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Every time we see diatoms, we have to give it to them: they’re just simply stunning.
They’re single-celled and major producers of the oxygen we breathe,
but the real reason we love seeing them is because of their frustules—
those silica shells they construct for themselves to live in.
They’re architects building stained glass walls to float in, and the effect is beautiful.
But apparently, diatoms are not content to rest on their ornate laurels.
Because some don’t just construct a home for themselves.
They construct a much larger structure that houses a whole gathering of diatoms,
an apartment building made of one long tube.
Yes, a tube.
They’re really striking to look at, like pieces of hay or strands of hair braided together.
The tubes we’re looking at right now come from Iceland.
Our master of microscopes James sent his assistant Ela there on a microbe hunt,
collecting samples from a bunch of different places.
But they saved the marine samples for last because
those organisms tend to be more delicate to handle.
So on this last collecting session,
James was on a video call, watching as Ela scanned the dock she was standing on.
And along the submerged parts of the dock,
James spotted tufts of brownish stuff peeking out as the waves broke.
So he asked Ela to grab some and bring them back.
The next day, she arrived at 6 am and crashed on the couch, while James
immediately grabbed the samples to take a look. And apparently, the entire time, he was saying,
“This is so beautiful.”
The samples that Ela brought back from the dock were teeming with diatoms.
It might seem surprising that the waters of Iceland can bring forth so much life,
especially during the cold and dark winter months.
But this matches James’ experience with the ponds in Poland he gathers samples from,
which often end up dominated by diatoms during the winter—
even as green algae numbers drop.
Diatoms seem to be fairly hardy in the dark.
One study found that diatoms survive longer than flagellates in extended periods of darkness.
The researchers didn’t find a specific reason why they’re able to tolerate the dark for so long, but
they theorized that perhaps the diatoms were more conservative in how they managed energy reserves.
Others have also suggested that their survival may be due to oils stored in
the diatoms, which may keep them better stocked compared to other organisms.
Their survival in winter means that when spring rolls around,
diatoms are often the first groups to bloom in polar waters.
And perhaps these tube-like structures are part of their success.
They’re not found as often in warmer waters, but things are different when it gets cold.
In 1994, a scientist found a whole bunch of these tubes along the Dutch coast in late winter.
And by a whole bunch, I mean there were more than
10 billion diatom cells living in tubes, per square meter.
These tubular colonies start with one diatom secreting a thread of
mucus from a pore, which it weaves into a tube.
Living in a mucus tube might not have the same romantic feel as the diatom’s
stained glass shells, but diatoms don’t have much need for romance.
As the tube gets longer and longer, the cell reproduces asexually, dividing and populating
the tube with more cells like it so they can travel through their shared home and add to it.
With every cell, a new roommate and construction worker is added,
a cell that can strengthen and add to the tube by producing more mucus.
At times, the cells might reproduce faster than the tube can expand,
at which point they might start to create a little side tunnel.
Their tube is a colony, and they might end up attached to surfaces
like sand particles, or a submerged Iceland dock.
And they’re kind of similar to colonies we’ve seen on this channel,
like Volvox and their spherical gatherings.
One thing that’s strange though is that based on what little we know about these tubes,
it doesn’t seem as if these diatoms do much to coordinate their activity.
This is different from volvox, where various cells take on different functions,
and they work together to create a better life for everyone.
But some of these diatoms act like they’ve constructed a crowded city street just to
ignore each other, a group of co-workers who don’t even say hi to each other in the hallway.
They’re little independent entities, countless ships passing in the night.
And for those living in narrower tubes, there’s no movement at all.
They’re simply stuck in place, next to a family member they don’t acknowledge.
But there must be a reason they live together in these tubes.
Otherwise, why bother with the time and energy it takes to start making a tube,
and to keep adding to it.
The tube might be a form of protection,
making the diatoms too big for microbial predators to consume.
But it’s probably also a way to help the diatoms access light through a few different mechanisms.
To start, the tubes help lift the diatoms away from the substrate they might have sunk to,
raising them towards any light that might penetrate the water.
And as they float in the water, the tubes allow the diatoms to
move with the rhythm of the waves, illuminating all sides in the process.
At least, that’s one of the possibilities for why these diatoms turn to tubes.
But stepping back from the “why,” it’s like we’re starting to see more of who diatoms are.
They’re builders.
They may never have set out to become that,
but their approach to the world around them has been to build, to assemble.
To make something functional and beautiful even if the beauty is not the point.
Thank you for coming on this journey with us as we explore the unseen world that surrounds us.
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