October 2017 Discover

60 DISCOVERMAGAZINE.COM

TOP: MEL CLARK PHOTOGRAPHY. BOTTOM: ERNIE MASTROIANNI/DISCOVER

When those plants decompose, it burns up oxygen, open-

ing the door to botulism-causing bacteria that thrive in

oxygen-starved environments. The mussels then suck up

those bacteria and are, in turn, eaten by gobies, which

become paralyzed and are easy prey for birds.

This is not a rare occurrence. Biologists estimate more

than 100,000 dead birds — including bald eagles, great

blue herons, ducks, loons, terns and plovers — have piled

up on Great Lakes beaches since the botulism outbreaks

turned rampant in 1999.

SHELL GAME

In 1993, the U.S. Coast Guard made exchanging ballast

water with mid-ocean saltwater mandatory, yet wave after

wave of new invasions kept rolling into the Great Lakes.

The problem was about 90 percent of the ships arriving

in the Great Lakes from foreign ports at that time came

fully loaded with cargo and therefore did not officially

carry any ballast water. But most tanks still carried loads

of sludge — up to 100,000 pounds of it — along with

thousands of gallons of residual ballast puddles that can-

not be emptied with a ship’s pumps.

Subsequent studies revealed these muddy puddles

swarmed with millions of organisms representing

dozens of exotic species that had yet to be found in

the Great Lakes. So by 2008, the U.S. Seaway operators

began requiring all Great Lakes-bound overseas vessels

to flush even their “empty” ballast tanks with mid-ocean

saltwater. No new exotic organisms have been found

in the Great Lakes since, a point shipping industry

advocates tout.

And in 2011, the EPA finally mandated treatment

systems for overseas ships discharging ballast in U.S.

waters. The systems, which will use things like chlorine,

ozone and UV light among other pesticides to kill ballast

dwellers, will not be required of all ships until sometime

after 2021. Although these treatment standards should

reduce the amount of life spilling into the lakes from

ballast tanks, think of the problem like a campfire. The

EPA’s treatment requirements are a little like the first gal-

lon of water you slosh on the fire at the end of the night.

It might knock down the flames, but it will take several

more gallons to properly soak the embers to ensure

you’ve snuffed their glow.

In preparing ballast treatment standards, which a

federal court ruled inadequate in 2015, the EPA turned

to some of the country’s best scientists in the field to help

establish a safe number of organisms that could be dis-

charged per cubic meter of water while still protecting the

Great Lakes and other U.S. waters from new invasions.

The only thing the panel could agree on is that the

fewer organisms allowed to survive in a ballast tank, the

better. Beyond that, they were at a loss because, they said,

you can’t just pick a magic number and call it safe.

Unless the number you pick is zero.

That is the number Isle Royale National Park Superin-

tendent Phyllis Green aimed for when she learned in 2007

that an invasive virus deadly to dozens of freshwater fish

species was creeping toward her rugged, forested island

in the middle of Lake Superior. Green’s focus instantly

turned to the island’s coaster brook trout — a beleaguered

native species that once numbered in the millions in Lake

Superior but is now counted by the hundreds. “If you

have only 500 fish and you have a disease that can kill fish

by the tons,” she says, “your motivation is pretty strong,

especially if your job is to preserve and protect.”

Green went straight to the captain of the Ranger III,

the 165-foot-long ship that ferries park passengers to the

island, 73 miles from its home port on Michigan’s Upper

Peninsula. Worried that the ferry might suck the rapidly

spreading virus into its ballast tanks while docked at the

mainland, she asked if there were any way to disinfect

that ballast before it was released into park waters. The

captain said no. “What happens,” Green replied, “if I tell

you that you can’t move this ship unless you kill every-

thing in your ballast tanks?”

That’s when the brainstorming started. Green’s goal

was to try to figure out how to make the Ranger III safe

to sail — not in years or even months, but in a matter of

days. She sat down with the captain, the ship’s engineer

NOAA scientists study mussels found in Milwaukee’s inner harbor.

Even at 350 feet below the surface of Lake Michigan,

the Carl D. Bradley’s stern wheel is encrusted in mussels.