Scientist Returns Home to Conduct Research

April 12, 2003

Nick Marinello

Back in her native Costa Rica, Karla Johanning had big ideas about her career in science. As her career has blossomed, however, those notions have shrunk considerably. In fact, they're downright microscopic. Johanning, a senior research scientist at the Center for Bioenvironmental Research at Tulane and Xavier Universities, is a molecular biologist and a principal investigator in a two-year study of how chemicals affect the endocrine systems of animals in Costa Rican waters.

Her interest in marine animals, however, started at the macro level. She received a BS in zoology from the University of Costa Rica, and earned graduate and doctoral degrees in the same field from the University of Rhode Island. Yet by the time her formal education was finished, she had developed an interest in biochemistry and did much of her graduate work in a comparative endocrinology lab, studying the way hormones work in different species.

That interest has served her well at Tulane, where Center for Bioenvironmental Research director John McLachlan has pioneered the study of environmental estrogens and their effect on organic systems. McLachlan is the co-principal investigator in the Costa Rican study, which received funding from the Costa Rican-USA Foundation.

The study, which will begin in June, is targeting three Costa Rican estuaries and will produce comparative assays describing the extent to which environmental estrogens resulting from pesticide runoff affect certain species of marine life.

"The sites are fed by rivers coming from high agricultural areas," says Johanning, who is interested in observing whether the chemicals being released into the water interfere with normal hormonal processing. "You find chemicals in the environment that because of their chemical structure resemble estrogen and either block or bind to the estrogen receptors."

Such chemical interaction can produce female traits in a male fish, for instance. The research, which including Johanning involves four scientists from the United States and four from Costa Rica, will target two species of marine life with economic importance to the two countries (red snapper and blue crab) and two species with special environmental relevance (olive ridley sea turtle and corals).

"The study of coral is very innovative," says Johanning. "Corals are very sensitive to estrogen and estrogen components."

While Johanning and her colleagues from the United States will initially spend 10 days in Costa Rica this June and then periodically return to the country, much of the ongoing tests will be conducted by faculty and students at the University of Costa Rica, Johanning's alma mater and partner in this study.

"I have always kept in touch with my old professors," says Johanning. "When I told them about wanting to make this proposal they got very excited because they had a grant that will be wrapping up in May studying contamination in the same waters. Our grant will be the second phase of this study."

While scientists in the first phase are looking at heavy metals and pesticides in ocean sediment, Johanning's team will examine pesticides in the tissues of organisms.

"We will use biological assays to look at environmental contaminants and hormonal disrupters," she says. "This research has not been done at this scale in the Southern Hemisphere," says Johanning, adding that she would like to extend the work to a third phase, one that examines the effect of environmental estrogens and its effect on human health in Costa Rica.

For example, how does the use of pesticides impact the health of banana growers? "Our ultimate goal, really, is to provide information that can be used in solving human health problems," she says. And while much of her time in Costa Rica will be spent training students and scientists in endocrine lab techniques, Johanning hopes to find herself out in the field, too, pulling in fish and crabs under sunny Costa Rican skies. After all, it's how she got her start.

Nick Marinello can be reached at

Tulane University, New Orleans, LA 70118 504-865-5000