Coming up next on Jonathan Bird's Blue World, a look alien invaders from other parts of
the world.
Hi, I'm Jonathan Bird and welcome to my world!
An ecosystem is a community of organisms living together in balance with each other.
In theory, a balanced ecosystem will stay balanced and healthy as long as nothing disrupts
the harmony of the inter-relationships between all the organisms.
Many things can throw the balance of an ecosystem out of whack.
For example, overfishing can remove certain animals from a reef ecosystem, creating a
gap in the food chain that causes the whole ecosystem to suffer.
But another, increasingly common, disruption of ecosystems comes in the form of invasive
species.
An invasive species is an organism that has been introduced into a ecosystem from somewhere
else, often causing a change in the balance of that ecosystem.
Perhaps one of the most well-known invasive species in North America is the Zebra mussel.
This harmless-looking mollusk lives in fresh water.
They call them Zebra Mussels because of the Zebra-like pattern on the shell.
The Zebra Mussel has invaded the Great Lakes, St. Lawrence River, and numerous smaller lakes
and ponds around the United States and Canada.
It was brought from Europe as larvae in the ballast water of ships.
When a cargo ship travels with a proper load, it settles down into the water to the depth
for which it was designed.
But sometimes on the return journey, there isn't enough cargo and the ship floats too
high in the water, which isn't safe.
So the ship has tanks called ballast tanks, which are filled with water to weigh the ship
down.
When the ship arrives at its destination, the ballast tanks are emptied.
Sometimes the water carries tiny planktonic invaders from another country, which are inadvertently
released into the environment.
Since cargo ships go up and down the St. Lawrence on their way from all over the world to the
Great lakes, ballast tanks are a big issue.
The zebra mussel was first detected in the Great Lakes in 1988.
Because it reproduces so quickly, within only a few years, everything in the Great Lakes
was soon covered in a layer of zebra mussels.
While the zebra mussel might not seem like much of a threat, they grow so densely that
they clog the water intakes of hydro-electric power facilities, the hulls of boats and ships,
docks and buoys.
It's estimated that the annual cost to control them in the Great Lakes exceeds 100 million
dollars a year!
Having never seen a zebra mussel, I head up to Clayton New York, to visit the beautiful
"thousand island" region of the St. Lawrence river.
I join David Doubilet, the famous National Geographic photographer on a shore dive in
the river to check out the mussels.
David lives nearby, and this is practically his back yard.
We're diving an old wooden-hulled shipwreck called the Islander right near shore.
As soon as I sink beneath the waves, I see zebra mussels attached to the wreck and the
rocks on the bottom.
Zebra mussels haven't been all bad, at least from a diving point of view.
Because they eat by filtering plankton from the water, Zebra mussels have massively improved
the underwater visibility in the river and the Great lakes by removing so much of the
plankton that clouds the water.
As I examine the bottom of the river, I start to notice that the rocks are moving.
Wait a minute!
Those aren't rocks…they're fish.
And they're not just any fish, they are round Gobies, another invasive species!
Round Gobies also came to the St. Lawrence from Europe…in ballast water!
Round Gobies are so good at eating and reproducing that their population has exploded in the
St. Lawrence.
These little bottom-dwelling fish are everywhere you look.
Why have they done so well here?
Guess what they love to eat?
You guessed it…Zebra Mussels.
But it's not all good news.
The Round Goby also eats the same crustaceans, worms and and insect larvae that are food
for native species like sculpin, so they are out-competing the local fish for resources.
On the flip side, it turns out that larger fish like Bass, Walleye, Salmon, and trout
all love to chow down on Round Gobies.
The result?
The influx of Round Gobies has fueled a come-back in several depleted species of larger fish!
1500 miles away, in the Caribbean, another invasive species is making waves.
The Lionfish is a beautiful but deadly invader.
This venomous fish has spines that act like syringes, filled with a deadly toxin.
Because of the excellent protection afforded by the spines, very few animals can actually
eat a fully-grown Lionfish.
A fish native to the Indo-Pacific, the Lionfish was thought to have been introduced to the
Caribbean in the 1980s by people releasing lionfish from the aquarium trade.
Thirty years later, there are literally millions of Lionfish in the Caribbean and the population
seems to be growing unabated.
Lionfish are voracious predators.
A single individual can eat dozens of fish a day.
And that's the problem…people are concerned that they are eating up all the other small
fish in the Caribbean and no predators exist to control their population.
Another opinion, however, suggests that the fish have only been able to take over so easily
because they are occupying a niche in the food chain that was vacant due to overhunting
of other species like grouper.
These critics argue that nature will eventually control the Lionfish population itself, through
prey availability.
To learn more, I head on down to St. Thomas in the U.S. Virgin Islands.
At the Coki Beach Dive shop I hook up with local dive Guru Peter Jackson.
We head down to his boat and load our gear.
We push off the dock and head out to the dive site.
This is no ordinary dive though.
We’re meeting up with a group of divers from the CORE Foundation, an organization
that is attempting to contain the Lionfish explosion in the waters of the U.S. Virgin
Islands.
I gear up to join the CORE Foundation on a dive.
Underwater, I follow divers Kitty Edwards, John Rubattino and Jason Quetel as they scour
the reef, looking for Lionfish.
As it turns out, Lionfish are not hard to find.
In fact, they are just about everywhere.
Jason takes aim with his speargun and snags a Lionfish.
Carefully, it is placed into a tube.
The spines are still quite dangerous even after the fish has been speared.
Just about everywhere I look, there are more Lionfish.
The CORE team misses a few, but they manage to bag more than a dozen Lionfish on a single
dive.
Unfortunately, this doesn’t even put a dent in the population of Lionfish at that one
dive site.
Following the CORE team has shown me just how invasive these fish are.
I really don’t think there is any stopping them in the Caribbean at this point.
Back on shore, they measure and pack up the fish.
They are going off to a researcher who will analyze the stomach contents to see what they
are eating.
As international shipping and transportation increases all around the world, plants and
animals are able to hitch rides and travel to places they never existed in the past.
These invasive species affect change in the ecosystems they invade.
It’s not always harmful to the environment, but one thing has become obvious—invasive
species are extremely hard to remove once they have been introduced, and may in fact
become a permanent addition to a local ecosystem, like it or not.
So when it comes to invasive species, it seems that the best and perhaps only solution is
to prevent the invasion in the first place.