Global warming has not harmed phytoplankton as much as previously thought

New Scientist : According to a study published in Nature Climate Change, the detrimental effect of ocean warming on phytoplankton populations has been overestimated. Phytoplankton are important because they convert carbon dioxide, a major greenhouse gas, into organic compounds that sustain the food chain. The microorganisms live near ocean surfaces, where there’s more sunlight, and rely on the mixing of warm surface water with deeper, nutrient-rich water to replenish their food supplies. However, climate change has reduced the mixing and, hence, the supply of nutrients. An earlier study found that warming oceans produce fewer phytoplankton. However, the researchers based their estimate not on the number of actual phytoplankton but on the amount of green chlorophyll detected. It has now been shown that phytoplankton can adjust the amount of chlorophyll they produce, depending on the amount of light they are exposed to. So although global warming is still causing a decline in phytoplankton populations, the magnitude of that decline is smaller than had been previously estimated.