Every drop of fresh water contains thousands of different organic molecules that have previously gone unnoticed. By measuring the diversity of these molecules and how they interact with the environment around them, research has revealed an invisible world that affects the functioning of freshwater ecosystems and can contribute to greenhouse gas emissions.
Small shallow lakes dominate the world’s freshwater area, and the sediments within them already produce at least one-quarter of all carbon-dioxide, and more than two-thirds of all methane released from lakes into our atmosphere. The new research, published in the journal PNAS, suggests that climate change may cause the levels of greenhouse gases emitted by freshwater northern lakes to increase by between 1.5 and 2.7 times.
“What we’ve traditionally called ‘carbon’ in freshwater turns out to be a super-diverse mixture of different carbon-based organic molecules,” said Dr Andrew Tanentzap in Cambridge’s Department of Plant Sciences, who led the research. “We’ve been measuring ‘carbon’ in freshwater as a proxy for everything from water quality to the productivity of freshwater ecosystems. Now we’ve realised that it’s the diversity of this invisible world of organic molecules that’s important.”