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To evaluate the performance of a continuous monitoring device (Waterlogger) developed at Iowa State University, a pilot study was conducted on Lake Onalaska, Wisconsin (Navigational Pool 7 of the Upper Mississippi River), between June 28 and October 4, 1990. The devices recorded subsurface (20 cm) temperature and dissolved oxygen and surface and subsurface (50 cm) light (photon flux of photosynthetically active radiation) every 6 minutes at eight sites. The Waterlogger device stores its measurements electronically on battery-powered memory (RAM) within the unit and can transmitted the recorded data directly to a personal computer. Conversion of the Waterlogger readings to calibrated engineering units is achieved...
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Large beds of Vallisneria americana declined in the backwaters of the Upper Mississippi River after a drought that occurred between 1987 and 1989. One hypothesis for this decline is that low light availability may have decreased net photosynthesis to the extent that overwintering tubers were not formed. Following the decline, light availability remained low. To determine what light levels would be necessary for the re-establishment of Vallisneria in the Upper Mississippi River, the long-term growth of plants in a backwater lake and in an experimental pond was measured while the surface and subsurface light were monitored continuously. Plants grown from tubers transplanted to 0�5, 1�0, and 1�5 m depth in the lake...
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