Marine Invaders

By Chris Mooney | February 12, 2010 10:03 am

This is the fifth in a series of guest posts by Joel Barkan, a previous contributor to “The Intersection” and a graduate student at the Scripps Institution of Oceanography. The renowned Scripps marine biologist Jeremy Jackson is teaching his famed “Marine Science, Economics, and Policy” course for what may be the last time this year (along with Jennifer Jacquet), and Joel will be reporting each week on the contents of the course.

In my favorite movie of all time, Jurassic Park, scientists clone a bunch of dinosaurs from the blood of prehistoric mosquitoes.  I’m sure you’ve seen it.  In the sequel, The Lost World, a Tyrannosaurus rex escapes from a cargo ship on mainland U.S. soil and wreaks havoc on my current hometown of San Diego—if this happened in real life, San Diegans would just shrug, grab their surfboards, and look for the next set of good waves.  What if the T-Rex hadn’t been tranquillized and returned to its island?  What if multiple dinosaurs had propagated on our continent and formed stable populations?  We would label them invasive species.  Or would we?  After all, dinosaurs were native to North America about 70 million years ago.  But I digress.

zebra mussel cluster - smallIn our most recent class, we unfortunately did not discuss whether the repopulation of our country with dinosaurs would constitute a species invasion.  We did, however, talk about many of the vectors that transport invasive species through the marine environment.  One such vector is the ballast water of ships:  a freighter will fill its ballast tank in one part of the globe with water and various organisms, traverse an ocean to deliver its cargo, and empty the water and non-native organisms into a new, unsuspecting region.  The result is an invasion of crustaceans, mollusks, and algae that might out-compete native species in new habitats.  The most famous ballast tank stowaway is probably the zebra mussel, native to the Black and Caspian Sea, which has invaded North American lakes.

There are several methods of managing invasive marine species, most of which are costly and none of which are easy.  One student shed light on some interesting technological advancements that might tackle the ballast water problem.  A ship could heat its ballast water to 40° Celsius with microwaves to kill any invader that may have hitched a ride.  Purging oxygen from a ballast tank with nitrogen could also wipe out the hitchhiking organisms, with an added benefit of preventing corrosion of the tank’s interior.

One method that almost always seems to spectacularly fail is biocontrol—introducing a new species to get rid of a problematic invasive species.  The history of biocontrol is rife with notorious blunders:  cane toads were introduced to Australia in 1936 to combat beetles that were ravaging cane fields.  The cane toads didn’t take well to the cane fields, however, and quickly spread throughout the country, reducing reptile biodiversity along the way.  In Hawaii, mongoose were introduced in the 1870s to control the rat populations (also invasive) that were eating valuable sugar cane.  Except the mongoose preys during the day, while rats feed nocturnally.  Whoops.  The mongoose instead decided to eat some endemic Hawaiian birds and threaten their fragile populations.

As globalization continues, more species invasions are inevitable, to the point where the term “native species” will become increasingly irrelevant.  Once established, invasives are extremely difficult to eradicate.  Prevention seems to be the most effective and most cost-effective way of dealing with this issue.  In the future, it will be interesting to see how marine ecosystems respond to more and more invasions.  To be honest, I’m not too worried.  After all, to quote the famous chaotician Dr. Ian Malcolm, “Life finds a way.”

CATEGORIZED UNDER: Environment, Marine Science

Comments (3)

  1. moptop

    We got zebra mussels in our lake and it changed the character of the lake markedly. They are filter feeders so they clarified the water significantly, which sounds like a good thing, but the walleye, the premier sport fish in the lake, liked it murky. :( Now we have alewives, which may be driving out the smelt, which were introduced in the 19th century, and in turn drove out other species. Except freshwater alewives are inedible to humans and problematic forage for other species.

    The pre-Columbian lake that lay here has been gone for centuries.

  2. Joel Barkan

    Moptop, I feel your pain. My grandparents have a cottage on Canandaigua Lake in western New York and it was invaded by zebra mussels about 15 years ago. The bottom went from squishy mud and rounded rocks to a bunch of algae and a layer of razor sharp mussels that used to cut my feet and forced us all to wear water shoes. It’s amazing how much of an effect a single species can have on an entire ecosystem.

  3. Alex A

    Maybe they could inject poison into the ballast water? If they could find something that kills marine life very effectively but breaks down in salt water on the journey then that could be cool.

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About Chris Mooney

Chris is a science and political journalist and commentator and the author of three books, including the New York Times bestselling The Republican War on Science--dubbed "a landmark in contemporary political reporting" by Salon.com and a "well-researched, closely argued and amply referenced indictment of the right wing's assault on science and scientists" by Scientific American--Storm World, and Unscientific America: How Scientific Illiteracy Threatens Our Future, co-authored by Sheril Kirshenbaum. They also write "The Intersection" blog together for Discover blogs. For a longer bio and contact information, see here.

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