Seasons Greetings

Flash News: Milkha Singh: India's legendary sprinter dies of Covid-19 complications at 91      - | -     Air Force is designing bird-like microdrones for warzone surveillance      - | -     Biden urges more Americans to get vaccinated but is silent on July 4 target      - | -     Fierce Capitol attacks on police in newly released videos      - | -     The sycophantic inner circle egging on Trump – and fueling his big lie      - | -     You probably need to thank a migrant worker for your daily milk      - | -     Giant Buddhist goddess in Japan gets face mask to pray for end of Covid-19      - | -     Satya Nadella's notable rise from a young engineer to Microsoft chairman      - | -     Google India announces $15 million grant to set up 80 oxygen plants     - | -     Inquiry into 'fake Covid tests' at Kumbh Mela     - | -     10,000 years of climate memory have been preserved in The oldest ice from The Alps     - | -     Nearly 900 New Yorkers administered with expired Covid-19 jabs     - | -     Once hardest hit, New York, California lifts most COVID-19 restrictions as vaccination rates top 70%      - | -     US surpasses 600,000 deaths from the coronavirus      - | -     Texas man arrested after allegedly dragging mom's ex behind truck and setting vehicle ablaze      - | -     China says nuclear fuel rods damaged, no radiation leak      - | -     Act of kindness: the Kashmiri man who is India’s biggest blood donor      - | -     Wooden satellite first of its kind aims to prove plywood can survive space      - | -     Biden says that America’s ‘back.’ One question lingers: For how long?      - | -     Donald Trump Jr. Slams 'Incompetent' Fauci, Claims He's 'Not a Scientist'      - | -     Head of 'world's largest family' dies in India      - | -     The evolution, how bad the COVID-19 variants can get?      - | -     Airplane uncovered at the bottom of a California lake likely to be from 1965 crash      - | -     US gun violence reaches 270 so far this year      - | -     Human smugglers with links to cartels operate on Facebook, a report alleges.      - | -     White rhino travels Taiwan to Japan looking for love      - | -     Extraordinary times, extraordinary measures': U.S. approach to vanquish pandemic      - | -     Colorado is smashing down barriers expands access to housing, jobs and state benefits to undocumented immigrants      - | -     India records more than 6,000 daily Covid deaths      - | -     Bitcoin to be official currency in El Salvador under three months      - | -     Reports of severe COVID or death after vaccination are rare in remote cases      - | -     Fauci sticks around lab leak theory and not changed mind, equates criticism with 'Attacks on Science'      - | -     No data Covid will seriously impact children in future waves: AIIMS Chief in India      - | -     How a blood test can tell if cancer treatment is working right away      - | -     Telegraph Fire, the ninth largest in Arizona history, reaches 76,260 acres; Mescal Fire 23% contained      - | -     Covid-19 variant 1st detected in India still a threat to US: Fauci      - | -     Death toll climbs to 63 after horrific collision of two trains in Pakistan      - | -     Biden admin threatens to sue Texas over migrant facility plans      - | -     When your biological father is your mother's fertility doctor: 'fertility fraud'      - | -     US seizes $2.3 million in bitcoin paid to Colonial Pipeline hackers      - | -     Sharks almost wiped out 19 million years ago, and scientists don't know why     - | -     Trump's grievances cloud Republican agenda heading into 2022     - | -     Unexplained brain syndrome grips Canada, 48 people affected     - | -     Vaccination rates drop, imperilling Biden’s July Fourth goal     - | -     "Hugely Discriminatory": India Opposes Vaccine Passports at G7 Meet     - | -     Fireball meteor over Brazil may have come from another solar system     - | -     U.S. Justice Dept got gag order on NY Times execs in fight over email logs - NYT     - | -     The slowing Covid-19 vaccination rate is worrying experts. Here's what some states are doing to change the trend     - | -     ‘Lazy’ AI: Researchers find that technology can misdiagnose COVID-19 by taking shortcuts     - | -     9-year-old driver and younger sister unharmed after crashing into semi-truck     - | -     Biden widens list of Chinese firms off-limits for investment     - | -     Fauci calls on China to release medical records of Wuhan lab workers; Chinese scientists rejects lab leak hypothesis     - | -     Supreme Court in India criticizes its government over Covid-19 vaccination drive     - | -      New York's Cuomo seeks state police help to probe war memorial vandalism     - | -     Largest meat producer getting back online after cyberattack     - | -     “Get a shot and have a beer, celebrate the independence from the virus”: Biden's new Covid strategy woos vaccine skeptics     - | -     China reports first known human case of H10N3 bird flu     - | -     Arizona plans to use hydrogen cyanide to execute prisoners – a lethal gas the Nazis used at Auschwitz     - | -     The Trump Organization wants to sell its D.C. hotel yet again.     - | -     Hiker dies after falling 500 feet from the summit of Mount Russell, Sequoia National Park     - | -     The Coronavirus variant found in India to be called 'Delta' in new WHO system     - | -     Four more Oath Keepers accused in alleged Capitol riot conspiracy     - | -     A 7-year-old boy welcomed a hero, swam for an hour to get help for his dad and sister stranded in a river     - | -     Vaccinated Americans are celebrating the 1st big holiday safely without masks. But for some, returning to normal is not so easy      - | -     Teenager severely burned imitating TikTok video, family says     - | -     Texas Democrats stage walkout to block passage of sweeping election overhaul package     - | -     Charge your phone in just 8 minutes? Xiaomi announces insanely fast 200W wired charging     - | -     Johnson & Johnson asks high court to void $2B talc verdict in favor of women who developed ovarian cancer     - | -     Senate eyes R&D bill to counter China, bolster manufacturing     - | -     How to combat misinformation around 5G     - | -     Microblogging platform Twitter fears for freedom of expression in India     - | -     COVID-19 cases spiking again at some ICE detention centers many blames Biden administration     - | -     Cyclone leaves coastal villages in eastern India, Bangladesh cut off by tidal surges      - | -     Giant tortoise thought extinct 100 years ago is living in Galapagos, Ecuador says      - | -     Biden administration backs Alaska oil project approved under Trump      - | -     Biden orders more intel investigation of COVID-19 origin – A trail that can lead to Chinese laboratory      - | -     WhatsApp sues India govt, says new rules mean end to privacy      - | -     39-year-old found dead inside Spanish dinosaur statue     - | -     Top U.S. health official calls for follow-up investigation into pandemic’s origins     - | -     COVID-19 vaccination could get you free beer, doughnuts and $1 million     - | -     Why India's outbreak is a threat to the world     - | -     Suspected smuggling boat tragedy in San Diego adds to Biden's migrant crisis woes     - | -     Maryland votes to nix state song, a Confederate call to arms     - | -     Kim Janey rewrites history, Boston's first Black and female mayor     - | -     Gunman kills 10 at Colorado supermarket in second US mass shooting in a week     - | -     Kamala Harris laughs when asked if she will visit the border raises sharp criticism online     - | -     Roger Stone under fresh scrutiny as Capitol attack investigation intensifies     - | -     Vaccines will likely not be mandatory for teachers: Biden’s Education Secretary     - | -     Fauci warns about potential for an oncoming resurgence of virus if restrictions eased     - | -     Biden plug relief to Americans, celebrates 'transformational' victory on COVID-19 relief     - | -     LA Schools to Reopen in mid-April & NY City will open high schools next week     - | -     Women are tired of explaining to men like Andrew Cuomo why sexual harassment is wrong     - | -     Biden signs orders on gender equity, nominates two women to be four-star commanders     - | -     Nation takes baby steps to normality after year in lockdown; "The virus isn't going to go away," says Harvard epidemiologist     - | -     Rumours of vaccine site giving jabs to anyone because of low demand. Hundreds lined up     - | -     Vaccine supply will "dramatically" increase in weeks ahead: Fauci     - | -     Biden calls it "Neanderthal thinking" slams Texas and Mississippi's decisions to lift COVID-19 mask mandates     - | -     This Is What GOP Feared. Now that Trump Has Governed with Executive Orders, Dems Plan to Do Same      - | -     Man Throwing 'Incendiary Devices' at ICE Detention Center Is Killed in Attack      - | -     Mueller Hearing Pushed Back a Week to Allow More Time for Him to Answer Questions      - | -     Trump Tells 4 Congresswomen of Color to 'Go Back' to 'Crime-Infested' Countries They Came From      - | -     GOP Congressman Invokes 'The Deep State'

