The seas are warm, too warm, as I noticed when my dive computer read 33C in northeast Tobago last week. Anybody who swam in the sea would have noticed this: “the seas were calm and nice!” But it isn’t so nice for marine life accustomed to living in water at least 4 degrees cooler, and that has many implications for people’s health.
If our body temperature rose to 40C, we’d need immediate medical attention. While we observe most corals for bleaching (turning white as the living organisms that keep corals alive leave due to heat stress) during marine heat waves, high temperatures impact all life in coastal waters.
Sponges, soft corals, fish, conch and lobster all suffer from heat stress. Less deadly impacts of heat stress to marine life include reduced reproduction and poor health, while extreme impacts include mass die-offs. Only last year, we experienced this in Tobago. Many coral species, marine sponges and sea fans bleached and died.
A red tide (harmful blooms of certain types of algae) along the Atlantic coast triggered by high water temperatures resulted in mass fish death along several beaches. This year, temperatures are warming even faster.
Warming seas also affect diving conditions. When I started diving 15 years ago, I wore a 5mm wetsuit and I’d be cold within an hour. Today, I dive in a rash guard and tights and on many occasions, the heat stifles me. At night, the air was cooler than the water. We were refreshed by the cool air after diving for hours at Mt Irvine, but what about the marine creatures that cannot escape the warming water?
Corals as indicators
This year, the National Oceanic and Atmospheric Administration (NOAA) updated the coral bleaching alert network, from two Levels of bleaching alerts: Level 1- risk of reef-wide bleaching, and Level 2 - mass bleaching and (mortality) death. The new system has five levels which explain expectations when temperatures go beyond Level 2. With Level 5 comes the risk of more than 80 per cent of the coral dying.
Tobago’s coral reefs have experienced marine heat waves annually for the last six years, with the most serious occurring in 2023 and 2024. Scientists predicted severe annual bleaching from 2040 on, but current trends show that this was an underestimate.
Human-caused climate change, which has increased heat-trapping carbon dioxide in the air, has already determined the climate conditions for at least another 10 years, and we must prepare for a warmer planet. While global action is improving, change is slow, especially for small islands that are both dependent on ocean resources and vulnerable to the impacts of climate.
We are part of our ocean and earth systems and need to take responsibility for our planet. In future, we can expect worse flooding and storm surge damage to coastal communities, and photos on classic sandy beaches to be spoiled by Sargassum. Expect more germs, chances for infections, more cases of ciguatera poisoning (ciguatoxins are found in fish that eat certain organisms, and are poisonous when eaten by humans), and red tides with impacts on our seafood and tourism sectors. Seafood will be scarcer and more expensive. Expect the next
generations to not know what a healthy coral reef looks like.
Healthy ocean, healthy islands
Not everything can be blamed on climate change. We have a long history of marine over-exploitation and minimal protection of marine habitats. We continue to think the ocean is vast, endless and untouched, never mind that we catch only half the number of fish at a quarter of the size as compared to 50 years ago. We need to connect the dots.
A good example is the tourism shift at Buccoo Marine Park from exploring the ocean on glass-bottomed boats to party tourism with raft-ups and beach parties in what should be a protected marine park.
The future of life on islands requires us to adapt, and we need to care for our marine domain which makes our islands livable. Climate change requires us to conserve natural biodiversity to reduce changes and avoid reaching points of no return. Urgent regulations are needed to protect our marine parks and stop over-exploitation of our fisheries. Governments need to invest now in food security and advocating ecosystem-based strategies for development.
Individually, we can make a difference to the health of the oceans by reducing fertilizer run-off, and avoiding oil spills. Not taking animals/coral from the sea, and not walking on reefs are simple steps that help. A healthy body will recover quicker from disease than an unhealthy one. We need to restore our natural resources to their healthiest state so that they – and therefore us – will survive climate disturbances. Children today need to be taught to appreciate the natural world, to respect and to learn to live with wild nature.
Dr Anjani Ganase is a coral ecologist and works on the reefs around Tobago.