Spatial Heterogeneity of Cyanobacteria and Diatoms in a Thermally Stratified Canyon-Shaped Reservoir

✍ Scribed by Enrique Moreno-Ostos; Luis Cruz-Pizarro; Ana Basanta; D. Glen George

• Publisher: John Wiley and Sons
• Year: 2009
• Tongue: English
• Weight: 384 KB
• Volume: 94
• Category: Article
• ISSN: 1434-2944
• DOI: 10.1002/iroh.200811123

✦ Synopsis

Abstract

Phytoplankton communities in lakes and reservoirs are seldom homogeneously distributed but usually aggregate in patches and gradients. In this study we have combined the use of in vivo spectrofluorometry and acoustic Doppler current profiling to investigate the effect of water movements on the spatial distribution of cyanobacteria and diatoms in a thermally stratified reservoir in SW Spain. The distinctive canyon‐shaped morphometry of the reservoir (El Gergal) favoured the development of a “conveyor belt” pattern of circulation aligned with the long axis of the reservoir. Under non‐regulated conditions, the spatial distribution of phytoplankton was almost entirely dependent on the interactions between advective transport and the buoyancy properties of the different functional groups of phytoplankton. The positively‐buoyant cyanobacteria accumulated near the surface and were then transported downwind by the surface drift currents. In contrast, the negatively‐buoyant diatoms sank in the water column and were transported upwind by the sub‐surface return currents. When deep water was abstracted from the reservoir, these distribution patterns were modified. The results are discussed in relation to the problem of acquiring representative water samples from the reservoir and the application of a simple empirical model to optimize the location of the station used for routine cyanobacteria sampling on the reservoir. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)