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[piano intro] - Hi there, I'm Frank Graff.

What's the connection between sharks and shipwrecks?

How our cities are becoming urban heat islands and how 3D printing can save fisheries.

We're talking the science of place, next on SciNC.

- [Announcer] Funding for SciNC is provided by the North Carolina Department of Natural and Cultural Resources.

[pensive music] ♪ - Hi again and welcome to SciNC.

You know, North Carolina's coast is a pretty sharky place.

73 species of shark are found off the coast.

Now don't worry, most could care less about people and most of those sharks are simply just passing through.

Sand tiger sharks, however, have moved into the shipwrecks off the coast.

Now, that's not a bad thing.

Scientists say on wrecks where sand tiger sharks hold sentinel, there's a greater variety of fish, but the question remains, why'd the sharks move in?

- You can't swim with a shark without just being fascinated by how this animal has evolved over the years of their tremendous success story and to see how they've adapted.

And in so many ways, there's so many species of sharks, that it's just, to me, a subject that there's no end of questions to ask.

- [Frank Graff] And to answer some of those shark questions, I'm in the ocean tank at the North Carolina Aquarium on Roanoke Island.

Yep.

That's me.

And that's Shawn Harper, the aquarium's Dive Safety Officer, and those are sand tiger, nurse and sandbar sharks.

Harper says the sharks behavior in the tank, mimics their behavior on the wrecks off the North Carolina coast.

- [Shawn Harper] Very indicative of what you would see here, the sand tigers, other shark species, such as the sandbar sharks are swimming around the wrecks.

- [Frank Graff] And that's why I'm in the ocean tank.

More on that in a moment.

But first let's go off the North Carolina coast, where more than 3000 shipwrecks, dating back to the first English settlements are found on the ocean floor.

Treacherous weather, ocean currents, shifting sandbars, and even World Wars gave the North Carolina coast the nickname, the Graveyard of the Atlantic.

But those wrecks have become the havens of ocean life, especially for sharks.

- The history of the wrecks is one very cool aspect of it.

The marine life that are associated with the wrecks, I'm a biologist, so that really attracts me and the fact that you can see these natural aggregations of large numbers of large sharks and be swimming shoulder to shoulder with them is just, there's not many places in the world that you get to do that.

- [Frank Graff] There are about 73 species of sharks that live or pass through North Carolina waters every year.

- [Shawn Harper] So it's not a scary aspect for me.

I'm always aware of their space and try to not encroach on them, to startle them or to make them aggravated in any way.

- [Frank Graff] But it's the sand tiger sharks that really intrigue scientists.

And it's not just because sand tiger sharks are the predominant species on the wrecks.

- Where these sharks go.

When they come back, how long they hang out, do they move from wreck to wreck or stay?

We do know just from where sand tiger sharks tend to aggregate and even watching their behavior in our aquariums and stuff, that they do like to be near structure.

They don't seem to like to be out in the wide open ocean.

- [Frank Graff] It turns out sand tiger sharks not only like to hang out on the shipwrecks off North Carolina's coast, scientists say the wrecks appear to play an important role in a sand tiger shark's life cycle.

- We're catching almost all big females on these shipwrecks off of North Carolina.

This is interesting.

I'm actually a veterinarian.

And so one of the tools that we use a lot for aquatic animals is ultrasound.

'Cause ultrasound relies upon sound waves it works really well in water.

We ultrasound fish and sharks all the time in our care, in our aquariums.

So we were ultrasounding them and not only are most of these sharks that we are catching off the wrecks in North Carolina big females, but most of them were pregnant.

So now we have a whole other big question, okay, why are they all pregnant?

And why are we not catching females that aren't pregnant?

Why aren't we catching males?

- Some of these females that are gestating are potentially hanging out on these wrecks for longer periods, whereas the males might be passing through seasonally and then other females that are taking their break from pupping might be also migrating through.

- [Frank Graff] Female sand tiger sharks give birth after a 12 month pregnancy, the eggs hatch inside the mother, there are normally two offspring.

- There's two big questions.

