Bleached coral reefs continue to provide nutritious seafood

Researchers studying coral reefs damaged by rising sea temperatures have found an unexpected ‘bright spot’ of hope for communities who depend on them for their food security.

Coral reef ecosystems support a variety of small-scale fisheries and the fish they catch are rich in micronutrients essential to the health of millions of people in the tropics, a new study from Lancaster University shows.

And, counterintuitively, as a result of bleaching events that kill corals and can transform the makeup of reef ecosystems, reef fisheries can remain rich sources of micronutrients, even increasing the nutritional value of some minerals.

The results, published in the journal A land, show that the availability of micronutrients from artisanal coral reef fishing may be more resilient to climate change than previously thought. This increased understanding is essential as continued global warming means that coral bleaching events are becoming more frequent and severe, placing increased stress on these vulnerable ecosystems.

Dr James Robinson, who led the study, said: “Our results underscore the continued importance of these fisheries to vulnerable coastal communities, and the need to protect against overfishing to ensure the long-term sustainability of the fisheries. reefs.

The researchers also caution that while these fisheries have proven to be more resilient to climate change disturbances than expected, understanding of the long-term impacts of climate change on coral reef fisheries and more data continues to emerge. other regions are urgent priorities.

More than 6 million people work in artisanal fisheries that depend on tropical coral reefs. Their catches help feed hundreds of millions of coastal people in areas with a high prevalence of malnutrition, causing stunting, wasting and anemia. However, until now, the nutritional composition of coral reef fish catches and how climate change might affect the nutrients available in reef fisheries has not been known.

This study, led by scientists at Lancaster University and involving an international team of researchers from Seychelles, Australia, Canada and Mozambique, benefited from more than 20 years of long-term monitoring data from the Seychelles, where tropical reefs were damaged by a large coral bleaching event in 1998, killing around 90 percent of the corals.

As a result of the mass bleaching event, about 60% of the coral reefs recovered to a coral-dominated system, but about 40% were transformed into algae-dominated reefs. These differences provided scientists with a natural experiment to compare the micronutrients available in reef fisheries with different climate-related ecosystem compositions.

Scientists, who used a combination of experimental fishing, nutrient analysis and visual surveys of fish communities in Seychelles, calculated that reef fish are important sources of selenium and zinc and contain minerals. levels of calcium, iron and omega-3 fatty acids. comparable to other foods of animal origin, such as chicken and pork.

They also found that iron and zinc are more concentrated in fish caught on reefs that were processed after coral bleaching and are now dominated by macroalgae such as Sargassum algae. These algae have high levels of minerals, which the researchers say is one of the main reasons that herbivorous fish feeding on algae that are found in greater numbers on processed reefs contain higher levels. high iron and zinc.

Robinson said: “Coral reef fish contain high levels of essential dietary nutrients such as iron and zinc, therefore contribute to healthy diets in places with high fish consumption. We have found that some rich reef species micronutrients become more abundant after coral bleaching, allowing fishing to provide nutritious food despite the impacts of climate change Protecting the catches of these local food systems should be a food security priority.

The researchers believe the findings underscore the need for effective local management to protect the sustainability of reef fisheries, as well as policies that further retain reef fish catches for local people and promote traditional fish-based diets. . These can help reef fisheries make the best contribution to healthy diets across the tropics.

Professor Christina Hicks, co-author of the study, said: “Fish are now recognized as essential for alleviating malnutrition, especially in the tropics where diets can lack up to 50 percent of the micronutrients needed for healthy growth. This work is promising because it suggests that reef fishing will continue to play a crucial role, even in the face of climate change, and underlines the vital importance of investing in the sustainable management of fisheries.

The results are described in the document “Climate-induced increases in micronutrient availability for coral reef fisheries”.

The authors of the study are: James Robinson, Eva Maire, Nick Graham and Christina Hicks of Lancaster University; Nathalie Bodin from Seychelles Fishing Authority and Sustainable Ocean Seychelles; Tessa Hempson of James Cook University and Oceans Without Borders; Shaun Wilson of the Australian Department of Biodiversity, Conservation and Attractions and the Oceans Institute, Australia; and Aaron MacNeil from Dalhousie University.

– This press release was originally published on the Lancaster University website

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