Without otter predation, sea urchins decimate Aleutian reefs

Scientists have linked sea urchins, otters and climate change to the destruction of reefs in the Aleutian Islands in a new study published in Science. Uncontrolled by sea otters, their natural predator, sea urchins are devouring the massive limestone reefs surrounding the Aleutian Islands — a process exacerbated by climate-driven changes in the marine environment, according to the study.

Brenda Konar, a University of Alaska Fairbanks professor at the College of Fisheries and Ocean Sciences and a co-author of the study, began diving in the Aleutians in the 1990s, just as the Aleutian sea otter population began to crash from killer whale predation. With otters gone, the urchin population boomed both in body size and density. They began eating more kelp, which grows on the reefs.

“In the past, there would be huge, vast kelp forests that went on for miles,” Konar said. “Now there are carpets of sea urchins everywhere — some places easily have 400 urchins per square meter. Kelp forests are essentially gone in the central and western Aleutians.” The Aleutian reefs and their kelp beds serve as nursery grounds for cod and other fish. The 1,200-mile archipelago helps support the annual multibillion-dollar Bristol Bay and Bering Sea fisheries.

Read the full story form University of Alaska Fairbanks here.