Marine 'hot spots' surprise researchers

Ocean warming such as that due to climate change may rearrange the distribution of marine life, harming some species, according to a new study conducted by researchers from Dalhousie University in Halifax.

However, the study published online Wednesday in the journal Nature, says it's too soon to know exactly what's happening to individual species. Lead author Derek Tittensor said his team's work is intended to serve as a baseline for future research.

The authors compiled maps of global marine diversity, collecting data on everything from corals, sea grasses and zooplankton to fishes, whales and seals — covering more species than previous studies. The study builds on the decade-long efforts of the Census of Marine Life.

One of its main findings was a consistent link between temperature and diversity, or the number of different species in an area.

"Temperature may well have a strong influence on the distribution of species in the ocean," Tittensor said. "And as the oceans warm in the future, we expect at least patterns of species distributions will change. They will shift. It's very complex, so we don't know exactly how things will look in 50 or 100 years.

'It may become too hot for some species, in which case you will have a problem with species potentially going extinct or suffering due to that.' —Lead author Derek Tittensor

"Species may move. We may find some places have more diversity as species move away from the equator. Some places may have less diversity. It may become too hot for some species, in which case, you will have a problem with species potentially going extinct or suffering due to that."

Marine animals that move might find their prey don't travel at the same speed, and they go hungry, or they encounter a new predator in their newly chosen habitat.

Researchers wanted to find out which species were where and why some places were greater "hot spots of diversity" than others.

They found two fundamental patterns: coastal species such as corals and coastal fish tended to peak in diversity around the equator, in places such as Indonesia and Southeast Asia.

Open-ocean creatures congregate in mid-latitude seas

For oceanic species, or open-ocean creatures, such as tunas and whales, the researchers found a peak in diversity away from the equator, about halfway between the equator and the poles.

Tittensor said the discovery is "surprising" because most terrestrial species peak in numbers at the equator, in places like rainforests in South America, "and we found that pattern for the coastal [marine] species."

The researchers said they were interested in how these newly mapped hot spots related to human impacts on the oceans.

Human activities such as fishing, habitat alteration and pollution were found to be particularly concentrated in areas of high diversity for marine species.

"Our research provides further evidence that limiting ocean warming and other human impacts will be particularly important in securing these hot spots of marine biodiversity into the future," the authors said.