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

 

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OTTERS AID SEAGRASS RECOVERY

To restore lost seagrass, just add some otters. According to a new study in Proceedings of the National Academy of Sciences, these adorable critters help counteract the harmful effects of fertilizer pollution.

Seagrass provides valuable marine habitat, sequesters carbon, and shields coastlines from storms. But nutrient run-off from farms can trigger overgrowth of algae, which then block sunlight from reaching the seagrass.

The researchers studied seagrass recovery in Elkhorn Slough, California, which has suffered from rising fertilizer pollution over the last several decades. In the early 1980s, only 2 hectares of eelgrass remained. But after sea otters arrived, the area of eelgrass growth expanded by six times.

The otters contributed to the recovery by eating crabs, the authors suggest. The number of sea slugs, which crabs prey on, increased. Those slugs then grazed on the algae, allowing the seagrass to flourish.— Roberta Kwok | 27 August 2013

Source: Hughes, B.B. et al. 2013. Recovery of a top predator mediates negative eutrophic effects on seagrass. Proceedings of the National Academy of Sciences doi: 10.1073/pnas.1302805110.

http://conservationmagazine.org/2013/08/sea-otters-aid-seagrass-recovery/

Image © Maksimilian | Shutterstock

Sharks are necessary for the ecological health of coral reefs

FOR decades, rangers in Yellowstone National Park, in the American West, had to cull the area’s red deer (known locally as elk, though they bear no resemblance to European elk, known locally as moose) because the animals’ numbers were grazing the place to death and thus threatening the livelihoods of other species. Many ecologists argued that the deer had once been kept under control by wolves, which had been hunted to extinction by people. When wolves were reintroduced to Yellowstone, in 1995, these arguments proved correct. The deer population fell to manageable levels, and culling stopped. Wolves, it turned out, played a crucial role in keeping the wider ecosystem intact. Now comes evidence that the same is true for another top predator: sharks.

Jonathan Ruppert of the University of Toronto, in Canada, and his colleagues reached this conclusion by studying data on shark activity around two groups of coral reefs between Indonesia and Australia. They gleaned their information from baited underwater video stations and also from records collected from those reefs between 1994 and 2008 by the Australian Institute of Marine Science. They have just published their results in the Public Library of Science.

The reef-groups in question, known as the Scott Reefs and the Rowley Shoals, are close to each other. They experience similar sea temperatures. And both were hit by powerful cyclones and affected by coral bleaching in the mid-1990s. One, however, turned out to be rich in fish species whereas the other is impoverished, and the one with more species seemed to recover faster from the storms and the bleaching. Dr Ruppert believes these differences are the result of the presence in one, and the absence in the other, of sharks.

The impoverished group, the Scott Reefs, has been fished for centuries by people interested in catching sea cucumbers, certain snails and sharks—all of which are internationally traded and fetch high prices. In recent decades the demand for sharks, in particular, has boomed, as China has grown richer and its citizens have been supping more shark-fin soup. The Rowley Shoals, by contrast, are a protected area where all fishing is prohibited.

It is hardly a surprise that fishing reduces a reef’s species diversity. But what did surprise Dr Ruppert and his colleagues was exactly how that diversity was diminished. For besides the species that fishermen are hunting (silvertip and grey reef sharks were three times as common around the Rowley Shoals as around the Scott Reefs), many other sorts of animal had suffered.

This was not because they were being caught accidentally. Sea cucumbers and snails are hand-picked by divers, and sharks are caught on lines, rather than in nets, with bait that attracts only carnivores. All this means there is little bycatch. Yet the Scott Reefs also lacked herbivorous species such as parrotfish, though midsized predators, like snappers, were more abundant than in the Rowley Shoals.

Dr Ruppert thinks that eliminating sharks means populations of the midsized predators they feed on rise and those predators’ prey then suffer the consequences. Hence the reduced numbers of parrotfish. Their absence, however, has knock-on effects. Seaweed grows more thickly without parrotfish constantly gnawing at it. That growth smothers young coral and probably, though Dr Ruppert cannot prove it in this particular case, makes it harder for reefs to recover from cyclones and bleaching. Healthy reefs, then, seem to need sharks in the way that healthy forests need wolves. It’s not much fun if you are a snapper or a deer. But Mother Nature prefers it that way.

Source: http://www.economist.com/news/science-and-technology/21586806-sharks-it-seems-are-necessary-ecological-health-coral-reefs-sea

Toxins found in Polar Bear brains

Denmark: In a new study, Arctic researchers have discovered an accumulation of perfluorooctane sulfonates (PFOS) – a PerFluoroAlkyl Substance (PFAS) – and several compounds of the perfluorinated carboxylate (PFCAs) grouping in eight brain regions of polar bears collected from Scoresby Sound, East Greenland.

