Tag: Ocean

Why the Megalodon Shark went Extinct

Published: June 20, 2022 8.29am EDT

Author Michael Heithaus

Imagine traveling back in time and observing the oceans of 5 million years ago.

As you stand on an ancient shoreline, you see several small whales in the distance, gliding along the surface of an ancient sea.

Suddenly, and without warning, an enormous creature erupts out of the depths.

With its massive jaws, the monster crushes one of the whales and drags it down into the deep. Large chunks of the body are ripped off and swallowed whole. The rest of the whales scatter.

You have just witnessed mealtime for megalodon – formally known as Otodus megalodon – the largest shark ever.

In one hand rests an enormous tooth from a megalodon; in the other hand, two teeth from a great white shark. The megalodon tooth is about six times as large as those of the great white.
At left, a megalodon tooth; at right, for comparison, two teeth from a great white shark. Mark Kostich/iStock via Getty Images Plus

About the megalodon

As a scientist who studies sharks and other ocean species, I am fascinated by the awesome marine predators that have appeared and disappeared through the eons.

That includes huge swimming reptiles like ichthyosaurs, plesiosaurs and the mosasaurs. These incredible predators lived during the time of the dinosaurs; megalodon would not appear for another 50 million years.

But when it did arrive on the scene, about 15 million to 20 million years ago, the megalodon must have been an incredible sight.

A fully grown individual weighed about 50 metric tons – that’s more than 110,000 pounds (50,000 kilograms) – and was 50 to 60 feet long (15 to 18 meters). This animal was longer than a school bus and as heavy as a railroad car!

Its jaws were up to 10 feet (3 meters) wide, the teeth up to 7 inches (17.8 centimeters) long and the bite force was 40,000 pounds per square inch (2,800 kilograms per square centimeter).

Not surprisingly, megalodons ate big prey. Scientists know this because they’ve found chips of megalodon teeth embedded in the bones of large marine animals. On the menu, along with whales: large fish, seals, sea lions, dolphins and other sharks.

An artist's conception of a megalodon shark, with black eyes and a mouth wide open, chasing a pod of striped dolphins.
An artist’s vision of what megalodon might have looked like. Megalodon was found in the warm ocean waters of the tropics and subtropics. Its teeth have been found on every continent except Antarctica. Corey Ford/iStock via Getty Images Plus

Are scientists sure megalodon is extinct?

Internet rumors persist that modern-day megalodons exist – that they still swim around in today’s oceans.

But that’s not true. Megalodons are extinct. They died out about 3.5 million years ago.

And scientists know this because, once again, they looked at the teeth. All sharks – including megalodons – produce and ultimately lose tens of thousands of teeth throughout their lives.

That means lots of those lost megalodon teeth are around as fossils. Some are found at the bottom of the ocean; others washed up on shore.

But nobody has ever found a megalodon tooth that’s less than 3.5 million years old. That’s one of the reasons scientists believe megalodon went extinct then.

What’s more, megalodons spent much of their time relatively close to shore, a place where they easily found prey.

So if megalodons still existed, people would certainly have seen them. They were way too big to miss; we would have lots of photographs and videos.Watch this PBS Eons video and learn more about the megalodon shark.

Why megalodon disappeared

It probably wasn’t one single thing that led to the extinction of this amazing megapredator, but a complex mix of challenges.

First, the climate dramatically changed. Global water temperature dropped; that reduced the area where megalodon, a warm-water shark, could thrive.

Second, because of the changing climate, entire species that megalodon preyed upon vanished forever.

At the same time, competitors helped push megalodon to extinction – that includes the great white shark. Even though they were only one-third the size of megalodons, the great whites probably ate some of the same prey.

Then there were killer sperm whales, a now-extinct type of sperm whale. They grew as large as megalodon and had even bigger teeth. They were also warmblooded; that meant they enjoyed an expanded habitat, because living in cold waters wasn’t a problem.

Killer sperm whales probably traveled in groups, so they had an advantage when encountering a megalodon, which probably hunted alone.

The cooling seas, the disappearance of prey and the competition – it was all too much for the megalodon.

