A study published June 5 in Science Advances combines NASA satellite data, ocean surveys, and genetic testing to show that warming ocean waters are reducing nutrient availability for phytoplankton, potentially reshaping marine ecosystems.
Key Findings
Researchers used satellite observations of carbon-to-chlorophyll ratios to infer nutrient stress in phytoplankton. The strongest stress occurs in subtropical gyres, where warm surface water suppresses upwelling of nutrient-rich deep water.
The South Pacific showed the most severe nutrient stress due to nitrogen and iron shortages. In parts of the North Atlantic, phosphorus shortages were observed but had milder impacts, possibly due to phytoplankton's ability to recycle phosphorus more efficiently.
Nutrient stress correlates with seasonal cycles and climate patterns like El Niño and the Pacific Decadal Oscillation.
From 2002 to 2021, sea surface temperatures rose over nearly 90% of the study area, and nutrient stress generally intensified.
Some Southern Hemisphere regions showed less stress increase than expected, likely because microbes that capture nitrogen from the air partially offset reduced mixing.
Implications
The study suggests some marine ecosystems may be more resilient to warming than models predict, but underscores the complexity of forecasting future changes.
Methods
The research team combined 20 years of data from NASA's Aqua satellite MODIS sensor with genetic markers from Prochlorococcus microbes collected on research cruises.