Freshwater Harmful Algal Bloom (HABs) of The Pacific Northwest

By Sarra Soladey


About HABs

Everywhere in the world, harmful algal blooms (HABs) have been increasing in occurrence and in the extent of stay. Both in marine waters and freshwaters the two types of HABs, toxin producers and high mass producers, are wreaking havoc on ecosystems, both in and out of the water. In the Pacific Northwest we deal with types of toxin producing HABs called cyanobacteria, also known as blue-green algae. Cyanobacteria releases toxins, promptly called cyanotoxins, which can affect liver, kidneys and the nervous system causing illness or even death. Factors that have helped caused this increase can be chalked up to climate change and increasing agricultural pollution. HABs when there is an abundance of nitrogen and phosphorus in the water which can come from farm water run off because farming materials like fertilizer and pesticides contain these. Other factors that HABs like are warmer water temperatures, which unfortunately for us is a common side effect of the increase of greenhouse gasses.


Focus Area

For my study into what types of cyanobacteria grow in the Pacific Northwest I focused on Washington, Clackamas, and Multnomah Counties in Oregon. The following waterbodies are only a few that are affected in Oregon. Cyanobacteria  have and will cause death or illness in pets and livestock, so be aware of what your dog may drink out on a walk. Many states are now testing waterbodies for levels of toxins in the water and will put advisories when they exceed a harmful limit. Here is the site for current advisories in Oregon,


Focus Area Map

Focus Area Table
Waterbody County Main Cyanobacteria
Blue Lake Multnomah Microcystic Aeruginosa
Fairview Lake Multnomah Anabaena sp.
Lake Oswego Clackamas Microcystic Aeruginosa
Laurelhurst Pond (Firwood Lake) Multnomah Microcystic Aeruginosa
North Fork Reservoir Clackamas Anabaena Planktonic
Timothy Lake Clackamas Anabaena sp.
Tualatin River Washington Anabaena Flos-aquae
Wapato Lake Washington Anabaena Flos-aquae

(to learn more about the bacteria and the cyanotoxin they produce click the link)




Click here

to read about general signs if a HABs Bloom is in your area. It is important to note that not all algal blooms are dangerous but the difference between the two maybe hard to tell. Be safe out there!



DOST PNRI. Harmful Algal Blooms (HAB) [Video File]. Youtube, March 29, 2017.

Reactions. What Makes Blue-Green Algae Dangerous? – Speaking of Chemistry [Video File]. Youtube, June 2, 2016.

Oregon Health Authority. Cyanobacteria Advisory Archive.

Oregon Department of Environmental Quality. Harmful Algae Bloom (HAB) Strategy.

United States Geological Survey. Upstream Factors Affecting Tualatin River Algae – Tracking the 2008 Anabaena Algae Bloom to Wapato Lake, Oregon.