Since the late 1980s, shallow lakes in Europe and North America have been receiving concerted attention from limnologists, fishery biologists and lake managers. These developments relate to deterioration of water quality in the lakes due to pollution and accelerated eutrophication, caused by increased urbanization and agriculture in the lake catchments, overexploitation of fish and higher water level fluctuations. The water-quality and management problems of lakes have led to a greater need for fundamental researches on shallow lakes in order to gain a deeper insight into the structure and functioning of the food web in these waters. New knowledge relating to littoral-pelagial interactions and the sediment-water interface has facilitated the development of new lake restoration techniques.

This volume, with 41 peer-reviewed papers, comprises the proceedings of the 5th International Symposium on Shallow Lakes, which was held at Dalfsen, The Netherlands, on 5-9 June 2005. It has the theme Shallow Lakes in a Changing World and deals with water-quality issues, such as changes in lake limnology, especially those driven by eutrophication and pollution, increased nutrient loading and productivity, perennial blooms of cyanobacteria and loss of biodiversity. The general consensus is that the lakes under restoration respond by showing an increase in water clarity followed by an increase in macrophyte coverage and biomass. Consequently, there is now ground for theoretical speculations on the so-called 'alternate stable states' observed in many such lakes under restoration.

Zusammenfassung
which method/approach to take for the deter- nation of reference conditions is dependent on The estimation of reference conditions is crucial the condition of the sites available for a certain in any ecological assessment programme (e. g. lake type: (a) where undisturbed or nearly undis- Moss et al. , 1996). These provide the baseline turbed conditions prevail, a validated spatial from which to determine lake change with time, network is preferred; (b) if degraded conditions and are necessary to evaluate a lake's current prevail then the preferred modelling approach status or potential for change. would be based on establishing a good relation- The most recent European water legislation, ship between stress and ecological response; (c) the water framework directive (WFD), prescribes expert judgement should be used as the last resort the assessment of ecological quality of surface and be accompanied by an acceptable validation waters using an ecological quality ratio (EQR). process. The EQR is de?ned as the ratio between the The TP status of a lake is mainly determined reference value and the observed value for a by its external nutrient supply. Phosphorus export given metric. from a catchment in an undisturbed area will As part of the assessment of ecological quality, depend on the natural fertility of the local rocks many European countries are choosing to devel- or glacial deposits, and the soils derived from op a quality classi?cation scheme for total ph- them.

Inhalt
Nutrient Dynamics.- Phosphorus reference concentrations in European lakes.- Benthic nutrient fluxes in a eutrophic, polymictic lake.- Modeling nitrogen cycling in a coastal fresh water sediment.- Sediment phosphorus cycling in a large shallow lake: spatio-temporal variation in phosphorus pools and release.- Nitrate dynamics in a reed belt of a shallow sand dune lake in Japan: Analysis of nitrate retention using stable nitrogen isotope ratios.- Temporal trends of ion contents and nutrients in three Kenyan Rift Valley saline-alkaline lakes and their influence on phytoplankton biomass.- Macrophytes.- Elongation and mat formation of Chara aspera under different light and salinity conditions.- Searching for allelopathic effects of submerged macrophytes on phytoplanktonstate of the art and open questions.- Allelopathic activity of Stratiotes aloides on phytoplanktontowards identification of allelopathic substances.- The role of aquatic macrophytes in microhabitatual transformation of physical-chemical features of small water bodies.- Assessment in two shallow lakes of a hydroacoustic system for surveying aquatic macrophytes.- Limnogy/Paleolimnology.- Combining limnological and palaeolimnological approaches in assessing degradation of Lake Pskov.- Sediment diatom assemblages and composition of pore-water dissolved organic matter reflect recent eutrophication history of lake peipsi (Estonia/Russia).- Factors influencing taxonomic composition and abundance of macrozoobenthos in extralittoral zone of shallow eutrophic lakes.- Food WEBS.- The role of cladocerans reflecting the trophic status of two large and shallow Estonian lakes.- Contribution of different zooplankton groups in grazing on phytoplankton in shallow eutrophic Lake Võrtsjärv (Estonia).- Horizontal dynamicsof Zooplankton in subtropical Lake Bianca (Uruguay) hosting multiple Zooplankton predators and aquatic plant refuges.- Functional response of Anodonta anatina feeding on a green alga and four strains of cyanobacteria, differing in shape, size and toxicity.- The role of herbivorous water birds in aquatic systems through interactions with aquatic macrophytes, with special reference to the Bewick's Swan Fennel Pondweed system.- Cascading trophic effects in pampean shallow lakes: results of a mesocosm experiment using two coexisting fish species with different feeding strategies.- Impact of hydrology on aquatic communities of floodplain lakes along the Daugava River (Latvia).- Lake Restoration.- Shallow lake restoration by nutrient loading reductionsome recent findings and challenges ahead.- Reaction of large and shallow lakes Peipsi and Võrtsjärv to the changes of nutrient loading.- Spatial and temporal diversity of small shallow waters in river Lunice floodplain.- Potential for the development of submerged macrophytes in eutrophicated shallow peaty lakes after restoration measures.- The importance of drawdown and sediment removal for the restoration of the eutrophied shallow lake Kraenepoel (Belgium).- Why biomanipulation can be effective in peaty lakes.- Mediterranean Lakes.- State of the art in the functioning of shallow Mediterranean lakes: workshop conclusions.- Changes in bacterial and ciliate densities with trophic status in Mediterranean shallow lakes.- The relationship between phytoplankton species dominance and environmental variables in a shallow lake (Lake Vrana, Croatia).- Comparative biodiversity of crustaceans and aquatic insects from various water body types in coastal Mediterranean wetlands.- Land use changes and associated environmentalimpacts on the Mediterranean shallow Lake Stymfalia, Greece.- EUropean Water Framework Directive.- Impact of climatic variability on parameters used in typology and ecological quality assessment of surface watersimplications on the Water Framework Directive.- Shallow lakes, the water framework directive and life. What should it all be about?.- Submerged macrophyte vegetation and the European Water Framework Directive: assessment of status and trends in shallow, alkaline lakes in the Netherlands.- Climatic Change.- Climate-induced shifts in an experimental phytoplankton community: a mechanistic approach.- Impact of climatic fluctuations on characeae biomass in a shallow, restored lake in The Netherlands.- Response of macro in vertebrates to warming, nutrient addition and predation in large-scale mesocosm tanks.- The role of temperature in the population dynamics of smelt Osmerus eperlanus eperlanus m. spirinchus Pallas in Lake Peipsi (Estonia/Russia).- Predicting the effect of climate change on temperate shallow lakes with the ecosystem model PCLake.- Shallow lakes theory revisited: various alternative regimes driven by climate, nutrients, depth and lake size.