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STAR Fellow Studies the Impact of Nutrient Pollution on Marine Invasive Species

Heidi W. Weiskel is a Ph.D. student in the Department of Environmental Science and Policy at the University of California, Davis. In U.S. coastal waters, there are now more than 500 non-native, marine plants and animals, nearly 300 of which reside in the San Francisco Bay where STAR Ph.D. student Heidi Weiskel is conducting her field research. Over the last century, the amount of dissolved nitrogen fertilizer in stream runoff entering the Bay has doubled as a result of changes to land-use policies and coastal habitat development. At the same time the number of invasive or non-native species has increased significantly. Heidi Weiskel wants to understand the relationship between this terrestrial pollution and marine invasive species so that native species and habitats can be protected.

Most of the current understanding of the relationship between nutrients and invasive species comes from land-based studies where excess nutrients allow invasive plants to spread. Invasive species can edge out their competitors in key elements of the nitrogen cycle. The nitrogen (N) cycle describes the key transformations from gaseous N2 in the atmosphere into nitrogen-containing compounds that are essential for life. These same relationships are less well understood in bottom-dwelling marine systems or higher up in the food chain. Heidi, in her quest to better understand these relationships in coastal marine ecosystems, is Heidi running a snail behavior trial. studying the growth and competitive dynamics of two mud snail species -- one native, one invasive -- under a variety of habitat and nutrient conditions in the mud flats of San Francisco Bay. From this work, she hopes to determine whether elevated nutrient levels give an advantage to the invasive snail over its native counterpart.Ilyanassa obsoleta on the left, with the native hornsnail Cerithidea californica on the right. Shells from San Francisco Bay. Photo by James T. Carlton

More broadly, Heidis research will provide a better understanding of the impact of pollution on ecosystems and how marine species can be affected by nutrients from urban runoff and farm fertilizers. This knowledge will allow resource managers to make wiser decisions on how best to protect native species and the habitats on which they depend.

For more information about her research, contact Heidi at:

Read more about Heidis research at:
http://www.des.ucdavis.edu/faculty/grosholz/people/weiskel.htm exit EPA

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