By freedivinguae

Recordings spout secrets behind blue whale behavior

 

Researchers are using underwater microphones to interpret and characterize the calls of blue whales swimming through Southern California’s oceans, revealing new insights into the behavior of these endangered marine mammals, according to new research being presented at the Ocean Sciences Meeting here on Tuesday.

Stretching nearly 30 meters (100 feet) long and weighing up to 172 metric tons (190 short tons), the endangered blue whale is the largest animal known to have existed. Though the exact purpose of blue whale vocalizations remains elusive, researchers think the  may use calls to maintain distance between one another, facilitate mating or signal the presence of prey, among other purposes.

To better understand these vocalizations, scientists recorded and analyzed more than 4,500 sounds from blue whales tagged with  and pressure sensors in and around Southern California’s Channel Islands between 2002 and 2016. Listen to a recording of two different whale calls here.

The new research compared three types of calling  with different diving patterns to uncover behavioral links.

The researchers found some variability in the times and under what conditions whales call or sing. The vocalizations varied depending on the whale’s sex and the dive’s purpose – behaviors with some similarities to other animals, according to Ana Širović, an oceanographer at the Scripps Institution of Oceanography in La Jolla, California, who will present the new findings Tuesday at the 2018 Ocean Sciences Meeting, co-sponsored by the Association for the Sciences of Limnology and Oceanography, The Oceanography Society and the American Geophysical Union.

“Understanding the context under which blue whales make calls is a critical step in developing non-invasive, non-lethal acoustic methods to study population trends and recovery status of this endangered species,” Širović said. “And as a species on top of the food web, understanding their status and contribution to the ecosystem is important for understanding the status of the ecosystem as a whole.”

 

The researchers found male whales were chattier at night, when it seemed the animals weren’t feeding. Males produce more calls than their female counterparts, Širović said, indicating some of the calls may aid in reproduction.

The researchers noticed great variability in the male whales’ use of single sounds, as opposed to songs composed of multiple sounds strung together. Other researchers have suggested these single calls could help maintain pair-bonding when males and females meet while foraging. Male bonobo chimpanzees employ a similar strategy, calling to nearby females when food is present, which boosts their chances of mating.

The researchers found dive behavior varies with the seasons, when whales spent more time in shallow waters during late summer and early fall. This may mean whales are hunting for more surface-dwelling prey at those times or traveling, according to the researchers.

The rate at which calls are produced varied within the time of day as well, where song production was highest at dusk and lower during the day. This could be because the whales time their singing for periods when prey is less densely aggregated, though the researchers did not measure prey abundance. A similar, energy-conserving behavior has been observed in European robins and nightingales, who adjust their singing in line with their energy reserves.

A shorter, less far-traveling call past  had associated only with foraging behavior seemed to be more socially complex than previously thought. Both males and females used this call during non-feeding dives, leading Širović and her colleagues to suggest it may serve as a close-range call to communicate only with nearby whales.

The research represents the most extensive analysis into the behavioral context of  calling in the region, according to Širović.

SOURCE:  https://phys.org/news/2018-02-spout-secrets-blue-whale-behavior.html#jCp

By freedivinguae

Whale sharks’ southern odyssey puzzles scientists

The travels of whale sharks Tiffany and Doug are causing a stir. As a marine species typically found in tropical waters off Western Australia’s coast, the pair inexplicably have headed south and showed up off the coast of Perth.

Tiffany is an 8m whale shark named after the female pilot who regularly flies scientists over the giants’ favourite haunts near Ningaloo Reef, 1250km north of Perth. Doug is named after a member of the CSIRO Oceans and Atmosphere team conducting a five-year, $5.4 million study of the reef ecology.

The puzzling arrival of Tiffany and Doug so far south is posing questions for scientist Richard ­Pillans and his team, which ­attached small transmitter tags to the mottled flanks of 10 whale sharks last year. “Given there are two of our 10 tagged whale sharks in exactly the same place at the same time, it’s very likely there are a lot more sharks out there as well,” he says. “There’s obviously something going on out there.”

As the largest living non-­mammalian vertebrate on earth, the whale sharks’ daunting size and gentle habits attract thousands of visitors to the World Heritage-listed Ningaloo Reef each year. Tourists swim alongside the whale sharks in clear Indian Ocean waters.

Perth residents eager to swim alongside Tiffany and Doug would have a hard time even finding them, says Dr Pillans. “Both sharks are in really deep water of 2000m to 3000m on the edge of the continental shelf. That’s really unusual for whale sharks, because more often they stay within 200m of the shoreline.

