The Tiniest Plankton

HEIDI: When you start to see the invisible aspects of how the ocean works, and how life in the ocean works, it’s infinitely captivating.

I mean, the ocean, it just conveys this sort of incredible power and beauty and you don’t need to know very much about the details of it to appreciate that. As soon as you start to explore the details, oh my god, it’s just like, Wow.

PENNY: You look at the ocean, you think it’s a bunch of water. And I see information. I see the ocean as dissolved information.

TITLE: The Tiniest Plankton

PENNY: It was in graduate school that I started studying cultures of phytoplankton and growing them myself and you know, bonding with them.

I just thought they were cool. They were pretty, and cool.

It was only as my career evolved, I started realizing, geez, they’re more than cool, you know, they’re, they’re, uh, you know, they’re running the earth. [Laughs]

Phytoplankton come in all different shapes and sizes. There’s thousands of different species, and most of them undescribed, undiscovered.

Diatoms are just exquisite. There’s one that is huge, you can actually see it with the naked eye.

Then there are some called pennates, they’re shaped like a cigar. They like have a little conveyor belt of slime that they make that they can move.

And then there are others that make these big chains and have huge spines coming out that are really beautiful.

Cyanobacteria, its ancestors completely changed the earth by building up oxygen in the atmosphere.

There are some dinoflagellates that are toxic these are the group responsible for what they call the red tide.

And then, Coccolithophores are my other favorite group. ‘Cause they make these calcium carbonate plates that are just gorgeous.

I do realize how attached I am to these organisms. Irrationally so.

HEIDI: I met Penny when I was a sophomore in college. I went into her office with a short list of faculty in the department that I’d like to do an undergraduate research project with. And she was on the list, and she said, “Oh, I have a project in my lab, why don’t you do that.” And it was very serendipitous, I said, “sure.”

Another mentor and colleague now, Dr. Robert Olson invited me to join a research cruise as a volunteer. In retrospect, that cruise was part of a series of cruises that had a huge impact on our understanding of the ocean.

The team I was helping was using a relatively new instrument called a flow cytometer, with a high power, very focused laser.

PENNY: They’re built to be in a hospital.

HEIDI: It was used extensively to take pictures of, like, blood cells, and other biomedical applications.

PENNY: But we thought, what would happen if you just took, you know, seawater full of plankton and put it through a flow cytometer?

And the experiment worked beautifully.

It was exciting because you could, for the first time, see phytoplankton patterns in real time.

HEIDI: We were collecting as fast as we could, samples from the ocean, bringing them onto the ship, and measuring them on the flow cytometer.

But the data had some mysterious really tiny signals showing up in it. And at first Rob thought they were just noise, some kind of instrument noise or some kind of junk in the samples and he was thinking of ignoring them, not really sure what to make of them, and then he noticed that they were changing a little bit.

PENNY: They were behaving a bit like they might be something alive.

HEIDI: When you looked at samples shallower in the ocean, they were smaller and harder to see.

PENNY: They would get brighter as you went deeper in the water.

HEIDI: if it was noise you wouldn’t really expect to see a pattern like that.

HEIDI: Rob and Penny uncovered that those tiny signals that we were seeing were associated with a phytoplankton that they named Prochlorococcus, which we now know is the most abundant photosynthetic organism on the planet, also the smallest.

PENNY: Nobody knew they even existed. And they’re so important. The food web in the oceans, everything in the oceans relies on them.

HEIDI: Basically they’re so small that you just can’t see them through a conventional light microscope. Flow cytometry was really the technological unlock.

PENNY: I like to say Prochlorococcus made itself visible to us.

PENNY: My colleague was telling me just recently how textbooks are changing, how they describe, for example, Columbus discovering America. And, um, that it’s now Columbus encountered America.

And I thought, perfect. We’ve encountered Prochlorococcus!

This is Ceratium.

That’s Prochlorococcus. There’s no doubt about it.

[Kisses the puppet] My heart throb. I am a little weird about it. It’s true.

But when you see a picture to scale of this little green film, that’s feeding the global oceans, which is 70% of the, of the earth.And you think that most people have never heard of phytoplankton. And I think, well, we need to fix that. [Laughs]

TEXT UNDER IMAGE OF PENNY RECEIVING MEDAL OF SCIENCE FROM OBAMA: In 2013, Dr. Chisholm was awarded the National Medal of Science for ‘encountering’ Prochlorococcus.