PW18 Field Biological Monitoring of Ecosystem Impairment
Exhibit Hall
8:00 AM - Wednesday
(PW272) The Use of Chronic In-Situ Toxicity Assessment as part of Site-Specific Critierion Development.
Goodfellow, W1, Rue, W1, McCulloch, W1, Connelly, R1, Dixon, K2, Christensen, L3, 1 EA Engineering, Science, and Technology, Inc, Sparks, MD, USA2 EA Engineering, Science, and Technology, Inc., Lincoln, NE, USA3 HDR Engineering, Inc., Omaha, NE, USA
ABSTRACT- A series of studies were conducted as part of a site-specific standard for ammonia for Salt Creek, NE. One of the major aspects of the overall assessment was the design and performance of an in situ toxicity testing program to calculate 30-day IC20 values for fathead minnows and channel catfish and use those data in combination with the other studies to develop a weight-of-evidence-based site-specific water quality criterion for this watershed. The in situ toxicity tests used caged fish continuously exposed for 30-days at nine in-stream locations to more accurately characterize the complex interactions of ammonia in the Salt Creek Watershed. Two fish species were selected for this program: fathead minnows (Pimpephales promelas) and channel catfish (Ictalurus punctatus). The selection of exposure chamber locations was based on in-stream concentrations of total ammonia, and natural concentrations of salinity. The experimental design evaluated two toxicological endpoints: mortality and growth; which were combined into a "biomass" determination. The 30-day IC20 value for the channel catfish 3.85 mg N/L based on biomass. The 30-day IC20 value for fathead minnows was >9.98 mg N/L, because there was less than a 20 percent decrease in biomass at downstram stations versus the control at the highest 30-day average in-stream exposure concentration biomass. This paper presents the findings of the in situ testing and provides a discussion as to the overall usefullness of the in-situ testing to the development of the site-specific criterion development.
Key words: Ammonia Toxicity, In Situ Testing, Chronic Toxicity, Site-Specific Criterion