The Pollution That Breeds: How the Great Lakes Stopped Invaders

In 1988, someone found a striped mussel the size of a fingernail in Lake St. Clair. Within a few years, zebra mussels coated pipes, boats, and the bottom of the Great Lakes, and they became the poster child for "it's too late." Andrew closes Marine Pollution week with the pollutant that breaks every rule: a living one that reproduces instead of diluting.

He follows two invaders. Zebra mussels rode in on ship ballast water, clogged power plant intakes, and stripped plankton from the base of the food web. Lionfish, likely released from home aquariums, spread from Florida across the Caribbean and cut the number of young native fish settling on reefs by about 79% in one experiment.

Then comes the fight back. Ballast water rules tightened between 1993 and 2008, and new invasions in the Great Lakes fell 85%, to the lowest rate in two centuries. In the Bahamas, keeping lionfish low on small patches of reef let native fish rebound by 50 to 70%. Andrew wraps with the role every boater and paddler plays: clean, drain, and dry, every time.

Takeaways:

• Invasive species are biological pollution, and they multiply over time.
• Zebra mussels arrived in ballast water and were found in Lake St. Clair in 1988.
• Densities at one Michigan power plant topped 700,000 mussels per square metre within a year.
• Lionfish likely reached the Atlantic through aquarium releases and now range from North Carolina to the Caribbean.
• Lionfish cut the number of young native fish settling on test reefs by about 79% in five weeks.
• Stricter ballast rules dropped new Great Lakes invasions from 26 to 4 per 13-year period.
• Keeping lionfish numbers low on targeted reefs let native prey fish rebound by 50 to 70%.
• Florida divers removed 31,773 lionfish in the 2024 Lionfish Challenge.
• Ontario has required boaters to drain water and remove plants and animals before moving a boat overland since 2022.
• Clean, drain, and dry every boat, canoe, kayak, or paddleboard between waterways.

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