|
Assistant Professor
Department of Biology University of St. Thomas 2115 Summit Avenue St. Paul, MN 55105 (651) 962-5166 gaston.small (at) stthomas.edu Curriculum vitae
 |
Ecosystem Ecology
and Biogeochemistry in streams, lakes, compost piles, and other interesting places... |
Research Interests
I am broadly interested in the movement of nutrients through ecosystems, the effect of anthropogenic nutrient loading on the biotic community, and the role that humans and other species play in transforming and retaining nutrients at the catchment scale. I have used a combination of field measurements and manipulations, laboratory experiments, and modeling to explore questions at the interface of biogeochemistry, hydrology, and food web ecology.
My current research activities include the following projects:
My current research activities include the following projects:
Simulated dye release on the St. Louis River using FV-COM hydrology model for the St. Louis River Estuary.
|
1. Tracing the fate of anthropogenic nutrients in an urban freshwater estuary.The St. Louis River Estuary is important for both industrial and ecological reasons, and represents the confluence of a large river with Lake Superior, with additional water and nutrient inputs from wetland streams, urban streams, and a large regional wastewater treatment plant. We are combining empirical measurements with a hydrodynamic model of the estuary to understand spatial and seasonal patterns in nutrient processing within this complex environment. Collaborators: Jacques Finlay (University of Minnesota), Emily Stanley (University of Wisconsin), Bob Sterner (University of Minnesota Duluth Large Lakes Observatory), Richard Kiesling (USGS) |
Preparing for sampling on the St. Louis River Estuary, with Shon Schooler (Lake Superior National Estuarine Research Reserve) and Emily Stanley (University of Wisconsin).
|
2. Retention of phosphorus in stream ecosystems. I am using data collected during and after an eight-year experimental P addition in a lowland tropical forest headwater stream to quantify P retention though biotic and abiotic mechanisms. I am interested in collecting similar data from other experimentally nutrient-enriched streams as well as utilizing sources of anthropogenic nutrient loading to investigate nutrient retention capacity across a variety of stream ecosystems.
Collaborators: Marcelo Ardon (East Carolina University), John Duff (USGS), Alan Jackman (USGS), Alonso Ramirez (University of Puerto Rico), Cathy Pringle (University of Georgia) |
 Rhodamine dye release in a small stream at La Selva Biological Station, Costa Rica |
 Fishes such as this cichlid have a high P demand and recycle this nutrient at very low rates in low-solute streams |
3. Interaction between stream nutrient loading and benthic food webs.My dissertation research showed that, in naturally high P streams, the entire invertebrate assemblage doubled in P-content due to feeding on P-enriched detritus and algae. Some consumers in high-P streams showed an elevated P-demand, indicating that microevolution can lead to stoichiometric heterogeneity across landscapes. My dissertation research also highlighted the importance of species identity in ecosystem-level nutrient recycling. My current work includes writing a review paper on the homeostasis concept in stream ecosystems.
Collaborators: Hal Halvorson (University of Arkansas), Marcia Snyder (EPA), Cathy Pringle (University of Georgia) |
Stream team at La Selva Biological Station. With Marcelo Ardon, Minor Hidalgo, John Duff, and Carissa Ganong.
|
4. Carbon transport and processing in tropical rivers.I analyzed a long-term neotropical stream chemistry data set to show that seasonal and inter-annual stream acidification is driven by CO2 inputs from soil respiration. We are currently measuring the seasonal contribution of in-stream metabolism to this CO2 loading, and to measure the capacity of stream microbes to utilize dissolved organic carbon of different qualities.
Collaborators: Marcelo Ardon (East Carolina University), Alonso Ramirez (University of Puerto Rico), Carissa Ganong (Northern Michigan University), John Duff (USGS), Cathy Pringle (University of Georgia) |
 Puerto Viejo river, La Selva Biological Station, Costa Rica  Puerto Viejo river during a flood |
Raised-bed plots filled with finished compost.
|
Brendan prepared for compost sampling.
|
5. Nutrient recycling and losses in urban ecosystems from composting coupled with Urban Agriculture.
Food waste is a significant biogeochemical flux in urban ecosystems, and composting coupled with urban agriculture can potentially recycle these nutrients back into the human food system. However, the availability of wood chips may constrain the scale of composting in many cities. Furthermore, nutrients lost during the composting process further diminish the efficiency of nutrient recycling and potentially contaminate groundwater and surface waters. We are measuring the effects of different wood chip:food waste ratios on the biogeochemistry and microbial dynamics of the composting process, and using the finished compost to measure the effects on crop yields and nutrient recycling efficiencies. Collaborators: Adam Kay and Brendan Sisombath (University of St. Thomas) |
|
6. Nitrogen and phosphorus dynamics in urban lakes.
Many urban lakes in the Twin Cities are impaired due to excess nutrients and algal growth, and numerous initiatives have been launched to reduce nutrient loading in an attempt to improve water quality. We are combining modeling and empirical measurements of N and P dynamics to better understand how current and potential management practices might impact water quality. Collaborators: Jacques Finlay and Anika Bratt (University of Minnesota) |
Saint Paul's Como Lake
|
