Tragedy Hits Pine Ridge Farm

At Pine Ridge Farm we have a small farm pond which measures about 1/2 an acre. This pond was stocked with several large mouth bass, a few large catfish, and 4 triploid carp (used to maintain the weed growth). This year we went from a cold spring directly into a hot, dry summer. This sudden change in temperature caused a huge algae bloom that completely covered the surface of the pond. I believe that this blocked light needed to allow photosynthesis, the production of oxygen. Realizing that this was a problem, I promptly treated the algae with a moderate dose of copper sulfate, which generally clears up the algae bloom in a few days. However, what I failed to anticipate was the effects of summer kill, described in this quote from the AquaNIC web site sponsored by the University of Minnesota:

Green plantonic (microscopic) algae are essential to oxygen production in farm ponds. Farm ponds normally have a faint green color, and the water should be clear enough to see around 2.5-3 feet vertically into the pond water. When there are enough nutrients present in the water, algae "blooms" occur and give the water a rich green or "pea-soup" color. Water clarity decreases as a result of these alga blooms to the point that your hand is not visible in as little as six inches of water. If these alga blooms are followed by periods of cloudy weather, there will be a potential of an alga die-off.

I believe that what happened was that the oxygen level was so low to begin with, and probably concentrated near the surface due to temperature stratification. Once the algae began to die off from the application of the copper sulfate, the decay process absorbed what little oxygen available to sustain the fish population. All together I estimate that we lost 300 pounds of fish. The real trick is to get rid of such a large quantity. Soon we'll be publishing our plan to restock in the spring, and how we intend to prevent a summer kill next year.

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