Rising carbon dioxide could leave tiny lake dwellers defenseless


water flea
water flea

As people continue to burn fossil fuels, levels of carbon dioxide in the atmosphere have been rising. Some of that excess has dissolved into the world’s oceans. But levels of this greenhouse gas have also been rising in some lakes, a new study finds. Too much of this CO2 in the water may leave some tiny animals in the water too sleepy to fend off predators. This could be a problem because they are an important part of many lake food webs.

These animals are water fleas. Not true fleas, they are a type of tiny crustacean. (As such, they’re related to shrimp and lobsters.) They get their name from the way they appear to jump about in the water. The ones studied here were two different species of pinhead-sized Daphnia (DAFF-nee-uh). They are at the bottom of many freshwater food webs. That means they serve as a primary entrée in the diet of somewhat bigger animals.

carbon dioxide graph
Average carbon dioxide levels (straight lines) increased in four German lakes over 35 years (top). (These levels were measured as the partial pressure of CO2 dissolved in the lake water in microatmospheres, a unit of pressure.) Each lake also showed an overall decrease in pH (bottom).

Long-term measurements of the chemistry of lake water are rare. But researchers found data on four lakes in Germany. Those data covered the period from 1981 to 2015. They showed how much CO2 levels had risen over that time, as pH levels dropped. (pH is a measure of acidity.)

Rising CO2 in the atmosphere has increased levels of the gas dissolved into Earth’s oceans. That has made them more acidic. Studies show that this ocean acidification alters the behaviors of many species. It’s been less clear whether rising CO2 levels also were affecting lakes and other bodies of freshwater. It also was not clear how freshwater critters might be coping with any change, says Linda Weiss….

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Marcela

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COO @oneqube | Angel Investor | Proud mom | Advisor @TheTutuProject | Let's Go #NYRangers
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