Predators are everywhere in the deep ocean.
But until recently, scientists didn’t always know who was eating who.
With unmanned vehicles and powerful cameras, they are uncovering these secrets.
Some predators eat what they find, like this king crab.
Sometimes prey becomes predator.
This brittle star grabbed a tiny squid On
our expeditions, many of the animal behaviors we see catch us by surprise.
This burrowing fish hides before pouncing.
Scientists control this remotely operated vehicle from a ship above.
In an instant, this big wreckfish has made a meal of one unlucky shark.
The wreckfish was fast.
But there are also slow-motion predators.
This starfish is stripping food off this branch of deepwater coral.
It may take several months – or even a year - to finish this meal.
Seeing these predators in action helps scientists understand the how ocean ecosystem fits together.
And it is pretty amazing to watch!
Now, let’s hear from an expert who studies these deep sea predators, marine biologist
Scott France…..along with our host, Debi Blaney.
Hello, I'm Debi Blaney, and I work for NOAA's Office of Ocean Exploration and Research.
And today, I have the distinct pleasure of talking to Scott France.
Scott is a marine biologist and professor at the University of Louisiana at Lafayette.
He has been involved in our deep-sea exploration work for many years.
Hi, Scott.
Thank you for joining us today.
Hi, Debi.
Nice to virtually join you today.
We just saw some impressive examples of predators eating their prey in the deep ocean.
And the scientists seemed pretty surprised by what they observed.
Why haven't we seen scenes like these before?
Yeah, we're always excited to see that kind of stuff.
And there are two primary reasons, and it's technology development and technology availability.
Cameras for use in the deep-sea were really only first being developed in the late 1960s
and 70s, and then remotely operated vehicles for scientific use really weren't common until
the 1990s.
We've had human occupied submersibles dedicated to science since the 1970s, but for a long
time, there were only one or two in operation.
And so, as you can imagine, demand for the use was really high, and the missions are
so focused on a specific objective that we didn't have the luxury of time to survey for
interesting behaviors.
So basically, as more programs develop deep-sea capable remotely operated vehicles, ROVs,
we have more opportunity for observations.
And so, the Okeanos Explorer program, in particular, is well suited to these sorts of observations
because they conduct these dedicated exploration dives that use high resolution cameras.
And importantly, they pay careful attention to lighting the environment that gives us
this opportunity to see these rare events unfold.
And I think another important aspect is that the Okeanos Explorer program makes all its
observations and data publicly available.
And so whatever scientists see, so too does the public.
There's a lot of hours of observation of the deep-sea that have been recorded there in
the research archives, and so they're not easily viewed by the public.
Yeah, you’re absolutely right, Scott.
We're really, really deep and it's very dark down there and there's no natural light.
So, having powerful lights will help us observe the environment.
What are some of the tricks predators use to find and catch their prey when we're talking
about the deep-sea?
Well, the first thing you have to consider is there's no sunlight in the deep-sea.
So, the answer typically won't be related to vision.
Probably the most important sense in the deep-sea would be chemo sensory.
Basically, the sense of smell detecting chemicals that are associated with prey in the water.
And once the predators get that scent, then it's just a matter of tracking down that scent
to its source.
So, most predators tend to move upstream into our current to find the prey because the scent
is coming downstream.
Many predators can also detect motion in the water, movement in the water, basically pressure
waves caused by swimming.
Even sea anemones are able to detect pressure waves and they change how their little steam
cells fire based on the pressure waves, and their knowledge of what's the size of the
prey.
You'll see shrimp and other crustaceans with these very long antennae that stream far from
the body.
Those would have sensory cells to detect the chemicals and the motion.
And one of my favorites is the tripod fish.
The tripod fish have modified fins that allow them to be propped up on the seafloor.
And they have these long, thin rays that extend forward, kind of like a radar dish.
And they're just kind of, I think, sensing motion, perhaps also chemo sensory smells.
And once they detect something, they'll swim off to get it.
Anglerfish have specialized lure right over the mouth, and sometimes those lures glow
and that'll attract the prey.
And they can feed on them.
And some siphonophores, these colonial jellyfish like animals, also have bioluminescent lures,
as well as stinging capsules that they use to paralyze prey such as small fish that get
close enough to them.
But we can also look at a lot of animals like corals and basket stars and sea lilies and
even some sea cucumbers that basically can employ a strategy that's like a spider's web.
That is, they're creating some kind of barrier in the water current that prey are going to
run into.
And these can be tentacles that can be arms, spines, even sheets of mucus.
And this is why corals grow up into the water.
