Marine heatwaves driven by Super El Nino cause severe physical and mental health issues in humans, researchers from Adelaide University and the University of Hong Kong have warned.
According to the experts, these extreme oceanic weather events can trigger conditions ranging from respiratory and cardiac problems to grief, anxiety and post-traumatic stress disorder. The warning comes as new climate data shows sea surface temperatures in the Pacific Ocean reached their highest levels ever recorded for July, driven by an intensifying El Nino pattern.
Data from the European Union's Copernicus Climate Change Service revealed that the temperature surge has already triggered severe marine heatwaves across Europe, with ocean conditions predicted to deteriorate further in the coming months.
Lead author Dr Laura Falkenberg, from Adelaide University in Australia, warned that ocean temperature spikes can no longer be viewed purely as environmental threats. "Marine heatwaves are no longer just recognised as an environmental issue; they are increasingly also perceived as a human health issue," Dr Falkenberg said. "They can intensify storms and atmospheric heatwaves, affect the availability and safety of seafood, disrupt livelihoods and contribute to anxiety, grief and other mental health impacts in communities that depend on healthy oceans."
Storms and Coastal Disasters
Marine heatwaves are prolonged periods of unseasonable warmth in sea surface waters, lasting anywhere from several days to multiple months. While sudden temperature spikes regularly cause mass die-offs of marine life and catastrophic coral bleaching, researchers stress that the events also directly threaten human life on land by supercharging the exchange of heat and moisture between the ocean and the atmosphere.
This rapid energy transfer dramatically intensifies tropical storms and terrestrial heatwaves in ways that long-term forecasting models struggle to predict. In 2023, marine heatwaves contributed directly to the rapid intensification of Hurricane Otis before it struck Mexico, displacing 34,500 families and causing more than $15 billion (£11.11 billion) in total damage.
During the same year, another intense marine heatwave worsened the severity of Typhoon Doksuri as it swept across Southeast Asia, affecting more than two million people. Beyond the immediate destruction and fatalities, Typhoon Doksuri triggered widespread outbreaks of crop and animal diseases across China, causing prolonged health and economic consequences for affected populations.
Toxic Algal Blooms and Food Security
Sudden marine temperature spikes also accelerate the growth of microscopic plants and phytoplankton, creating massive and highly toxic algal blooms. While algal blooms occur naturally, marine heatwaves produce events that are faster, larger and significantly more toxic than those driven by standard gradual ocean warming.
These toxic explosions pose severe health risks to coastal residents. Swimmers exposed to the algae can develop skin-irritating rashes, while individuals with compromised immune systems face dangerous medical complications. Furthermore, toxic algae accumulate in marine wildlife, contaminating seafood supplies and risking widespread food poisoning.
The researchers noted that food sustainability is heavily at risk globally, given that approximately 3.2 billion people rely on seafood for at least 20 per cent of their daily dietary protein intake. Disruption to fish stocks and marine ecosystems threatens both nutrition and economic stability across coastal regions.
Mental Health and Community Impact
Beyond physical illness, the study highlights the profound mental health toll inflicted by dying ocean ecosystems. "Many people rely on healthy oceans not only for food and income, but also for recreation, cultural identity and their overall sense of wellbeing," Dr Falkenberg explained. "When marine ecosystems suffer, the impacts ripple through communities."
The report pointed to a devastating marine heatwave off the coast of South Australia in 2025, which drove sea temperatures 2.5°C (4.5°F) above average. Combined with elevated nutrient levels, the heatwave triggered an unprecedented algal bloom that spanned 7,741 square miles (20,050 square kilometres) of ocean and lasted from March 2025 until February 2026.
During the nearly year-long bloom, large numbers of local marine animals were killed, including a great white shark. Researchers documented widespread cases of "eco-anxiety", grief, frustration and depression among local residents, alongside physical ailments such as asthma and respiratory irritation. "We are seeing increasing evidence that these changes can contribute to eco-anxiety, grief and other mental health challenges, particularly for people who feel deeply connected to the marine environment," Dr Falkenberg said.
Public Health Reform and Climate Dynamics
In response to the growing crisis, the research team is urging governments and public health agencies worldwide to integrate marine heatwave forecasts into formal public health planning, treating ocean heatwaves with the same urgency as land-based heatwaves. "If we only respond after disasters occur, we will continue to experience greater impacts than if we had acted proactively," Dr Falkenberg warned.
The current phenomenon is tied to the El Nino-Southern Oscillation (ENSO), a recurring climate pattern in the tropical Pacific Ocean that alternates irregularly between warm El Nino and cool La Nina phases every two to seven years. During an El Nino phase, ocean surface temperatures rise across the central and eastern tropical Pacific, while equatorial easterly winds weaken or reverse direction. This disrupts global weather patterns, reducing rainfall over Indonesia while increasing precipitation across the tropical Pacific Ocean.
Conversely, La Nina produces below-average ocean temperatures in the central and eastern Pacific, strengthening easterly winds and increasing rainfall over Indonesia while drying out the Pacific. When neither phase dominates, the system remains neutral with ocean surface temperatures remaining close to long-term averages.
