As an ecologist, I seek to both improve our general understanding of aquatic ecosystems and to determine how material and energy pathways are influenced by human induced changes. My recent research has focused on identifying how these pathways are influenced by temperature and nutrient gradients –two important drivers of ecological dynamics that are also primary drivers of global change. My research seeks to answer two questions:
- How do nutrient supply and temperature influence the growth and nutrient balance of organisms?
- How do these individual responses sum to shape ecosystem processes?
Addressing these questions -central to both basic ecological understanding and conservation- requires work at multiple levels of organization and a diverse set of approaches. I use mathematical modeling, laboratory/field experiments, field surveys, and meta-analyses to achieve my research goals. I also use emerging frameworks such as ecological stoichiometry and the metabolic theory of ecology to build linkages between nutrient and energy cycles and scale across multiple levels of organization. An integrative approach is essential for understanding how aquatic systems respond to human activities across scales of complexity, time, and space.
Page Under Construction, please excuse our dust.
Recent and on-going research projects
(1) Interactive effects of temperature and nutrient supply on the structure and function of stream ecosystems.
Our ongoing NSF funded research in Iceland focuses on understanding the consequences of two dominant global change drivers, warming and nutrient enrichment, on the structure and function of stream ecosystems. We will quantify the interactive effects of warming and nutrient enrichment on carbon and nutrient cycling as well as the flows and fate of energy and materials in stream food webs.
I will post more about this project soon, but you can follow our day-to-day struggles and victories on our team blog.
(2) Understanding the influence of water temperature on nutrient limitation and cycling in streams (RANNÍS postdoctoral fellowship).
My recent RANNÍS postdoctoral fellowship focused on understanding how climate warming influences nutrient limitation and demand in stream ecosystems. I will examined how nutrient limitation and demand varies across a stream water temperature gradient for epilithic communities exposed to warming for weeks, years, and decades. I also explored how nutrient limitation and demand scales from populations to communities to ecosystems.
(3) Predicting the effect of climate warming on ecosystem processes in streams.
This is the research I conducted for my first postdoctoral position. We used geothermal streams in the Hengill region of Iceland to ask how temperature influences the structure and function of stream ecosystems. My work focused on how temperature influences whole-stream nutrient uptake, ecosystem production, and ecosystem respiration.
(4) Using a stoichiometric framework to understand how diet phosphorus content influences animal growth and fitness.
Diet phosphorus content can be one important determinate of food quality for many animals. As a result, the phosphorus content of animal diets can determine not only how rapidly animals grow, but their competitive ability, and the role they play in nutrient cycles. My work on this theme has two primary thrusts. First, I use Daphnia (because it is both well-studied and behaves nicely) and laboratory experiments to improve our understanding of competitive tradeoffs between maximizing growth rate and minimizing phosphorus limitation of growth. Second, I use meta-analysis to examine how diet phosphorus content influences the growth and condition of animals. As part of Woodstoich II, I worked with colleagues to conduct a meta-analysis of how, in part, diet P influences animal P homeostasis. Jon Benstead, his students, and I recently completed a meta-analysis examining the effect of dietary P content on fish growth.
Just a special note here about Woodstoich, a scientific “happening” about all things stoichiometric. I was one of the postdoctoral organizers of Woodstoich III.
(5) Quantifying the importance of animal mediated nutrient cycling in streams.
Some of my earliest work in ecology focused on animal mediated nutrient cycling. Animals can shape nutrient cycles when they release nutrients ingested in excess back to their environment. Animal mediated nutrient cycling can influence algal community structure, shape the size and quality of nutrient pools, and is one mechanism linking animal diversity to ecosystem functioning. My more recent work in this field explores how stoichiometric predictions of nutrient recycling are influenced by selective feeding, a common behavior in streams that has rarely been incorporated into nutrient cycles. You can read more about this study here.
(7) Understanding longitudinal variation in the role of fine particulate organic matter (FPOM) in stream nutrient cycles.
I became interested in fine particulate organic matter (FPOM) when I was studying animal mediated nutrient cycling in California streams. There is a lot of animal waste in the FPOM pool –maybe its all animal poo. Anyway, FPOM is colonized by microbes and plays an important role in the structure and function of stream ecosystems. As a first step towards understanding the links among animals, FPOM, and ecosystem functioning, I conducted a study examining how the quantity, quality, and activity of FPOM changes along a river network (again in California).