How Heatwaves Could Be Harmful to Lake Phytoplankton

A recent study carried out in Finland reveals a potential consequence of climate change on an organism that is essential to the survival of the planet. That organism is phytoplankton, which could see its biomass reduced due to heatwaves.

Often referred to as a one of Earth’s “lungs,” phytoplankton is an essential organism for the survival of the planet, since it absorbs a large portion of atmospheric CO2 and plays a key role in the food chain of the marine ecosystem. Almost invisible to the naked eye, it is found in surface waters, most often in the oceans, but also in lakes. The problem lies in the fact that in hot weather, surface waters become less dense and form a mixed layer above the colder, deeper waters, explains a study recently published in the journal FreshWater Biology. Phytoplankton occur mostly in this mixed layer, and its depth is regulated by weather.

“Ongoing climate change influences surface waters through meteorological forcing, which modifies the physical structure of fresh waters including the mixed layer, but effects on phytoplankton biomass are poorly known,” explains the study, conducted by researchers at the Department of Biological and Environmental Science at the University of Jyväskylä, Finland.

To determine the potential impacts of heatwaves on phytoplankton biomass, the study authors focused on Jyväsjärvi, a boreal lake in central Finland. The scientists carefully monitored meteorological variations during the first half of a stratification period of this lake — when distinct thermal layers are created in response to elevated temperatures. This revealed that in cooler, windier weather, phytoplankton biomass is likely to increase. But during heatwaves, and with low wind speeds, the opposite occurs. In other words, the biomass of phytoplankton decreases.

“Our study suggests that increasing air temperature relative to water temperature and declining wind speeds have potential to lead to reduced phytoplankton biomass due to a shallower mixed layer during the first half of the stratification period,” the study authors write. They conclude: “further work is needed to understand how the characteristics of lakes regulate the responses of lakes to climate change at different phases in the annual cycles of lakes.”

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(This story has not been edited by News18 staff and is published from a syndicated news agency feed)