We don't really know where they mate.

And possibly even more importance, from a species standpoint, is we don't know where they pup.

It appears that these wrecks are what you might call a gestation ground.

So for whatever reason, this is where these pregnant females, one of the things we have learned, we do know about sand tiger sharks is that they have a biennial or triennial reproductive cycle.

So they get pregnant one year, then they take one or two years off to resume their energy stores.

So those non-pregnant females are living somewhere else in those off years.

- [Frank Graff] North Carolina Aquarium researchers are joining with scientists at aquariums and universities along the east coast to better understand sand tiger shark behavior.

Part of that research involves catching the sharks and inserting a tiny tracking device into the shark's underbelly.

- This is the transmitter that is inside the sand tiger shark.

These would last for up to 10 years.

So once a shark is tagged, we can follow that animal for quite a long period of time.

- Receivers to record the shark's movements are attached to shipwrecks.

There are 39 receivers on coastal shipwrecks off the North Carolina coast.

- This is actually the acoustic receiver, it's essentially like a little hydrophone so it's listening for pings from the acoustic tags that are on the sand tiger sharks as well as other species of fish that researchers have tagged.

So it's listening and then recording.

Up here is the hydrophone at the very top, so that's where the signals are being received, inside here is basically the electronics that are recording and storing all that data and the batteries that keep it running.

- [Frank Graff] Some early findings indicate sand tiger sharks are migratory with a range from Georgia to New York and they swim from structure to structure.

- [Emily Christiansen] They also tend to follow temperatures a lot.

So we don't know if something has to do with the thermoclines in North Carolina, we're very close to the Gulf Stream here in this area where these wrecks are.

We don't know exactly, but that's part of the things that we're trying to tease out from the information of timing and movements and when they come and stay on the wrecks and when they leave.

- Sand tiger sharks have been a staple of public aquariums for as long as I can remember.

They do well in aquariums, but for as long as we worked with them, there's still gaps in our knowledge about these animals.

And so I feel like it's kind of a way that aquariums, public aquariums can return the favor.

- Which brings us back to the aquarium's ocean tank.

I'll admit I was a little nervous even with Shawn diving with me, but I was mostly in awe watching a creature so graceful, so powerful, so beautiful, despite the teeth.

And so mysterious.

While sand tiger sharks are comfortable on shipwrecks, people are finding cities less comfortable places to live.

As our climate warms, cities are becoming what are called urban heat islands.

Now think about it, concrete, asphalt, reflective windows, not much grass and trees and those heating effects vary across different areas and different populations of a city.

As we continue our State of Change Project, producer Michelle Lotker shows us how researchers are taking the temperature of urban heat islands.

- [Michelle Lotker] Ah, the urban jungle.

Except it generally has a lot more concrete than an actual jungle.

And that makes it hotter.

- The science behind it is relatively simple.

On a sort of 10,000 foot level, hard surfaces tend to be hotter.

Dark surfaces tend to be hotter.

Soft surfaces tend to be cooler.

Shade tends to be cooler.

Unfortunately, within built environments, within these urban areas, we have lots of areas where we have lots and lots of impervious, hard dark surfaces that hold onto heat and make those areas very, very, very hot.

And we have fewer areas with green space and shade that tend to be cooler.

And because these two can be really close to each other, you can see huge amounts of variation, sometimes 15 to even 19 or 20 degree differences between areas within the same city on the same day.

- [Michelle Lotker] We call these hotspots, urban heat islands and with global temperatures on the rise, that heat can turn deadly.

- Heat is our number one weather related killer.

And we often don't think about that.

We see the floods, we see the hurricanes, we see the fires on TV.

It's kind of hard to show heat on TV, but we know that a lot of people die in days with extreme heat and also nights that are extremely hot.

We already have hot parts of the city historically, and we're adding a few degrees more warming to that and we know they're just going to get more unbearable.

So what we're trying to do is find out where those parts of the city are so that we can introduce some heat mitigation measures.

- [Michelle Lotker] There's a lot of weather data available.

