Even bleached coral reefs can provide millions with nutritious seafood

Photo: Pixabay/BANITAtour

As global temperatures continue to rise, the mass bleaching of coral reefs in the tropics is set to become ever more common. These reefs support a stunning diversity of marine life so any harm to them can be catastrophic.

That we’ve known, but a new study by scientists at Lancaster University in the United Kingdom offers a ray of hope for the hundreds of millions of people who depend on tropical reefs worldwide for their nutrition.

Small-scale fisheries, the scientists say, may be more resilient to climate change than previously thought, explain the researchers.

Better yet: even after mass bleaching events, reef fisheries can remain rich sources of micronutrients. In fact, they can increase in nutritional value for some key minerals such as iron and zinc, the scientists discovered.

The scientists reached this conclusion after analyzing the nutrient contents of 43 tropical reef fish species in the Seychelles where a large-scale bleaching event in 1998 killed off some 90% of local corals.

In time some 60% of the coral reefs in the area recovered while the rest transformed into reefs dominated by seaweeds, which enabled scientists to compare the availability of micronutrients in reefs with these different compositions. Based on their findings, they report that “coral reef fish contain similar levels of iron, selenium, and zinc as chicken, pork, and beef and higher levels of calcium and omega-3 fatty acids.”

Specifically, iron and zinc were more concentrated in fish caught on reefs that have been transformed after the mass bleaching into marine ecosystems dominated by macroalgae such as seaweeds. These seaweeds have high levels of key minerals, which is why herbivorous fish that feed on them end up containing higher levels of iron and zinc. By eating these fish, people in turn can have access to these minerals in their diets.

“Coral reef fish contain high levels of essential dietary nutrients such as iron and zinc, so contribute to healthy diets in places with high fish consumption,” said James Robinson, a scientist at the university’s Environment Centre.

“We found that some micronutrient-rich reef species become more abundant after coral bleaching, enabling fisheries to supply nutritious food despite climate change impacts. Protecting catches from these local food systems should be a food security priority,” Robinson explained.

“More than six million people work in small-scale fisheries that rely on tropical coral reefs. Their catches help to feed hundreds of millions of coastal people in regions with high prevalence of malnourishment, causing stunting, wasting and anaemia,” the scientists explain in a statement.

“However, until now, the nutritional composition of coral reef fish catches, and how climate change might affect the nutrients available from reef fisheries, was not known,” they add.

That said, overfishing, pollution and other stressors likewise pose grave threats to many reefs in the tropics and more data is also needed on how reefs elsewhere are faring in the face of increasing water temperatures.

Importantly, tropical reefs will need to be better managed and protected so that they can continue to provide local people with sustainable sources of fish for their traditional fish-based diets, the experts stress.

“Fish are now recognised as critical to alleviating malnutrition, particularly in the tropics where diets can lack up to 50% of the micronutrients needed for healthy growth,” Professor Christina Hicks, a co-author on the study, said.

Reef fisheries can continue to play a crucial role in the diets of people in coastal communities even in the face of climate change, but it will be vitally important to invest in sustainable fishing practices, Hicks added.