They want to get their polyps that have the tentacles off the bottom because at the bottom,
water isn't moving.
And so, they get it up into the faster flow.
And that's also why you see a lot of other animals climbing up on corals.
They're basically hunting from the perch that is the coral.
Wow.
That's very interesting.
And how do prey avoid their predators or escape them?
Yeah, that's a tough living.
Some prey have very powerful muscles that they use for rapid escape.
Good examples of that would be squat lobsters and shrimp.
They have these muscular abdomens that they can tuck underneath them.
And then they dart backwards, hopefully away from the prey…excuse me…away from the
predator, and not to the predator.
Some species have a tube that they can retract into.
This is very common among worms.
And there's even one group of worms that's evolved to live with deep-sea octocorals such
that the coral secretes a tunnel and the worms live in a tunnel.
And so, you can find one colony of corals with about 100 different worms all living
protected in their little tunnels.
Other species will dig burrows into the sea floor that they can quickly retract into.
This behavior has really surprised some ROV pilots who attempt to sample a sea pen colony
that suddenly disappears into the sea floor when they sense the vibration.
And then there are specialists that like to distract predators.
For example, there are some squid that will release ink and mucus and that sort of combines
and it forms something they call a pseudomorph that just kind of hangs and drifts in the
water, that inky mucus, and so the predator goes there while the squid takes off in a
different direction.
There are even some deep-sea swimming worms that produce bioluminescent light, excuse
me, I’m going to say that again.
There are even some deep-sea swimming worms that produce bioluminescent light in structures
that fall off the worm.
So, the predator might chase the light ball while the worm swims away in the dark.
So that's pretty cool.
Oh, I did not know that, I had no clue.
Swimmer.
So how is predatory behavior in the deep ocean different from, say, the jungle?
Probably the biggest difference is the density of animals is much lower in the deep sea.
So, on average, things are really widely spread out.
The probability of a chance encounter between a predator and a prey is therefore pretty
low.
And this is why predators really have to rely on these senses like humans, sensory or smell,
in order to find their prey.
And that low probability is why, historically, we don't often get to see many of these predator-prey
events, which is why it's so great that we have so many opportunities now.
And why is it important for us to learn about predators who prey in the deep ocean?
Well, ultimately, all living organisms, including animals, need energy to survive.
Prey is energy for predators.
Humans are predators.
Some of our prey, like many fish, are predators of smaller animals.
And to understand how communities and organisms function, we need to understand who is eating
who.
Understanding predator prey relationships is an important step in the conservation of
any community.
But there's a bigger picture answer, and that is the flow of carbon and carbon compounds
through our ecosystem.
Carbon compounds are the key molecules for holding and transferring energy among organisms,
and lots of carbon is bound up in the tissue of organisms.
Of course, carbon compounds are also causing problems for our climate as they build up
in our atmosphere.
But the marine ecosystem is actually able to absorb a lot of that carbon.
And so, it's important for us to know basically where is that carbon going.
In the marine ecosystem and by understanding predator prey relationships, we have a clearer
picture of how that carbon is moved through the ecosystem.
Awesome.
And we saw several scenes of predator prey behavior that were really fast, the shark
going after the swordfish, the grouper going after the shark.
But we also saw a scene of a sea star feeding on a coral.
And I know that can be a very slow process.
Can you talk more about that?
Yeah, in general, a lot of processes in the deep sea are fairly slow.
The deep sea is very cold.
The average temperatures are below four degrees Celsius.
It's like the temperature in your refrigerator.
And that means metabolism is low.
That's basically the generation of energy that keeps you alive.
And if that's low, the pace of life is very slow.
When you eat a meal, it takes a very long time for it to digest.
And so, there are many species that have actually sort of adapted the strategy where they will
have a big meal and then they can rest for weeks or even months.
So, we made these observations of sea stars feeding on corals and we've had the opportunity
to go back to the same coral after 18 months.
And we've seen that the sea star has really only moved a few inches and is still feeding.
So that means one predator is feeding on the same prey for more than a year.
And that's just because it's taking a very long time to digest.
So one meal lasting a year and a half or longer.
Yeah, that's quite a refrigerator.
That's pretty cool.
Is there anything else you want to share with us today?
Just, I hope everyone watching the Okeanos Explorer videos derives as much pleasure as
deep-sea scientists do.
Certainly, our objective is to learn as much as we can about this vast underexploited ecosystem.
But we're all fans of this amazing and spectacular imagery.
So please enjoy.
Thank you, Scott, and good day to you.
Bye Debi.