New York University Abu Dhabi (NYUAD) student and faculty researchers have studied the extreme temperatures of the Arabian Gulf to better understand how fish diets change in response to thermal stress, providing important insights into how diets may shift in other parts of the world under future climate change.

Researchers analyzed the contents of 146 stomachs from three different fish species, Arabian angelfish, Dark damselfish, and Paletail damselfish. Samples were collected seasonally over one year, providing the first detailed description of what fish in the southern Arabian Gulf eat and demonstrating how their diets change when sea temperatures fluctuate from cool at the start of the year to extremely hot during the summer.

One of the most significant findings has been that coral is the major component in the diets of all three fish species. “It’s fascinating because none of these species are known to consume coral in any meaningful quantity in other regions,” said John Burt, associate professor of biology and principal investigator of the NYUAD Marine Biology Lab.

“Our study provides some amazing insights into the unusual nature of fish diets in the thermally extreme southern Arabian Gulf, allowing us to start making predictions about how reef fish diets in other parts of the world might shift as climate change makes those areas warmer,” Burt added.

Climate change is altering the ecology of the world's coral reefs, affecting fish feeding behaviors and food availability for millions of fish that rely on reefs for their main meals. As Arabian Gulf sea temperatures can reach up to 37 degrees Celsius in the summer, the region provides invaluable opportunities to study the diets of local fish that have adapted to these extreme temperatures.

The research also explored the diets of Arabian angelfish, demonstrating that while angelfish are mainly known to specialize on sponges elsewhere in the world, off the shores of the UAE sponges account for only a very small portion of their diets.

“Sponges are fairly rare in southern Arabian Gulf reefs, so it appears that angelfish are switching their diets away from their preferred food to one that is much more common here: coral,” Burt concluded.

Diets of damselfishes also changed dramatically over the course of the year, the study found, fluctuating from periods where they mainly consumed coral to periods when their diets widened to include a suite of other organisms in the spring. It was determined that broadening diets by season might be a strategy to build up energy reserves quickly before the onset of the summer heat.

The research originated as a Capstone project led by NYUAD alumna Rasha Shraim, a biology major who graduated in the Class of 2016. The project used next-generation sequencing approaches to examine fish stomach contents rather than traditional microscopic surveys.

“Traditionally, researchers would have to pore over microscopes and visually sort through and try to identify small and partially digested pieces of foods. The metagenomics approach used in this study proved to be a fast and effective means of quickly identifying the materials in stomachs, including a wide variety of items that could never be identified using traditional approaches,” Burt noted.

The full article is freely available to the public in the journal Frontiers in Marine Science.