A study analyzing the excrement of Arctic whales collected over about 20 years in the Arctic Ocean found that with rising sea temperatures, toxic algae are increasingly entering the food chain.
A joint research team from the United States and China, including the National Oceanic and Atmospheric Administration (NOAA), published findings on Oct. 10 in the international journal Nature that show clues about the impact of ocean warming on the Arctic ecosystem and food security for humans.
Due to global warming, the waters of the Arctic are becoming warmer than in the past. In particular, as sea surface temperatures consistently rise, the area of ice melting from the ocean surface has also expanded.
Such conditions are very suitable for the reproduction of marine toxic algae. Toxic algae refer to the types of phytoplankton that produce harmful substances among the microalgae that naturally exist in the ocean. When they multiply rapidly, toxins accumulate in the water and affect the entire food chain through fish or marine mammals that consume them.
To study the impact of marine toxic algae, the research team collected the excrement of Arctic whales that feed on plankton in the Arctic Ocean. They analyzed the amount of algal toxins in the excrement of 205 Arctic whales captured from the Beaufort Sea between 2004 and 2022 and compared it with environmental factors such as ocean temperature, ice melt area, wind speed, and atmospheric pressure.
As a result, it was clearly shown that toxin concentration tends to increase as sea temperatures rise and ice melt areas decrease. As the ocean becomes warmer and ice diminishes, harmful algae thrive more easily, and their toxins accumulate more in marine life, including whales.
In particular, the neurotoxin 'saxitoxin' produced by toxic algae has been found in more than half of the whales almost every year. Another neurotoxin, domoic acid, has been increasingly detected in 100% of cases recently.
The research team noted, "Algae that produce saxitoxin exist in seed form on the seafloor and quickly grow in warm seawater, reproducing in large quantities," and "Algae that produce domoic acid may travel from the south to the north with ocean currents or toxic species may also exist in the Arctic locally."
The problem is that Arctic whales are a primary source of protein for indigenous Arctic communities. As various marine organisms, including whales, are exposed to toxic algae, the safety of those who consume them may also be threatened.
The research team warned that it is necessary to strengthen monitoring systems for toxic algae to ensure food safety and health for communities that rely on marine life in the Arctic, stating that as climate change accelerates, tracking these toxic substances could become more serious.
References
Nature (2025), DOI: https://doi.org/10.1038/s41586-025-09230-5