4 Mysteries of the World's Oceans

Despite covering more than 70% of the surface of our planet, we know strikingly little about the mysteries of the oceans’ depths. In fact, it’s often stated that we know more about the surface of the moon than the bottom of the ocean, and in many regards, this is entirely true. It’s surprisingly difficult to study the murky depths from the lack of sunlight and crushing water pressure, not to mention just how hard it is to send an actual, rather fragile human down there.

This means that despite living in an era of unbelievable technological innovation and scientific discovery, the ocean still holds many baffling questions that leave researchers scratching their heads, and without further ado, here are 4 that we’ve yet to crack.

The Narwhal Conundrum

Everyone is familiar with the narwhal, the famed unicorn of the sea with its sleek body and signature tusk. It’s an elusive whale that lives mostly in the waters around the arctic, and since we’ve begun studying it, we’ve learned quite a fair bit. For example, we know that its diet consists almost entirely of halibut and cod, and that they’re quite picky when it comes to anything else. They can dive as deep as 1500 meters, or almost 5000 feet, and can hold their breath for nearly 30 minutes.

We’ve even observed narwhals communicating with each other, using various clicks and whistles.

But for all we know about them, we still can’t seem to figure out exactly what that darn tusk is for. The tusk is actually a canine tooth, and it continues to grow throughout the narwhal’s life, reaching a maximum length of 3 meters or about 10 feet. And while every male has a tusk, only about 15 percent of females have one, and its significantly smaller. And, fun fact, about one in every 500 males has two tusks.

But what is its purpose? For the longest time, it was assumed that they represented a secondary sex characteristic, with a longer tusk indicating a more dominant male in the social hierarchy. Evidence for this included observations that males would often rub their tusks together, an exercise known as tusking, as if they were comparing sizes.

Others have suggested that the tusk is used to break surface ice to allow the narwhal to breathe. This would be pretty helpful, considering that a fair number sadly die of suffocation when they get trapped under thick pack ice and can’t break through. Following the topic of survival, it’s also been suggested that the tusk is used for hunting, which seems logical enough. In fact, drone footage from 2016 showed Narwhals smacking fish with their tusk, stunning them just long enough to be easy prey.

But every one of these ideas has its issues. It can’t be something that is inherently crucial for survival, because females live longer than the males on average, no tusk required. And the mating dominance theory lost a lot of favor when it was found that males were actually quite gentle when tusking, quite different from the aggressive, often violent displays of strength seen during mating seasons in other species around the world.

Things got even more confusing when sample analysis showed that the tusk contains as many as 10 million nerve endings, setting it apart from similar features on other animals like a rhino’s horn which is more like a fingernail and has no nerves at all. This means that it likely gathers information about the water and relays it to the brain, this could be anything like temperature, salinity, detecting sensitive vibrations, or even sensing nearby prey. And if this is all true then it means that when Narwhals rub their tusks, they are possibly exchanging information about the environments they were recently swimming through.

It’s all very strange, and again, any hypothesis seems weird because if it is indeed so useful, it’s quite odd that the females would live longer without having one. Or maybe the males are just so inferior in some way that they need the tusk to level the playing field, but there isn’t any evidence for this.

So for now, it seems that the exact purpose of this mysterious creature’s tusk will remain out of reach.

Secrets of the Whales

Of all the majestic animals that roam the oceans, perhaps none are as awe-inspiring as whales. Sperm whales dive for food at unfathomable depths, plunging up to 2,250 meters or 7,400 feet below the surface. Humpback whales often live purely off fat reserves and can go without food for up to 7 months at a time. And, of course, the gargantuan blue whale is the largest known animal to have ever existed on earth.

There used to be millions of whales populating the oceans, including hundreds of thousands of blue whales, but exploitation in the 1900s caused their population to plummet, and several species are now threatened with extinction, only having a few thousand left roaming in the wild.

What this means is that it’s rather hard to study them, and there’s quite a bit we just don’t know.

For starters, breaching. Some whales breach several times per hour, including some of the bigger ones, like humpback and sperm whales. The incredible sight of one of these behemoths launching out of the water and splashing back down as it rolls over is certainly one of the craziest things you can witness from a boat, but its purpose is still a bit of an enigma.

