Graduate Thesis Or Dissertation
 

Effects of the insecticide dieldrin on benthic algae in laboratory streams

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/dz010t038

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  • The accumulation of dieldrin and its effects on species composition of benthic algal communities were studied in laboratory streams. Effects of dieldrin on photosynthetic and respiratory rates of the blue-green alga Phormidium retzii were determined using a Gilson Differential Respirometer. Dieldrin concentrations ranging from 0.05 to 7.0 ppb were maintained in the water of laboratory streams for periods of two to four months. In four experiments dieldrin concentrations in algae ranged from 0.1 to 200 ppm indicating that increases in concentration up to 30,000 times that of the water had occurred. Communities dominated by filamentous algae accumulated greater concentrations of dieldrin than those in which unicellular diatoms were dominant. Algae exported from the streams were responsible for removal of some of the accumulated pesticide from the system. Regression analysis related the abundance of 15 common taxa of algae to dieldrin concentration; time; and either light intensity or current velocity. The diatoms Synedra rumpens and Achnanthes minutissima were significantly less abundant in streams receiving dieldrin. Changes in the abundance of other algae were related to variations in current velocity, time, and light intensity. Photosynthetic and respiratory rates of P. retzii were affected only slightly by high concentrations of dieldrin. Photosynthetic rates increased during the first four hours after initial exposure to 148 ppb dieldrin. After 24 hours exposure to the same concentration there was no significant difference between the rates of treated and control material. No differences in respiratory rates were observed during the first five hours after initial exposure to 93 ppb dieldrin. However, after 24 hours exposure the respiratory rate of algae exposed to the same concentration was significantly lower than that of the unexposed material.
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