And that’s why you’ll never find a modern-day megalodon tooth.From NatGeo

Flesh Eating Bacteria Found in Sargassum

https://www.fau.edu/newsdesk/articles/perfect-pathogen-storm.php

‘Pathogen’ Storm: Vibrio Bacteria, Sargassum and Plastic Marine Debris

Beach, Sargassum, Seaweed, Brown Microalgae, Vibrio, Plastic Marine Debris, Public Health, Florida

Some cultivation-based data show beached Sargassum appear to harbor high amounts of Vibrio bacteria. (Photo credit: Brian Lapointe, FAU Harbor Branch)

By gisele galoustian | 5/18/2023

A new study uncovers how the interplay between Sargassum spp., plastic marine debris and Vibrio bacteria creates the perfect “pathogen” storm that has implications for both marine life and public health. Vibrio bacteria are found in waters around the world and are the dominant cause of death in humans from the marine environment. For example, Vibrio vulnificus, sometimes referred to as flesh-eating bacteria, can cause life-threatening foodborne illnesses from seafood consumption as well as disease and death from open wound infections.

Since 2011, Sargassum, free-living populations of brown macroalga, have been rapidly expanding in the Sargasso Sea and other parts of the open ocean such as the Great Atlantic Sargassum Belt, including frequent and unprecedented seaweed accumulation events on beaches. Plastic marine debris, first found in surface waters of the Sargasso Sea, has become a worldwide concern, and is known to persist decades longer than natural substrates in the marine environment.

Currently, little is known about the ecological relationship of vibrios with Sargassum. Moreover, genomic and metagenomic evidence has been lacking as to whether vibrios colonizing plastic marine debris and Sargassum could potentially infect humans. As summer kicks into high gear and efforts are underway to find innovative solutions to repurpose Sargassum, could these substrates pose a triple threat to public health?

Pages: Page 1, Page 2

Some corals like it hot: Heat stress may help coral reefs survive climate change

“Until recently, it was widely assumed that coral would bleach and die off worldwide as the oceans warm due to climate change,” says lead author Jessica Carilli, a post-doctoral fellow in Australian Nuclear Science and Technology Organisation’s (ANSTO) Institute for Environmental Research. “This would have very serious consequences, as loss of live coral — already observed in parts of the world — directly reduces fish habitats and the shoreline protection reefs provide from storms.”

“Even through the warming of our oceans is already occurring, these findings give hope that coral that has previously withstood anomalously warm water events may do so again,” says Carilli. “While more research is needed, this appears to be good news for the future of coral reefs in a warming climate.”

via Some corals like it hot: Heat stress may help coral reefs survive climate change.

Our Sick Oceans

Life on Earth has gone through five “mass extinction events” caused by events such as asteroid impacts; and it is often said that humanity’s combined impact is causing a sixth such event. The IPSO report concludes that it is too early to say definitively. But the trends are such that it is likely to happen, they say – and far faster than any of the previous five.

“What we’re seeing at the moment is unprecedented in the fossil record – the environmental changes are much more rapid,” Professor Rogers told BBC News. “We’ve still got most of the world’s biodiversity, but the actual rate of extinction is much higher [than in past events] – and what we face is certainly a globally significant extinction event.”

The report also notes that previous mass extinction events have been associated with trends being observed now – disturbances of the carbon cycle, and acidification and hypoxia (depletion of oxygen) of seawater. Levels of CO2 being absorbed by the oceans are already far greater than during the great extinction of marine species 55 million years ago (during the Paleocene-Eocene Thermal Maximum), it concludes.

via BBC News – World’s oceans in ‘shocking’ decline.

‘Great Garbage Patch’ in the Pacific Ocean Exaggerated

Claims that the “Great Garbage Patch” between California and Japan is twice the size of Texas is “grossly exaggerated” said the research which reckons it is more like one per cent the size.

Further reports that the oceans are filled with more plastic than plankton, and that the patch has been growing tenfold each decade since the 1950s are equally misleading, the new research claimed.

In reality it often cannot even be seen from the deck of a passing boat, said the latest analysts from the Oregon State University professor of oceanography Angelicque White.

Recent research by scientists at the Woods Hole Oceanographic Institution found that the amount of plastic, at least in the Atlantic Ocean, hasn’t increased since the mid-1980s – despite greater production and consumption of materials made from plastic, she pointed out.

via ‘Great Garbage Patch’ in the Pacific Ocean not so great claim scientists – Telegraph.

Stingray Migration

Like autumn leaves floating in a sunlit pond, this vast expanse of magnificent stingrays animates the bright blue seas of the Gulf of Mexico.

Taken off the coast of Mexico’s Holbox Island by amateur photographer Sandra Critelli, this breathtaking picture captures the migration of thousands of rays as they follow the clockwise current from Mexico’s Yucatan peninsula to western Florida.

Measuring up to 6ft 6in across, poisonous golden cow-nose rays migrate in groups – or ‘fevers’ – of up to 10,000 as they glide their way silently towards their summer feeding grounds. Thanks to Ramon Brunings.

via The great ocean migration… thousands of majestic stingrays swim to new seas | Mail Online.

%d bloggers like this: