You Poured it Where?A Case Study in Invasive Species

Nancy BouryIowa State University

Please get into groups of 3-4 students

Take 5 minutes to review your notes on the case and the NY Times article

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What is the problem?

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What is the problem?• Alex is helping Jim move.• Jim has an old, well-established saltwater aquarium

that he is tearing down for the move.• While Jim is upstairs helping to pack his fish, Alex

starts draining the tank.• Jim comes down and catches Alex in the act of

dipping a bucket in the tank and finds out that Alex had planned to dump the water into a nearby storm drain.

• Jim stops him “just in time” (or so he thinks).

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CQ#1: Jim was horrified that Alex planned to dump the water down a storm drain because:

A. This tank had a serious fungal contamination problem.

B. The water would enter the potable (drinkable) water system unchanged.

C. The tank contains algae known to be invasive.

D. The chemicals present in tank would damage the local plant life.

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CQ#2: In your opinion, which single trait of the Aquarium-Mediterranean strain of Caulerpa taxifolia makes it particularly well desirable for use in public and private saltwater aquariums?

A. Resistance to temperature fluctuations.

B. Bright coloration.C. Rapid reproductive rate.D. Resistance to herbivores (it

produces toxins).

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What are some of the traits that make Caulerpa particularly invasive?

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Aquarium-Mediterranean strain Caulerpa taxifolia traits

• Grown in saltwater aquariums:– How is that different from “in the wild”?

• Produces a toxin:– What impact would this have on aquatic herbivores?

• Reproduces asexually:– Why is this significant?

• Smallest “reproductive unit” is a 3-5 mm fragment

– How can it spread?

Image Credit Greig Peters, Regional Water Quality Control Board, Bugwood.org 8

CQ#3: An advantage of asexual reproduction over sexual reproduction is that asexually reproducing species generally have a ___:

A. Higher mutational frequency from parental to F1 generations.

B. Greater genetic diversity within the population.C. Higher rate of reproduction than sexually

reproducing species.D. Greater photosynthetic capacity.E. Greater resistance to fungal and viral pathogens.

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Caulerpa taxifolia’s history of invasion• Caulerpa taxifolia – Used in aquariums – discovered in 1984.• In the late 80’s and 90’s, it expanded into the Mediterranean.

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CQ#4: The Aquarium-Mediterranean strain of Caulerpa taxifolia is particularly invasive because:

A. It was artificially selected to possess traits favorable to aquarium life.

B. Each outbreak of Caulerpa taxifolia is the result of human activity.

C. It has natural predators that would normally control its spread. Those predators are becoming endangered species.

D. It also reproduces sexually, giving more diversity to the population of this particular strain of Caulerpa taxifolia.

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Why is the invasion of Caulerpa taxifolia a problem?

Take a minute to discuss this with your group

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CQ#5: In terms of local ecosystems, why is the invasion of the Mediterranean strain of Caulerpa taxifolia a problem?

A. The toxins it makes will accumulate in the top predators due to bioamplification.

B. It is a poor food source, and herbivores will lose their native food supply.

C. It is a clonal species, and clones are inherently dangerous to any ecosystem.

D. It doesn’t photosynthesize, so won’t fix carbon dioxide. Carbon dioxide levels will rise and contribute to global warming.

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Other reasons this invasion is detrimental?

• Replaces rich, diverse communities with a monoculture.

• May outcompete endangered species.• Caulerpa is a poor member of the first trophic

level because it is toxic. • Invasions lead to alterations in the species

richness and abundance of life in the community.

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CQ#6: A coastal lagoon reports a small (2″ square) area of Mediterranean-strain Caulerpa taxifolia. From the list below, what is the most likely source of this vegetation?

A. Nearby farmers producing nitrate-rich runoff.B. Ozone depletion leading to an increase in mutation

rate.C. Greenhouse gases changing the potential ecological

niche for the seaweed.D. Poorly treated urban waste entering the water

supply.E. Misuse of antibiotics to treat viral infections.

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CQ#7: Could Alex’s dumping the water from an aquarium transfer Caulerpa to local waterways?

A. Yes, if the local waterways are saltwater.

B. No, not even if local waterways are saltwater.

Rachel Woodfield, Merkel & Associates, Inc., Bugwood.org

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Jim Cleans the Tank

What steps does he take?

Why?

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CQ#8: If you were Alex, would you report the Caulerpa dumping incident to the local U.S. Fish and Wildlife Service?

A. YesB. No

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Alex’s Assertion: “It can’t happen here.”

In your group, please review the 2002 Science article about

Caulerpa taxifolia.

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“California Tries to Rub out the Monster of the Lagoon.”

By J. WithgottScience Vol 295 March (2002)

pp. 2201-2202.

Rachel Woodfield, Merkel & Associates, Inc., Bugwood.org

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In 2000, the Mediterranean strain of Caulerpa taxifolia was identified in

California.

What can southern California do about this invasive algae?

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CQ9: When Rachel Woodfield started eliminating Caulerpa taxifolia in California, the algae occupied approximately 10,000 m2 in Huntington Harbor and 200 m2 in Agua Hedionda Lagoon. From the graph below, predict how much of Huntington Harbor would be covered with the algae after two years if it was left alone.

A. 1 m2

B. 40 m2

C. 10,000 m2

D. 40,000 m2

E. 120,000 m2

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CQ#10: You are in charge of an anti-Caulerpa program in a coastal region, what would you do FIRST to control a small patch of the “killer seaweed” found at the bottom of a local fishing harbor?

A. Educate the local populace about the dangers of Caulerpa taxifolia to the ecosystem.

B. Ban the sale and transport of Caulerpa taxifolia in the state you live in.

C. Treat all affected areas with a bleach solution and remove the dead flora and fauna.

D. Introduce sea slugs to the affected areas. The sea slugs will eat the seaweed.

E. Develop safe, non-invasive alternatives to Caulerpa for saltwater aquarium enthusiasts to use.

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What did California do?

Nova News Minutehttp://www.pbs.org/wgbh/nova/minutes/i_3008.html

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The Plan Part I: Remove the Algae

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The Plan Part II: Educate the Populace

• This is what the Southern California Caulerpa Action Team (SCCAT) did:– Surveys found that 52% of southern California

aquarium retailers sold Caulerpa, 95% sold “live rock.”

– Legislation was passed that banned sale, transport or ownership of Caulerpa.

– Educational brochures were developed.– Collecting samples was banned.

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CQ#11: Do you think this plan was successful?

A. YesB. No

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Here’s what happened:

CQ#12: If you were Alex, would you report the incident to the local U.S Fish and Wildlife Service?

A. YesB. No

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What did it take to eradicate Caulerpa taxifolia in California?

• $7 million• 6 years • Early, multi-disciplinary approach

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Cost of invasive species to the U.S. economy

• $137 billion spent each year for ALL invasive species.

• Homeowners spend $500 million/year.• $100 million spent to control aquatic weeds

that clog waterways.

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For Further Reading…

Killer Algae by Alexandre Meinesz and Daniel Simberloff, University of Chicago Press, 1999.

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