You can easily access a prediction of what your week is gonna be like, sometimes down to the hour.

- But the data that we have to measure temperature is from our cell phones, from weather stations, that data is very sparse and it represents generally large areas.

As we walk through an urban area, we may go under some trees and it's really shady and cooler.

We may walk across that parking lot surface, it's much hotter.

We experience temperature variably throughout an urban area.

The problem is, is that the existing data from weather stations is not fine enough to actually measure those differences.

- Let's go attach this to your car.

- Yeah, let's do it.

- [Michelle Lotker] To better understand the true exposure and experience of heat in Raleigh, Durham and Chapel Hill, the Museum of Life and Science partnered with local organizations and communities to take on-the-ground measurements of heat in the summer of 2021.

- [Max Cawley] So this project was a little bit different from perhaps a traditional scientific study in that so much of the data collection and then a lot of the analysis afterwards is going to be done and publicly owned and available by the people that live there.

- [Michelle Lotker] Routes throughout the cities were developed with community input and then volunteers carried sensors along those routes, three times during the sampling day, morning, midday, and evening.

Data was collected by car, by bike, and on foot.

The data collected painted a powerful picture.

- The data did indeed show that there were urban heat islands.

It also found that there are existing heat disparities on that neighborhood by neighborhood, or sometimes block by block level.

July 23rd was around 88, 89 degrees, which is pretty much the typical summer day that you'd expect here in central North Carolina.

On that day, in the evening, we reached a temperature difference of about 11 degrees, which is a pretty remarkable finding.

It means that within our study area and indeed here in Durham, some neighborhoods, sometimes only miles apart, were 11 degrees warmer than neighborhoods that were close by to them.

A lot of what we have found is that if you live in an urban area, you're not just doomed to live in a warmer area.

There are pockets, individual, small level areas that are warmer than other parts of the urban area.

- [Michelle Lotker] One of those pockets is the historically significant Hayti neighborhood in Durham, which was heavily altered by urban renewal policies in the late 1960s.

- If you look at any of the photographs or some of the video on what the Hayti community, the district looked like prior to 147, even this venue, when it was a church, there're trees, there's just a beautiful canopy of greenery.

Folks could walk the sidewalks and sit out and just enjoy the environment.

All of that was destroyed.

Data and studies have shown that in general, in other parts of Durham, there might be 60% canopy, but in the Hayti community's only 17% canopy, that's deplorable.

You've got a lot of residents who can ill afford to be paying higher cooling costs, but that's exactly what they're having to do because it's so hot in the evenings, it's not cooling off indoors because that heat is being held.

And it's just really another indication of how the injustice plagues, plagues communities like Hayti of color.

We continue to be impacted by systemic racism and policies and practices that are totally, totally unjust.

- [Michelle Lotker] The publicly available data gathered in this study can be used to support changes in policy and infrastructure that will increase heat resiliency.

- We can plant trees.

Parks are great.

We can also put things like bus shelters in areas that have shade or build canopies over them.

We can direct people to cooling centers on really hot days.

There are some really tangible things we can do that are almost low hanging fruit.

- [Michelle Lotker] UNC Chapel Hill's data driven, enviro-policy lab facilitated a hackathon, where people dug deeper into the data.

- The idea of a data science hackathon is to open up the data, get mentors, people who are climate scientists, or have some knowledge about urban heat or public health and get people together to try to come up with creative solutions, data analysis, visualization, to help better understand the problem of urban heat exposure and what we can do about it.

Globally, 65% of people will live in cities by 2030 and that number will just continue to increase over time.

- [Max Cawley] Equitable planning to make sure that we are not only dealing with these urban heat islands, but also dealing with it in a responsible way, means making sure that we include residents in the phases of planning so that whatever happens in these areas is led by their priorities and their preferences.

- Still in the ocean, but not nearly as deep, for our next sense of place because fish have found their place on artificial reefs.

- Our conservation effort is all about building sustainable and growing fisheries.

And that starts with healthy, sustainable habitat.

