Date

November 12, 2012

Time

10:00 am

Location

RW432

Caren Scott, Exit Seminar

Host: Ann Zimmerman/Don Jackson

ABSTRACT

Littoral zone primary production is under-studied relative to the pelagic zone, despite recent work indicating its importance to the lake as a whole. Benthic extracellular material, shown to be important for food web dynamics and stabilization of the surrounding ecosystem in the marine intertidal, is even less frequently studied in lakes. I examined the environmental and community level drivers of benthic primary production, and found production to increase over the summer and to decrease with disturbance. I also found that maximum photosynthesis and efficiency under sub-saturating light both increased with depth, contrary to the existing, laboratory-derived paradigm of a trade-off between the two. I also examined how benthic primary production and environmental factors influenced the amount of extracellular material. I found that loosely bound colloidal extracellular material was affected by *in situ*photosynthesis and algal community composition, whereas tightly bound capsular extracellular material was affected only by date, indicating that capsular material is refractory in lakes just as it is in marine systems. Contrary to what is seen in marine systems, however, there were no direct effects of the environmental factors, possibly the result of physical differences between these systems. I also performed the first cross-ecosystem comparison of extracellular material. Despite relatively few studies from lakes and streams, and methods which have not been standardized, I found that lakes were similar to marine intertidal zones both in their median amounts of extracellular material and their relationships between extracellular material and chlorophyll a. This relationship appeared to be quite different in streams. While the above studies will improve future estimates of lake carbon budgets and whole-lake production, my development of a permutation test for path analysis, and a novel application of the Bayesian principal components analysis, will assist all ecological studies that are often restricted in their sample sizes or compromised by missing data.