, have demonstrated that a significant majority of global oceanic plankton, along with numerous unicellular organisms inhabiting lakes, peatlands, and other ecosystems, might reach a tipping point. Here, instead of absorbing carbon dioxide, they begin to do the opposite. This change is a result of the way their metabolism responds to warming.
Most of the plankton in the ocean — things like diatoms, dinoflagellates — are mixotrophs. They’re also common in lakes, peatlands, in damp soils, and beneath fallen leaves. To understand how these impacts might scale up, the researchers developed a mathematical model to predict how mixotrophs might shift between different modes of metabolism as the climate continues to warm.Celsius
The models suggest that, eventually, we could see these microbes reach a tipping point — a threshold beyond which they suddenly flip from carbon sink to carbon source, having a net warming effect instead of a cooling one. “Right before a tipping point, their abundances suddenly start to fluctuate wildly,” Wieczynski said. “If you went out in nature and you saw a sudden change from relatively steady abundances to rapid fluctuations, you would know it’s coming.”
When Wieczynski and his colleagues included higher amounts of such nutrients in their models, they found that the range of temperatures over which the telltale fluctuations occur starts to shrink until eventually the signal disappears and the tipping point arrives with no apparent warning.