What you're designing is an area where small fish, juvenile fish, can hide from predator fish and have an opportunity to grow up and spawn.

- [Frank Graff] It's a muggy, humid summer morning over the Pamlico River, we're near Bath Creek and loaded onto that barge, anchored near the middle of the river.

Are 100 examples of what could be the future of artificial reef construction.

- We will monitor this and see.

We've used a ton of recycled materials.

This is a new product that we have not used in North Carolina yet, but we are eager to see how it performs as reef material.

- [Frank Graff] Those cubes are made of concrete, roughly three feet by three feet wide.

They weigh about 2000 pounds.

The rectangular holes are for fish to swim through.

The cubes will be spaced roughly 10 feet apart to create the artificial reef.

But what's really unique about the cubes is how they were made.

The artificial reef cubes were 3D printed by Raleigh based, Natrix.

This will be the first 3D printed artificial reef ever built in North Carolina's waters.

- Each of these box here is about a two by two inch box hole.

Essentially every single box is where we'll have one needle injecting a finite amount of water, which will diffuse out and create a ball.

And so every single one of these will create its own little diffused ball of concrete, which will merge together and form a shape.

So you can see the preview of that shape here and all the voids there, which will have fish swimming in or oysters growing.

- A couple main differences from a traditional 3D printer where they're using a wet mix going through a single head.

We use hundreds of injection needles and we're actually printing the water.

So we've got an aqueous solution here, and these are running through a series of pumps with controller boards and just like an IV pump at the hospital, right, that gives you medicine, we know exactly how much liquid we're injecting at every single position in the printer here.

So as we move along, we'll continue to print layer by layer, right now it's printing the bottom layer.

After that the head will come up and it'll look at the instructions from the digital file and print the next layer.

- [Frank Graff] Once injected into the dry concrete mix, the water flows and diffuses where it wills, it forms into a shape about the size of a baseball and all those individual shapes combine and form a three dimensional structure.

- [Matt Campbell] We have control on where to put the hardened structure and where do we wanna have void space.

So unlike a lot of processes that we've been doing since Roman times, if you mix something, it's gonna fill up the size of the container, we have the capability to create something more like Swiss cheese, right?

So we can use less material, we can create all kinds of niches and voids and crannies for fish or crabs or other organisms.

- With our technology, we can develop something that looks like it belongs in the water.

And so it works through reactive diffusion.

So it makes these rounded edges just like nature would.

So it looks very naturalistic.

And the crevices, the bumpiness, all of this makes it more amenable to the aquatic organisms, for them to attach, for them to hide in, for them to forage in.

- [Frank Graff] The engineers at Natrix say, all those uneven surfaces are key.

The reefs mimic nature.

- Nature is irregular and you have lots of variation in that.

And so all of that complexity creates bio-diversity.

So different types of animals and they all work symbiotically together in this beautiful way to create the natural systems that we see out there.

- [Frank Graff] The technology also allows for structures to be customized to where they will be used.

The smaller reefs are designed for shoreline protection, to break up waves and stabilize a coastline.

Larger structures are used for artificial reefs.

- [Leonard Nelson] We're matching both the energy environment, what's causing some of the erosion if we're protecting the shorelines.

And then also the ecological environment.

- [Frank Graff] Research clearly shows that if built correctly and in good locations, artificial reefs boost fish and shellfish populations.

North Carolina Division of Marine Fisheries maintains 43 ocean artificial reefs and 25 estuarine reefs.

They're all built using what are called materials of convenience.

- We use a variety of materials, really, depending on the habitat.

At this reef site, we have some other pre-cast concrete products, things called reef balls that are basically concrete domes.

We have some recycled culvert pipe, concrete pipe.

Other places we use aggregate rock like limestone and granite, primarily for oyster habitat, for oysters to grow on and settle on.

And out in the ocean, we use the concrete pipe as well as cleaned ships and vessels.

- [Frank Graff] The 3D printed reefs offer new possibilities.

- [David Sneed] So now we've gone from materials of convenience to actually designing structure, that creates real habitat for the fish populations that we're trying to conserve and grow.

