As temperatures rise, so do reports of algae blooms in marine waters.

The Island County Public Health Department was notified of a “red tide” in Holmes Harbor on South Whidbey. People called to ask if it’s safe to swim, harvest crab or allow their dogs into the water.

A red tide does not indicate toxins in the water. Reddish water is often caused by Noctiluca, an algae bloom that is harmless to humans. Some people say it looks like streaks of tomato soup in the water.

Red tides are not uncommon in Holmes Harbor and Penn Cove in summer. A basket of mussels hangs from a private dock near the south end of Holmes Harbor and a trained volunteer collects a sample every two weeks for testing.

Other volunteers collect shellfish for testing along several shores of Island County. Mussels filter food from the water column so they usually indicate the presence of biotoxins before clams and oysters that feed in the sand.

The Island County Public Health Department works with the State Department of Health and trained volunteers to monitor both shellfish and water quality on Whidbey and Camano Islands.

Biotoxins naturally occur in marine waters and can cause Paralytic Shellfish Poisoning, Amnesic Shellfish Poisoning and Diarrhetic Shellfish Poisoning, which can cause serious illness and sometimes even death.

These toxins cannot be cooked or frozen out. Marine biotoxins are not visible to the naked eye. The only way to determine if water and shellfish are safe is to test them in a lab. Once shellfish are tested, the results are sent to the State Department of Health and the County Public Health Departments.

Appropriate signs are posted at those sites to alert the public.

The latest test results indicate safe shellfish in Holmes Harbor but these toxins can change overnight.

It’s important to call the state hotline number, 1-800-562-5632, or visit their clickable map at www.doh.wa.gov/shellfishsafety.htm before harvesting or eating shellfish.

If the tests show a presence of biotoxins, the Health Department closes the beach until further testing shows the toxins have cleared.

Water samples are taken weekly throughout the summer at some of our popular beach parks. The State Department of Ecology’s BEACH program funds water sampling at Freeland County Park, Dave Mackie Park at Maxwelton Beach, and Windjammer Park and swimming lagoon in Oak Harbor.

If water quality test results indicate high levels of harmful fecal coliform bacteria, signs are posted on those beaches until water quality improves.

Beaches contaminated with harmful bacteria are a public health risk. Beaches that are near a sewer or stormwater outfall pipe, or a marina, have permanent swimming and shellfish advisories.

To find the latest test results from your favorite beach visit www.ecy.wa.gov/programs/eap/beach/

Maribeth Crandell is an employee for Island County Public Health.