PM06 Linking Aquatic Toxicology with Ecosystem Indicators
Exhibit Hall
8:00 AM - Monday, 10 November 2003
(PM120) Biological indicators used to measure pesticide effects on steelhead in Hood River, OR.
St. Aubin, C1, Foster, E2, Grange, F2, 1 Portland State University, Portland, Oregon, USA2 Oregon Department of Environmental Quality, Portland, Oregon, USA
ABSTRACT- In 1998, Hood River Basin steelhead (Oncorhynchus mykiss) were listed as threatened under the federal Endangered Species Act. The causes of steelhead population declines were unknown but pesticides were identified as one potential stressor. Water samples were analyzed for total organophosphate insecticides using liquid-liquid extraction and GC-NPD. Composite macro-invertebrate samples (8 Hess/sample/site) were collected two weeks before and two weeks after pesticide applications using a Hess sampler. Juvenile steelhead held in cages in-situ were sampled and analyzed for brain acetylcholine esterase (AChE) activity from each site once per week for three weeks to measure effects from different exposure intervals. Water samples collected in June 2001 and 2002, downstream from orchards during pesticide applications, had detections of pesticides above state water quality standards. Multi-variate analysis of macro-invertebrate samples (2001) before and after spray applications showed significant differences between impact sites and reference sites (ANOSIM results global R = 0.454, p value = 0.002). PCA analysis indicated metals (Cu and Zn), simazine, and azinphos methyl were affecting two of the impact sites (Lower Neal creek, Lenz creek) with axis I and II explaining 71.4% variability between sites. Mean brain AChE activity at two impact sites (Lower Neal creek = 209.9) and (Lenz creek = 253.6) were significantly different from reference site (Upper Neal creek = 336.6) and (Hatchery controls = 285.6). This investigation indicates that pesticides may be adversely affecting threatened steelhead directly and indirectly in the Hood River Basin.
Key words: macro-invertebrates, Biological indicators, acetylcholine esterase, salmonids