“Presumably there’s an up­welling of cold, nutrient-rich water that’s being forced up, creating a mass food opportunity like krill, one of their favourite foods.”

Adult females are rarely seen at Ningaloo Reef. “Whale sharks give birth to live young which are less than a metre long, and we know very little about where this occurs,” Dr Pillans said.

The Ningaloo Outlook project, a partnership between CSIRO and BHP, hopes to shed light on such aspects, and on the reef’s complex ecosystem.

“One of the aims is to look at the impact of ocean warming on the distribution of whale sharks on the WA coast, but we haven’t got a good handle on that yet,” said Dr Pillans. “None of the previous tagged sharks have come this far south.”

That Tiffany and Doug were found 130km off Perth’s coastline may be unusual, but another tagged whale shark, Roger, made a longer journey, from Ningaloo to Queensland’s Gulf of Carpentaria, about 3500km away.

Last year a tagged animal made it to Christmas Island, 1500km northwest of Ningaloo.

“One of the hard things with whale sharks is to keep the tags on them for long enough to get meaningful data,” said Dr Pillans. “Nine to 12 months is basically what we’re aiming for in order to track them as they move away from Ningaloo.”

Whether Tiffany and Doug’s travels are motivated by food or sexual frolic is unknown.

 

SOURCE: https://www.theaustralian.com.au/news/nation/whale-sharks-southern-odyssey-puzzles-scientists/news-story/5da913009054317bed9a19b8c9d6d566

By freedivinguae

Coral Scientists Eye ‘Radical Intervention’ To Save The World’s Reefs

WASHINGTON — Some of the nation’s leading coral scientists stressed Thursday that the situation facing coral reefs is nothing short of desperate — and a drastic cut in global carbon dioxide emissions won’t be enough to protect corals from deadly bleaching events and other environmental threats.

In hopes of giving the reefs a fighting chance, a newly formed committee of the National Academies of Sciences, Engineering and Medicine will review a variety of potential intervention strategies, from genetic modification of coral species to spraying salt water into the atmosphere to shade and cool reefs.

At the committee’s first meeting on Thursday, Mark Eakin, coordinator of the National Atmospheric and Oceanic Administration’s (NOAA) Coral Reef Watch, said the “severity” of what has occurred between June 2014 and May 2017 — the “longest, most widespread, and possibly the most damaging” bleaching event on record — has changed the scientific community’s perspective about what should be done.

“The dire situation is here now,” he told the 12-person committee at its first meeting on Thursday. “We know that climate change is accelerating and accelerating bleaching. And so we need to make sure that this study isn’t something that talks about some nice areas of science but is too little and too late for the corals.”

 

Coral bleaching is a phenomenon in which stressed corals expel algae and turn white, often as a result of warming ocean temperatures. If not given time to recover, bleached corals can perish. The recent event — just the third global bleaching event in recorded history — devastated reefs around the globe. Among the hardest hit was Australia’s Great Barrier Reef, where 93 percent of corals were impacted by bleaching and an estimated 29 percent of shallow water corals perished.

Often called “rainforests of the sea,” coral reefs provide habitat for more than 25 percent of the planet’s marine species and generate goods and services valued at $375 billion each year.

The project, titled “Interventions to Increase the Resilience of Coral Reefs,” is expected to take up to two years and will assess both the risks and benefits of intervention strategies. It is sponsored by NOAA.

Tom Moore, manager of NOAA’s Coral Reef Restoration Program, said the agency’s position is that saving the world’s reefs will require a multi-pronged approach that includes “immediate and aggressive action” to combat climate change, ongoing restoration and more drastic measures.

“We are trying to buy time here until hopefully we get things in check on a global scale,” he said.

Although still hopeful, Moore and others are realistic about the challenges ahead. They stressed that the enormity of the problem and a lack of resources means the scientific community will face tough decisions.

A recent United Nations-backed study found that “annual severe bleaching” will impact 99 percent of the world’s reefs within the century if humans do not take swift action to curb greenhouse gas emissions.

“Tomorrow’s reefs are not going to look like yesterday’s reefs,” Moore said.

Among the “radical intervention” techniques Eakin highlighted in his presentation were Australia’s plan to circulate cool ocean water onto a handful of critical reef sites and another idea to spray ocean water into the air to create aerosol particles that would shade and cool reefs during bleaching events.

The most sobering appeal came from Joanna Walczak, a regional administrator at the Florida Department of Environmental Protection. Over the last three years, she says she helplessly watched the majority of the reef-building corals off Florida’s southeast coast collapse due to an unknown disease outbreak.