PFASs and precursor compounds have been used in a wide variety of commercial and industrial products over the past six decades.

There has shown a dramatic increase and dispersal of these substances around the world over the past four decades, and an increasing amount of information is becoming available on the toxicity of these compounds.

In the new research, the scientists, from Carleton University in Canada and Aarhus University in Denmark, used the polar bear as a sentinel species for humans and other predators at the top of the food chain.

Polar bears in East Greenland have toxins in their brains, which can impact the endangered animals’ fertility, Danish researchers have discovered. What’s worse is that the polar bears have not have ingested products containing the dangerous perfluoroalkyl substances (PFAS) accidentally.

Dr Robert Letcher, Carleton University, explained: “We know that fat soluble contaminants are able to cross the brain-blood barrier, but is it quite worrying that the PFOS and PFCAs, which are more associated with proteins in the body, were present in all the brain regions we analysed.”

Professor Rune Dietz, Aarhus University, added: “If PFOS and PFCAs can cross the blood-brain barrier in polar bears, it will also be the case in humans. The brain is one of the most essential parts of the body, where anthropogenic chemicals can have a severe impact. However, we are beginning to see the effect of the efforts to minimise the dispersal of this group of contaminants.”

Dietz’s team has studied 500 polar bears in East Greenland for the past 30 years.

The products in question are everyday items like Teflon pans and textile coatings. Precisely because they don’t dissipate into the environment, they travel up the food chain once they’ve been ingested by a lowly fish species. They also travel far distances inside the bodies of the various fish species and marine mammals, which is how they arrive in polar bear habitats. “When you get to the top of the food chain, where the polar bear reside, you get the highest concentration of these toxins,” explains Dietz.

Another recent study from Aarhus University has documented that PFOS concentrations in Greenlandic polar bears and ringed seals started to decline after 2006. Other wildlife populations closer to the sources in Europe and North America have also shown a decline prior to the Greenlandic animals.

Dietz commented: “It is promising to see that the PFAS are on the decline. This development should be encouraged by the authorities globally.

“In the meantime my best advice to the consumers is to go for environmentally labelled products. But avoiding products is difficult, because PFASs are so widespread in many kind of products and they are rarely declared.”

Though no conclusive evidence exists, PFAS are suspected of damaging the brain, liver and reproduction.

“There are higher levels of PFASs in the brains of Inuits (Greenlanders) as well,” explains Dietz.

Even more worryingly, people in industrialized countries who have never eaten marine mammals have PFASs in their brains, too. But, if they eat neither marine mammals nor fish, how do they ingest the toxins? Researchers at the Norwegian Institute for Air Research are the science world’s detectives, trying to establish how the poisonous substances enter our bodies.

“The increase in PFASs in humans and polar bears is very frightening,” notes Dietz. “The good news is that production of products using these pollutants peaked in 2006. But it’s worrying that there’s still very little regulation of PFASs in China.”

Sources:

http://www.metro.us/newyork/news/national/2013/07/29/researchers-find-toxins-from-distant-countries-in-brains-of-polar-bears/

http://www.paneuropeannetworks.com/detail/news/environmental-toxins-found-in-polar-bear-brains.html

Rune Dietz Blog: http://dce.au.dk/old/danmarksmiljoeundersoegelser/en/blogs/dietz/

other papers published: http://www.researchgate.net/profile/Rune_Dietz/publications/1?sorting=published

Rune Dietz Conference May 2010: http://ec.europa.eu/enterprise/sectors/chemicals/files/reach/docs/events/pfoa-dietz_en.pdf

Polar Bear Specialist Group: http://pbsg.npolar.no/en/

Other Polar Bear’ threats:

http://www.esajournals.org/doi/abs/10.1890/08-1036.1

Oceana: Shark Myths vs. Facts

Confused about sharks? We’re here to dispel some of the biggest myths about sharks:

1. Myth: Sharks are hungry man eaters looking for any chance to attack.

Fact: Sharks are not hunting humans. Most “attacks” on humans are mistakes due to poor water visibility or are inquisitive bites. This is why there are so many more bites than fatalities.

2. MythSharks are all the same.

Fact: Shark species are incredibly diverse with very different sizes, shapes, habitats, diets and behaviors. There are approximately 500 shark species, but only three (white, tiger and bull) are responsible for the majority of all bites.

