Diurnal Patterns of Mixing Depth and its Influence on Primary Production in a Shallow Lake
✍ Scribed by Brigitte Nixdorf; Wolf-Gunther Pagenkopf; Horst Behrendt
- Publisher
- John Wiley and Sons
- Year
- 1992
- Tongue
- English
- Weight
- 768 KB
- Volume
- 77
- Category
- Article
- ISSN
- 1434-2944
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✦ Synopsis
The influence of turbulence induced mixing on phytoplankton metabolic processes was investigated by hydrophysical and biological measurements in the eutrophic shallow lake GroBer Muggelsee (mean depth = 4.9 m). To trace spatial and temporal changes in the mixing depth, high resolution temperature profiles were recorded and analysed.
The vertical transport of algae in the mixed layer was simulated by the lift method, which allows an adjustment of the depth and the velocity of particle movement in a wide range (0.5-10 m, 0.03-3 cm . s-I). The results of this dynamic incubation were compared with those of the conventional static incubation.
In general, turbulence induced mixing enhances the areal daily primary production. Net oxygen production in cycled bottles is increased up to three times compared to the areal 02-release of algae which were incubated at a fixed position. This was proved particularly during afternoon incubation indicating the increasing importance of mixing during the course of a day. Changes in the mixing depth have only weak influence on primary production. There is a tendency towards higher O2-production as the mixing depth increases. Remarkable diurnal changes were observed in community respiration and compensation depth. Furthermore, the influence of photoinhibition, O,-saturation of the lake water and the diurnal changes in Chl a-concentration on primary production were measured and discussed. Contents 1.