“I’ve gone through many, many different stages of grief, from visceral sadness to disbelief and anger. I’ve definitely had some despondence and actually was planning for a career change because I really, truly didn’t see hope for a while there,” she told the committee via a video feed. “But I’ve ultimately come through all of that and have made it back with focus and determined action to do everything in my power to make a difference with whatever little time we have left.”

Florida is already out of time, Walczak added. And with the rate that corals are currently being lost, officials there have had to completely shift their management strategy, from reactive to proactive. Among the ideas being entertained are large-scale disease treatment on the largest coral colonies and culling, which Walczak said means “specifically sacrificing some to potentially save the rest.”

“I’m going to make a really hard ask of you all,” she told the committee. “I need precautionary principle-based, expert-opinion-derived leaps of faith. Because after all I’ve seen, I’m ready to take these risks now.”

The study by the National Academies kicks off as the Trump administration abandons the Obama administration’s efforts to combat climate change and works feverishly to promote fossil fuel production in its quest for “energy dominance.” President Donald Trump — who famously dismissed climate change as a Chinese hoax in 2012 — has surrounded himself with like-minded climate change skeptics, including Environmental Protection Agency Administrator Scott Pruitt, who this week suggested global warming may be beneficial to humans.

SOURCE: https://www.huffingtonpost.com/entry/coral-reefs-intervention-noaa_us_5a7df39fe4b0c6726e133b4f

 

By freedivinguae

Animals with Cameras: Remarkable moment TV seal enjoys a fish supper with dolphins

BREATHTAKING scenes of a seal working with dolphins to feast on fish have been captured by an ingenious underwater camera.

 

The mother fur seal filmed herself feasting on a giant “bait ball” of anchovies from a tiny lens fitted to her back by a wildlife television crew.

These remarkable scenes of the seal powering through the swirling mass of small fish corralled by a school of dolphins have given scientists a unique insight into the marine mammals they have been studying for more than 20 years.

In just two hours, Gordon Buchanan’s Animals with Camera team not only came up with gripping scenes from the shark-infested waters off Australia’s Kanowna Island, their footage has explained some of the holy grail mysteries of how fur seals survive in such a harsh marine environment.

By fitting a tiny waterproof camera to one of the island colony’s 15,000 seals, scientists have discovered how they evade the attentions of marauding great white sharks as well as the way they eat a wide array of prey and even team up with dolphins for spectacular feasts.

Professor John Arnould from Melbourne’s Deakin University was left awestruck as the camera relayed crystal clear shots of the mother’s seal hunting forays back to shore.

Footage first shows how she clambers from the nursery colony over rocks into the sea and then takes a seaweed manicure to remove parasites off her luxuriant fur.

Then, she gets down to the business of hunting, ever alert to the huge great white sharks that patrol the waters on the look out for their favourite food – fur seals.

The mother seal is filmed hugging the sea bed as this prevents her being attacked from below, one of the favourite ambush techniques of great whites.

Although the seal has to surface to breath every eight minutes, she performs a series of barrel rolls so she can spot any sinister shark in the vicinity.

While her own hunting strategy sees her capturing a cuttle fish and octopus, it the sight of a dolphin pod creating the anchovy bait ball that leaves Professor Arnould almost nonplussed.

He says: “I’ve learnt so much from the camera footage that it’s hard to know where to start.

“We’ve discovered they eat a lot more of some prey types than we previously thought and some prey we didn’t know they consumed.

“And we’re beginning to understand just how much time and effort these animals devote to vigilance and predator avoidance.”

SOURCE: https://www.express.co.uk/news/nature/915968/animals-camera-television-dolphins-fish-seal-anchovies-kanowa-island

By freedivinguae

Monterey County scuba diver and the oldest American remains ever discovered

 

 

Seaside – About 130 feet below sea level in an underwater cave on the Yucatan Peninsula, Seaside resident Alberto “Beto” Nava and a team of divers found the remains of a teenage girl. She would prove to be the oldest set of American remains yet discovered — a direct descendent of Central America’s first residents.

Her story will be told in a NOVA special premiering on KQED at 9 p.m. Wednesday, called “First Face of America.”

“At the beginning we didn’t really know she was going to be such an important set of remains,” said Nava, recalling the fateful find back in 2007. The team had found a near-complete skeleton, skull still intact, surrounded by the bones of about 40 ancient animals, including saber tooth tigers, giant sloths, cave bears and a mastodon.

“It was incredible — and a big responsibility,” Nava said.

