Macrophyte responses to water level fluctuation in Fenno-scandinavian Lakes - Applying a common index

摘要

Hydromorphological pressure caused by artificial water level regulation is one of the major factors influencing the distribution of aquatic vegetation in Fennoscandinavian lakes. More than 350 lakes in Finland and 900 lakes in Norway are regulated or were artificially created (MARTTUNEN et al. 2006). Aquatic macrophytes are key indicators of hydromorphological changes in lakes due to their sensitivity to water level fluctuation as shown in several Nordic studies (RORSLETT 1989, HELLSTEN 2001, PARTANEN & HELLSTEN 2005, KETO et al. 2006). Aquatic macrophyte data are very often collected by diverse sets of field methodology; the term "macrophyte" is also unclear, ranging from a very strict definition of hydrophytes to a wide definition that includes helophytes and even some shore plants. Therefore, full scientific comparison of different national datasets is difficult although implementation of the European Water Framework Directive demands relatively uniform datasets for a common intercalibration exercise. The aim of our study was to compare Finnish and Norwegian macrophyte data from regulated and non-regulated lakes to develop a common index for estimation of the ecological status of regulated lakes.