What is Causing the Algal Blooms?

Remember the equation: sunlight + temp + nutrients = bloom. We have had a relatively mild spring in terms of solar radiation coming into the holiday weekend. I know this both from the meterological data and from the fact that I received dandy sunburn on my pale skin over the weekend. So, part one of the equation was definitely satisfied in the past few days. As for temp, water temps were in the mid 60’s all the way up to the holiday weekend. By Monday, water temps were over 80 F in the shallow bays. 15-20 degrees F in a matter of days is hard on almost everything in our lakes except for aquatic plants and algae. Lastly, we have nutrients. Over the past few seasons we have documented that as beneficial native aquatic plants wake up and start growing in the spring, there is a marked decrease of phosphorus concentrations in the water column. This is ideal and what we are trying to foster. If the nutrients are taken up by beneficial aquatic vascular plants, they will not be available to algae for blooming. This is nature’s form of algal control and in an intact and diverse aquatic ecosystem, it is very effective. But, every year there is more and more phosphorus entering our lakes. We have identified the major sources and the CLPOC has taken actions to minimize the gross inputs. Last year at this time we saw a similar effect with terrestrial inputs (grass clippings, Aspen and other tree pollen and “fuzz”, fertilizers, erosion…) are washed or blown into the lakes. They breakdown and can release a tremendous amount of nutrients. The nutrients are released at a rate that exceeds the rate native beneficial aquatic plants can take them in and lock them up and away from nuisance algae. This spring has been a banner year for flower, bloom, pollen production and much of it has ended up in the lakes. Looking out my window as I write this there is so much Cottonwood fuzz in the air that it looks like it is snowing and this has been going on for the past two weeks or longer.