There are many, many theories, and evidence to support several of them. It’s possible that breaching is a form of communication to other whales, especially since breaches occur more often in groups. Since whales are known to communicate by slapping their fins or tail on the surface, it would make sense that breaching would be a similar way to communicate when visibility is poor. People have also put forward the idea that the immense smacking of the whale coming back down is perhaps intended to stun prey below the surface.

Another theory is that breaching is a quick way to get rid of parasites. Cyamids, or whale lice, are nasty little buggers that find their way into the skin folds, nostrils, and eyes of whales, and they’re bound to be irritating. Since whales don’t have hands to wipe them away, blasting them off with a majestic breach and a big smack down would certainly do the trick.

But perhaps the easiest explanation to accept is that, along with some combination of the previous answers, breaching is a just a form of play. An easy way for young calves to get out some pent up energy and develop better spatial awareness and control over their body.

Another question about whales that has yet to be answered concerns their iconic singing. Their enchanting tunes echoing throughout the depths are so fascinating that a copy of them even made it onto Voyager I. But why exactly they do it is still up in the air.

Specifically, humpback whales and blue whales in the Indian Ocean produce songs up to 30 minutes long, with repeating sounds and ethereal notes. Their songs have been recorded and analyzed time and time again, broken down into phrases, units, and sub-units. Over 19 years, similar patterns or notes could be spotted across many songs, but the same song was never sung twice, and there were very few similarities between different songs. Researchers even found that their tone has been getting lower since the 1960s, possibly as a way to distinguish their songs from the background noises of ships.

So what are they for? They might be for echolocation, or they could be a way to bond with other members of their pod. One of the most interesting theories is that whales create songs simply for the thrill of it, because they find it entertaining. Almost as if they’re appreciating a basic form of art.

This would certainly be a fascinating answer, but not all that surprising considering that whales are among the most intelligent creatures on the planet, and have shown their level of consciousness on more than one occasion.

For example, in 2005, crab fishermen off the coast of San Francisco spotted a humpback whale caught in the many ropes they’d lowered into the water. With weighted ropes tangled around its face, flippers, and tail so tightly that it was cutting the whale’s blubber, the animal was struggling to move, and it was clear that it wasn’t going to be able to escape on its own. A daring rescue operation commenced as divers arrived on the scene and descended with the intent to cut him free.

At first, the whale panicked as the divers approached, thrashing around and actually posing somewhat of a danger to its saviors, but after a while it calmed down and watched them intensely. When the final ropes were cut and the whale was free, instead of immediately bolting away to safety, he swam in circles around the divers, and then approached them all individually, nuzzling them and gently tapping them with his flippers before swimming off, as if spending a little time to thank them.

It’s not exactly testable by science, but if it turned out that whales were more intelligent than we gave them credit for, it could explain much of their strange behavior like breaching and singing. But for now, we’ll have to just keep making guesses as to why these gentle giants do the things they do.

The Deep Dark

Certainly the most unsettling entry on this list, the deepest parts of the ocean remain largely unexplored. Only between 10 and 20 percent of the global ocean floor has been mapped in detail, with the crushing pressure a main factor as to why it’s so difficult. But this pressure doesn’t stop life from surviving, in fact, in the places most inhospitable to humans, life actually thrives. And not just boring microscopic life that hangs out near hydrothermal vents, but entire ecosystems of predators, prey, and scavengers, some of which are quite frightening.

The giant squid, for example, was really only thought to be the stuff of legends for many years, and it wasn’t until 2004 that a nearly complete specimen was captured on accident and examined. Surviving at depths of a thousand meters or 3300 feet, it’s understandable why we simply never came across them before.

And that begs the question, if the giant squid could go unnoticed for so long, what other monstrosities are hiding where the sunlight can’t reach?

And we’re not talking about the Megalodon here, because let’s be straight, it’s extinct and there’s no chance of it still being around today. What we are talking about is something called Deep-Sea Gigantism, or Abyssal Gigantism, the tendency for deep sea invertebrates to be much larger than their shallow-water relatives. The giant squid is a perfect example of this, as is the Japanese spider crab, species of giant clams, and more.

