Oceans are changing color now due to rising temperatures, according to researchers in a new study published in the journal Nature. The ocean’s color is a benchmark of its health, and the steady change throughout nearly half of the world’s oceans indicates that its ecosystem is falling out of balance, which scientists hope will spur climate and ocean action across the world.
The study, called “Global climate-change trends detected in indicators of ocean ecology," showed that global warming caused specific types of phytoplankton to grow, leading to algae blooms that reduce oxygen in the surrounding area and release toxins into the water. According to the researchers, the changing color is the clearest indicator of the phytoplankton change.
Phytoplankton is a microscopic algae found on the ocean’s upper layers because they feed from sunlight. Phytoplankton generates approximately half of the atmosphere’s oxygen, according to the Woods Hole Oceanographic Institution (WHOI), a non-profit organization that specializes in marine research. “Phytoplankton also form the base of virtually every ocean food web. In short, they make most other ocean life possible,” WHOI explains. Without these tiny organisms, life in the ocean would not be sustainable. However, too-large quantities lead to dangerous algae blooms and toxins.
The changing ocean colors are a symptom of these conditions and demonstrate how warming oceans threaten the delicate ecosystem. “The shift in ocean color indicates that ecosystems within the surface ocean must also be changing, as the color of the ocean is a literal reflection of the organisms and materials in its waters,” said an MIT press release.
The study’s researchers, including scientists from the Massachusetts Institute of Technology and National Oceanography Center in the U.K., used data from a sensor aboard the Aqua satellite, which has been collecting data on the oceans’ color for around 20 years, to determine that ocean color is a better indicator of phytoplankton growth than chlorophyll.
But the researchers hope that knowing how warming temperatures impact ocean health will be a call to action and open up new solutions. Senior research scientist Stephanie Dutkiewicz said simply, “We hope people take this seriously.”
The observed trends indicate that phytoplankton patterns have changed over the last 20 years. By monitoring the ocean over time, scientists can find changes within aquatic ecosystems, opening up new insights into the impact of climate change on phytoplankton and ocean health.
This color shift will have long-term impacts because it affects the level of light that can penetrate the water. Disruptions like these are detrimental to the oceans’ ecosystems, essential to global food and nutrition systems. But the researchers hope that knowing how warming temperatures impact ocean health will be a call to action and open up new solutions. Senior research scientist Stephanie Dutkiewicz said simply, “We hope people take this seriously.”
Cael, B. B., Kelsey Bisson, Emmanuel Boss, Stephanie Dutkiewicz, and Stephanie Henson. “Global Climate-Change Trends Detected in Indicators of Ocean Ecology.” Nature 619 (July 2023): 551-554. https://doi.org/10.1038/s41586-023-06321-z.
Chu, Jennifer. “Study: The ocean’s color is changing as a consequence of climate change.” Press release, the Massachusetts Institute of Technology. July 12, 2023. https://news.mit.edu/2023/study-oceans-color-changing-climate-change-0712
Chasan, Aliza. “Oceans Are Changing Color, Likely Due to Climate Change, Researchers Find.” CBS News, July 12, 2023. https://www.cbsnews.com/news/oceans-changing-color-climate-change/.
NASA Earth Observatory. “Phytoplankton Flourish in the North Sea,” n.d. https://earthobservatory.nasa.gov/images/151484/phytoplankton-flourish-in-the-north-sea.
Quaglia, Sofia. “World’s Oceans Changing Colour Due to Climate Breakdown.” The Guardian, July 14, 2023. https://www.theguardian.com/environment/2023/jul/12/worlds-oceans-changing-colour-due-to-climate-breakdown-study-suggests.
Woods Hole Oceanographic Institution. “Phytoplankton,” n.d. https://www.whoi.edu/know-your-ocean/ocean-topics/ocean-life/ocean-plants/phytoplankton/.