Bullshead Algae, Gone

[pikergolf]

Figured I'd get hopefully one last trip in before the lake goes to he!!. Got there, no algae, none, water vis. about 6 or 8 ft. Was out Sat. after a big blow the night before and the lake was a lot better than the previous week, but over the course of 8 hrs. it was multiplying so fast you could almost see it grow. Today nothing. Sat. I was marking fish like crazy in deep water, today I think I saw one on the sounder, I think the water is so clear they move away from the boat. Fish were scattered all over the lake with lots rising, but I never caught one with the fly in the path of the boat. Got almost all casting to the side off the wind drift. Anyone who can explain the algae phenomenon?

[Ronbill]

The planktonic algae growing in most of Alberta's lakes are actually cyanobacteria (aka blue-green algae). These are photosynthetic bacteria that inhabit and compete with true algae. Interesting thing about cyanobacteria is that they are able to regulate their buoyancy in stable (stratified) surface waters. This allows them to migrate vertically to the depth of water with optimum light intensity for photosynthesis (hence growth). Optimum light intensity differs with species of cyanobacteria and generally, true algae can't do this.

As a result of this, cyanobacteria migrate up and down the water column throughout the day depending on sunlight intensity. They rise up to the surface in the morning during lower sunlight intensity and then as light intensity increases through the day, they sink back down and become less noticeable.

I must qualify that this phenomenon occurs only during early growth stages of cyanobacteria communities. Once populations get large and particular lakes/reservoirs experience lengthy periods of wind, cyanobacteria can become over-buoyant and stranded near the surface. Once stranded, they lose the capability to sink back down and ultimately die from high sunlight intensity resulting in what we commonly call algae blooms.

[pikergolf]

Thanks Ron, so does this mean they are done for the year.? The weather yesterday was stable and sunny I was expecting a lot of algae, the weather previous was also stable and sunny but with a persistant haze, did they come up because of the haze?

[Ronbill]

No this doesn't mean they are done for the year. Cyanobacteria cycle from one species to the next in succession. So long as sufficient nutrient (phosphorus) remains and the water column is stable enough, cyanobacteria will dominate the plankton community. You are right that perhaps the haze reduced light intensity drive the cyanobacteria to migrate to the surface.

[coyotezh]

well educated! thanks Ronbill!