The team was affiliated with Global Underwater Explorers, a non-profit that unites scuba divers, conservationists and scientists to promote underwater exploration. They were working their way through the Sac Actun cave system and happened upon a 100-foot pit, now known as Hoyo Negro — or Black Hole.

Much of the Yucatan’s extensive cave network has yet to be surveyed. “It’s one of the few places where you can still explore without having a rocket,” said Nava. Not knowing what they would find, he and the team discovered the remains of a 4-foot, 10-inch girl, estimated to be roughly 15 or 16 years old, preserved there for over 12,000 years.

An anthropologist working with the team suggested naming the remains, and the group deemed her Naia in reference to the nymphs of Greek mythology that care for fresh waterways, Nava said. Naia is now kept at Museo Nacional De Antropología in Mexico City in the most secure vault, alongside precious artifacts like the death mask of Mayan ruler K’inich Janaab Pakal I.

Since the find, researchers have studied Naia extensively. By analyzing her DNA, they traced her ancestral lineage to northeast Asia. About 26,000 years ago, a “land bridge” connected Asia and the Americas, and ancient peoples made their way across it. Naia was the first skeleton with early American features that could be identified as an early descendant of those migrants.

The Global Underwater Explorers have continued to dive at Hoyo Negro and have cataloged the site for the last 10 years. Scuba is pretty much Nava’s full-time career now. He spends four months a year in Mexico and the remaining months in Monterey as a scuba instructor.

Seeing him in this light, you might not guess he started out in computer science.

After a successful 15 years as a Bay Area engineer, Nava swapped software for scuba. For years, he had lived close to work and came to Seaside on the weekends to dive. “At some point, I decided to do the opposite,” he said.

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Nava moved to Seaside about nine years ago, and soon cut back on engineering to work with the Global Underwater Explorers. That said, Nava has found a unique way to merge his passion for diving with his original job. His current project is to create a detailed 3D model of Hoyo Negro.

“The researchers that we work with won’t ever be able to go into the site,” he explained. “So by making this 3D model, we bring the site to them.”

Nava collects images of Hoyo Negro as he dives, then brings the data to UC San Diego, where his is a visiting scholar. The school’s Center of Interdisciplinary Science for Art, Architecture and Archaeology (CISA3) has a number of advanced tools for displaying 3D models of archaeological sites. One of these is known as the WAVE, essentially a tunnel-shaped virtual reality environment, as well as a spherical projection system you can walk into.

“You feel like you’re back on the inside,” said Nava, remarking on how closely the models resemble the real site. UC San Diego doctoral students are also building applications to make the models easily accessible to researchers in the field.

Though 10 years have passed since Naia was first discovered, the research surrounding her story has only gained momentum. “I give more and more time to it as I go,” said Nava. He is looking forward to the premiere of “First Face of America” and more people engaging with Naia’s story.

 

SOURCE: https://www.mercurynews.com/2018/02/06/monterey-county-scuba-diver-and-the-oldest-american-remains-ever-discovered/

By freedivinguae

Manatees are gentle giants

I’m continuing with my exploration of the wonders of Florida by taking a closer look at the Florida manatee.

Also known as the West Indian manatee (Trichechus manatus latirostris) or the sea cow, the manatee was one of the original 78 species included on the endangered species list when the Endangered Species Preservation Act was passed into law in 1966.

Manatees appear in the fossil record around 50-60 million years ago. This is older than most of our modern bird species by many millions of years. So these animals have been around for a very long time. There are many fossilized remains found in Native American rubbish piles pre-dating the arrival of early Spaniards.

Manatees live in Brazil, Mexico, southeastern U.S. and the Caribbean islands.

The Florida manatee is one of two subspecies of the West Indian manatee. The other subspecies is the Antillean manatee, which occurs from Brazil to Mexico.

The Florida manatee is found along the Atlantic coast from the Carolinas, Georgia and Florida and also in the Gulf of Mexico, from Florida to Texas. However the main concentration is found in and around Florida.

Manatees are large marine mammals, with adults weighting on average 1,000 pounds, with some as much as 1,500 pounds. They have an average length of 12 to 14 feet. Like elephants, they continue to grow throughout their lives. The largest manatee ever recorded was 13 feet, 4 inches long, weighing over 3,200 pounds. When you first see one of these animals up close, you realize how massive they are.

These large aquatic mammals are gray and sparsely covered with hair. They have large forelimbs, which are better described as flippers, and have no hind limbs. They do have a large wide tail used for swimming, and when you see them swimming, they look like they are in extreme slow motion.

They have tiny eyes, but can see very well. And although they don’t have any external ear openings, they hear very well. They have flat valves that cover their nostrils when underwater. Being air-breathing animals, manatees need to surface every three to five minutes to breath, but they can remain submerged up to 15 minutes if necessary.

