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Study Reveals That Bleached Coral Reefs Are Still a Source of Nutritious Seafood

Scientists investigating coral reefs damaged by the rise in sea temperatures have found an unanticipated ‘bright spot’ of hope for coastal communities that rely upon them for food security.

Study Reveals That Bleached Coral Reefs Are Still a Source of Nutritious Seafood.
A recovering coral reef, Seychelles (Image Credit: © Professor Nick Graham).

A new Lancaster University-led study states that coral reef ecosystems play a supportive role to various small-scale fisheries – and the fish they catch are abundant in micronutrients important to the health of millions of people in the tropics.

Moreover, counter-intuitively, following bleaching events that destroy coral and can alter the composition of reef ecosystems, reef fisheries can continue being abundant sources of micronutrients, even growing in nutritional value for some minerals.

The findings, published recently in the journal One Earth, reveal that micronutrient availability from coral reef small-scale fisheries may be more robust against climate change than formerly believed. This increased insight is vital as progressive global warming means coral bleaching events would become more recurrent and more severe, causing greater stress on these susceptible ecosystems.

Our findings underline the continuing importance of these fisheries for vulnerable coastal communities, and the need to protect against over-fishing to ensure long-term sustainability of reef fisheries.

Dr. James Robinson, Study Lead, Lancaster University

The scientists also warn that while these fisheries have shown to be more resilient to climate change disturbance than previously estimated, continued insight into the long-term impacts of climate change to coral reef fisheries, and more data from other areas, are vital priorities.

Over six million people are employed in small-scale fisheries that depend on tropical coral reefs. Their catches are a source of food for hundreds of millions of coastal people in regions with a high incidence of malnourishment, causing wasting, stunting and anemia.

But, until now, there was no adequate knowledge about the nutritional composition of coral reef fish catches, and how the nutrients available from reef fisheries could be influenced by climate change.

This study, guided by researchers from Lancaster University and involving an international team of scientists from Canada, the Seychelles, Australia and Mozambique, gained from over two decades of long-term monitoring data from the Seychelles, where tropical reefs were destroyed by a large coral bleaching event in 1998, annihilating about 90% of the corals.

After the mass-bleaching event, about 60% of the coral reefs recovered to a coral-controlled system, but approximately 40% were transformed to reefs controlled by seaweeds. These changes provided a natural experiment for the researchers to compare the micronutrients available from fisheries on reefs with various climate-triggered ecosystem compositions.

The researchers, who used a mix of nutrient analysis, experimental fishing and visual surveys of fish communities in the Seychelles, deliberated that reef fish are vital sources of zinc and selenium and contain levels of iron, calcium and omega-3 fatty acids compared to other animal-based foods, such as pork and chicken.

They also learned that zinc and iron are more concentrated in fish caught on reefs that have recovered after coral bleaching and are currently dominated by macroalgae such as Sargassum seaweeds. These seaweeds possess high levels of minerals, which, scientists believe, is the main reason why the algal-feeding herbivorous fishes found in bigger numbers on transformed reefs possess higher levels of zinc and iron.

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. 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.

Dr. James Robinson, Study Lead, Lancaster University

The team trusts that the results emphasize the need for well-planned local management to safeguard the sustainability of reef fisheries, as well as effective policies that retain more reef fish catches for local communities and boost traditional fish-based diets. These can enable reef fisheries to ideally contribute to healthy diets throughout the tropics.

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. This work is promising because it suggests reef fisheries will continue to play a crucial role, even in the face of climate change, and highlights the vital importance of investing in sustainable fisheries management.

Professor Christina Hicks, Study Co-Author, Lancaster University

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

Journal Reference:

Robinson, J.P.W., et al. (2022) Climate-induced increases in micronutrient availability for coral reef fisheries. One Earth. doi.org/10.1016/j.oneear.2021.12.005.

Source: https://www.lancaster.ac.uk

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