(gentle upbeat music begins) (bird chirping) (gentle upbeat music continues) Welcome to Virginia's Eastern Shore.

We're on the southern tip of the Delmarva Peninsula, a giant strip of land containing parts of three states separated from the rest of the world by the most awesome body of water, the Chesapeake Bay, and we're having a bit of a watershed moment; I mean literally.

We're talking about watersheds.

It's the topic of today's episode of "Spotlight Earth."

(gentle upbeat music continues) (gentle upbeat music continues) We're at Kiptopeke State Park in Cape Charles, Virginia, near the mouth of the Chesapeake Bay.

We're just three miles up the coastline from the Chesapeake Bay Bridge-Tunnel, which connects Virginia Beach to the Eastern Shore of Virginia.

Kiptopeke is a perfect spot to explore, to see native plants and wildlife, and to just relax with nature.

This park, like so much of the Chesapeake Bay and its watershed, has lots of ecological diversity.

It's just beautiful out here.

I've still got a lot more to discover here, and while I get into that, I'm gonna toss it to my co-host, Michael, who's in the studio standing by to talk more about watersheds.

Thanks, Jarrell.

What a spectacular place.

Picking up where Jarrell left off, let's talk more about watersheds.

According to NOAA, that's the National Oceanic and Atmospheric Administration, a watershed is a land area that channels rainfall and snow melt to creeks, streams and rivers, and eventually to outflow points such as reservoirs, bays, and the ocean.

We can think of a watershed as a moving example of the effect of gravity on water.

Everything on and in the earth obeys the rules of gravity and is attempting to move to the center of the earth.

Yep, everything, even the molecules in your body.

Gravity is what is holding you onto the surface of the earth.

Gravity makes water flow downhill, following the shape of the landscape until it finally reaches its goal: the oceans of the world.

We call the surface of the oceans sea level.

A watershed can also be called a catchment or a drainage basin; a catchment because the bigger body of water is catching the water from the smaller tributaries or a drainage basin because the water's draining or flowing from the tributaries into the basin or larger body of water.

This is how water runs down and drains into the body of water at its base.

As it rains, water from these higher points of elevation drain to lower areas.

The Chesapeake Bay watershed works just like this.

Another term we want to get to know better is estuary, and for that, let's head back to Jarrell at Kiptopeke State Park, That age-old question: What is an estuary?

The Chesapeake Bay is an estuary.

In fact, it's the largest estuary in the United States and the third largest estuary in the world.

An estuary is a place that is partially enclosed by land, where fresh water from rivers and streams mixes with salt water from the ocean, so the salinity or salt content is constantly changing.

The Bay, along with all those rivers and streams that feed into it, make up what we call the Chesapeake Bay Watershed, and that covers some 64,000 square miles and includes parts of six states: New York, Delaware, Maryland, West Virginia, Pennsylvania, and of course Virginia, plus the District of Columbia.

That means water from all these states goes into the Bay, traveling through those rivers, streams, and tributaries ending up in the Chesapeake.

So the scale of this enormous watershed makes managing the Bay very challenging with so many different political and geographical differences, and that is also why we need to pay attention to everything in our water, because for instance, if someone in Upstate New York spills oil, it could end up here in Virginia in the Chesapeake.

There are more than 17 million people living in the Chesapeake Bay Watershed and managing all of them is a huge environmental challenge.

More than 30 years ago, the Chesapeake Bay Preservation Act was put into place to help keep the Bay clean.

The idea behind the Chesapeake Bay Act is to protect our water from lots of environmental issues.

It does this by regulating land use to minimize the disturbance of environmentally delicate coastal areas.

Its goal is to stop nutrients like nitrogen, phosphorus, and sediment, like pieces of dirt and rock pollution, from getting into the Chesapeake Bay.

How could you not want to protect something so beautiful and biodiverse?

Too many of those aforementioned nutrients can lead to something called eutrophication, and that can be a big problem for the Bay.

Ellen is standing by in the lab with all the scary details.

Yes, Jarrell.

Eutrophication is frightening indeed.

It's one of the most serious issues we see in the Chesapeake Bay.

Eutrophication is caused by runoff pollution.

Eutrophication can seem like an upside-down concept because we think of plants in the water as good things.

We know that through photosynthesis, plants produce oxygen and aquatic systems need oxygen.

Fish breathe oxygen just as we do, but in the water they get some extra help from gills, taking in dissolved oxygen from the water.

Eutrophication is when there isn't enough oxygen in the water for everything beside the plants.

The problem comes when excess nitrogen and phosphorus from fertilizer and pollutants get into the water.

It causes plant life to explode and then die.

Then the decomposers explode to eat up the dead plants.

These decomposers breathe in so much oxygen that they use it all up and the oxygen levels plummet.

With no oxygen to breathe, this causes death across the ecosystem.

Today in the lab, we're going to do a scientific investigation to see how this happens.

I've gathered the following items: aquaculture, fresh water, two clear containers; I've labeled one as control and one with a plus sign and the words nutrients; a light source, pipettes, some liquid fertilizer, several glass slides, a microscope and a pen to record our data.

We start by setting up two different ecosystems in these containers.

Since these represent fresh-water aquatic ecosystems, we need to add the same amount of fresh water to each: 250 milliliters.

Since we know that both ecosystems have naturally occurring plankton and nutrients, we're gonna add three drops of the aquaculture into each of our containers and one drop of liquid fertilizer.

To mimic an influx of excess nitrogen and phosphorus, let's add an additional drop of fertilizer to the +nutrients ecosystem.

Now I'm gonna take a drop of water from each container and drop them onto the slides labeled to match the container.

(lively music) When we look at them under the microscope, we see that they each have the same number of plankton.

But what happens when we compare them over time?

We're going to put both containers in a location that has access to light but not direct sunlight.

Then each day for the next four days, we'll take samples and record the number of plankton appearing in each sample.

(lively music continues) All right, all the data's in.

How has the number of plankton in each container changed over our observation period?

Let's plot these data points onto a line graph.

We see that the additional nutrients caused an increase in plankton.

When this happens in the Bay and its tributaries, it leads to eutrophication and dead zones; not good.

There are several ways to reduce the number of nutrients that seep into our waterways.

If you live near water, plant native plants near the shore to create a buffer zone, additionally, consuming less meat will reduce the demand for livestock that produce large amounts of nutrient-heavy waste.

Purchasing soaps and detergents that don't contain phosphates will help, and you can cut back on the amount of fertilizer you use on your lawn.

This will lessen the amount of nutrients in our wastewater.

No matter where you live, you can help prevent eutrophication and protect our water.

Let's check back in with Jarrell at Kiptopeke State Park.

Hey, Jarrell, how's the water looking over there?

It looks and feels great, and when we work together to address environmental issues, we can assure that these resources are available for future generations.

And you can do your part by making sure that your trash never reaches our waterways and by avoiding using chemicals on your lawn and over-fertilizing.

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