Martin Mörtl

Ecological effects of water-level fluctuations in lakes: an urgent issue

Water-level fluctuations (WLF) affect the ecological processes and patterns of lakes in several ways. Aquatic habitats and feeding or breeding grounds are gained or lost, as light, climate and wave impacts change to mention only a few phenomena. While the phenomenon of WLF has been studied in many rivers (better known as flood pulse, Junk & Wantzen, 2004) and environmental flows (Coops et al., 2003), so far it has not received due attention in lakes (Coops et al., 2003). A potential reason for why WLF in lakes have been overlooked for such a long time may be that central Europe and North America—the cradles of limnological research—are situated in landscapes which have been shaped by man for long time. Most central European lakes have been regulated since the middle ages; therefore, naturally fluctuating lakes such as Lake Constance (Fig. 1) are rare today.

Effects of water-depth and water-level fluctuations on the macroinvertebrate community structure in the littoral zone of Lake Constance

In a 2-year field study, abundance, biomass and community structure of benthic macroinvertebrates and their seasonal dynamics were assessed along the depth gradient in the stony littoral zone of Lake Constance, Central Europe. The macroinvertebrate community patterns differed significantly between the depth zones, partly because of species turnover, but mostly as a result of different dominance structures. These distinct differences should be considered when designing surveys of benthic invertebrates also for applied purposes, since sources of variation should be kept small and particularly on hard substrates, extensive efforts are required to obtain sufficient data for a powerful statistical analysis. A large seasonal variability in the macroinvertebrate communities of the eulittoral zone indicates a strong influence of physical disturbances, particularly of water-level fluctuations. The community pattern of the drift line samples was influenced by the previous development of the water level. The cumulated water-level fluctuations and their net tendency accounted for three quarters of the variation in a PCA. Since Lake Constance is the only large pre-alpine lake whose water level is not extensively regulated, the uniqueness of the littoral community should have implications for nature conservation measures.

Ecological effects of water-level fluctuations in lakes.

Ecological effects of water-level fluctuations in lakes: an urgent issue.- Potential effects of water-level fluctuations on littoral invertebrates in lowland lakes.- Effects of water-level regulation on the nearshore fish community in boreal lakes.- Natural lake level fluctuation and associated concordance with water quality and aquatic communities within small lakes of the laurentian great lakes region.- Climate change and lakeshore conservation: a model and review of management techniques.- The impact of water-level regulation on littoral macroinvertebrate assemblages in boreal lakes.- Quantitative trends of zebra mussels in Lake Balaton (Hungary) in 2003-2005 at different water levels.- Patterns, origin and possible effects of sediment pollution in a mediterranean lake.- Temporal scales of water-level fluctuations in lakes and their ecological implications.- Effects of water-depth and water-level fluctuations on the macroinvertebrate community structure in the littoral zone of lake constance.- Flooding events and rising water temperatures increase the significance of the reed pathogen pythium phragmitis das a contributing factor in the decline of phragmites australis.- Leaf litter degradation in the wave impact zone of a pre-alpine lake.- Use of the water-level fluctuation analysis tool (Regcel) in hydrological status assessment of finnish lakes.- Mass mortality of the invasive bivalve Corbicula fluminea induced by a severe low-water event and associated low water temperatures.- An extension of the floodpulse concept (FPC) for lakes.- Effects of water-level fluctuations on lakes: an annotated bibliography.