- [Michael] So here's our second disk
and you can see the white and the black segments on the disk
and what you do is you lower it
until you can no longer discern white from black.
And you can see that that happened very, very quickly
in this case.
[Frank] In fact, the disc disappeared from view
when it reached about one quarter meter underwater.
That's a little more than one foot deep.
It's not much and that murky water is a good indicator
of the problems facing North Carolina's
largest natural lake, Lake Mattamuskeet.
It is beautiful on the surface
but deep down which is only a few feet
in the shallow body of water, the lake is in trouble.
- [Michael] So what that means is that there's not a lot
of light at all getting to the bottom.
- [Frank] Essentially, no light means no life.
- We've become really concerned
with declining water quality in the lake
as well as declines in our aquatic grasses
which we call submerged aquatic vegetation
and this submerged aquatic vegetation is one
of the key foods for all these migratory water fowl
that come here in the winter time.
Back in the nineties, we first noticed the loss
of grass on the west side of the lake
and then over the past three years
we've seen significant declines of grass
on the east side of the lake.
Like it's virtually disappeared.
- [Frank] So scientists are scrambling
to understand the lake's water issues.
But to do that, you've got to know what's in the water.
- So our water sampling stations in the lake are set up
in both basins, in the east and the west basins.
We're at our farthest east station
on the east side right now
and what we do is we take water samples,
we do water quality analyses, we do light analyses,
at all these stations with the goal of trying
to provide a comprehensive picture
of what the lake looks like in terms
of light availability at the bottom
which is important for the sea grass restoration
or the aquatic vegetation restoration that we talked about
and also water quality in general
because that's become problematic.
Too much algae is not a good thing
so generally speaking when you lose plants
they're often replaced by algae.
And that, we have found, has been the case here.
- [Frank] Researchers know the amounts of nutrients
and chemicals flowing into the lake have increased
and that is fueling algae blooms.
Those chemicals include fertilizers and pesticides.
There's also been an increase in sediments dumping
into the lake.
Scientists need to understand the total effects
of the algae blooms, the growing suspended sediment load,
and the connection to the poor water quality.
- [Michael] And they have different sensors
that measure different factors about water qualities.
We know conductivity which can be converted into salinity,
we know temperature, we know dissolved oxygen,
we know fluorescence which can be converted
into units of chlorophyll which is an indicator
of how much algae there is in the water column.
- So right now I'm trying to get measurement half a meter
below the surface.
We know what it was like in the past, like historically,
what the lake was like and the water quality.
And so we know that there's a problem.
We know basically what's causing the problem
and we're trying to figure out a little bit more details
about the water quality and how we can improve it
and what the ecological benefits will be.
- We're also interested in the total amount of light
and so we have this
photosynthetically active radiation sensor or PAR
and so this goes down into the water
and tells you how much light there is
at every depth where we measure it.
- [Frank] Because the water quality is so poor
sunlight can't reach the bottom of the lake
and that means underwater grasses are dying
all over the 18 mile long, 7 mile wide lake.
Those grasses feed migrating water fowl,
provide breeding grounds for fish,
and filter the water.
The lake's fish and the crab populations are dropping.
- This half of the lake anyway, was doing really well
so the mystery is what's happened in the last few years.
If we can get it back to where it was
that would be great.
We'd call that a success.
- [Frank] It's likely low rainfall
and changing flood trends are also contributing
to the lake's poor water quality.
Water isn't flushing through the lake as it did in the past.
Climate change may have permanently altered
that water cycle.
So researchers say everything is on the table
in terms of what is cost effective
and what will be effective
in stabilizing lake Mattamuskeet.
- But in the end, what we'd like to do is
to restore or to rehabilitate.
Realistically, it's hard to say what natural is
for this system but we know what better is
in terms of both the function of the ecosystem
and in terms of the things that it does for the people
who live here.
So this is an internationally renowned water fowl resource.
It's a place where people come to hunt,
they come to bird watch,
it's something that is of value to the world.
But also at the most basic level,
this lake is connected to the community.