Hot summer days at Clear Lake normally mean algae blooms. It’s also the time when many local residents and visitors complain about the algae and demand that the county do something about it.
Algae are tiny water plants that cycle normally between the bottom and the surface, floating up and sinking down. During daytime hours algae generates oxygen within the lake. During the night algae consumes oxygen.
Clear Lake is a naturally eutrophic lake. Eutrophic lakes are nutrient rich and very productive, supporting the growth of algae and aquatic plants. Algae has been part of Clear Lake for tens of thousands of years. Research shows that Clear Lake has only been clear for very short periods, mainly during the winter months. Algae normally starts to form in May and can continue to bloom until well into October. Blue-green algae (Cyanobacteria) is one of the more common forms of algae and is actually a bacteria and reproduces by photosynthesis. To add to the confusion there are more than 100 species of algae in Clear Lake. However, not all bloom each year.
The question that just about everyone is asking is how do we get rid of it? It’s much easier to prevent it from growing in the first place rather than trying to eradicate it after it has spread around the lake. Algae needs nutrients to grow and the best preventative method is to control the amount of nutrients flowing into the lake. Nutrients, especially phosphorus, wash into the lake from nearby farm land and even the hills. These nutrients combined with hot and sunny weather are ideal conditions for algae growth.
Getting rid of the blue-green algae once it has become established is a challenging task. One of the most effective methods is by aerating the water. Spraying water on the algae mats causes them to break up and sink to the bottom. In fact, a number of lakeside residents spray daily around their docks with water to disperses the algae. The sprayed water aerates the algae and causes it to sink to the bottom. Another effective method is to equip a pontoon boat with high-pressure water hoses and spray the algae mats. This would be a good project for the county to embrace. The county could purchase the pontoon boats and equip them. Volunteer crews could man the boats and cruise the shoreline spraying the mats.
Algae is not always bad. The algae in Clear Lake forms part of the natural food chain and keeps the lake fertile and healthy. Because of the lake’s relative shallowness and warm summer temperatures, the algae serves another important purpose. It keep the sun’s rays from reaching the bottom, thus reducing the growth of water weeds, which choke off the lake.
The rains that arrive in the fall will disperse the algae. Actually, it doesn’t take much rainfall to get rid of the algae but that won’t happen until well into November. Most of the algae will be gone by the middle of September.
Whereas the algae in the south end of the lake often has a bad odor, there is also algae forming late in the afternoons in the north end. Most of this algae in the north end is the green algae and is considered the good algae because it supports phytoplankton, which young fish feed on. However, the nuisance blue-green algae could be just a week or two away. It all depends on how much hot weather we receive.
Whereas algae occasionally clogs up outboard motors and fouls the beaches, for the most part it doesn’t hurt the fish in the lake. The one exception is back in the channels where fish get trapped and die from a lack of oxygen.
A number of people are wondering why there is so much blue-green algae in the south end of the lake and little in the north end. The prevailing winds at Clear Lake are normally west to northwesterly and they tend to push the algae to the south end. The other factor is that because the lake is shallower in the north end massive weed growth there uses up the nutrients the algae needs. Later in the summer the weeds die off in the north end, freeing up nutrients that lead to blue-green algae blooms there.
I remember some of my visits to Lake County in the early 1960s and the lake was covered from shore to shore with algae. Most of the local residents accepted the algae as part of the history of Clear Lake. Nothing much has changed in the 50 years since then and I expect the algae will be here for another 100,000 years.
