I expect this is just the beginning.
Populations of marine animals will migrate to new areas less suited for them (or try and fail), causing disruptions in their new location, spurring more migrations….
When this happens, local fishing industries collapse because their prey is gone and new invasive species either aren’t edible or aren’t caught with the gear they have (like Lionfish, inedible to most fish and mammals, and all but impossible to catch except by spear fishing).
Between ocean acidification, deep water warming, overfishing, invasive species, pollution, loss of ice packs, and other as yet unknown factors, the ocean’s ability to produce food is going to be severely limited in the near future. It already is, in fact.
The crab collapse isn’t the canary in the coal mine, it’s not even the first miner to drop dead. It’s like 1/4 of the entire night shift just disappeared….and they are all the engineers that keep things functioning.

This is like a massive corn blight on land. It not only kills the corn, it takes out everything that relies on corn too, like pigs, chickens, cattle, goats, pretty much any livestock, and an insanely large percentage of the calories humans eat too. A shitload of the ocean relies on crab meat, and more rely on crabs to keep the ocean floors clean….important if we don’t want clouds of hydrogen sulfide erupting from the ocean making all coastal states dead zones.

But.....Bruhathkayosaurus might have been between 40–44 m (131–144 ft) in length and 175–220 tonnes in weight according to some estimates.
Certain rorquals from the Pliocene possibly rivaled the size of modern blue whales.

https://en.m.wikipedia.org/wiki/Bruhathkayosaurus

It's worth considering there were likely many yet undiscovered large marine animals who either were Chondrichthyes (cartilagenous, no bones) or lived in deep seas where any skeletal remains are still hidden.

If you love marine animals be vegan. Animal agriculture is the #1 most destructive force on the planet.....

You aren't just killing a chicken when you eat them, the chain of consequences has far more reach which is why the UN is advising people to stop eating animals. We are effectively replacing the environment's massive biodiversity with 3 types of farm animals. We'll be lucky to make it to the 22nd century:

https://www.theguardian.com/environment/2010/jun/02/un-report-meat-free-diet

Wrap your lips around a vegan "beef" patty. They are winning awards these days, so no excuses :-)

Hey now...it clearly said BIO-FLOURESCENT, not bioluminescent....so not fake. Biofluorescence is a relatively unstudied feature of some sea life where their coloring fluoresces under certain wavelengths. It's being found all over the animal kingdom, but apparently this is the first reptile found to show it.
Yes, they are shining some light (likely black light) to cause the fluorescence.
It's unknown how this feature might help marine animals. In land plants, it's often used to attract certain insects with colors/patterns they recognize....perhaps the markings on turtles allow other turtles to recognize differing sub species for 'racial purity'?

They live in that area, so they know what to expect. The behavior by this lion was relatively strange. I'd personally have wondered if marine animals can acquire rabies, rather than any of the typical dangers they might present. Either way, I'm sure these guys were ready to bludgeon it in the head and paddle for the shore if anything.

Lions aside... look at those fish! Whew! Man those look amazing. I kind of can't blame the lion!