Sunlight decreases the toxicity of golden algae, according to a study published in the Journal of Plankton Research.
Golden algae (Prymnesium parvum) kills millions of fish worldwide annually. Since the 1980s, the fish death toll due to the plant’s toxin has increased, particularly in rivers and lakes in Texas.
"Golden algae is aggressive and very unique because it can produce its own toxins, swim, photosynthesize and feed on other organisms," says co-author Bryan Brooks, associate professor at Baylor University, in a press release. "If we can figure out what stimulates and decreases the growth of this algae, we might be able to control it."
Scientists believe that multiple chemical and physical factors affect the toxicity of the plant, but until now were unsure how sunlight affects the plant’s toxicity to fish in inland waters.
The team at Baylor University cultured algae in artificial sea water and filtered out the organisms to test the effects of sunlight exposure on the toxins in the water. They found that after exposing the water to full or only 50 percent sunlight for eight hours, it became non-toxic to the test fish.
Furthermore, exposure of toxic water to sunlight for just two hours rendered the water safe for the test fish."What we think happens in terms of the large fish kills is that sunlight only penetrates down so deep in a lake, so in a lake with golden algae blooms, fish located at greater depths may be exposed to more algal toxins," says Brooks.
The authors note that more research is needed into the effects of the day-night cycle and other environmental factors on toxin production.