Algae Growth in Cold Water.

[gregsfc]

I work at a national fish hatchery rearing over 300,000 pounds of trout species per year in Tennessee. I'm always finding interesting relationships between our water quality and other water issues and testing protocols, etc for our discharge and how these things often relate to pool chemistry (except of course chlorine). Lately I found a contradiction to what goes on at the hatchery versus outdoor pool information provided here. The latest Youtube video states that algae has a hard time growing in colder water, but at our hatchery where our water flow is sourced from an average depth of 95' from a reservoir, our big-time algae growing season as water runs through our raceways is about one month after the reservoir stratifies when the water temps drop very fast in just a few weeks (down to 42 degrees some years) up until mid May when it's usually back up around 50 or 51 degrees. Then throughout the Summer, Fall and early Winter, as the water temp keeps climbing until late December or early January when it all starts over again, algae growth is next to nothing. So what I don't understand is...that if algae has a hard time growing in cold water, why is it that is during that time when it's working us to death trying to keep water flowing through the containment screens when it's under 50 degrees Fahrenheit, but then hardly grows at all above 50?

 

[YippeeSkippy]

We're not saying it doesn't grow....its just much slower, stunted perhaps by the cold temps in pools. I mean, you've got stuff in that water that pools shouldn't have.... like fish? Pooping fish?? I dunno... maybe someone else will chime in and have the one answer you seek.

Consider my post as just a bump

Maddie

 

[JoyfulNoise]

The Wikipedia entry on Algae says it best -

Algae is an informal term for a large, diverse group of photosynthetic eukaryotic organisms that are not necessarily closely related, and is thus polyphyletic.

You can read that link to get an idea of how complex the world of algae is. There are plenty of algae species that live and thrive in freezing cold water, saltwater, fresh water, brackish waters, etc, etc, etc. Since you worked in a hatchery, you obviously could not put chlorine in the water or anything that was phytotoxic as that would likely harm the fish as well as the algae. As you well know, algae will rob your fish of vital nutrients and use up most of the available oxygen in water which is why you had to spend some much time mechanically removing it.

In swimming pools, the types of algae that are present are limited to the blue-green variety, yellow mustard algae and black algae species (one can also get water molds and bacterial slime without proper chlorine levels). These species tend to see their reproduction rates plummet to near zero (not quite but very close) when water temperatures fall below 57F or so. This is why a fully sanitized pool that is closed late in the season when the water temps reach 60F and is opened very early before the water temps get above 60F can be virtually clear water that needs very little chlorine to start it up.

 

[gregsfc]

Thanks for the replies. So probably different species of algae than what is in a pool is the best answer. The worst areas for growth at the hatchery are actually between the fish raceways where the fish are not located. The water falls six inches at that point from what we call dam boards between every 100' raceway in serial. It's about a five foot section. But some trout species eat algae (rainbow) and some do not (brown and brook trout). The raceways with browns and brook trout get strings of algae along the concrete walls up to 18" long and the floor gets like carpet each annual cycle while those fish are in there for several months solid. After those fish are distributed and the raceways emptied, we'll pressure wash and remove all the algae. The rainbow trout raceways keep it move out better and doesn't build up quite so much, but we pressure wash them as well. The raceways with the real bad algae build up work us to death in the Spring trying to keeping the screens unclogged so the water doesn't rise up and put fish out on the pavement. I don't think the average hatchery deals with algae growth like we do for what ever reason; never heard other staffs talk about it; and they look at me odd when I do. I've often wondered if it could some way be mitigated sans chlorine.

I had thought that it may be that, for some reason, phosphorus or some other mineral level may be higher during that higher growth period (maybe not even related to water temps), but we don't get time to study things like that which work us to death. I mean, we are a gov't agency duty station, and so it's not like private industry where they constantly look for ways to reduce labor costs. We are already there so they use and abuse us and that keeps managers from having to do a lot of brain work.

 

[gregsfc]

We also engage in a weekly activity called flushing where we take a long-handled brushes and scrub the worst areas and screens and sweep the floor from end to end in concept to sweep out old feed to keep ammonia from building up but we do it also to help slow algae buildup. We have 104 raceways. We have three employees each week who do the flushing. We have five who do the work, but the flushing ends up being rotated with feeding and other tasks, but flushing is our most labor consuming and most monotonous task on station. We are tied with Norfork National Fish Hatchery for the largest hatchery in the southeast U.S. geographically speaking, but they can rear up to 450,000 compared to our 320,000 lb/year, because they have more water flow. We are Dale Hollow NFH. We both use a reservoir as our water source with plenty of issues with that including nitrogen super saturation; and periods of low dissolved oxygen and at times, high dissolved metals such as manganese and iron (only in the Fall before stratification).

 

[cfherrman]

Would some sort of uv lighting work?