NASA study links warming oceans to nutrient stress in marine microorganisms

A study published on 5 June in Science Advances indicates that warming ocean waters are reducing nutrient availability for microscopic marine organisms, potentially reshaping global marine ecosystems. Researchers from NASA combined two decades of satellite data from the Aqua satellite’s Moderate Resolution Imaging Spectroradiometer (MODIS) sensor with genetic testing of the microbe Prochlorococcus to track phytoplankton stress. The analysis revealed that rising temperatures decrease upwelling, leading to a decrease in chlorophyll relative to carbon in phytoplankton, which serves as an indicator of nutrient stress.

The research tracked the condition of phytoplankton, which form the base of ocean food webs, by inferring stress through subtle shifts in the ratio of carbon to chlorophyll observed from space, rather than measuring nutrients like nitrogen, iron, and phosphorus directly. When the amount of chlorophyll decreases relative to carbon in satellite data, it indicates that the plankton are stressed. The research team linked large-scale satellite observations with genetic markers in Prochlorococcus, a tiny but abundant marine microbe that shows signs of nutrient stress in its DNA. The result is a global map revealing where phytoplankton are thriving and where they are struggling.

Warming waters decrease upwelling, which leads to stress on marine microorganisms due to limited availability of vital nutrients. Plankton communities are the base of the marine food web on which important economic activities rely. The study utilised data from NASA’s Aqua satellite’s MODIS sensor collected between January 2010 and May 2016, alongside plankton samples collected on research cruises around the world.

Laura Lorenzoni, Program Scientist for NASA’s Ocean Biology and Biogeochemistry Program, emphasised the importance of sustained, high-quality remote sensing observations to track ocean health. She noted that as the ocean continues to change, the ability to observe and track its health through these observations has never been more important. This monitoring is fundamental, given the reliance of economic activities on the marine food web.

The study suggests a potential to reshape marine ecosystems, but the specific long-term ecological outcomes and timeline for these changes are not detailed in the source material. The exact magnitude of the impact on specific economic activities reliant on marine food webs is also not quantified in the provided text.