October 8, 2026 — If $6.00 diesel, wind farms, and whales aren’t enough to keep fishermen awake at night, they can start contemplating the global decline in phytoplankton. From around the world, in almost every ocean except the high polar latitudes, scientists are documenting declines in phytoplankton and population shifts from nutritious diatoms to less nutrient-dense, often toxic dinoflagellates.
Phytoplankton forms the foundation of the marine food chain and supplies 50 percent of the Earth’s oxygen—every other breath we take is thanks to phytoplankton. Declines reported from the Gulf of Maine to the Caribbean to the Indian Ocean and South China Sea might deserve front-page coverage, but as in many disaster movies, warnings from science are often dismissed until the implications can no longer be ignored.
In 2025, a team of U.S. scientists led by Greg Silsbe released a paper, Global Declines in Net Primary Production in the Ocean Color Era, assessing ocean health largely based on satellite imagery from 1997 to 2022. “Here we show that statistically significant decreases in NPP [net primary production] have occurred in almost half of the ocean and these changes are dominated by declines in the tropical and subtropical stratified ocean,” the authors say. “A deeper analysis confirms that strengthening nutrient limitation is largely driving declining NPP. Climate-mediated shifts in NPP represent a fundamental perturbation to biogeochemical cycles that can further weaken global fisheries.”