Central OC Times

Computer models have long predicted that human-induced climate change would significantly alter ocean nutrient cycles. Researchers from the University of California, Irvine, have now provided field-based confirmation of these changes. Their study, published in the Proceedings of the National Academy of Sciences, reveals unexpected shifts in marine nutrient cycles as global temperatures rise.

"Model studies have suggested that when the ocean warms it gets more stratified, which can drain certain parts of the surface ocean of nutrients," said Adam Martiny, a professor at UC Irvine and one of the study's lead authors. This study is the first to confirm these impacts on nutrient cycles due to climate change.

The research team, led by graduate student Skylar Gerace, examined 50 years' worth of data from the Global Ocean Ship-based Hydrographic Investigations Program (GO-SHIP). They found a significant decrease in phosphorus levels—a key nutrient for marine food webs—in southern hemisphere oceans over this period.

"There can be cascading effects up the food web," explained Gerace. Phytoplankton rely on phosphorus for nutrition; a decline affects their quality as food for zooplankton and fish. Surprisingly, nitrate levels—a crucial component for ecosystem functioning—have remained stable so far. However, Martiny cautioned that future declines could still occur as climate conditions evolve.

Martiny stressed the importance of programs like GO-SHIP in providing empirical data necessary to verify model predictions about marine ecosystems. For example, while models predicted declining nitrate levels by now, observations indicate otherwise.

"It's in general really hard to demonstrate long-term climate impacts on the ocean because there's so much variability," said Martiny. "Ours is now part of a small collection of studies that demonstrates these long-term impacts."

Future research will focus on quantifying how altered nutrient cycles affect marine ecosystems globally amid ongoing climate change. "We aim to investigate how this nutrient metric relates with broader ecosystem dynamics throughout the ocean," Gerace stated.

This research was funded by grants from several organizations including the National Science Foundation and NASA. The University of California, Irvine continues its commitment to excellence through initiatives like its Brilliant Future campaign and maintains its reputation as a leading public university with substantial contributions to education and research.

For more information about UC Irvine's initiatives or access to faculty expertise for media purposes, resources are available online at their official websites.