae blooms grow in stagnant or slow-moving water and often cause water to appear scummy on the surface.

Both types of algae – planktonic blooms and benthic mats – can produce toxins that are harmful to people and pets.

Information about advisories and locations where possible benthic algae mats have been identified is available on the Public Health website.

Additional resources:

• Toxic algae mats brochure
• Toxic algae mats postcard
• Public Health harmful algal blooms webpage
• Public Health current advisories webpage

Information provided by Clark Co. WA Communications.