So we wanna make sure we've got a good firm base that's gonna stay in place wherever we build the system.

And then as you said, it's gonna grow.

There's different layers on top of that, that are gonna attract the fish and the shellfish that are gonna grow in that area.

- And if your sense of place includes waterfalls, you're in luck.

North Carolina's mountains have plenty of them.

In fact, Brevard County alone has 250 waterfalls.

NC Culture Kids looks at the factors that make waterfalls special.

- Hey, everyone, Emily here at Hanging Rock State Park.

I am here to talk to Ranger Jonathan about some waterfalls.

Hey Jonathan.

- Hey, how are you?

- I'm good.

I have a question for you.

So I have heard that this state park specifically is the perfect place to see some waterfalls.

Why is this park so special?

Why here?

- So what makes this park special is our elevation change.

So we have three peaks here that are over 2000 feet in elevation.

Another thing which makes the park great is the quartzite, which makes up Hanging Rock.

It's a metamorphic rock and it's very hard and resistant to physical and chemical weathering.

The quartzite forms a hard escarpment, which helps form the waterfalls.

- Awesome.

Let's go check 'em out.

- Yeah, let's go.

- Woo, Jonathan, I think my legs are starting to understand what you meant about steep elevation.

They're getting a little tired.

- Well, we're about halfway there now, only a little farther to go.

- Great.

Let's go.

Wow, Jonathan, this is breathtaking.

- This is atop of Hanging Rock.

Hanging Rock is part of the Sauratown mountain chain and off in the distance we can see Moore's Knob and Cook's Wall.

So as we're looking out, we're a thousand foot in elevation higher than the surrounding piedmont.

That's what makes our mountain a monadnock.

So a monadnock is a solitary mountain, it's a peak that is much higher than the elevation that's surrounding the mountain and what makes a monadnock is this hard capstone of quartzite.

It prevents weathering to the underlying rock.

So when everything over top weathers away, the quartzite remains as the peak.

- Interesting.

I wonder also, why does this mountain stop here?

- It stops here 'cause the mountain itself has a capstone of the quartzite.

The quartzite's very resistant to weathering and it prevents the rock from underneath being eroded away.

So as the overburden or rocks over top of Hanging Rock erodes away, it just lays behind this hard quartzite.

- [Emily] So that's what makes these views just absolutely spectacular.

Wow.

- Well, welcome to Lower Cascade Falls.

- Wow.

This is so wonderful.

Jonathan, this waterfall is incredible, but tell me, how did this waterfall actually form?

How did it come to be?

- [Ranger Johnathan] So the erosion force from the water actually carves a channel through the bedrock.

So it carves through the softer rock till it meets the harder quartzite, which is an escarpment that forms the waterfall.

As the waterfall continues to fall over this escarpment, it increases erosion at the base of the falls and that's what produces the plunge pool that we see here.

And it's great habitat for fish and aquatic organisms.

- [Emily] Wow.

So what kind of plants or animals live around this waterfall?

- So the waterfall makes a microclimate.

The constant spray and moisture makes a high humidity.

So plants like liverworts, mosses, ferns, they love the high humidity and they'll grow in areas next to the waterfall.

Our park probably has its own particular species of lichens and mosses here because we have the presence of the waterfalls and the quartzite.

- Jonathan, thank you so much for taking me out here to Hanging Rock and for showing me the special geology that makes these waterfalls so unique.

I have one more question before I take a look at the rest of the waterfalls.

Is there anything else I need to know before I make my journey?

- [Ranger Jonathan] So when you're here visiting the falls, you need to be mindful of your safety.

So stick to the trail.

And if you do go around the waterfall, please don't climb on the rocks, 'cause the same conditions that allow the spray cliff community plants to thrive also create slippery conditions on the rocks so you could fall and hurt yourself.

- That is really good to know.

I definitely don't wanna fall and I will remember that as I make my way to the rest of the waterfalls.

- And that's it for SciNC for this week, be sure to check us out online.

I'm Frank Graff, thanks for watching.

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