The ocean's carbon flow is being slowed by marine heat waves, which are periods of abnormally warm waters that can persist at the ocean's surface for months. These heat waves, similar to those experienced on land, can alter environmental chemistry and disrupt biological processes. While the catastrophic loss of megafauna is a clear indicator of a distressed ecosystem, researchers are now gathering data to understand how microbial organisms at the base of the ocean's food webs are also responding to heat waves. A new study published in Nature Communications documents two successive heat waves in the northeastern Pacific Ocean over a decade. The interdisciplinary team used autonomous robotic floats, research cruises, and satellite data to observe how microbial communities in the region reorganized in response to the extreme events. They found that the production of organic matter increased at the ocean surface during the heat waves, but the carbon-rich particles didn't sink or rise; they just stayed in place. This discovery highlights the impact of marine heat waves on the biological carbon pump, which is crucial for the ocean's ability to sequester carbon. The biological carbon pump, driven by phytoplankton, transports carbon from the atmosphere into the ocean's carbon cycle. However, when the food web gets tangled due to heat waves, the pump can malfunction, leading to increased concentrations of particulate organic matter at the ocean's surface. This can have significant implications for the ocean's capacity to sequester carbon and mitigate climate change. The study also emphasizes the importance of 'big data' in ocean biogeochemistry, as researchers can now collect and analyze datasets spanning beyond the length of a research cruise. The Global Ocean Biogeochemistry Array (GO-BGC) instruments, a subset of the Argo array, play a crucial role in monitoring the ocean's vital signs before, during, and after heat waves. Despite the advancements, there are still lingering uncertainties and concerns about the future of ocean monitoring, particularly in the context of budget cuts and the need for more investments. The study invites further discussion and collaboration among researchers to better understand the impacts of marine heat waves on the ocean's carbon flow and the biological carbon pump.
