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Heidi Weiskel |
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Research Interests
My research focuses on the relationship between disturbance and species interactions in marine systems. I am particularly interested in the effects of two distinct disturbances-nutrient pollution as an abiotic disturbance and burrowing behavior as a biotic disturbance-and their effects on native and invasive gastropod species in San Francisco Bay. What effects do increased nutrients have on marine species? Do nutrients affect invasive species differently than native species? Can nutrient pollution shift the competitive balance in favor of marine invasive species, thereby potentially accelerating the invasion of future as well as current introductions?
I am examining the biotic disturbance caused by bioturbation by the introduced Atlantic mud snail Ilyanassa obsoleta and the abiotic disturbance caused by high nutrient influx into the nearshore benthic environment in San Francisco Bay (Bay). Ilyanassa was introduced to the west coast in the early 1900s and is sympatric with the native mud snail Cerithidea californica in the Bay. They occupy similar habitats and may function as trophic species. Using a factorial design with multiple nutrient levels and species combinations in the field, I am testing how growth rates and sediment characteristics are altered by nutrient additions, via changes to the microphytobenthic community.
Our current understanding of the relationship between nutrients and invasive species is largely based on responses measured in terrestrial primary producers. Studies of terrestrial plants have shown that invasive species capable of fixing nitrogen or partitioning nutrient resources can edge out their competitors (Ehrenfeld 2003, Fargione et al. 2003, Levine et al. 2003). In these systems, therefore, increased nutrients facilitate the spread of plant invasions. However, these same relationships remain relatively unexamined in marine systems and for higher trophic levels. My work focuses on how nutrients affect primary producers, which in turn affect herbivores in estuarine communities. I aim to learn how increased nutrients in marine systems can influence invasion success and how nutrient increases might affect native-invasive species interactions and alter benthic communities.
New Invasions
In addition to working with Ilyanassa and Cerithidea, I plan to investigate the effects of nutrients on invasion success in a new invasion I have discovered. In 2005 we found the first reported population of the Japanese mud snail Batillaria attramentaria in San Francisco Bay. Then, in the spring of 2007, I found another population in Bodega Harbor. We have been surveying these populations and attempting their eradication. See this PowerPoint from ESA 2007 in San Jose, CA for more details on that study: CLICK HERE
The new invasion also provides an opportunity to study the effects of nutrients on invasion success in a new invasion while the populations remain. I will be implementing this study over the next few months, so stay tuned!
In conclusion, nutrient loading and invasive species are unlikely to disappear as threats to estuarine systems but a greater understanding of their interactions and effects on native species can facilitate better protection for native species and the habitats on which they depend. As human development pressure mounts along the coast, studies that connect pollution and ecosystem health are increasingly important, as are studies that deepen our understanding of the relationship between pollution and species interactions. So in addition to being fun to do, I hope my dissertation will lend insight into these important issues!
Cerithidea californica and Ilyanassa obsoleta in nutrient trials in San Francisco Bay, 2007.
Batillaria attramentaria discoveries in San Francisco Bay and Bodega Harbor, 2005-2007.
My research has been supported by the National Science Foundation (NSF) BioInvasions Integrative Graduate Education and Research Traineeship (IGERT) at UC Davis and the San Francisco Bay National Estuarine Research Reserve. This fall I am starting an Environmental Protection Agency-Science to Achieve Results (EPA-STAR) Fellowship and will be a Science Fellow in the California-Federal Bay-Delta (CALFED) program.
CV in pdf format
Keywords: marine invasions, nutrients, competitive interactions, multiple disturbances, invasion success, primary production, estuarine dynamics, eutrophication, Ilyanassa obsoleta, Cerithidea californica, Batillaria attramentaria