July 3, 2014
New Study Finds Ocean Ecosystems Naturally Engineered By Whales
Brett Smith for redOrbit.com - Your Universe Online
Whales have often been viewed as the lonely nomads of the seas, but a new report has found that these large mammals are actually great engineers of marine ecosystems.Published in Frontiers in Ecology and the Environment, the new study reviewed several decades of research on whales from around the world and found they play a powerful and positive role with respect to ocean function, global carbon storage, and ecosystem productivity.
"For a long time, whales have been considered too rare to make much of a difference in the oceans," said study author Joe Roman, a conservation biologist at the University of Vermont. "The decline in great whale numbers, estimated to be at least 66 percent and perhaps as high as 90 percent, has likely altered the structure and function of the oceans.”
As long-lived species, whales safeguard the ocean against the expected effects of climate change by acting as a stabilizing force, the study team argued. Sperm and baleen whale affect the oceans through their consumption of countless fish and invertebrates, while acting as prey to other predators like killer whales. Even when they die – the whales’ carcasses drop to the seafloor and support many species that rely on these "whale falls."
"As humpbacks, gray whales, sperm whales and other cetaceans recover from centuries of overhunting, we are beginning to see that they also play an important role in the ocean," Roman said. "Among their many ecological roles, whales recycle nutrients and enhance primary productivity in areas where they feed."
Whales increase productivity by feeding in deep waters and releasing fecal plumes near the surface, the researchers said. This whale waste supports plankton—a cyclical phenomenon described as a "whale pump." Whales also transfer nutrients thousands of miles by feeding at high latitudes and calving at lower latitudes.
While the fishing industry might see whales as competition, the new study indicates further recovery of whales "could lead to higher rates of productivity in locations where whales aggregate to feed and give birth," which supports more robust fisheries. In making their case, the study authors cited a recent investigation of four coastal ecosystems that showed potential for large increases in whale abundance without “significant changes to existing food-web structures or substantial impacts on fishery production."
The study also highlighted the role whales play in death, dropping to the sea floor, sequestering carbon there and supporting numerous scavenger species.
"Dozens, possibly hundreds, of species depend on these whale falls in the deep sea," Roman noted.
"Our models show that the earliest human-caused extinctions in the sea may have been whale fall invertebrates, species that evolved and adapted to whale falls," Roman added. "These species would have disappeared before we had a chance to discover them."
The study team emphasized future observations of whales should reveal "evidence of undervalued whale ecosystem services” and "this area of research will improve estimates of the benefits—some of which, no doubt, remain to be discovered—of an ocean repopulated by the great whales."
Image 2 (below): Huge blue whales plunge to 500 feet or deeper and feed on tiny krill. Then they return to the surface—and poop. This 'whale pump' provides many nutrients, in the form of feces, to support plankton growth. It's one of many examples of how whales maintain the health of oceans described in a new scientific paper by the University of Vermont's Joe Roman and nine other whale biologists from around the globe. Credit: Frontiers in Ecology and the Environment