PARENT SESSION
Oral Session #25: River and Riparian Restoration I.
Presiding: M.A. Madej
Tuesday, August 6. 8:00 AM to 11:30 AM. Mohave Meeting Room, TCC.
Do river dyamics determine plankton and turbidity of floodplain lakes along the Lower Rhine?
ROOZEN, FRANK*,1, VAN GEEST, GERBEN1, IBELINGS, BAS2, ROIJACKERS, RUDI1, SCHEFFER, MARTEN1, BUIJSE, TOM2, 1 Wageningen University and Research Centre, Wageningen, The Netherlands2 RIZA Institute for Inland Water Management and Waste Water Treatment, Lelystad, The Netherlands
ABSTRACT- River restoration in the Netherlands imply numerous new water bodies to be excavated in the floodplains of the River Rhine. Size, depth and connectivity to the river of these future lakes can in part be designed, raising the question of how these aspects of lake morphometry and river dynamics affect water clarity and plankton biodiversity. A field survey of 93 lakes in the summer of 1999 and a three year monitoring campaign of ten lakes from 1998 until 2000 have been performed in order to unravel the driving forces behind the ecological dynamics in these infrequently studied ecosystems. Various ecological, hydrochemical and hydrological data have been collected and analysed. Lake clarity and plankton dynamics were highly determined by in-lake processes and lake depth, rather than by the river dynamics. Only the strong differences in responses to water level fluctuations in the river seemed to determine lake clarity and even plankton compositon. Hydrochemistry of the lakes showed clear differences but did not seem to strongly influence the plankton of the lakes, nor the turbidity. The presence of vegetation and benthivorous fish seem to be the driving forces behind lake clarity, the first enhancing clarity and the second deteriorating it. Both vegetation and fish are strongly influenced by the river dynamics, indicating that lake plankton and clarity can be "designed" as long as guidelines for restoration are focussed on the development of vegetation and fish in the newly excavated lakes along the Lower River Rhine.
KEY WORDS: river restoration, plankton, lake clarity, hydrology