 3. Myth: All sharks are voracious predators.

Fact: Basking sharks and whale sharks, the two largest species of sharks, are filter feeders that feed on fish eggs and other tiny organisms.

4. Myth: The only good shark is a dead shark.

Fact: Sharks play a vital role in keeping marine ecosystems balanced and healthy. Additionally, sharks help coastal economies through ecotourism. Many people are willing to pay large sums of money for the opportunity to dive with sharks.

5. Myth: If a shark attack has not occurred, it means they do not live in that area.

Fact: Sharks inhabit all of the world’s oceans – from inshore, coastal waters to the open, deep-blue sea – and some can even be found in freshwater rivers and lakes.

6. Myth: Sharks have walnut-sized brains.

Fact: Sharks can exhibit complex social behavior and some species can communicate with body language, live in groups and even hunt in packs. Sharks and rays have some of the largest brains among all fish, with brain-to-body ratios similar to birds and mammals.

7. Myth: All sharks must swim constantly.

Fact: While most sharks do need to swim continuously in order to pass water over their gills and breathe, some sharks are able to actively pump water over their gills while resting on the sea floor.

8. Myth: Shark fins grow back if they are cut off.

Fact: A finned shark thrown overboard will drown, bleed to death or be eaten by other sharks.

9. Myth: Shark fins are flavorsome, nutritious and offer medicinal properties.

Fact: Shark fins offer no flavor or nutritional value. In fact, as top predators, sharks accumulate contaminants from their prey, such as mercury, which has serious health effects even at low doses.

10. Myth: Sharks have no predators.

Fact: The greatest threat to sharks is HUMANS. Each year, tens of millions of sharks are killed for their fins. We are disrupting the ocean ecosystem by killing too many sharks.

Source: http://oceana.org/en/our-work/protect-marine-wildlife/sharks/learn-act/shark-myths-vs-facts

Seven National Wildlife Photo Contest Shark Pictures

Although as an editor for National Wildlife magazine I’m accustomed to seeing some of the world’s best nature photography, I never cease to be amazed by the quality of work that participants enter in the annual National Wildlife Photo Contest. Excellent shots even of species that until recently were rarely photographed show up in the contest every year, such as the following pictures of great white sharks and whale sharks.

great white shark, National Wildlife Photo Contest, NWF, Federation

One of the world’s most widely recognized predators, a great white shark cruises the waters off Mexico.

A Top Sea Predator

The white shark is perhaps the ocean’s most widely recognized predator, but it is still a creature experts know little about. However, new research is unlocking some of the mysteries of white shark behavior.

A growing body of evidence suggests that the world’s white shark population is broken into three units, one centered off South Africa, another off New Zealand, and a third, the northeastern Pacific population, that ranges between California and Hawaii.

white shark, national wildlife photo contest, NWF, federation

A great white shark breaks the surface off South Africa, a prime feeding ground where white sharks prey on seals and sea lions.

Studies conducted during the past decade show that white sharks in the northeastern Pacific Ocean have been isolated from other sharks populations for tens of thousands of years (as a species, great whites date back about 60 million years, and sharks as a group about 450 million). From late summer to early winter these sharks patrol four distinct hunting areas off California and migrate to spend the rest of the year in the open Pacific midway between California and Hawaii, an area biologists call the shark café, on the assumption that the sharks are eating there. However, at this time no one knows for sure what the sharks do in the café. The region may be a mass breeding site, or it may be where females give birth—the site of birthing areas is still a mystery.

A Killing Machine?

Studies off New Zealand indicate that white sharks are not born killers. The jaws of young sharks less than nine feet long are not strong enough for attacking large prey. Biologists working off California have found that the white shark’s diet changes with age, the animals often shifting from fish to mammals as they mature, but even that pattern is flexible—individual sharks tend to specialize in particular types of prey from a selection that includes seals, sea lions, dolphins, fish and squid.

Studies off South Africa and California reveal that sharks seek deeper waters when hunting. The dark upper body of the shark blends in with darker waters and ocean floors in coastal areas, allowing the hunter to lurk in spots frequented by seals and seal lions.

white shark, National Wildlife Photo Contest, Federation, NWF

A white shark plies the clear waters off Isla Guadalupe, Mexico. The dark upper body and white underbelly help the shark conceal itself from prey.

