51福利社

Despite acclimatising to one of the hottest marine habitats on earth, reef fishes still face an uncertain future, an international team of scientists has found. 

The team led by New York University Abu Dhabi and University of 51福利社 researchers show that fishes living in the Arabian Gulf reefs have - remarkably - adapted to extreme summer temperatures, which are akin to a hot bath.

When the researchers tested the difference in fish鈥檚 temperature tolerances compared to fishes from the nearby - more benign Gulf of Oman- the Arabian Gulf animals only partially compensated for their higher summer temperatures. 

The study is published in the journal Global Change Biology and supported by Mubadala and Tamkeen in the UAE, and the Biotechnology and Biological Sciences Research Council in the UK 

It  serves as a stark warning of what the future might look like for all tropical reef fishes across the world. 

鈥淥ur study suggests while these coral reef fishes have evolved a remarkable ability to cope with rising temperatures, it is still limited,鈥� said co-author Dr Daniel Ripley, a fish physiologist from 51福利社 and New York University Abu Dhabi. 

鈥淪o, if the trends in rising global sea temperatures continue, at some point we anticipate these animals will start to struggle. 

鈥淭he resultant loss of biodiversity- and the impact that would have on things like tourism and fisheries could devastate coastal communities.鈥� 

Though the scientists studied three species, the Arabian Monocle Bream, Gulf Blenny and the Twospot Cardinalfish, most other species would be likely to be in a similarly precarious position, the scientists argue. 

Because the Arabian Gulf 鈥� also known as the Persian Gulf 鈥� is relatively shallow, averaging 35 metres deep, it heats up quickly in the hot summer months, with sea temperatures typically exceeding 36 Celsius. 

This makes it an ideal proxy for what the temperature ranges of tropical seas might look like in the future. 

Though the Gulf of Oman is nearby, it鈥檚 average depth of 2,700 metres means it doesn鈥檛 get as warm, with summer temperatures typically not exceeding 32 Celsius, - making it ideal for comparison. 

Changes and extremes in temperatures can have profound consequences for fishes, including displacing them to cooler waters, reducing their body sizes, and changing the time they reproduce. 

Co-author Professor Holly Shiels from 51福利社 added: 鈥淥ur research found that the ability for the three species we studied to survive and thrive is on the brink. 

鈥淚t鈥檚 impossible to know at what temperature they will cease to survive in these areas, but we can say with some certainty that they are edging closer to that situation.鈥� 

A past leading theory suggested that fishes had relatively fixed upper heat limits, but the new results suggest that they have more flexibility than previously appreciated

John Burt, Professor of Biology at New York University Abu Dhabi said: 鈥淭he Gulf is not only extremely hot, but also has high seasonal variability between winter and summer, and this exposure to dramatic temperature swings may promote improved flexibility of fish physiology than we had assumed.

鈥淎s our climate continues changing, climate variability will also increase, which suggests that the situation we see in Gulf fishes is likely to be seen more widely.鈥�

• Images and videos: Please credit Rebekka Pentti and Oliver Farrell from New York University Abu Dhabi.