PARENT SESSION
PM11 - Sediment Toxicology
Monday, 18 November 2002
8:00 AM to 6:30 PM
Exhibit Hall

(P305) Characterization of sediment associated microbial enzyme activity from agricultural drainage systems.

Milam, Cristi^*,1, Scheuerman, Phil², Farris, Jerry³, McBride, Ashley³, Bouldin, Jennifer³, ¹ EA Engineering, Science & Technology, Sparks, MD, USA² East Tennessee State University, Environmental Health Sciences Laboratory, Johnson City, TN, USA³ Arkansas State University, Environmental Sciences Program, Jonesboro, AR, USA

ABSTRACT- An ongoing evaluation of the structural and functional components of agricultural drainage ditches in Northeast Arkansas suggests that these often-overlooked aquatic systems play a valuable role in the remediation of pesticides and nutrients directed to receiving streams. Seasonal (spring and summer) evaluation of microbial enzyme activity, fecal coliform, and nutrient loading of 10 drainage ditches that ranged in size from relatively small (draining ~20 hectare) to significantly larger ditches (draining >400 hectares) resulted in variation of enzyme activity between sites. The affect of nutrient loading into ditches was assessed by comparing nutrient levels to specific microbial enzyme activities (e.g., dehydrogenase activity, glucosidase activity, galactosidase activity, alkaline phosphatase activity and acid phosphatase activity). For example dehydrogenase activity ranged from nondetectable to 138 g formazin produced/ml of sample. All sites had detectable acid or alkaline phosphatase activity, indicating that these sites were probably phosphate limited during the sampling period. These data suggest that landscape features involving ditch size, extent of vegetation and drainage, and sediment type help structure microbial processes acting on discharges from intensive agricultural production. Furthermore, since nutrient loading is at the forefront of many of the recent TMDL listings, measurement of microbial activity associated with prominent landscape features may support critical design considerations for better management of agricultural drainage.

Key words: Agriculture, Drainage Ditches, Microbial Enzyme Activity, Sediments