[MUSIC PLAYING]
ANTHONY RICCIARDI: This is the St. Lawrence River at Montreal.
It's the gateway to the world's largest freshwater
ecosystem, the Great Lakes.
You wouldn't know it, but right beneath these waters
there's an ecological battlefield.
Wars are being fought--
wars for space, wars for resources,
wars between exotic and native species.
And we're not sure who's winning.
Biological invasion is an ancient process.
It's been around throughout the entire history
of life on the planet.
Species have always changed their ranges.
They've always spread into new regions.
But what's happening now is fundamentally
different in terms of rate and spatial scale.
When ships cross the high seas, they
have to carry weight so as to avoid bobbing like a cork.
And this weight is provided in the ballast tanks.
At any given moment, it's been estimated
that between 5,000 and 10,000 species are
in motion in ship ballast tanks around the world.
These species are taken up in the water at the home port
when the ship has taken on ballast water
and are discharged at the new port of call.
DAVID LODGE: One helpful way to think
about it is to start big, sort of think globally, and realize
that every port on Earth is connected by shipping, maybe
directly if a ship goes from point A
to B, maybe indirectly if a ship has gone
into other ports in between.
So the potential exists for species in any port on Earth
to be delivered to the Great Lakes region.
So the study of these species combines
understanding trade and human movements of species
with the ecology of these species.
LISA JONES: Today we're in this launch canal.
It's just west of Montreal, about 45 minutes.
This launch canal is just off of the St. Lawrence River.
And today we're going to be jumping into the water,
sampling the wall to look at the composition of the zebra
and the quagga mussel along the wall here.
Zebra mussel is an exotic mussel that
was introduced in the late 1980s into the Great Lakes
through ballast water.
They have since spread up into the St. Lawrence River area,
along with the quagga mussel.
They are both invasive species.
They've come from the Black and Caspian Seas.
And although they're closely related,
there are subtle differences between the two species.
And one of the things is looking at who comes in and colonizes
first, looking at differences in species, life history,
traits that can help to predict which species are
going to be more successful.
So right now we're processing those samples
that were taken from the Soulanges Canal.
We have about a 12-year data set.
So we're documenting the change of mussel composition
in that area.
There used to be a high abundance of native mussels.
And now oftentimes what you'll see
is just a whole bunch of empty native mussel shells littering
the bottom where they once used to be.
So if a native mussel's sitting in the sediment from here,
we have an exposed hard substrate
to which zebra mussels and quagga
mussels can attach themselves onto the hard substrates
of the native mussels.
The problem with this is that you get enough zebra and quagga
mussels attached to the native mussel,
therefore suturing the two valves together,
this muscle can no longer filter feed.
And sometimes even due to the sheer weight
of the other exotic mussels on it,
it topples into the substrate and can no longer feed.
And, thus, it dies.
ANTHONY RICCIARDI: Essentially what we're seeing here
is an ecological takeover.
Over the past two centuries, nearly 200 species
that we know of about have become
established in the Great Lakes.
These species have replaced native species,
have become pests economically and ecologically,
have fouled industrial water supply systems
and fouled municipal water supply systems,
have posed a threat to fisheries.
Unless shipping is very well controlled,
unless we have a more effective way at keeping species that
are delivered through ballast water or keeping them out,
then we can assume invasions will continue.
DAVID LODGE: Many of the species we're
concerned about do come from other continents.
But many of them also come from other parts of North America.
SPEAKER 1: All right.
I got it.
BRETT W. PETERS: What do we got?
SPEAKER 1: Got plenty of rusty crayfish--
BRETT W. PETERS: Surprise, surprise.
SPEAKER 1: --it looks like.
Don't see any native crayfish yet.
Probably won't.
DAVID LODGE: It's useful to think about these invasions
just like we think about a flu virus
or any other infectious disease moving across the country.
When there's a lake close to your lake that's infected,
that means that you're now much more likely to be infected.
BRETT W. PETERS: Rusty crayfish are actually
native to the Ohio River area of Ohio
and parts of Kentucky, some parts of Indiana.
And they were moved up to this area in the Upper Midwest most
likely by anglers who would use them as bait for fishing.
A lot of times when species are transported just a few hundred
miles, they can have very significant impacts.
Rusty crayfish essentially clear cut the whole bottom.
That's very important because vegetation
serves as the food base for lots of other organisms
and also as habitat for small fishes.
So when rusty crayfish come out, all you are left with
is pretty much a lake with lots of rusty crayfish and not much
else.
DAVID LODGE: What we're working on now
is a technique in which we could combine intensive trapping
with increasing the numbers of predatory fish
that would make the reduction in crayfish sustainable.
BRETT W. PETERS: Got some?
SPEAKER 2: Oh, yeah.
BRETT W. PETERS: Awesome.
SPEAKER 2: Oh, yeah.
Oh, yeah.
BRETT W. PETERS: Today we are collecting fishes
using fyke netting.
And we're going to perform gastric lavage,
a non-lethal method of examining the stomach
contents of the fish.
Jodi, the next one is a small mouth bass.
SPEAKER 2: All right.
BRETT W. PETERS: 296 grams.
We're most interested in knowing which fish species
and what sizes of fish species are
eating what sizes of crayfish.
SPEAKER 2: Now you can see a crayfish claw.
BRETT W. PETERS: Oh, yeah.
That's definitely a crayfish.
Yup, he's clear.
And with that information we will
be able to determine what fish community will
be most effective at controlling rusty crayfish.
DAVID LODGE: We invest so much effort and resources
in studying invasive species because they
are one of the top five causes of changes in ecosystems
globally.
In fact, the changes that invasive species are causing
proceed much more rapidly than climate change.
With the increased scientific understanding
that's come from recent research we're
helping to guide legislation that
would address the ballast water pathway
and other pathways that bring species
that will be harmful to these natural ecosystems.