Features & Columns

Sharks almost wiped out 19 million years ago, and scientists don't know why

viewsViews 204

Sharks almost wiped out 19 million years ago, and scientists don't know why

2021-06-07 06:57:20

By K. Shalini

When Earth's temperatures spiked and oxygen levels in the ocean plummeted some 252 million years ago, most life on the planet was doomed. Some estimates suggest the extinction event, a mass extinction known as the Great Dying, killed off up to 70% of all land species but marine animals felt the impact even greater. As much as 96% of all species in the world's oceans perished.

A previously unknown extinction event caused shark populations to collapse 19 million years ago.

But not sharks. The slender prowlers of the deep persevered. "They're the ultimate survivors," says Elizabeth Sibert, a paleobiologist and oceanographer at Yale University. The next extinction event, at the end of the Triassic period, couldn't kill them off and neither could the asteroid that ended the reign of the dinosaurs some 66 million years ago.

The longevity of sharks is legendary but they may have come much closer to extinction than we once believed, according to a new study, published in the journal Science on Thursday. The research, led by Sibert, shows that a previously unknown extinction event pushed sharks to the brink 19 million years ago, leaving only about one in 10 sharks in the open ocean alive.

"Something happened that knocked out 90% of them overnight," Sibert says. What that something was remains uncertain, but it was definitely devastating. The asteroid that wiped out the dinosaurs resulted in the extinction of just 30 to 35% of all shark species -- this event was two to three times worse.

How did Sibert and her co-author Leah Rubin, a doctoral student at the State University of New York College of Environmental Science and Forestry, stumble upon this enigmatic marine die-off? It was a bit of a surprise, involving some deep-sea detective work and a mountain of microfossils.

Buried treasure

When a marine animal dies, its remains descend into the abyss, decomposing from whole creature to constituent parts. Tiny pieces of the fallen, like the scales present on a shark (denticles) and teeth from fish rain down upon the ocean floor and, over time, pile up in the sediment.

"The ocean floor is basically a graveyard for all of the life that's living anywhere in the water column," says Sibert.

Each denticle or tooth is like a tiny headstone. As they're embedded into the sediment, they leave a fossilized record of life. These fossils are known as "icthyoliths." And denticles don't just get subsumed by the sediment when a shark dies either. "They shed their denticles throughout their whole life," notes Rubin. "That makes them a really abundant fossil." 

Extracting a cylindrical core of sediment allows scientists to analyze the types of icthyoliths embedded within -- giving them a good proxy for what the ocean ecosystem looked like across deep time. The deeper you dig, the further back in time you can travel.

The sediment cores used in the study come from two locations in the Pacific Ocean, one northern and one southern site, and cover a timescale of 40 million years. They were gathered from about 3.5 miles below the surface by the JOIDES Resolution, a research vessel that can drill into the seafloor.

It's no easy feat to analyze the icthyoliths within each core sample, however. The fragments are incredibly small, sometimes smaller than half the width of a human hair and they come in a dizzying, beautiful array of shapes and sizes. 

