domingo, 16 de diciembre de 2012

Coral sperm bank offers last ditch hope for restoring health of reefs

Coconut Island, HI - Just before sunset, on the campus of the Hawaii Institute of Marine Biology, Mary Hagedorn waited for her mushroom corals to spawn.

As corals go, Fungia is fairly reliable, usually releasing its sperm and eggs two days after the full moon, but this time they were late.

Eventually, as Dr Hagedorn and her assistant watched, one coral tightened its mouth and seemed to exhale, propelling a cloud of sperm into its bath and the water bubbled like hot oatmeal.

A reproductive physiologist with the Smithsonian Institution, Dr Hagedorn, 57, is building what is essentially a sperm bank for the world's corals. She hopes her collection - gathered in recent years from corals in Hawaii, the Caribbean and Australia - will someday be used to restore, and even rebuild, damaged reefs.

She estimates that she has frozen 1 trillion coral sperm, enough to fertilise 500 million to 1 billion eggs. In addition, there are 3 billion frozen embryonic cells; some have characteristics of stem cells, meaning they may have the potential to grow into adult corals.

Dr Hagedorn's collection is the only one of its kind. While corals can reproduce asexually - that is, fragments of coral can grow into clones of their parents - Dr Hagedorn points out that only sexual reproduction maintains genetic diversity within populations, and with it a species' capacity to survive and adapt to change.

For corals, the number of likely partners is shrinking. As climate change warms the oceans, corals are becoming more vulnerable to disease and bleaching.

In recent years, bleaching events have grown from local curiosities to global phenomena and, in some cases, are so severe and long-lasting that the corals cannot recover. Meanwhile, rising carbon dioxide levels are acidifying the oceans, inhibiting the growth of coral skeletons and weakening the bones of reefs.

In the central and western parts of the Pacific Ocean the extent of living coral is thought to have shrunk by half between the early 1980s and 2003. If this decline continues, almost all of the world's reefs will be on their way to oblivion by 2050.

Dr Hagedorn supports traditional conservation strategies, such as marine refuges, but is preparing for their failure. While she freezes coral sperm and eggs for future use, colleagues are refining techniques for raising coral in captivity and for reintroducing young corals to their natural habitats.

But she and her colleagues have to struggle to raise money for her efforts, which are often seen as a distraction from the more immediate job of habitat protection.

Last northern autumn, she and a group of colleagues travelled to Australia at the invitation of the Australian Institute of Marine Science. Using techniques developed by Dr Hagedorn, they froze sperm and cells from colonies of Acropora tenuis and Acropora millepora, two of the roughly 400 coral species native to the Great Barrier Reef.

viernes, 14 de diciembre de 2012

Researchers monitor red tides in Chesapeake Bay

Gloucester Point, VA — Researchers at the Virginia Institute of Marine Science continue to monitor the algal blooms that have been discoloring Chesapeake Bay waters during the last few weeks. These "red tides" occur in the lower Bay every summer, but have appeared earlier and across a wider area than in years past, likely due to last winter's warmth and this summer's heat.

Red tides are caused by dense blooms of tiny marine plants called algae that contain reddish pigment. Algae are normal components of all aquatic environments, but can produce what is known as a "harmful algal bloom" or "HAB" when they bloom in significant numbers and generate toxic byproducts. HABs can be harmful to both marine organisms and human health.

Professor Kim Reece, a member of Virginia's Harmful Algal Bloom Task Force, is the focal point for HAB research and monitoring at VIMS. Reece, fellow VIMS professor Wolfgang Vogelbein, and other colleagues at VIMS partner with representatives from the Virginia Department of Health, the Marine Resources Commission, the Department of Environmental Quality, and Old Dominion University to track the appearance of algal blooms within Virginia waters and to determine whether the bloom organisms pose any threat to marine life or human health.

There is currently no evidence of harm from the recent blooms, which were first observed in early to mid-July. Study of samples taken in the York River near VIMS' Gloucester Point campus show that they comprise dense aggregations of Cochlodinium polykrikoides, a single-celled marine dinoflagellate.

Reece says "Blooms of this and closely related species may harm oyster larvae and other marine life, and are associated with fish kills and economic loss in Japan and Korea, but we've had no reports of any of these effects in local waters this year." Fish and crab kills reported in the Bay during Cochlodinium blooms in previous years are likely due to low levels of dissolved oxygen, which are associated with blooms of many different species and occur when the algal cells die, sink, and decay.

Virginia residents who have observed a patch of water that is colored red or mahogany and are concerned should contact Virginia's toll-free Harmful Algal Bloom hotline at (888) 238-6154.

Algal blooms are not uncommon in lower Chesapeake Bay during the spring and summer. Algae respond to the same conditions that encourage plant growth on land, and thus are most likely to form blooms when waters are warm and nutrient rich. Excess nutrients from farms and yards, sewage treatment plants, and the burning of fossil fuels are one of the biggest challenges facing the Bay.

