Warming oceans are trapping shellfish in hotspots they can't escape
Many species are expected to be displaced as the world continues to warm and natural habitats are transformed, and this is true both on land and at sea. Scientists studying more than half a century of data on bottom-dwelling shellfish have uncovered evidence of a destructive feedback loop, in which generations of these marine creatures are becoming trapped in warmer areas that threaten their survival.
The research was carried out at Rutgers University and throws up some counter-intuitive revelations concerning the migration of marine species. Many creatures will respond to warming waters by traveling to cooler areas for refuge, but the scientists found a number of species that do just the opposite, a phenomenon they call “wrong-way migration.”
These include sea scallops, blue mussels, clams and quahogs, which the team notes are valuable resources for the shellfish industry, with the team drawing its conclusions from more than six decades of data on more than 50 species off the north-east coast of the US. Around 80 percent of the species studied could no longer be found in their traditional habitats, turning up in shallower, warmer waters instead.
“These deeper, colder waters of the outer shelf should provide a refuge from warming so it is puzzling that species distributions are contracting into shallower water,” says lead author of the study Heidi Fuchs.
According to the scientists, warming waters are causing these species to spawn earlier in the spring and summer. This exposes the larvae to wind patterns and water currents they normally wouldn’t experience, which carry the weak swimmers into areas they wouldn’t normally reside.
Once there, they are already less likely to survive, but the ones that do and go on to reach adulthood become part of a destructive feedback loop, with these warmer regions again causing the earlier spawning of their larvae, and the cycle then repeats.
While this study only looks at bottom-dwelling invertebrates from one general location, the findings are consistent with trends observed in other animals whose habitat is being affected by climate change. This is sometimes called the “elevator to extinction” phenomenon, where animals like birds and butterflies are driven to higher and higher altitudes to escape increasing temperatures until they can no longer be found in areas they originally inhabited.
The research was published in the journal Nature Climate Change.
Source: Rutgers University