Thursday, July 18, 2024

OUR GEM: Harmful algal blooms pose risk

| June 16, 2024 1:00 AM

Freshwater algae are a natural and important part of lake, river and stream ecosystems. They produce oxygen by photosynthesis, take up nutrients such as phosphorus from water and are the foundation of aquatic food webs. As with many things in life, there can be too much of a good thing. 

Algae can grow excessively if conditions are right. They can be unsightly, smelly and a nuisance during peak recreation months. If conditions are right (actually, wrong) some species of “algae” can produce toxins with potential health risks. 

Excess algae is usually referred to as a “bloom,” and blooms containing those species that produce toxins are referred to as “harmful algal blooms." These HABs are caused by cyanobacteria, sometimes referred to as blue-green algae, some of which can — but not always — produce cyanotoxins.  

What do they look like? 

There are many species of cyanobacteria, and their appearance can vary. HABs can appear as discolored water, streaks or globs of scum, and/or thick green mats or scum along shorelines. The blooms can also vary in color. They can be soupy green, iridescent green or brown. There are many examples and tools to help identify HABs contained in the links at the end of this article. 

A common aquatic plant often mistaken as a HAB is duckweed, a tiny, free-floating aquatic plant found in lakes, wetlands and slow-moving bodies of water in clusters. Filamentous green algae are also commonly mistaken as a HAB, along with pine pollen accumulating on water. 


Some contributors to HABs are known and others not. Also, not all HABs produce toxins. The determining factors for whether toxins are actually produced in a HAB are not well understood. 

Warmer water temperatures, longer growing seasons and excessive nutrients from runoff across the landscape have been linked to HABs. However, there are factors that are still unknown. 

The Environmental Protection Agency states on their website that, “Scientists are learning that … the ratio of nitrogen to phosphorus, organic nutrient supply, temperature, and light attenuation, play important and interacting roles in determining HAB composition and toxin production. The precise drivers of toxin production are still an active area of research.” Future research can help us to understand and better predict the occurrence of HABs. 

What are the risks? 

HABs can have harmful health effects to the skin, liver and nervous system when accompanied by cyanotoxin production. Although uncommon in our region, HABs can cause serious illness to our pets and wildlife. HABs can also have an economic impact, not only in the expense of monitoring, reporting and research, but also through decreases in recreational activity that our region relies on for revenue.  

How should you protect yourself, family and pets? 

The main way to protect yourself, family and pets is to stay out of waters that exhibit HAB conditions or have a HAB posting. If you, your family or pets do encounter potential HABs, rinse with clean water. Do not eat fish from a water body with suspected HABs. 

How to do your part 

Reduce your nutrient footprint by minimizing the amount of fertilizer and water you apply to your yard. Be mindful of pet waste and other nutrient loads, such as loose soil, that make their way to our waters via storm drains and surface runoff. Support local agricultural upgrades in your community such as riparian area restoration or enhancements.

Suspect a HAB?  

You can report a potential HAB and get more information about HABs from the Idaho Department of Environmental Quality’s website. The Idaho Department of Health and Welfare and Panhandle Health District issue recreational health advisories for HABS and other health concerns. 

Working together, these entities inform the public if there’s a confirmed HAB and if a health advisory is needed to keep the public safe from potential risks.  

Recreation is at the heart of our community. We must all do our part in protecting our waters and the people that enjoy them.   

The Our Gem Coeur d’Alene Lake Collaborative is a team of committed and passionate professionals working to preserve lake health and protect water quality by promoting community awareness of local water resources through education, outreach and stewardship. Our Gem includes local experts from the University of Idaho — Idaho Water Resources Research Institute, Coeur d’Alene Tribe, Idaho Department of Environmental Quality, the Basin Environmental Improvement Project Commission, Kootenai Environmental Alliance and the Coeur d’Alene Regional Chamber of Commerce.

    A harmful algal bloom in Cocolalla Lake.