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The Alqueva reservoir (southeast of Portugal) is the largest artificial lake in western Europe and a strategic freshwater supply in the region. The reservoir is of scientific interest in terms of monitoring and maintaining the quality and quantity of water and its impact on the regional climate. To support these tasks, we conducted numerical studies of the thermal and gas regimes in the lake over the period from May 2017 to March 2019, supplemented by the data observed at the weather stations and floating platforms during the field campaign of the ALentejo Observation and Prediction (ALOP) system project. The 1D model, LAKE 2.0, was used for the numerical studies. Since it is highly versatile and can be adjusted to the specific features of the reservoir, this model is capable of simulating its thermodynamic and biogeochemical characteristics. Profiles and time series of water temperature, sensible and latent heat fluxes, and concentrations of CO2 and O2 reproduced by the LAKE 2.0 model were validated against the observed data and were compared to the thermodynamic simulation results obtained with the freshwater lake (FLake) model. The results demonstrated that both models captured the seasonal variations in water surface temperature and the internal thermal structure of the Alqueva reservoir well. The LAKE 2.0 model showed slightly better results and satisfactorily captured the seasonal gas regime. [ABSTRACT FROM AUTHOR]

A new freshwater diatom species was described from southwest Europe (Portugal), based on morphological and ultrastructural characteristics. Fragilaria misarelensis Almeida, C.Delgado, Novais & S.Blanco is characterised by lanceolate valves, with slightly capitate ends, alternate striae and lacking spines joining adjacent cells, which are solitary. The valve shape of Fragilaria misarelensis, when compared to similar forms, is unique, as revealed by a thorough literature survey of Fragilaria species, geometric morphometry and discriminant analysis. Fragilaria misarelensis sp. nov. was frequent and abundant in central Portugal, in poorly mineralized watercourses under low anthropogenic influence, characterised by neutral pH, low conductivity and high dissolved oxygen concentration. The analysis of type material belonging to similar species, Fragilaria capucina fo. sublanceolata-baikali, F. capucina fo. lanceolata-baikali and F. nevadensis, contributed to improving their characterisation and illustration, also supporting the delimitation of the new Portuguese species. Fragilaria capucina fo. sublanceolata-baikali and F. capucina fo. lanceolata-baikali were considered to differ substantially from F. capucina and raised to species level as Fragilaria sublanceolata-baikali (Flower & D.M.Williams) Novais, C.Delgado & S.Blanco, comb. et stat. nov. and Fragilaria lanceolata-baikali (Flower & D.M.Williams) Novais, C.Delgado & S.Blanco, comb. et stat. nov. [ABSTRACT FROM AUTHOR]