Marine Animals Follow Cooler Waters To Escape Climate Change
September 13, 2013

Marine Animals Follow Cooler Waters To Escape Climate Change

Brett Smith for - Your Universe Online

Like humans headed for air-conditioning during the hot summer months, mobile marine life will often move en masse to avoid rising temperatures.

With climate change expected to drive ocean temperatures up a few degrees, a team of American and Canadian scientists decided to investigate how shifting temperatures might affect the large scale movements of marine life, in a new report published Friday in the journal Science.

According to the report, marine creatures regularly keep up with regional "climate velocity," or the pace and direction in which ecosystem changes such as ocean temperature move. Based on 43 years of data tracking over 120 million animals from 360 species living around North America, the team found that 70 percent of changes in animals' preferred depth and 74 percent of changes in latitude could be associated with regional-scale fluctuations in ocean temperature.

"If we follow the temperature, which is easier to predict, that provides a method to predict where the species will be, too," said study author Malin Pinsky, currently an assistant professor of ecology and evolution at Rutgers University.

"Climate changes at different rates and in different directions in different places," he said. "Animals are basically being exposed to different changes in temperature."

Study data was culled from marine surveys taken from 1968 to 2011 by American and Canadian fishery-research centers and government organizations. The survey information included surface and bottom temperatures, as well as the complete mass of animals in nine areas with major significance to North American fisheries.

The research team said the data showed that sea creatures follow a "complex mosaic of local climate velocities.”

Temperature changes for all North American waters moved north an average of 4.5 miles per decade, but in parts near Newfoundland that pace was a much faster -- 38 miles north every ten years. In areas off the West Coast, temperatures moved south at 30 miles per decade, while in the Gulf of Mexico the pace ranged from 19 miles south to 11 miles north per decade.

Animal movements were just as varied. Cod living near Newfoundland moved 37 miles north per decade, while lobster off the northeastern US coast headed north at 43 miles per decade. Meanwhile, pink shrimp along the Gulf Coast fisheries moved south 41 miles per decade, the study found.

Pinsky said that efforts to predict fish migration haven’t been as vigorous as campaigns to prevent overfishing. He suggested that regulators should consider how fish populations are being affected by both changing climates and fishing tactics.

"We don't want to restrict fishing when not needed, or blame climate change for a species collapse when fishing is to blame," Pinsky said. "There have not been many attempts before to connect fine-scale biological data with fine-scale climate data. Our research implies that climate can be very useful for predicting marine distribution shifts. We expect these species to follow climate velocity in the future."

First proposed in 2009, local climate velocity could explain why up to 60 percent of land and sea species have not headed for cooler ecosystems or deeper waters, the researchers said. They noted that animals tend to follow regional temperature factors, which may deviate from rising global temperatures.

"We're just starting to understand how climate affects species, and it's been common to talk about broad patterns like species shifting toward the poles as climate warms," Pinsky said. "The problem has been that many species are not shifting toward the poles, and even of those species that are, some are shifting quickly and others slowly. Scientists were asking themselves, 'Why aren't certain species doing what we expect?' It turns out they are, we just had to alter our expectations."