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Summary
From March to November 1989 and from May to August 1992 dissolved oxygen concentration (DO), water temperature and flow was measured continuously in the River Spree near above Berlin. Physiographic conditions were very constant for 20 km before the station. Neither significant tributries nor waste water discharges contribute to the flow or water quality of the highly eutrophicated, free flowing river stretch. The autotrophic community was dominated by planktonic blue-greens and diatoms (KÖHler 1993).
Primary production (P) and respiration (R) of the river community was estimated by a modification of Odum's (1956) single station oxygen time curve analysis.
DO showed a predictable seasonal pattern with increasing supersaturation during the spring phytoplankton bloom, a sharp drop to a clear water stage in June with lowest values, varying values in summer (mostly below saturation) declining in September, and growing DO nearly reaching saturation in November. Other eutrophic lowland rivers in Germany behave similar.
In 1989 P averaged 3.1, R 4.2 mg/(l·d), and P/R was 0.75 during the whole growing season. The distinct seasonal changes of P and P/R mainly depend on changes in phytoplankton concentration, whereas R is mainly controlled by benthic community respiration.