Whales as ecosystem engineers

“Consider the subtleness of the sea; how its most dreaded creatures glide under water, unapparent for the most part,” wrote Herman Melville in Moby Dick. Today, we no longer dread whales, but their subtlety remains. “For a long time, whales have been considered too rare to make much of a difference in the oceans,” notes University of Vermont conservation biologist Joe Roman. That was a mistake.

Whales as ecosystem engineers

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.

In a new paper, Roman and a team of biologists have tallied several decades of research on whales from around the world; it shows that whales, in fact, make a huge difference—they have a powerful and positive influence on the function of oceans, global carbon storage, and the health of commercial fisheries. “The decline in great whale numbers, estimated to be at least 66% and perhaps as high as 90%, has likely altered the structure and function of the oceans,” Roman and his colleagues write in the July 3, 2014, online edition of Frontiers in Ecology and the Environment, ” but recovery is possible and in many cases is already underway.”

“The continued recovery of great whales may help to buffer  from destabilizing stresses,” the team of scientists writes. This recovered role may be especially important as climate change threatens  ecosystems with rising temperatures and acidification. “As long-lived species, they enhance the predictability and stability of marine ecosystems,” Roman said.

Baleen and , known collectively as the “great whales,” include the largest animals to have ever lived on Earth. With huge metabolic demands—and large populations before humans started hunting them—great whales are the ocean’s ecosystem engineers: they eat many fish and invertebrates, are themselves prey to other predators like , and distribute nutrients through the water. Even their carcasses, dropping to the seafloor, provide habitat for many species that only exist on these “whale falls.” Commercial whaling dramatically reduced the biomass and abundance of great whales.

“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.” They do this by feeding at depth and releasing fecal plumes near the surface—which supports plankton growth—a remarkable process described as a “whale pump.” Whales also move nutrients thousands of miles from productive feeding areas at high latitudes to calving areas at lower latitudes.

Sometimes, commercial fishermen have seen whales as competition. But this new paper summarizes a strong body of evidence that indicates the opposite can be true: whale recovery “could lead to higher rates of productivity in locations where whales aggregate to feed and give birth,” supporting more robust fisheries.

As whales recover, there may be increased whale predation on aquaculture stocks and increased competition—real or perceived—with some . But the new paper notes ” a recent investigation of four coastal ecosystems has demonstrated the potential for large increases in whale abundance without major changes to existing food-web structures or substantial impacts on fishery production.”

In death, whale carcasses store a remarkable amount of carbon in the deep sea and provide habitat and food for an amazing assortment of creatures that only live on these carcasses. “Dozens, possibly hundreds, of species depend on these whale falls in the deep sea,” Roman notes.

“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 said, “These species would have disappeared before we had a chance to discover them.”

Until recently, ocean scientists have lacked the ability to study and observe directly the functional roles of whales in marine ecosystems. Now with radio tagging and other technologies they can better understand these roles. “The focus of much marine ecological research has been on smaller organisms, such as algae and planktonic animals. These small organisms are essential to life in the sea, but they are not the whole story,” Roman said.

New observations of whales will provide a more accurate understanding of historical population dynamics and “are likely to provide evidence of undervalued whale ecosystem services,” note the ten scientists who co-authored this new paper, “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 .”

Source: http://phys.org/news/2014-07-whales-ecosystem.html#jCp
Explore further: Scientists use DNA to identify species killed during early whaling days

Journal reference: Frontiers in Ecology and the Environment


On Whales, divers, encounters and recreational boats impact on marine wildlife


When I started my internship with WDC in Plymouth, Massachusetts, I thought I had a pretty good understanding of the issues that whales of all shapes and sizes face. I’ve read the articles, seen clips on the news, and shared in the horror of the grisly pictures of mangled or deceased whales that are posted online.
As the summer has gone on and I spent more time on whale watching boats, collecting data for the organization, I felt more and more comfortable in my knowledge of the issues the great whales that I watched must face everyday.
We practiced Whale SENSE, a program with special attention to the guidelines on how to safely whale watch, and spread the word about the issues of vessel strikes, entanglements, and loss of habitat. We educated the throngs of whale watchers, taking advantage of their excitement and awe of the giant creatures they were seeing to enlist their support in the whales’ continued protection. But reading words and looking at pictures does not give you the full picture of these issues, or prepare you for the anger and frustration felt while watching it happen.
During a sunny day in early July, three whale watching boats followed a single humpback whale, Nile, using guidelines learned in the Whale SENSE program. You could hear the cries of excitement from all the boats each time Nile surfaced, rolled, and dove, eventually situated in the middle of the boats. The mass of passengers and myself all watched then as a recreational boater, wanting to get a better view, drove through the middle of the whale watching boats and where Nile had just dove moments before. Elizabeth, a fellow intern, and I held our breaths, tracking the boat with our eyes and hoping Nile would surface far away. Even the passengers behind us could feel the tension and were as helpful as they could be, eagerly sharing with us the name of boat. As Nile resurfaced a few hundred yards away from all the boats, we relaxed briefly, until the irresponsible boater spotted her as well. He revved two propeller engines and raced towards her, only slowing when he was within one hundred yards, approaching her closely from behind.
Among issues such as whaling and pollution, vessel strikes are one of the major threats to large whales and other cetaceans, even threatening the survival of entire species. A lack of awareness of these issues and the proper training on how to approach large whales, or to avoid them all together, perpetuates the problem. All cetaceans are vulnerable to boat collisions, which can include injuries such as broken bones, blunt trauma, and severe lacerations from propellers. These cuts can later can become infected and kill the animal if it hadn’t died from the force of the strike already (Richard Caddell).
Luckily, Nile was not harmed by this boat and made the wise choice to keep doing what whales do and swim gracefully onwards. While as interns we have been warned of irresponsible boaters, seeing it for yourself is a hard thing to handle. I was surprised by the amount of anxiety and anger that over came me at the ignorance and carelessness of some boaters, and the overwhelming feeling of helplessness. All that I, and the hundreds of whale watch passengers, could do was watch. We took our pictures and wrote down the boat’s identification numbers and would submit a report in the coming days, but whether that boat or any other dangerous boaters would ever hear from the authorities is beyond our control.
In the case of maritime laws and their enforcement, their existence is helpful but it is difficult to track violations. While it may seem that little action can be taken during the moment, the real action must be taken on shore, with education, awareness, and the occasional monetary fine for bad behavior. What makes people behave better than the knowledge that their bad actions come with dollar signs attached?
I don’t see recreational boaters as people intentionally seeking out whales to do harm. I only see people who are there to do the same thing we are, admire the magnificence of these creatures. Unfortunately their lack of knowledge of the appropriate and safe way to do that put these creatures, and the boaters themselves, in danger. We need everyone’s cooperation to protect these whales, so spread the word – we all share the responsibility of protecting our oceans.