They are gentle giants, spending most of their day sleeping and feeding on aquatic plants. They consume about 150 pounds of vegetation each day. They use their eyesight to find the food.

Female manatees become sexually mature at four to five years of age. Mothers give birth to a single calf once every two to five years. Only rarely do they have twins.

Calves weigh about 75 to 90 pounds upon birth and are over 6 feet long. Since these are marine mammals, the calves suckle milk from their mothers for the first five to six months and start eating aquatic vegetation at three to five months.

Most calves stay with their mothers for up to two years before moving out on their own. During this time, the calves learn what kinds of plants are good to eat, where the warm water refuges are located, and the migratory route from their mothers.

Today there are about 6,300 manatees in Florida. This is up from a low of about 1,200 25 years ago. They are still on the endangered species list, but due to improved protection and reduction in direct threats to their habitat, they are now recommended to be moved to the threatened species list.

I’m always drawn to writing stories about endangered species. I have always felt that education is the key to helping save wildlife from extinction. I have dedicated my entire career, over 30 years, to environmental education, hoping that as our society becomes educated about wildlife, we can make better decisions to save our planet and all the wildlife it holds.

It warms my heart to see such a magnificent animal doing much better than the first time I saw a manatee back in the 1970s.

If you are ever in Florida it would be well worth your time and effort to see these magnificence marine mammals.

SOURCE: http://www.swnewsmedia.com/chanhassen_villager/news/opinion/columnists/manatees-are-gentle-giants/article_c88dbde5-bcad-5c95-a49e-0856139b67f7.html

By freedivinguae

How Freediving With Baited Whale Sharks Is Actually Killing Them

As recreational freedivers, we all have our bucket list of sea creatures, wrecks, and diving spots that we are dying to see, whether it be floating with majestic eagle rays, circling the USS Liberty in Indonesia, or exploring Ras Mohammed National Park in Egypt. But as conscientious divers who respect and love the ocean, there is a thin line between an organic, once-in-a-lifetime experience, and knowingly participating in unethical behavior that harms our beloved sea.

Freediving with whale sharks is an experience most freedivers yearn for, and it can be hard just waiting around for one to appear if it is even the proper season for them. There are tours around the world that can guarantee snorkeling, swimming, and scuba diving with these gentle giants. But what exactly makes these companies so confident that they can guarantee to spot whale sharks?

The Problem with Baiting

Whale shark tours, like the ones in Oslob, Philippines, have no problem assuring their customers a selfie with whale sharks due to their baiting practices. In Oslob, fishermen use a certain type of krill as bait, called uyap, to lure the whale sharks to the boats, and then dispatch snorkelers and divers into the water for the experience to begin. The issue with baiting is that the natural krill whale sharks eat in Oslob is seasonal. Their migratory patterns are established by following their food. Therefore, when the natural krill becomes out-of-season, fishermen obtain krill from neighboring islands like Ilo-Ilo and Bacolod, which contain different types of plankton, and miss out on the different nutrients that they get just by migrating with their natural food source.

Wild animals should not depend on humans for food, and limiting the nutritional value of a whale shark’s diet is unacceptable. Imagine yourself living only off of tacos. Yes, of course, it sounds good in theory, but imagine the face your doctor would make with that information. Let’s also not forget the possible contamination of the bait that comes from outside of Oslob during transportation and the loss of nutrients from storage.

Changes in Migratory Patterns

Remember how whale sharks migrate depending on where their nutritious plankton float off to? They are naturally very mobile creatures and travel long distances, but as they get used to being fed by humans and stop having to forage for their own food, they stay longer than normal in these feeding areas. It is still too early for scientists to see the ramifications of these differences in migration patterns, but long-term effects can include changes to their breeding patterns, which in turn will affect the reproduction of an already vulnerable species.
Common Injuries

Even though there are rules and regulations that attempt to govern the way tourists interact with whale sharks, it becomes very difficult to enforce them. Since whale sharks are not aware of these human rules and associate boats with food, they typically chase the boats instead of instinctually avoiding them. They constantly bump into or rub against them, which causes reactions and injuries to the skin. It gets even more dangerous when they confuse non-tourist boats with tourist boats and get severely injured by the propellers. It is typical to see many scars and injuries around the mouth and dorsal fins of baited whale sharks at these tourist hotspots.

