Researchers examining the effects of rising sea temperatures on coral reefs have identified an unexpected ray of hope for populations that rely on them for food security.
According to a recent Lancaster University-led study, coral reef ecosystems support diversified small-scale fisheries, and the fish they catch are rich in micronutrients critical to the health of millions of people in the tropics.
Surprisingly, even after bleaching episodes that kill coral and change the composition of reef ecosystems, reef fisheries can remain significant suppliers of micronutrients, with some minerals’ nutritional value even increasing.
The findings, which were published today in the journal One Earth, suggest that micronutrient availability from coral reef small-scale fisheries may be more adaptable to climate change than previously anticipated.
This improved understanding is crucial because, as a result of continuous global warming, coral bleaching events are growing more frequent and severe, putting increasing stress on these fragile ecosystems.
Dr. James Robinson, who led the study, said: “Our findings underline the continuing importance of these fisheries for vulnerable coastal communities, and the need to protect against over-fishing to ensure the long-term sustainability of reef fisheries.”
While these fisheries have proven to be more resilient to climate change disturbance than expected, the researchers warn that a better knowledge of the long-term implications of climate change on coral reef fisheries, as well as more data from other places, are a critical priority.
Small-scale fisheries that rely on tropical coral reefs employ more than six million people. Their captures help feed hundreds of millions of coastal residents in areas where malnutrition is common, resulting in stunting, wasting, and anemia.
The nutritional makeup of coral reef fish captures, as well as how climate change can alter the nutrients available from reef fisheries, were unknown until recently.
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
This research, led by Lancaster University scientists and involving researchers from the Seychelles, Australia, Canada, and Mozambique, drew on 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 an estimated 90% of the corals.
Around 60% of coral reefs reverted to a coral-dominated system after the mass-bleaching event, but around 40% were changed into seaweed-dominated reefs. The scientists were able to compare the micronutrients available from fisheries on reefs with various climate-driven ecosystem compositions as a result of these changes.
Reef fish are important sources of selenium and zinc, and contain levels of calcium, iron, and omega-3 fatty acids comparable to other animal-based foods like chicken and pork, according to the researchers, who used a combination of experimental fishing, nutrient analysis, and visual surveys of fish communities in Seychelles.
They also discovered that fish taken on reefs that have been changed following coral bleaching and are now dominated by macroalgae such as Sargassum seaweeds had higher iron and zinc concentrations.
Researchers believe that the high mineral content of these seaweeds is one of the reasons why algal-feeding herbivorous fishes observed in greater numbers on altered reefs have higher iron and zinc levels.
Dr. Robinson said: “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.”
The findings, according to the researchers, highlight the need of good local management for reef fisheries sustainability, as well as policies that keep more reef fish captured for local people and support traditional fish-based diets. Reef fisheries can use them to help people eat healthier in the tropics.
Professor Christina Hicks, a co-author on the study, said: “Fish are now recognized 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.”
The study’s authors include: James Robinson, Eva Maire, Nick Graham and Christina Hicks from Lancaster University; Nathalie Bodin from Seychelles Fishing Authority and Sustainable Ocean Seychelles; Tessa Hempson from James Cook University and Oceans Without Borders; Shaun Wilson from the Department of Biodiversity, Conservation and Attractions in Australia, and Oceans Institute, Australia; and Aaron MacNeil from Dalhousie University.