Sibert would sift through dry sediment under a microscope and separate out the denticles for this project, a task she's become good at after picking almost 200,000 out of the ocean dirt in her studies. After isolating the denticles, it was Rubin's job to help identify and describe their characteristics, to differentiate them from each other.

The denticles glisten under light, radiating blues, muted greens and oranges, and are given names as descriptive as "Two Big Lobes" (for a denticle containing, well, two big lobes) to the more fanciful "Whale Blow" and "Wrinkly Kite." You can see a selection of them in the image to the right.

The denticles tell the story. There are almost 1,300 in the study, with 85 distinct geometric shapes. The majority of them described by Sibert and Rubin are from prior to 19 million years ago, with only a few dozen found in the sediment cores after that time. The denticles disappear... so what happened to the sharks?

Extinction X

The denticles show a decline in shark numbers and diversity around 19 million years ago but there's no obvious cause behind the event. "It really, truly is a mystery right now, we don't know what happened," says Sibert.

The key to solving the mystery will be understanding the period of time the sharks seemed to almost disappear. It's known as the "Miocene" and Sibert describes it as a "transition period" for the Earth. Around 15 million years before the sharks mysterious extinction event, Earth was slowly becoming an "ice house" planet and a permanent ice sheet was growing over Antarctica. Even so, the planet was still much warmer than it is today.

"If I showed you a map," Sibert says "you'd kind of recognize everything but overall it would look just a little bit off."

The oceans of the time weren't all that different to the oceans of today, though you wouldn't find things like tuna, swordfish or seabirds. Whales and dolphins were yet to evolve, too. Unfortunately, there's not a lot of high quality records of this time in the Earth's history -- scientists just haven't spent a lot of time looking at it and it also seems to be poorly preserved in the deep sea sediments collected by drilling programs.

So there's not a lot of evidence to catch the shark killer, so to speak, but there are avenues to investigate. Discovering Extinction X in this unremarkable period of the Earth's history is just the tip of the iceberg.

"This paper definitely offers a ton more questions than it offers answers," says Rubin.

Could there have been an environmental driving force that caused the shark's decline? It's hard to say. Carbon and oxygen levels don't show any unusual aberrations but scientists could use a lot more data around this time point. Did this occur across all the world's oceans and in other marine life? Sibert thinks this was a global event, but we need more records.

And what about other bodies of water? Lakes and coastal sediments might show a different phenomenon again. How did land animals fare during this time? Are there other chemical proxies that can tell us about what the environment was like for them?

Sibert even suggests a pathogen, like a virus, could be responsible for the decreasing numbers, though it would be much harder to show this was the case.

For Sibert, the extinction stands out. Given that sharks have been around for 400 million years or more, surviving multiple mass extinction events, she believes something really significant must have happened and the sharks may be a doorway to understanding bigger changes to the Earth system during the early Miocene. "There's more data waiting to be found," says Rubin.

One of the major concerning aspects is that populations never really had a chance to bounce back from this event. Finding this history in the fossil record highlights the fragility or the marine environment and how difficult it can be for species to recover when they are pushed to the brink of extinction.

Post Your Comment

Most Recent News

Euro 2020: Bottled It! Ronaldo Sparks Coca-Cola Conundrum

19 June, 2021

  Bottled it! Ronaldo sparks Coca-Cola conundrum  ...More

Euro 2020: Portugal v Germany Match Preview

19 June, 2021

  Portugal v Germany match preview  ...More

Football: NFL and Black College Football Hall of Fame Host Inaugural General Manager Forum and 4th Quarterback Coaching Summit

19 June, 2021

  -posted by Daniel Mogollon, Staff Writer; Image: Baltimore Ravens executive vice president Ozzie Newsome’s with 2018 first-round pick Lamar Jackson. (Image Source: Patrick......More

Get Published

Want to publish your own articles?

Create an account, and submit your articles, photos and/or videos. They will be reviewed by our professional copy editors, and if it is approved, it will be published for all our readers to view.