PARENT SESSION
Poster Session #63: Late Breaking and Newsworthy Papers.
Friday, August 9. Presentation from 8:00 AM to 9:30 AM. Exhibit Hall B & C, TCC

Longitudinal changes in macroinvertebrate production in a stream affected by urban and agricultural activities.

Shieh, Sen-Her^*,1,2, Ward, J.³, Kondratieff, B.¹, ¹ Colorado State University, Fort Collins, CO² Providence University, Shalu, Taiwan³ ETH/EAWAG, Ueberlandstrasse, Switzerland

ABSTRACT- Benthic samples were collected during a one-year period (September 1993-August 1994) to examine macroinvertebrate production at 6 sites along the plains section of the Cache la Poudre River, Colorado, impacted by urban and agricultural activities. Site 1 which was least impacted by human activities possessed the lowest secondary production (26.0 g AFDW m^-2 y^-1). Site 2 enriched by treated effluents from wastewater treatment facilities and characterized by high inorganic nutrients possessed the highest secondary production (60.5 g AFDW m^-2 y^-1). Sites 3-6 impacted by agricultural activities have intermediate secondary production levels (31.8-52.0 g AFDW m^-2 y^-1). These sites were characterized by high values of hardness, alkalinity, and conductivity, and high standing stocks of aquatic vascular plants. Collector-gatherers were the most dominant functional group, contributing from 39% of the total production at site 1 to 92% at site 2. The non-Tanypodinae Chironomidae were the most important collector-gatherers, contributing from 73% of the functional group production at site 4 to 96% at site 2. Hardness and aquatic vascular plants appeared to play major roles in determining levels of production and functional group composition in the stream reach. Community P/B ratios reflected changes in species composition and environmental conditions at the 6 sites. Smaller and faster growing taxa (e.g., Chironomidae and Simulium spp.) resulted in higher community P/B ratios and production at the sites impacted by urban and agricultural activities.

KEY WORDS: macroinvetebrate production, urbanization, agricultural activities, functional groups