[upbeat music] - [Narrator] Brazil, famed for its beaches, it's lush beauty, it's diverse ecosystems deep within the Amazon rainforest and of course, it's parties.

- Last time I was in Carnival?

- [Interviewer] Last time you were at Carnival.

- That was five years ago just before accepting the position here.

- [Narrator] Rio native, Dr. Catharina de Souza says she came to the United States to make a contribution.

Now she's a Research Professor at the Center for Marine Science at the University of North Carolina, Wilmington.

It's here where they study things like coastal ecology, marine mammals, and what they eat, like plankton.

- Microalgae are part of the plankton.

So basically the microalgae are teeny plants, sorry, tiny plants.

- [Narrator] Microalgae get their food mainly from nutrients, like nitrogen and phosphorus.

So, the more food in the water, the more microalgae reproduce, supporting that food chain.

[light music] But sometimes there's an excess of it.

And that often comes from things like fertilizer runoff from farms.

That's called eutrophication.

And that's when the microalgae reproduce exponentially, leading to what are called algal blooms.

Why can algal blooms be bad?

Among other things, they can consume oxygen and block sunlight from underwater plants.

Fish and other life can't find food causing entire populations to leave or even die.

On top of that, a bloom that's thick muck can impact recreation and even bring down property values.

- We have lots of different microorganisms in the plankton, good and bad.

Most of the time you have the good ones, they are the predominant.

But you have also some bad species.

And under certain conditions, these bad species, they proliferate.

The bad ones, inside their cells, they produce the toxins.

- [Narrator] So the bad blooms, the toxic blooms, are the basis for de Souza's work.

- In the the left, the cells are passing and then you see small squares around the cells.

- [Narrator] De Souza and her team study individual species of algae with devices like this and actually take pictures of them in order to find out what's inside.

- Those are new.

- [Narrator] They're building a microalgae collection thanks to a $600,000 grant from the National Science Foundation.

And while field samples are widely used to study algae in their components, what de Souza's doing is actually growing cultures of microalgae in her lab to catalog which are toxic, which are harmful, or both.

- Once you find the culture that can produce a toxin, then the chemists, they need a lot, so they can do their jobs and describe the molecule.

- [Narrator] Call it a library that currently holds around 500 species, some from as far away as New Zealand.

And she wants to get that number to 1000.

- And then you take a little bit of this like and you pour it like that.

- [Narrator] De Souza is working to make this collection available to other researchers around the state and the country.

- It's the source of information.

For example, the agencies that perform the monitoring, perhaps they're looking at species in the microscope and they have no idea that the species can be toxic.

- It's a step down freezer.

- [Narrator] But building a library requires too much space and that's where this device comes in.

- So what it does is over a short period of time goes from 20 degrees down to -40.

What that allows us to do is not completely, instantly freeze the samples that we're putting in there.

This helps us in that we can bring these back to life.

And the way it helps the overall lab is we don't have to keep everything in large cultures so that we can keep things in small amounts and basically freeze their evolution at any particular time.

- [Narrator] She says the library can be seen as a public health tool, particularly as some species can cause paralysis, damage the liver and impact the community.

[light music] In the summer of 2019, three dogs were playing in a pond near downtown Wilmington and died from an algal bloom.

De Souza's team visited the pond the next day and took field samples, but they couldn't find the species or even see it.

But the toxin they determined was a neurotoxin called anatoxin.

Anatoxin can come about during periods of warm water temperatures.

- They're so strong that the dogs, they just were playing there and that was enough, you know, to cause their death.

And so that's the other thing.

Some toxic microalgae, they don't need to be in very high concentrations to have an effect.

- [Narrator] So how do some microalgae, for some reason, spontaneously produce toxins?

De Souza says they're not sure yet and says that might be more of a philosophical question.

Whatever the reason, she hopes that with the expansion of this library, she and her colleagues will have created a better defense and greater understanding of what dangers lurk in the microscopic world.

- [Dr. De Souza] Mostly what it can do right now is to detect them that they're in the water because they affect people.

We need to know our enemy.