All of these inevitable injuries do not even account for the bodily harm that will be inflicted on them by their only known predator: humans. Tour guides and rules may state that there should be a specific distance kept between tourists and whale sharks, but often there are so many groups of people at once, sometimes trapping the whale sharks, that accidental touches are inevitable. This does not account for the tourists who are touching the sharks on purpose, whether it’s capturing the perfect selfie or attempting an original photo by standing on the whale shark. Even the fishermen who feed the sharks often put their feet inside of the water and keep them pressed against the whale shark’s mouth, to keep them from jostling the boat. The issue with so many careless touches is that humans have bacteria that the sharks are not naturally exposed to, which can leave them prone to infections.

What Are Your Options?

There are plenty of spots in the world to witness these majestic sea creatures in the wild, naturally foraging for their own food, sticking to their instinctual migratory patterns, and lazing around, unharmed by the humans and boats they should be characteristically wary of. In fact, here is a handy list of the best locations to swim and dive with whale sharks by month.

Armed with this information, freedivers have a choice. We can shut our eyes when we witness mistreatment, photoshop whale shark scars out of our photos, and capture our next awe-inspiring profile photo. Or, we can avoid unethical practices and companies, and spread our knowledge to those who are not aware, slowly forcing these tourist traps into extinction.

SOURCE: https://www.deeperblue.com/freediving-baited-whale-sharks-actually-killing/

By freedivinguae

Climate change may have made sea turtle populations in the Great Barrier Reef turn female

Is Australia’s Great Barrier Reef losing its male sea turtles?
A new study has found that green sea turtle hatchlings in one of the world’s largest colonies are increasingly female, and this trend has been ongoing for decades, with warming global temperatures the suspected culprit.

Sea turtles, as well as some other reptiles, lack sex chromosomes. Their gender is determined by the environment of the nest while the embryos are incubating, and by nest temperature in particular. Warmer sand tends to produce higher numbers of female hatchlings, making sea turtles and other reptiles particularly vulnerable to a warming Earth. Moreover, the range of temperatures that produce 100% males or 100% females spans only a few degrees Celsius.

The study’s authors developed a novel method to determine sex ratios of free-ranging turtles from specific regions of the Great Barrier Reef. The researchers matched the sex and age class of green sea turtles to the nesting beaches from which they hatched by combining basic field methods with genetic and hormone analyses.

Lead author Michael Jensen, of the National Oceanic and Atmospheric Administration’s Southwest Fisheries Science Center, said in an email to Mongabay-Wildtech that where turtle populations from genetically distinct rookeries feed together, scientists have been able to estimate the rookery origin of these turtles through their DNA.

“The novelty of this work was the multidisciplinary approach that combined genetic and endocrine data from the same turtle,” Jensen said. “We assessed the secondary sex ratios of turtles at foraging grounds – as opposed to looking at primary sex ratios of hatchlings produced on a specific nesting beach. We believe our approach offers a better way of tracing trends in a population’s sex ratio. Foraging grounds encompass turtles of different life stages (juveniles, subadults and adults), which represents different generations of turtles and therefore many years of hatchlings produced from regional nesting beaches. That gave us a window into sex ratios produced over time from different rookeries.”

Wrangling turtles for their DNA

Virtually no turtles nest in the middle stretch of Australia’s 2,300 kilometer (1,400 mile)-long Great Barrier Reef, so the northern and southern breeding populations are genetically distinct.

The researchers sampled 411 turtles at foraging sites (74 of them during a 2008 study) in the middle section. Turtles of many ages from distinct nesting areas congregate in these shallow waters to feed, so sampling there allowed the researchers to estimate sex ratios of turtle cohorts from various beaches over the past 50 plus years.

They first had to catch the turtles – “rodeo-style” – which consisted of finding, following, and hand-catching the animals from a small boat, then bringing them to shore to process them. Assigning age class was easy and based on the length of each animal’s curved carapace.

The researchers distinguished adult males turtles from females by noting their longer tails and measuring testosterone in blood samples. Sea turtles lack external sex-based traits until they reach maturity, however, so the scientists also physically examined most of the immature turtles to ensure they’d assigned gender correctly.

Laparoscopy, the surgical technique used to definitively determine a turtle’s sex, runs a thin tube into the turtle to briefly examine its reproductive organs. The turtle recovers from the procedure in a couple of days, so researchers have been testing less-invasive and labor-intensive techniques to assess sex ratios of immature turtles.

Measuring a turtle’s testosterone level required a far simpler blood sample, allowing the researchers to process hundreds of turtles with high accuracy.

The researchers linked each turtle back to the beach from which it hatched by analysing DNA from skin tissue samples and ran models to group the foraging turtles based on their genetic similarity. Female and male green turtles along Australia’s east coast will feed in various preferred foraging grounds but return to the area around their nesting beach to mate.

