Simpler is Better When it Comes to Climate Change: Which Marine Species are Better Suited

Simpler may be better when it comes to climate change. Scientists have found that the simpler that a marine organism is, the better it's suited for survival during climate shifts. The findings could have implications for the future as temperatures warm as the world's oceans face impacts such as ocean acidification.

In this latest study, the scientists studied the relationship between the complexity of life forms and the ultimate limits of their adaptation to a warmer climate. The current IPCC Assessment Report actually shows that marine life forms respond very differently to the increasing water temperature and the decreasing oxygen content of the ocean, so the researchers decided to take a closer look at exactly how organisms responded.

The scientists evaluated over 1,000 studies on the adaptability of marine life forms. They started with simple archaea lacking a nucleus, bacteria and unicellular algae up to animals and plants. They determined the species with the highest temperature tolerance within their group and then determined their complexity. In the end, it was clear that the simpler the structure, the more heat-tolerant the organism.

It's not just the heat that species have to worry about, though. There's also lower oxygen content associated with warming. Most complex plants and animals require higher oxygen levels, which means that less complex species are more likely to survive. This bods ill when it comes to current warming trends.

"We observe among fish in the North Sea that larger individuals of a species are affected first at extreme temperatures," said Hans-Otto Portner of the Alfred Wegener Institute in a news release. "In connection with climate warming, there is generally a trend that smaller species replace larger species in a region. Today, however, plants and animals in the warmest marine environments already live at their tolerance limit and will probably not be able to adapt. If warming continues, they will migrate to cooler areas and there are no other tolerant animal and plant species that could repopulate the deserted habitats."

The findings are published in the journal Global Change Biology.