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Coral reefs altered by rising sea temperatures and bleaching are far more resilient than previously thought and can still provide important fish nutrients to millions of people who rely on them for food, according to a new study by researchers at Dalhousie University and other international institutes.

The findings, published today in the journal One Earth, show that reef ecosystems support diverse small-scale fisheries and the fish they catch are rich in micronutrients vital to the health of millions of people in the tropics.

The researchers, from Dalhousie, Lancaster University and the Seychelles, Australia and Mozambique, also found that the availability of micronutrients from these fisheries may be able to withstand the impacts of climate change better than previously thought. In particular, reef fisheries can remain rich sources of micronutrients -- even increasing in nutritional value for some minerals -- after bleaching events that kill off coral.

Aaron MacNeil, an associate professor in Dalhousie’s Department of Biology and co-author of the study, says this work is significant since coral bleaching events are becoming increasingly frequent and severe, placing greater stress on these vulnerable ecosystems.

“More and more we are realizing that marine fish are critical to good health and nutrition for millions, providing a readily available source of up to 50 per cent of essential micronutrients that people need to grow and be healthy, particularly among tropical nations. This work shows us that marine fish will continue to do so in the face of climate change, underscoring the need for effective fisheries management for many years to come,” says Dr. MacNeil.

The researchers caution that while these fisheries have proved to be more resistant to climate change disturbance than expected, understanding the long-term effects of climate change on reefs and acquiring more data from other regions are urgent priorities.

More than six million people work in small-scale fisheries that rely on tropical coral reefs. Their catches help feed hundreds of millions of coastal people in regions with high malnutrition. However, until now, little was known about the nutritional composition of coral reef fish catches and how climate change might affect their nutrients.

This study used more than 20 years of monitoring data from the Seychelles, where an estimated 90 per cent of tropical reefs were killed by a large coral bleaching event in 1998. Bleaching occurs when water becomes too warm and corals expel an alga that causes the coral to turn white.

Following the mass-bleaching event, around 60 per cent of the coral reefs recovered, but around 40 per cent were transformed to reefs dominated by seaweeds. These differences provided a natural experiment for the scientists to compare the micronutrients available from fisheries on reefs with different climate-driven ecosystem compositions.

“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," said co-author Dr. James Robinson of Lancaster University.

Dr. MacNeil is available to discuss the results and how they underline the need for effective local management to protect reef fisheries, along with policies that retain more reef fish catches for local people.

Photos, credits available here.

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Media contact:
Alison Auld
Senior Research Reporter
Communications, Marketing and Creative Services
Dalhousie University
Cell: 1-902-220-0491
Email: alison.auld@dal.ca