Where the boys are (not)

The scientists showed that the northern part of the Great Barrier Reef, in particular, has been producing mainly females for more than 20 years by determining the genetic origin of turtles from each sex relative to their life stage. They found that turtles that had hatched on the cooler southern nesting beaches showed a “moderate” sex bias (65%–69% female), similar to reports from feeding grounds located in the southern region. However, nearly all the turtles (87% of adults and over 99% of both juveniles and subadults) that originated from beaches in the warmer northern portion of the Great Barrier Reef were female.

The scientists estimated monthly temperatures of the sand on the key nesting beaches using air and sea surface temperatures from 1960 to 2016. They found sand temperatures consistently remained above the “pivotal” temperature of 29.3°C (84.7°F) – the value corresponding to a roughly equal number of male and female hatchlings – starting around 1980.

Some imbalance in the female-male ratio may be expected and potentially beneficial. Male sea turtles tend to breed more frequently and with more individuals than females do, which may mitigate some of the imbalance.

Nevertheless, scientists have seen turtle sex ratios become increasingly female-dominated over the past few decades, and they fear that warming air and sea temperatures may begin causing single-sex populations that cannot sustain themselves.

Moreover, the authors state in their paper, “extreme incubation temperatures not only produce female-only hatchlings but also cause high mortality of developing clutches.”

“While some of the decreased hatching success [that researchers in Australia have observed] might be explained by high temperatures, many other factors influence hatching success (for example, flooding of the nest from increased water table),” said Jensen. “We are just now beginning to understand the problem, so we have more work to do before we can begin to suggest ways to address it. The good news is that a lot of research is now focusing on understanding the influence of environmental factors on sea turtle hatchlings’ success.”

Researchers have seen over decades that warming temperatures alter the sex of sea turtle hatchlings; this study is the first to document the trend in a major wild population.

The findings suggest that wildlife managers consider strategies to lower incubation temperatures at key nesting sites of sea turtles and other temperature-dependent species around the world. Moisture and shade from coastal vegetation, for example, also affect sea turtles’ incubation and, thus, the sex of hatchlings, by keeping sand temperatures cooler.

Avoiding extreme incubation temperatures, the authors state in their paper, would help “boost the ability of local turtle populations to adapt to the changing environment and avoid a population collapse or even extinction.”

Jensen and colleagues hope their work will encourage others to do similar studies, as it offers a rapid way to monitor trends in turtle population sex ratios.

“However, the success of this method depends on many factors, such as accessibility to large sample sizes of turtles at foraging grounds, understanding the genetic characterisation of rookeries that might be contributing to the foraging grounds, and the degree of genetic structure among those rookeries,” said Jensen. “So whether this method will work in other regions and other species should be assessed on a case-by-case basis.”

SOURCE: https://scroll.in/article/866949/climate-change-may-have-made-sea-turtle-populations-in-the-great-barrier-reef-turn-female

By freedivinguae

Why are coral reefs important, and why are they dying?

More than 11 billion pieces of plastic larger than five centimetres wide are littering coral reefs across the Asia-Pacific region, according to a recent study.

That is enough plastic to make it from Earth to the moon and nearly halfway back.

Researchers who published the study last week in Science Magazine believe that the amount of plastic in coral reefs will grow by 40 percent in the next seven years.

Meanwhile, the researchers found that the chance of corals becoming infected with a disease increased from four percent to 89 percent when they were draped in plastic.

Plastic pollution is just one factor that is putting the world’s coral reefs at risk.

Coral reefs may have been around for as long as 500 million years, but scientists are warning that they might be gone or decimated by the end of the century.

Al Jazeera examines why coral reefs matter and if they can be saved.
What are coral reefs?

Corals are invertebrate animals. Individual coral animals, called polyps, live in groups of hundreds to millions of genetically identical polyps called colonies.

Reefs are created by hard corals which secrete a skeleton that can turn into giant structures like Australia’s Great Barrier Reef, the largest living structure on the planet.

In 2001, the UN estimated that the total surface area of coral reefs measured 284,300 square kilometres (sq km), which is just shy of the size of Italy.

More than half of the earth’s coral reefs is distributed over only five countries: Indonesia, Australia, the Philippines, France (including its overseas territories) and Papua New Guinea. Their reefs are the size of small countries themselves. Indonesia’s 51,020 sq km worth of reefs, for example, is nearly as big as Costa Rica.

