When the sea gets unusually warm for a long time, it can hurt people as well as marine life. Scientists now see these marine heatwaves as a public‑health problem.
Researchers from Adelaide University and the University of Hong Kong say we have paid too little attention to how hot oceans affect humans. Recent storms, such as Hurricane Otis in 2023 that caused over $15 billion in damage in Mexico, and Typhoon Doksuri, which impacted more than two million people in Asia, have both been linked to unusually warm water.
In South Australia, a large algal bloom caused by hot water led to many health complaints among people living near the coast.
How Marine Heatwaves Harm People
A study in Nature Sustainability explains that prolonged hot water can start a chain of problems: stronger storms, less safe seafood, loss of jobs that depend on the sea, and more anxiety for coastal communities.
"Marine heatwaves are no longer just an environmental issue; they are also a human‑health issue," says Dr. Falkenberg.
These events can make storms and heatwaves on land worse, damage the supply and safety of fish and shellfish, and create long‑lasting worries about food security for billions who rely on the ocean for protein.
Stronger Storms and Unsafe Seafood
Very warm water gives extra energy to tropical storms, increasing the chance of injury, death, and displacement from flooding.
Hot water also fuels harmful algal blooms. When these blooms happen, they can poison fish and shellfish, making them unsafe to eat and exposing beachgoers to toxic water.
Even after the heatwave ends, fewer fish and lower catches can threaten the food supply for people who depend on seafood.
Mental‑Health Impacts of a Changing Ocean
People whose jobs, traditions, and sense of identity are tied to the sea can feel deep stress when the ocean changes. In 2025, a toxic algal bloom in South Australia was linked to high levels of eco‑anxiety, grief, frustration, depression, as well as breathing problems and asthma.
"Healthy oceans give us food, income, recreation, and a sense of belonging," Dr. Falkenberg notes. "When marine life suffers, those feelings are shaken, leading to anxiety and other mental‑health challenges."
Calling for Public‑Health Planning
Scientists suggest that health agencies should use marine‑heatwave forecasts when planning for coastal safety. By working together—ocean researchers, health officials, and resource managers—communities can become more resilient before disasters strike.
"Recognizing these health impacts is the first step toward better protection," says Dr. Falkenberg. "Proactive policies that link ocean health to human health will safeguard both people and the marine world they rely on."