M. B. Lakly & J V. McArthur

RESULTS

I. Pen Branch Recovery Status

	Substantial recovery in abundance and diversity of macroinvertebrates. Similar to 15 year post-thermal Steel Creek in 1984.
	Dominant instream habitat structural components and riparian development & interaction different from reference systems.
	Significant differences in organic matter storage and export
	No significant community differences were detected using standard biotic indices.

II. Significant Structural and Functional Differences
•	Post-thermal Pen Branch is dominated by macrophytes that trap and retain FPOM resulting in a community dominated by collecting invertebrates and those that shred or pierce plant tissue.
•	Reference systems lack macrophytes but have abundant debris dams that retain organics. This results in a macroinvertebrate community that scrape organic surfaces (biofilm) and shred trapped organics.
•	Differences in instream habitat structure are reflected in the relative abundances of functional feeding groups. Collector gatherers were numerically dominant and have been removed for comparisons.
CONCLUSIONS
•	The post-thermal recovery of the macroinvertebrate community in Pen Branch has been substantial and similar to other post-thermal streams on site.
•	However, alterations in instream structural components and physical changes in Pen Branch drive functional differences in the macroinvertebrate community. This indicates a post-thermal shift in energy source.
•	Traditional biotic indices may not detect these functional differences. However, investigation of functional feeding groups across streams illustrates the long-term effects of thermally induced geomorphic change on the current biotic community structure and function.
	Home | Abstract | Objectives | Sites & Sampling | Results & Conclusions