SOURCE: http://www.aljazeera.com/indepth/features/coral-reefs-important-dying-180128135520949.html

By freedivinguae

A rare glimpse into the world of the Red Sea’s dolphins and whales

The Red Sea is one of the world’s least studied regions when it comes to whales and dolphins – until now. A report was released recently that brings together historic records and the latest information on a range of the sea’s mammal species. This will supply some of the information needed for science based conservation measures. I interviewed Giuseppe Notarbartolo di Sciara, one of the reports’ authors who is also among the region’s most respected marine mammal specialists, on the findings and their implications.

What is special about the Red Sea and the habitat it provides to whales and dolphins?

While huge progress has been made globally in our ecological knowledge of marine mammals, this hasn’t been the case for the Red Sea. With the exception of dugongs, very little is known about the Red Sea’s mammals. This is one of the main reasons we put this report together, conducting and collating research from 1983 to 2017.

Among the things we learned was that the fertility of the Red Sea’s environment affects marine mammal presence in the region.

Life in any ocean starts from the water’s productivity. This is the ability of phytoplankton (microalgae) to bloom because of the nutrients contained in the water, like phosphates and nitrates. This is triggered by upwelling currents that bring nutrient-rich deeper waters to the surface. This fertilises the phytoplankton, which need sunlight. The phytoplankton bloom gets eaten by zooplankton, which are then eaten by little fish, and so on up the food web.

Such upwellings are rare in the Red Sea. This makes it a hard place to live for the great whales, which need big swarms of krill, small crustaceans, to survive.

This could be why only a few whale species have been able to colonise the Red Sea.

We also found out more about how dolphins – which are known collectively with whales as cetaceans – survive in the Red Sea.

The environment is better for smaller dolphin species like spinner dolphins and pan-tropical spotted dolphins. Spinner dolphins take advantage of a community of smaller critters living in what scientists call the deep scattering layer. It’s mostly made up of small crustaceans, fishes and squid. They live in a narrow layer that rises towards the surface at night to feed, and returns to the depths during the day to shelter. It provides the critical source of food for the dolphins to tap into in an otherwise poor marine environment.
What threats do cetaceans face in the Red Sea?

What worries me most is that the Red Sea is crossed by a huge amount of ship traffic carrying oil. It is a key strategic channel: an estimated 4% of global oil supply passes through it. The proportion sounds small, but it represents a vast amount of oil. A major accident would be disastrous for marine life in the narrow Red Sea.

An immediate and obvious threat today is disturbance by tourists. For example, spinner dolphins enter a reef in an area known as Samadai, on the southern coast of Egypt, to rest. They do this because they’ve been hunting at night and the reef gives them protection from sharks during the day.

The tourism industry discovered this and started to advertise swimming with dolphins in the area. It very quickly became a mess, creating an outcry on social media calling for people to stop bothering the animals. Fortunately, the Egyptian government took action and I helped to explore the situation and draft a plan. There is now a large area of the reef that is completely off limits to tourism, and the dolphins have enough space to rest.

Unfortunately these situations aren’t always so well managed. Another area called Sataya, also in Egypt, has no management plan and the spinner dolphins are very stressed. It’s likely the entire reef area will be taken over by people and the animals will be pushed out.

In terms of fishing, I’m aware of situations in which particularly Yemeni fishermen travel widely across the Red Sea to hunt sharks for the Far East fin trade. I know that they have been using dolphin meat as bait for catching sharks. But we really don’t know how big this practice is or its impact on dolphin populations.
What immediate and longer-term steps should be taken to mitigate the threats

It would be great to have a model in the Red Sea similar to the one applied in the Mediterranean and Black Seas. Since 2002 there’s been an agreement between most countries bordering those seas. It commits the coastal countries to protecting those seas’ cetaceans. Something like that would be extremely helpful in the Red Sea, and raise their visibility at the policy level.

It’s also important to protect marine mammal habitats in the Red Sea. This could come partly from the identification of important marine mammal areas, work that’s being done by a task force established within the International Union for Conservation of Nature. The identification of the areas is based on specific criteria, and is modelled on earlier work on birds. The areas are critical for some aspect of a species life, for example feeding, breeding or migrating. Identifying them gives decision makers an easy tool to help select which areas need protection.

The task force is in the process of identifying these mammal areas in large portions of the southern hemisphere, and there are plans to do this in the Red Sea in 2019.

David Obura, Adjunct Fellow, The University of Queensland

This article was originally published on The Conversation. Read the original article.

SOURCE: https://mg.co.za/article/2018-01-30-a-rare-glimpse-into-the-world-of-the-red-seas-dolphins-and-whales