Blue green algae summary

HLWA president Geoff Harvey wrote the following excellent summary of the recent blue green algae bloom. We’re still trying to get this published as a guest editorial in the CDA Press but wanted to share it on the website in the meantime.  

Hayden Lake residents most likely read the short health advisory news article in the Coeur d’Alene Press or if you boat or fish on the north part of Hayden Lake you probably have seen the seen the posted advisory:  blue green algae bloom, potentially toxic.  The algae bloom has faded and health advisory has been lifted, but the episode provides us residents and users of Hayden Lake with a clear message.

  The algae found is one of the most primitive life form, a cyno-bacteria, more closely allied with bacteria than higher plants.  The life form is given the name algae because it practices photosynthesis like more sophisticated plants.  In fact, this life form and its brethren are believed to have oxygenated earth’s atmosphere in the distant past.  The blue green algae arealso capable of fixing their own nitrogen from the air.  Some of these life forms, including the Anabenna recently identified in the lake, are capable, under some environmental conditions, of producing a neurotoxin that is deadly to mammals, including humans, if ingested.   Pets and small children are at highest risk, because of their small body size, hence the warnings by Panhandle Health District and the Idaho Department of Environmental Quality.

 The conditions that permitted this algae bloom are often present during the summer in the Lake’s northern arm.  The north arm of Hayden Lake is a consequence of the Lake’s impoundment by the Hayden Lake dike.  The dike raised the Lake’s normal summer high water mark and flooded pastureland along Hayden Creek north of Henry’s point, the natural terminus of the Lake.  This shallow area of the Lake is only four to six feet deep during the summer months.  Each summer it fills with aquatic plants and these, together with higher than normal spring runoff, increase the phosphorous content of the northern arm’s waters. Algae need the high phosphorous content to rapidly proliferate.  Rapid proliferation of any algae is referred to as a bloom. The higher volume and depth of the main pool of the lake dilutes incoming waters to the point that blooms are much more unlikely.  The algae in the recent bloom were likely present for some time unnoticed in the weedy waters of the north arm.  North winds that occurred a day or two prior to the alarm, likely pushed water containing the algae out into the main lake where it was starved for nitrogen and rose to the surface to fix the nitrogen it requires from the atmosphere.  When the algae concentrated at the surface, it became noticeable to the public and DEQ, and testing was completed and the alarm sounded.

 The preceding rather involved discussion of this event makes a simple point: our alteration and our very presence around Hayden Lake create situations that can become a danger to public health.   The impoundment created the weed problem in the northern arm and other artificial shallows of the lake.  The weeds likely help create nutrient conditions that can, given the correct water temperatures, spawn potentially dangerous blue green algae blooms.  No less threatening is the hazard to safe boating from the debris washed into the lake or the docks parts left to drift about at high water.  Hayden Lake, like all of our lakes, has departed from its natural state, when development occurred. Hayden Lake needs a certain level of active management through projects like phosphorous control, aquatic weed and debris removal that will control these hazards.  The fact is clear to most that the state and county have neither the interest nor funding to manage these problems which exist on many of our lakes in North Idaho.  Fortunately Hayden Lake has formed around it a Watershed Improvement District that has been dormant since the 1960s but has the potential to manage many of these problems and spread the management cost among all the watershed landowners in an equitable manner.  The Governor has reconstituted the board of this district through appointments until an election can be held.  Through the Hayden Lake Watershed Improvement District, Hayden Lake’s residents can have an opportunity to manage those bad situations created by humans altering the natural state around the lake.  Find out more about the Hayden Lake Watershed Improvement District by visiting the Watershed Association’s website at

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