Scientists discover zooplankton that turns red during winter

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Scientists discover zooplankton that turns red during winter

December 20, 2017 - 08:18
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Apparently, Rudolph's nose isn't the only thing that turns red during winter...

Copepods (Leptodiaptomus minutus) from Lake Simoncouche, (a) under the ice in winter (27 January 2017) and (b) in summer (18 September 2017).

During winter, food is scarce and many animals tend to slow down, become dormant and some of them even hibernate. However, as some researchers from Université du Québec à Chicoutimi, Saguenay, Québec, Canada found out, this is not the case for some species of zooplankton.

Zooplankton serve as food for fish and other marine animals in the ocean or river. When the scientists examined water samples taken every few weeks from Lake Simoncouche in Quebec, Canada under the microscope, they discovered that during winter, two species—Leptodiaptomus minutus and Cyclops scutifer—accounted for 63 and 22 percent respectively of the lake’s biomass.

In addition, the tiny organisms were vigorously zipping about and had turned a bright red colour. Not your typical sluggish wintertime behaviour.

"We saw that they were very active! They were not dormant at all. I was very surprised, because in winter there is no light, there is no algae to eat," said Guillaume Grosbois.

The scientists speculated that the red pigment serves as a preservative for the zooplankton's extra body fat they had accumulated during the autumn. According to the press release, "The copepods get most of their calories from algae. They can stay active for the entire winter [...] because they accumulate fats as temperatures drop during the autumn, eating everything they can find and feasting on dying algae as the ice closes. But stored fats, especially valuable fatty acids, are vulnerable to damage through peroxidation caused by free radicals."

Unfortunately, the fatty acids that they accumulate are vulnerable to damage as a result of per oxidation by free radicals. To minimise such damage, the red pigment that appears during winter has antioxidant properties that protects the zooplankton's cells by tying up the free radicals. Then, when the winter season comes to an end, the red pigmentation is reduced and becomes less visible as the zooplankton turns its attention on reproduction.

With climate change asserting its influence by shortening the duration of the ice cover, Grosbois wonders whether the shorter freezing period will give the zooplankton sufficient time to accumulate enough fatty acids to reproduce successfully in the spring. This will subsequently impact whether the fish would have sufficient food.

"We need to study this time more. Everything that happens in the winter will have an impact on spring, summer, and fall. So if we want to understand what is happening in the ecosystem, we need to know more about the winter,” said Grosbois.

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