If a whale falls in the ocean, and no one’s around to see it, does it still create a complex,
unique ecosystem?
Turns out, it does.
A whale fall is what happens when a whale dies out in the open ocean and its body sinks
really far -- to at least a thousand meters down.
Deep down in the cold, dark water, there isn’t much food around. So when a whale carcass
shows up, all that nutritional goodness totally changes the ecosystem of the ocean floor.
The first natural whale fall ever studied was discovered accidentally by a team of scientists
in 1987, during an expedition in a specially-designed submarine known as a deep submergence vehicle.
The bacteria the team found growing on the whale bones were similar to those you’d
find in places like hydrothermal vents, and they even discovered some new species of clams.
So marine biologists started looking for more whale falls to study, and eventually realized
that these bacteria and clams were part of a whole unique ecosystem.
It all starts with stage one: just after the whale dies, when its body reaches the ocean
floor.
The first scavengers to show up are creatures like sleeper sharks, hagfish, and tiny, shrimp-like
crustaceans called amphipods, which start to strip the flesh down to the bone.
Combined, these animals can eat 40 to 60 kilograms of tissue per day. But even at that rate,
it can take a few years for them to finish off something the size of a whale.
Once they’ve polished most of it off, it’s time for stage two.
A swarm of invertebrates moves in, bringing crustaceans, molluscs, and bristly polychaete
worms -- a type of worm that’s good at surviving in extreme environments, like the coldest
parts of the ocean
They feed on anything that’s left over, plus the sediment surrounding the whale, which
is now packed with bits of decomposing tissue.
Some of these animals have never been spotted anywhere else, like a species of snail found
on that first 1987 whale fall that led to the discovery of a whole new family of aquatic
snails.
After about two years, mats of bacteria colonize the whale bones, kickstarting stage three.
These bacteria feed on lipids -- the fats and oils -- from the whale bones, turning
them into hydrogen sulfide gas, which would be very toxic to most forms of life.
But in this case, it’s a key part of the whole ecosystem.
All that hydrogen sulfide creates a sulphophilic, or sulfur-loving, community made up of the
bacteria, the organisms that feed on them, and other scavengers that show up late to
the party.
An average of 185 different sulfur-loving species end up in each whale..
This stage can last for decades -- 50 to 100 years -- and it’s a lot like some of the
other strange things you’ll find on the ocean floor like hydrothermal vents and cold
seeps.
These vents are cracks in the ocean floor that spew hot, mineral-rich stuff into the
ocean, and the seeps are briny pools of liquids and gases that include lots of sulfide and
methane, also on the ocean floor.
Since all these places provide so much potential food on the seafloor -- which is otherwise
pretty barren -- life tends to take over.
It’s kinda hard to study environments so far down, though, so we’re still learning
about the different species found on whale bones, and how they’re related to those
found at deep sea vents and seeps.
And it’s not totally clear how the organisms that colonize a whale fall get from place
to place, or how they find the carcass at all.
Biologists are also trying to figure out how whaling, which would have lowered the number
of whale falls, might have changed life on the seafloor,.
They’re working to answer these questions by studying artificially-placed whale bones
and other kinds of sunken biomass, like wood and kelp, to learn more about the organisms
that move in.
The life forms that colonize these places have had to evolve all kinds of adaptations
to survive without oxygen or sunlight, surrounded by chemicals that would be toxic to anything
else.
So if you want to learn more about some of the strangest examples of life on Earth, a
dead whale is an excellent place to look.
And SciShow is another good place to learn about weird life-forms! So if you want to
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