[gentle music] - I know the idea of eating an oyster grosses some people out, but I love them.

[bright music] That's really good.

And lately, I've developed a real respect for the people that grow them, because farming oysters is not easy.

[oysters clacking] [bright music] And something keeps happening to this growing industry.

Oyster farmers will come out to their farms to find that a huge chunk of their crop, like 70, 80, 90%, has died.

- We weren't seeing anything one day, and the next, day we went out, and it was just like, it was just all dead shell.

- So I came down to Morehead City, North Carolina to talk to some of the people who were trying to figure this out.

Why are so many oysters dying and what can we do about it?

[bright upbeat music] So we are here to look at the Duke Aquafarm, it's basically like a small version of an oyster farm that students can learn from.

- [Employee] This line is kind of, you know, it's connecting all of the bags.

- Is it keeping kinda locked in place?

- Keeping them attached here- - Okay.

- To the floor.

- [Rossie] A quick primer on how oyster farming works.

Farmers buy what they called seed oyster, basically tiny baby oysters.

- So in this silo here, there's about 17,000 oysters.

- [Rossie] Cuties.

Farmer Tyler Chadwick grows his oysters here until they're big enough to stay inside these bags.

As the oysters get bigger, farmers move them into bags with larger holes so they can do what they do best, filter the water for nutrients.

- So it's moving rocks.

Yeah, it's moving rocks.

It's what we do for a living, is move rocks.

- Basically, we put out oysters that were this size last August, and by now, they've grown up to this size and it's May.

- [Rossie] This rapid growth is a very vulnerable time for oysters.

They are pumping so much of their energy into growth that they have less energy for their immune system.

So if they're exposed to pathogens, they're not as able to fight them off.

- But a dead oyster will basically start to gape.

What happens is that the muscle at the end of the oyster, whenever they die, the muscle basically relaxes, and so the shell opens, and that's that gaping you see.

- How we know when an oyster is dead is when we pull the bag up, and you hear that sound?

[shells clacking] That's what we hear.

- [Rossie] That's the sad sound.

- That's the sad sound.

What we want to hear is, listen to this.

Nope, see, that one's dead.

You hear that?

So that one's dead.

What we want to hear is, you hear that, sounds like two rocks hitting together?

- [Rossie] Sounds like money.

- Yes, that's right.

- [Rossie] Like in any other farming, sometimes crops die, but these mass mortality events don't seem normal, and scientists are trying to find solutions, because this is a critical time in this industry.

Many farmers aren't large enough to weather big losses yet.

- We put all this time and all this hard work into it, and then it's finally time for us to harvest, and we pull 'em up, and we gotta dump 'em in the road.

That's what happens with our dead oysters, they become driveway.

- [Rossie] So there's no single bacteria or disease that's causing all this mortality.

There's a lot of factors involved.

More development on the coast means more potential pollutants, extreme temperature fluctuations due to climate change, and also the fact that there's just more oyster aquaculture happening in the area.

But here's what we do know.

North Carolina is known for its really salty waters.

That's partly why oysters here taste so good.

But high salinity causes everything in the water to grow really quickly, including the microbes that kill oysters, which occur naturally in the water.

There's a simple sounding solution to this problem.

- What if we don't grow oysters at high salinity?

Move them up the estuary, maybe just move them during the summer when the mortality risk is highest, or have nurseries at low salinity and only bring them down to high salinity for a couple weeks to finish them.

They taste better at high salinity.

- [Rossie] There's also a longer term shift that scientists think needs to happen.

We need local seed oyster.

Most farmers like Tyler get their seed from Virginia, which means those oysters aren't adapted to live in North Carolina.

But establishing an oyster hatchery is incredibly expensive.

- It's a huge expense, and right now, the outcome is uncertain.

We have really good initial evidence that our North Carolina drive oyster lines work better.

That's just a few years of study.

- [Rossie] In the short term, the team is growing their own oysters alongside local farmers, and bringing them back to the lab to dissect them and identify which bacteria are killing them.

They hope to develop a warning system so that when they see the bacteria they think will kill the oysters, they can give farmers a heads up that it's coming.

- This is a problem for everybody.

We want to make sure that this industry stays resilient in the face of things like climate change.

And as mortalities break out, everybody has the same goal, and that's to promote and keep the oysters healthy and alive, 'cause they're a great resource.

- Now, I might not have a PhD behind my name, but I work in the water.

This is my livelihood, this is something that I deal with every single day.

I'm doing my part to better our water quality.

I'm in it for the long run.

I can consider myself a farmer, and as long as I can afford to grow oysters, I'll keep doing it.