Climate change forces Mediterranean sea life to new depths - study

The first-of-its-kind study from Tel Aviv University found that many Mediterranean sea life has moved around 55 meters deeper to colder waters as the temperature climbs.

Fish are seen swimming below the Mediterranean Sea, where climate change has forced many animals to swim to new depths. (photo credit: Dr. Shevy Rothman)
Fish are seen swimming below the Mediterranean Sea, where climate change has forced many animals to swim to new depths.
(photo credit: Dr. Shevy Rothman)

As climate change impacts the environment, the world's seas and oceans are among the most effective, harming the habitats of animals all over the world. And in the Mediterranean Sea, it seems many animals are being forced to adapt, heading into deeper and cooler waters to survive, according to a new study from Tel Aviv University (TAU).

In a first-of-its-kind study, published in the academic journal Global Ecology and Biogeography, the TAU scientists analyzed 236 different species.

According to the data, many species such as fish, crustaceans and mollusks such as squids are migrating to on average 55 meters deeper in the Mediterranean in order to avoid warming temperatures closer to sea level.

This depth is within the range of a temperature of 6 degrees Celcius. 

Of course, not all of this was uniform. Cold-water species were naturally found deeper than warm-water ones, for example.

Fish are seen swimming below the Mediterranean Sea, where climate change has forced many animals to swim to new depths. (credit: Dr. Shevy Rothman)Fish are seen swimming below the Mediterranean Sea, where climate change has forced many animals to swim to new depths. (credit: Dr. Shevy Rothman)

The fate of animals when their habitats are altered due to climate change is a common question many experts ponder as global temperatures continue to rise. 

The fact that animals, including maritime animals, have had to change their habitats due to climate change is itself nothing new. Previous observations have noted that narwhals, who primarily live and hunt in inlets and fjords in the Arctic, have been forced to move to the open ocean as their habitats shrink.

But the Mediterranean is far different than the Arctic, which is one of the fastest-changing ecosystems on the planet due to climate change.

“It should be remembered that the Mediterranean was hot in the first place, and now we are reaching the limit of many species’ capacity,” explained Prof. Jonathan Belmaker, whose PhD student Shahar Chaikin led the study. 

“Moreover, the temperature range in the Mediterranean is extreme – cold in the northwest and very hot in the southeast. Both of these factors make the Mediterranean an ideal test case for species’ adaptation to global warming.”

Already, the average temperature rises by a degree every three decades or so. However, climate change has only accelerated this process.

The findings of this study have profound implications for the planet as climate change continues to worsen. This is true for both the Mediterranean and the world at large. 

Essentially, this forecasts future changes that will occur in marine environments as temperatures continue to climb. Knowing this now could hopefully give humanity time to prepare accordingly for these changes.

“Our research clearly shows that species do respond to climate change by changing their depth distribution,” Chaikin said in a statement. 

“And when we think about the future, decision-makers will have to prepare in advance for the deepening of species. For example, future marine nature reserves will need to be defined so that they can also provide shelter to species that have migrated to greater depths. And on the other hand, fishing in the future will involve fishing the same fish at greater depths, which means sailing further into the sea and burning more fuel.”

Temperature changes are also apparent on land, with some experts projecting a rise in global temperatures by 2.9 degrees Celcius by the year 2100. This will no doubt affect many species, and at this rate that could one day include humanity itself. But right now, it is maritime animals that are showing these effects.

“Even if species deepen to escape the warm waters and this rapid adaptation helps them, there is still a limit – and that limit is the seabed,” Belmaker added. “We are already seeing deep-sea fish like cod whose numbers are declining, probably because they had nowhere deeper to go.”