Stroud Center Awarded Grant to Study Agricultural Contaminants

450 338 Stroud Water Research Center


CONTACT: Diane Huskinson, Stroud Water Research Center

Avondale, PA – Lush and tropical Costa Rica is home to a rich variety of plant and animal species. The Rio Sierpe in the southwestern part of the country supports some of the Earth’s greatest biodiversity, and the high annual rainfall makes it well suited to rice farming in particular. However, pesticides and other contaminants from agriculture in the surrounding watershed pose an unknown threat to terrestrial and aquatic ecosystems and to humans who eat contaminated fish and shellfish.

To evaluate those threats, Stroud™ Water Research Center will work with the Rainforest Alliance and the Sustainable Agriculture Network in a new study. Scientists will not only identify contaminants but also contaminated species that threaten humans who consume them.

The study is funded with a grant from the Blue Moon Fund, a landscape conservation group that focuses on regions of high biodiversity in Asia, North America, and the Tropical Americas.

Adrian Forsyth, vice president of programs for the Blue Moon Fund, says the Stroud Center was chosen for the grant because of its long history of fieldwork in Costa Rica. He commented, “Stroud Water Research Center is the premier institution focused on fresh water in North America and possibly the world. We are proud to work with them in understanding and protecting the Rio Sierpe wetlands, which are among the most important in Central America.”

“Although a great deal has been done in the U.S. to reduce the risks to humans posed by pesticides used in agriculture, these threats still exist in the developing world,” said Dr. William H. Eldridge, assistant research scientist at the Stroud Center. Eldridge along with Drs. Bernard W. Sweeney and David B. Arscott, director and assistant director of the Stroud Center, make up the study’s research team.

Pesticides can reach streams in a variety of ways, and earlier research conducted by Stroud Center scientists has revealed that contamination is not limited to the site of application. Pesticides applied by plane or during the rainy season, a common practice in the area, can travel by wind and rainwater runoff to other areas such as drinking water supplies, freshwater habitats, and protected lands.

Yet contaminant levels in the drinking water supplies are likely to be too low to detect using standard techniques, so researchers will collect fish and macroinvertebrates that are more fatty and longer living. That’s because pollutants, which are stored in fat cells, rise within an organism as it grows, and aquatic organisms may bioaccumulate environmental contaminants to more than 1 million times the concentrations detected in water.

“The species that are likely to pose the greatest threats to humans,” said Eldridge, “are those that are eaten regularly and that live in some or all of the Rio Sierpe near agricultural areas,” so the team will collect samples from a variety of species. By testing contaminant levels in both sedentary organisms such as mussels and far-traveling ones like the black snook, the scientists can compare local and regional threats.

The study will take place over the next 12 months, and researchers will make two trips to Costa Rica to collect samples — once during Costa Rica’s rainy season in the summer and again during the dry season in late fall. The trips are timed to coincide with agricultural pesticide applications, and the Rainforest Alliance will help identify areas likely to be contaminated. The researchers will return to the Stroud Center to analyze the samples they collect from those sites.

“This study will help us to better identify how pesticides and contaminants transfer and accumulate throughout an ecosystem,” said Chris Wille, chief of agriculture at the Rainforest Alliance. “Results from this study may offer valuable insight into the long-term implications of pesticide use that could be used to refine the Sustainable Agriculture Network standards that guide better farming practices.”

The research findings may offer additional insight into how agriculture impacts streams and rivers, and in turn, human health, in Pennsylvania as well as in Costa Rica. Eldridge added, “Any one farm or sector of agriculture may have a significant impact on human health. On the other hand, when one farm adopts more environmentally sustainable farming practices, threats to humans may be reduced.”