It’s well within the realm of possibility that in the deep of the middle of the Pacific Ocean there could be colossal octopi, jellyfish bigger than anything we’ve ever seen, massive lobsters, and much more. The imagination’s the limit simply because the majority of this dark realm is completely unexplored.

This might be one mystery that gets at least somewhat resolved in the near future though, as there is currently a massive undertaking by the United Nations to provide a complete map of the ocean floor by 2030. Project Seabed 2030 has already contributed a substantial amount of data about the bottom of the oceans, but whether or not they’re on track to hit that 2030 deadline is anybody’s guess. But remember, this is just the bottom of the ocean. There’s still thousands of meters of unexplored water above that remaining in the shadows, with a seemingly unlimited potential for scientific wonders to be unveiled.

An Eely Mystery

We’ll end off with a mystery that was partially solved in just the last couple years, and it’s all about eels.

Put simple, eels are weird. Especially European eels. They’re catadromous, meaning they spawn in the ocean but live most of their life in fresh water. They begin their life as tiny, largely transparent larvae that drift around in ocean currents for months before floating to coastal or freshwater habitats.

Once they’ve reached freshwater, they begin a remarkable metamorphosis, transforming into ‘glass eels’, still transparent but beginning to resemble an eel. Eels will then spend years, or even decades, living in this freshwater environment before reaching sexual maturity, at which point they start to change in shape and color. When they’re ready to reproduce, they leave their freshwater home and venture back into the sea, heading to where their own life began to spawn younglings before dying.

For the longest time, researchers just took wild stabs at figuring out this mysterious life cycle. No one had observed European eels laying eggs, giving birth, or mating. To make things even weirder, eels don’t have genitalia, and the only way to differentiate between males and females is to wait until they reach sexual maturity, dissect them, and carefully analyze their gonads.

But of course, this wasn’t known until modern times, leaving Aristotle back in the day so baffled by their mere existence that he concluded they must spontaneously spring up from mud. In the 18th century, an Italian scientist finally found an eel’s ovaries, but a male had yet to be identified, leaving everyone scratching their heads looking for their elusive testicles. Even Sigmund Freud got sucked into the quest, because of course he did, and in a few weeks during his time in University he dissected hundreds of eels, which he claimed had all been of the female variety since he’d failed to find any eel family jewels.

He finally found the treasure he’d been seeking in eel number 400.

What Freud didn’t know is that eels don’t necessarily have a determined sex at birth like humans do. When eels hatch, they are sexless, and develop their sexual characteristics later in life, meaning Freud probably chopped up more than a few would-be males before they had a chance to show it.

But this was still only a single piece of the mystery. More information was uncovered when researchers began breeding eels in captivity, which is when they found that they had to use hormones to speed up sexual maturity as it normally takes up to 20 years. Turns out that females release millions of eggs into the water, which are then fertilized by the males. Still, though, this had yet to be observed in the wild.

It was long believed that the location of this massive birth cycle was in the Sargasso Sea, a region in the Atlantic Ocean, but researchers always lost the eel’s tracks before actually finding anything. It wasn’t until 2022 that the Sargasso Sea was confirmed as the breeding ground when satellite tags tracked the eels throughout the entire return journey.

This was a big step in confirming an important part of their life cycle, but much of the process has still yet to be observed in the wild, unexpectedly leaving the humble eel as one of the most mysterious creatures the ocean has revealed to us thus far.

Key Takeaways

• Scientists remain uncertain why narwhals have tusks, with theories including mating dominance, ice-breaking, hunting, and environmental sensing, though none fully explain why most females lack them.
• Whale breaching and singing purposes are still debated, with hypotheses ranging from communication and parasite removal to play, echolocation, bonding, or even artistic expression.
• Only 10-20 percent of the global ocean floor has been mapped in detail, leaving vast deep-sea ecosystems and potential undiscovered species largely unknown to science.
• The Sargasso Sea was confirmed in 2022 as the European eel breeding ground, yet much of their complex life cycle, including wild mating and spawning, remains unobserved.
• Deep-sea gigantism suggests enormous undiscovered invertebrates may inhabit unexplored ocean depths, with the United Nations aiming to map the entire seabed by 2030.

Sources

• Original Side Projects video: 4 Mysteries of the World’s Oceans
• Hero image source by Diego Delso / openverse, by-sa.

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