"There are three main ingredients for an algal bloom," explains Reece. "Warm waters that favor rapid growth of algal cells, abundant nutrients to fertilize that growth, and wind and tidal-driven currents to confine the cells into a dense aggregation. Our recent heat and rains provide ideal conditions for bloom formation, so we'll continue to monitor whether the ongoing blooms become a cause for any concern."

Real-time monitoring of algal blooms is not an easy task, as it involves developing and applying DNA tests to rapidly identify -- from among a huge variety of mostly benign microorganisms -- the particular algal species that have been observed to produce toxins. Development of these molecular DNA assays is a prime focus of Reece's research at VIMS.

Monitoring also requires daily collection of water samples from all across lower Chesapeake Bay. Analysis of these samples at VIMS shows that Cochlodinium is currently blooming in the York, James, Elizabeth, and Lafayette rivers; Mobjack Bay; and near the mouth of the Bay in the vicinity of the Hampton Roads Bridge Tunnel.

miércoles, 12 de diciembre de 2012

Divided dolphin societies merge for first time

Sydney, NSW - Two become one: the unification of these two socially distinct groups of bottlenose dolphin demonstrates the intelligence and social adaptability of the species.

A unique social division among a population of bottlenose dolphins in Australia's Moreton Bay has ended, according to a new study. The dolphins lived as two distinct groups that rarely interacted, one of which foraged on trawler bycatch.

But scientists think that a ban on fishing boats from key areas has brought the two groups together. They believe these socially flexible mammals have united to hunt for new food sources. The findings are published in the journal Animal Behaviour.

Bottlenose dolphins have large brains and quickly learn new behaviours. Using a wide range of sounds to communicate with other members of the group, or "pod", they have been observed showing remarkable individual and social intelligence:

The Moreton Bay dolphins were thought to be the only recorded example of a single population that consisted of groups that were not associating with each other in a split dubbed "the parting of the pods". But since the study that discovered the rift, trawlers have been banned from designated areas of the bay leading to a 50% reduction in the fishing effort.

A key area of the bay to the south, where the social split was observed by the previous study, has been protected. The changes gave scientists a unique opportunity to observe the adaptability of dolphin society. The "trawler" dolphins from Moreton Bay had previously fed on the bycatch from boats while the "non-trawlers" found other sources of food.

"There's never been really any experiments looking at social structure... where you can compare what it was like before and what it is like now," said Dr Ina Ansmann, marine vertebrate ecologist, University of Queensland, and the study's lead author.

Analysing how the population interacted before and after trawling meant the team could assess how the dolphins' social network had changed. "The dolphins had basically re-arranged their whole social system after trawling disappeared so they're now actually interacting again," Dr Ansmann told BBC Nature.

The scientists identified individual dolphins by the marks on their dorsal fin and recorded which animals were associating with which.

"Each dolphin has small injuries like nicks and notches, cuts and things like that on the fin so they all have a very unique looking dorsal fin." This technique meant that Dr Ansmann could observe changes in behaviour, in some cases down to the individual dolphins which had been studied in the 1990s to reveal the original division.

The "trawler" dolphins of Moreton Bay benefited from the bycatch thrown back from fishing boats "Presumably they're sharing information, co-operating and things like that." One of those males is now fully integrated into a single community.

Dolphins operate in what is called a fission-fusion society, forming groups and then splitting up to form different groups. Through complex communication and social intelligence, bottlenose dolphins often work as a team when hunting for food and Dr Ansmann believes this may be what lies behind the unification.

"When relying on natural food sources I guess it's more important for them to interact with others, or to learn from others, or to co-operate with others to get to these food sources," she said. The results suggest that a flexible social structure may be an important factor in how dolphins exploit a wide range of resources in the marine environment.

lunes, 10 de diciembre de 2012

A whale of a hearing system

New York, NY - Kina, a false killer whale, was the focus of a study about how marine mammals hear. A group of scientists led by marine biologist Paul Nachtigall discovered whales can "close" their ears, decreasing their sensitivity to loud noises underwater.

Scientists have long known that man-made, underwater noises – from engines, sonars, weapons testing, and such industrial tools as air guns used in oil and gas exploration – are deafening whales and other sea mammals. The Navy estimates that loud booms from just its underwater listening devices, mainly sonar, result in temporary or permanent hearing loss for more than a quarter-million sea creatures every year, a number that is rising.

Now, scientists have discovered that whales can decrease the sensitivity of their hearing to protect their ears from loud noise. Humans tend to do this with index fingers; scientists haven't pinpointed how whales do it, but they have seen the first evidence of the behavior.

"It's equivalent to plugging your ears when a jet flies over," said Paul E. Nachtigall, a marine biologist at the University of Hawaii who led the discovery team. "It's like a volume control."

The finding, while preliminary, is already raising hopes for the development of warning signals that would alert whales, dolphins and other sea mammals to auditory danger.

Peter Madsen, a professor of marine biology at Aarhus University in Denmark, said he applauded the Hawaiian team for its "elegant study" and the promise of innovative ways of "getting at some of the noise problems." But he cautioned against letting the discovery slow global efforts to reduce the oceanic roar, which would aid the beleaguered sea mammals more directly.

The noise threat arises because of the basic properties of seawater. Typically, light can travel for hundreds of feet through ocean water before diminishing to nothingness. But sound can travel for hundreds of miles.

The world's oceans have been getting noisier as companies and governments expand their undersea activities. Researchers have linked the growing racket to deafness, tissue damage, mass strandings and disorientation in creatures that rely on hearing to navigate, find food and care for their young. The danger has long been a political football.

In 2008, the Supreme Court heard a lawsuit by the National Resources Defense Council against the Navy over ocean noise; the court ruled that naval vessels had the right to test sonar systems for hunting submarines. But environmentalists saw a tacit victory in getting the nation's highest court even to consider the health of sea mammals in a debate over national security.

The latest development took place at a research facility off Oahu – at an island where the opening shots of "Gilligan's Island" were filmed. Scientists there are studying how dolphins and toothed whales hear. In nature, the mammals emit sounds and listen for returning echoes in a sensory behavior known as echolocation. In captivity, scientists taught the creatures to wear suction-cup electrodes, which revealed the patterns of brainwaves involved in hearing.

The discovery came in steps. First, Nachtigall and his team found that the animals could adjust their hearing in response to their own loud sounds of echolocation, mainly sharp clicks. The scientists then wondered if they could also protect their ears from incoming blasts.

The team focused on a false killer whale named Kina and sought to teach her a conditioned behavior similar to how Pavlov taught dogs to salivate upon hearing a bell.

First, the scientists played a gentle tone repeatedly. Then they followed the gentle pulse with a loud sound. After a few trials, the warning signal alone caused Kina to decrease the sensitivity of her hearing.

"It shows promise as a way to mitigate the effects of loud sounds," said Nachtigall, founding director of the Marine Mammal Research Program at the University of Hawaii. "People are generally very excited about it."

In May, Nachtigall and his colleagues presented the findings to acoustic scientists and groups meeting in Hong Kong, including the Acoustical Society of America. The team cited the protective deafening as a potential way to help sea mammals cope with noisy blasts from naval sonars, civilian air guns and other equipment.

In the future, the team plans to expand the research to other species in captivity and ultimately to animals in the wild.

"We have a problem in the world," Nachtigall said of the oceanic roar. "And we think the animals can learn this response very rapidly."

Scientists unconnected to the mammal research called it important.

"It's a big deal," said Vincent M. Janik, a prominent marine biologist at the University of St. Andrews in Scotland. In an email, he said it revealed a rare ability among the planet's creatures.

Carl Safina, president of the Blue Ocean Institute, a conservation group in Cold Spring Harbor, N.Y., called the discovery a potential window into what sea mammals may already do on some occasions to protect their hearing.

"I've sometimes wondered why these high intensity sounds don't cause problems all the time," he said in an interview. "Maybe it's that, once the animals hear something very loud, they can adjust their hearing – dial it down and protect themselves."

Scientists say the extraordinary hearing of sea mammals evolved to compensate for poor visibility beneath the waves and to take advantage of the unique qualities of seawater. Sound travels five times faster than in air and undergoes far less diminishment.

The heads of whales and dolphins are mazes of resonant chambers and acoustic lenses that give the animals not only extraordinary hearing but complex voices. The distinctive songs of humpback whales appear to be sung exclusively by males seeking mates.

In recent decades, scientists have linked the human cacophony to reductions in mammalian vocalization, which suggests declines in foraging and breeding. And the problem is poised to get worse: In May, the Navy disclosed draft environmental impact statements (Atlantic and Pacific operations) that said planned expansions could raise the annual hearing losses among sea mammals to more than 1 million.

Zak Smith, a lawyer with the Natural Resources Defense Council, recently called the new estimates "staggering." A question of science, Nachtigall said, is whether the levels of protective deafening found in Kina can be increased. The team plans to study the auditory response in such species as bottlenose dolphins and beluga whales before trying it on wild populations.

The big political hurdle is financing, he said. Federal support for the sea mammal research has declined in recent years, and industry is only starting to show interest in the finding.

"I'm pulling in money where I can," he remarked. Nachtigall said the research was costly because sea mammals need high levels of care.

But he called it revealing and rewarding. "When it comes to whales and sound," Nachtigall said, "we're just starting to understand."