By Terry Knight ? Record-Bee Outdoors writer
LAKE COUNTY — As predicted the algae is back on Clear Lake and local residents are demanding the county do something about it. Clearing the entire lake of algae is an impossible task. It is also one of the most misunderstood conditions on the lake. Algae has been part of Clear Lake for 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 April and can continue to bloom until well into October. Blue-green algae is actually a bacteria and it 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. For example one species of algae that”s presently causing so much concern in the South County is lyngbya. It is relatively rare in Clear Lake.
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 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 that are flowing into the lake. Nutrients, especially phosphorus, wash into the lake from nearby farm land and even the hills. Clear water also plays a major role. Even though the lake level was higher than normal this past spring, the water clarity was exceptional and there were times when you could see down to a depth of nearly 10 feet. That”s one reason why there are so many aquatic weeds and now algae. The sun can penetrate to the bottom which in turn creates ideal conditions for both weed and 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 will cause them to break up and sink to the bottom. In fact, a number of lakeside residents daily spray around their docks with water which disperses the algae. The sprayed water aerates the algae and causes it to sink to the bottom. Another method that has been effective in the past 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.
The rains that will arrive this 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. Actually, most of the algae will be gone by the middle of September.
Whereas the algae in the south end of the lake has a bad odor, there is also algae forming late in the afternoons in the north end. Most of this algae is the green algae and is considered the good algae because it supports phytoplankton which the young fish feed on. But the nuisance blue-green algae could be just a week or two away. It all depends on much hot weather we receive. It should also be noted that the yellow scum you see on weed mats isn”t algae, it”s decaying matter and is widely spread throughout the Lakeport area.
Whereas the algae will occasionally clog up outboard motors and foul 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 have been 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 this year the north end had a massive growth of aquatic weeds which used up the nutrients that the algae need. Now that the weeds have started to die off in the north end, these same nutrients will be used by the algae and there will be blue-green algae blooms.
Algae can be traced back on Clear Lake for more than 10,000 years. 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 that I have been familiar with the lake and I expect the algae will be here for another 10,000 years.