White sharks generally look for a seal silhouetted against the sky and attack by swimming straight up, hitting the luckless prey with such speed that a two-ton, twenty-foot shark may burst completely out of the water, its quarry locked in its jaws.

great white shark, nationla wildlife photo contest, nwf, federation

A white shark rockets from False Bay, South Africa. Hunting sharks move deep in the water and look for a seal or sea lion sihouetted against the surface. When they find one, they attack so fast that they fling themselves from the sea.

However, if a seal survives the initial attack with little or no damage, odds are it can use its greater agility to escape.

white shark, south africa, national wildlife photo contest

A hunting great white shark crashes back into the sea at False Bay, South Africa.

The Shark-Human Connection

Although great whites are coastal hunters, attacks on humans are relatively rare. In 2012, about seventy people were attacked by sharks of all kinds worldwide, with seven fatalities. About sixty percent of these attacks were on people lying on surfboards with hands and feet in the water—from the water below, they would resemble a seal. Often, after a first attack on a surfer, white sharks seem to realize their error and move on without a second attack.

Most sharks are harmless to humans. About half of the worlds’ approximately 360 shark species are less than 3 feet long; only 4 percent exceed 12 feet, and three of those feed on plankton, including the world’s largest, the whale shark—which at 30 feet long and about 5 tons is the largest animal in the world that isn’t a whale (the smallest shark is the pygmy ribbontail catshark, which grows to about 6 inches long).

 

whale shark, national wildlife photo contest, federation, NWF

A whale shark glides through the sea off Darwin Island in the Galapagos. Despite a mouth that might be 5 feet wide, this largest of shark species feeds on tiny things, such as fish eggs.

Humans pose a greater danger to sharks than sharks do to humans. About 30 million to 70 million sharks are killed annually by humans, both as untargeted species taken by the commercial fishing industry and as targets for trade in fins for soup, a luxury item in Asia that can price fins at up to $50 a pound. As a result, great whites as well as other species are steeply declining, some as much as 90 percent in the past two decades. Biologists fear that sharks will be past the point of recovery if better management is not initiated soon.

Loss of sharks can have far reaching ecological and economic effects. Destruction of sharks in recent years along the U.S. Atlantic coast allowed cow-nosed rays to stage a population explosion; heavy feeding by the rays later caused a collapse in bay scallop fisheries.

whale shark, largest shark species, largest fish species, national wildlife photo contest

National Wildlife Photo Contest entrant Gary Moore was boating off Kona, Hawaii, when this whale shark came up to the vessel and followed it for 5 or 10 minutes. Whale sharks are among the species harmless to humans.

Source: http://blog.nwf.org/2013/06/seven-national-wildlife-photo-contest-shark-pictures/

Sharkwater, the truth will surface

“An eye-opening film…visually stunning… this movie will change the way you see our oceans.” – Bonnie Laufer, Tribute Magazine

For filmmaker Rob Stewart, exploring sharks began as an underwater adventure. What it turned into was a beautiful and dangerous life journey into the balance of life on earth.

Driven by passion fed from a lifelong fascination with sharks, Stewart debunks historical stereotypes and media depictions of sharks as bloodthirsty, man-eating monsters and reveals the reality of sharks as pillars in the evolution of the seas.

Filmed in visually stunning, high definition video, Sharkwater takes you into the most shark rich waters of the world, exposing the exploitation and corruption surrounding the world’s shark populations in the marine reserves of Cocos Island, Costa Rica and the Galapagos Islands, Ecuador.

 

n an effort to protect sharks, Stewart teams up with renegade conservationist Paul Watson of the Sea Shepherd Conservation Society. Their unbelievable adventure together starts with a battle between the Sea Shepherd and shark poachers in Guatemala, resulting in pirate boat rammings, gunboat chases, mafia espionage, corrupt court systems and attempted murder charges, forcing them to flee for their lives.

Through it all, Stewart discovers these magnificent creatures have gone from predator to prey, and how despite surviving the earth’s history of mass extinctions, they could easily be wiped out within a few years due to human greed.

Stewart’s remarkable journey of courage and determination changes from a mission to save the world’s sharks, into a fight for his life, and that of humankind.

Genre: Documentary
Running time: 89 min.
Director: Rob Stewart
Studio: Alliance Films
Producer(s): Rob Stewart
Screenplay: Rob Stewart
Cast: Rob Stewart, Paul Watson, Dr. Erich Ritter, Susan Backlinie, Godfrey Merlin, Mark Butler, Dr. Boris Worm, William Goh, Vic Hislop, Dr. Samuel Gruber, Rex Weyler, Carlos Perez Cembrero, Patrick Moore, Lisa Anastario, Larissa Gilligan

 

Find more on:  http://www.sharkwater.com