Chemical Compositions Of Lakes Leaves Clues To How Global Warming Will Affect Underwater Ecosystems
The chemistry of a lake depends largely on the climate and its basin geology. But as human activities have started to significantly alter the chemical composition of lakes, more analysis on the ecology of lakes and their contribution to the carbon cycle might be necessary. An international team of researchers have conducted an in-depth analysis on the composition of organic compounds in lakes now, to begin this investigative process.
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"Lake water is like a very thin broth with several thousand ingredients in the recipe, all with different properties," director of the study Lars Tranvik said in a press release. "At the same time many of the molecules are common in a broad spectrum of different environments. For instance, in the extremely complex chemical mixture we have found the same components as colleagues have described from the Congo. And they react to environmental factors in the same way in the tropics as in Sweden."
Lakes are active participants in the carbon cycle even though they occupy only a small fraction of the Earth's surface. They are sites for storage and release of atmospheric carbon dioxide because huge quantities of organic material flow into lakes from the surrounding areas, where microorganisms then break them down in the water.
Most of the organic matter - the majority of which is organic carbon - is present in the water in a dissolved form consisting of thousands of different molecules. The present study is the most comprehensive investigation ever, looking into the composition of these organic compounds and the processes in lakes and their catchments that eventually produce them.
The researchers studied the chemical composition of the dissolved organic matter in 120 lakes throughout Sweden, while also factoring in climate change, among other things.
The researchers also culled data from a national environmental survey, which monitored water chemistry and other properties of lakes, along with detailed analyses of the organic material using an instrument known as a high-resolution mass spectrometer.
The results showed that both the biological and chemical composition of a lake can vary from environmental factors. For example, if a lake holds water for a longer time upstream before releasing it downstream, then molecules from the surrounding forests and wetlands are largely broken down. "This leads to a completely different chemical composition, where the content of compounds that are produced by plankton in the lakes is more dominant," said lead author Anne Kellerman, in the release.
By analyzing and comparing lakes in different climates, scientists can predict the future chemical compositions of lakes, and see how they change from warming climates and increased precipitation. "We're now continuing our investigations of the chemical diversity of nature by trying to figure out what mechanisms underlie the patterns we're finding," Tranvik said in the release. "What determines that organic material in some cases is preserved in nature for a long time, and why is it degraded quickly under different circumstances?"
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