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Highlights  The General Lake Model (GLM) is stress tested against 32 globally distributed lakes.  There was low correlation between input data uncertainty and model performance.  Model performance related to lake-morphometry, light extinction and flow regime; deep, clear lakes with high residence times had the lowest model error.

Stable isotope analysis of the potential prey and predator can be combined with gut content analysis to quantify the diet. This dietary knowledge allows the quantitative assessment of the role of key species in energy and contaminant transfer, their impact on prey communities, and their susceptibility to perturbation. The diet of Mysis relicta was examined in Lake Ontario in spring, summer, and autumn using both techniques. Mysids fed on the bottom during the day and in the pelagia and on the bottom at night. A trophic fractionation of 2.2‰ N between mysids and their prey provided the best correspondence between the observed stable isotope signature of mysids and that estimated from their diet. Tissue turnover rate of d 13 C was slow compared with that of d 15 N. Diatoms formed 50% of the assimilated diet in May. In September, 25% of large mysids feeding on the bottom contained amphipod parts and 20% contained phytoplankton. The remainder of the diet consisted of zooplankton and rotifers. The contribution of amphipods and phytoplankton could not be quantified. Revised daily consumption estimates, based on this new diet information and clearance rate estimates of consumption, gave daily consumption estimates similar to those estimated from previous bioenergetic modelling.

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Modeling studies examining the effect of lakes on regional and global climate, as well as studies on the influence of climate variability and change on aquatic ecosystems, are surveyed. Fully coupled atmosphere-land surface-lake climate models that could be used for both of these types of study simultaneously do not presently exist, though there are many applications that would benefit from such models. It is argued here that current understanding of physical and biogeochemical processes in freshwater systems is sufficient to begin to construct such models, and a path forward is proposed. The largest impediment to fully representing lakes in the climate system lies in the handling of lakes that are too small to be explicitly resolved by the climate model, and that make up the majority of the lake-covered area at the resolutions currently used by global and regional climate models. Ongoing development within the hydrological sciences community and continual improvements in model resolution should help ameliorate this issue.It has been long understood that lakes and reservoirs can influence local and regional climate, as open water has significantly different radiative and thermal properties compared with soil or vegetated surfaces. It is not surprising then, that various attempts have been made over the years to include the effects of terrestrial surface water in global and regional climate modeling studies, though the effects considered are usually limited to the flux exchange of moisture, heat, and momentum with the overlying atmosphere. On the other hand, the effect of climate variability and change on thermal structure, water quality, and aquatic ecosystems-also long known to be important-is generally only evaluated in the context of individual lakes or reservoirs. Even though very elaborate models exist for examining these issues, they are generally not run fully coupled with global or regional climate models, presumably because of the computational expense or the complexity of such an exercise (or both). Yet to understand the role of lakes and reservoirs in the climate system, fully coupled models must be developed in which key lacustrine processes relevant on climate timescales are integrated within the climate model. This is especially clear given the recent (and growing) awareness of the importance of lakes and reservoirs in the global carbon balance (St. Louis et al. 2000;Tranvik et al. 2009;Williamson et al. 2009). Nutrient loading, biogeochemical cycling, food webs, and ecosystems will all need to be represented, in addition to the thermal structure, mixing regimes, and ice cover that are usually considered in climate modeling studies (i.e., if lakes and reservoirs are considered at all). Modeling techniques exist for all of these, yet it would appear that a fully coupled atmosphere-land surface-lake model that would meet the needs of both the terrestrial