Littoral diatoms are important contributors of the primary production in shallow aquatic ecosystems and they can be used as indicators of the trophic status. The aim of the study was to develop an index to assess trophic status of Hungarian lakes as suggested by the Water Framework Directive. In spring of 2005 and 2006, epiphytic diatom samples were collected from 83 shallow lakes. Weighted average method was used to develop and test the TP model. In the developed TP model correlation between the observed and diatom inferred TP was high (r 2 = 0.96, n = 67). The optimum and tolerance TP parametrics of 127 species were determined and trophic indicator and sensibility values were defined for the Trophic Diatom Index for Lakes (TDIL). The TDIL was applicable to assess the ecological status of Hungarian shallow lakes. According to the TDIL the ecological status of 4 lakes were in excellent, 25 in good, 21 in medium, 21 in tolerable and 12 in bad status.

Identification and management of the groundwater quality are of utmost importance for maintaining freshwater resources in arid and semi-arid areas, which is essential for sustainable development. Based on the quality of the groundwater in various areas, local policymakers and water resource managers can allocate the usage of resources for either drinking or agricultural purposes. This research aims to identify suitable areas of water pumping for drinking and agricultural harvest in the Tabriz aquifer, located in East Azerbaijan province, northwest Iran. A groundwater compatibility study was conducted by analyzing Electrical conductivity (EC), total dissolved solids (TDS), Chloride (Cl), Calcium (Ca), Magnesium (Mg), Sodium (Na), Potassium (K), Sulfate (SO4), Total hardness (TH), Bicarbonate (HCO3), pH, carbonate (CO3), the and Sodium Adsorption Ratio (SAR) obtained from 39 wells in the time period from 2003 to 2014. The Water Quality Index (WQI) and irrigation water quality (IWQ) index are respectively utilized due to their high importance in identifying the quality of water resources for irrigation and drinking purposes. The WQI index zoning for drinking classified water as excellent, good, or poor. The study concludes that most drinking water harvested for urban and rural areas is ‘excellent water’ or ‘good water’. The IWQ index average for the study area is reported to be in the range of 25.9 to 34.55. The results further revealed that about 37 percent (296 km2) of groundwater has high compatibility, and 63 percent of the study area (495 km2) has average compatibility for agricultural purposes. The trend of IWQ and WQI indexes demonstrates that groundwater quality has been declining over time.

Scale and frequency of changes in a lake's physical structure, light dynamics, and availability of nutrients are closely related to phytoplankton ecology. Since phytoplankton assemblages were first described, phytoplankton ecologists concluded that these assemblages provide insight into phytoplankton responses to environmental changes. Objectives of this study were to investigate ecology of phytoplankton during a complete hydrological cycle in the deepest natural lake in Brazil, Dom

Lake Balaton (Hungary), one of the largest lakes in Europe, has undergone eutrophication and restoration during the last two decades. The first quantitative phytoplankton records date back to the 1930s, and since that time thousands of data have been published or accumulated in counting protocols or computer sheets. These data provide material for both scientific analyses (e.g. effects of global change) and applications (e.g. estimation of reference state for the Water Framework Directive). The ALMOBAL phytoplankton database was developed to provide computing support for these applications. It stores data in standardized forms, handles synonyms and allows analyses to be conducted on the basis of floral records, numbers or biomass. The analysis includes records of about 3000 phytoplankton samples taken during the past 60 years from two representative basins in Lake Balaton. This article represents the first attempt at historical reconstruction of the ecological status and compares it with changes in trophic state and current water quality. The results indicate that the phytoplankton biomass and community structure found in the early 1960s could be regarded as reference conditions. Statistical analyses support the view that late summer phytoplankton assemblages are the most sensitive indicators of trophic change, and clearly show the eutrophication of the lake that occurred from the mid-1970s to the mid-1990s and the restoration during the last decade. An additional advantage is that, since quality estimation is based on relative biomass, the method can be used to reconstruct water quality in cases when counting protocols are available, but some basic data for quantitative estimates are missing.

The hypothesis that physical constraints may be as important, if not more important, than\ud biological ones in shaping the structure of phytoplankton assemblage was tested by analyzing longterm (11–29 years) phytoplankton series in eight lakes and nine sites located along a latitudinal gradient in the Northern hemisphere. Phytoplankton biomass was used and similarity of assemblages in same months of the annual data sets was then calculated by subtracting the Bray–Curtis dissimilarity index from 1. The extent of biological and physical forcing was partly based on ‘‘expert evaluation’’: the importance of four physical (light availability, temperature, conductivity, and sediment stirring up) and five biological variables (basic nutrients [SRP-, DIN-, SRSi-availability] as estimators\ud of competition straight, importance of grazing, and importance of parasitism) was evaluated month by month by arbitrarily scaling from 1 to 5 the intensity of each variable and then summing them in the appropriate subgroup. Since the number of\ud physical variables is less than that of the biological ones, the latter was rescaled to reach the same maximum attainable value of physical variables. The results showed an extremely high variability, making evident that each lake, although showing the same\ud metabolic processes, behaves as an individual with regard to its phytoplankton structure. More generally, it was possible to highlight a largely more important role of physical constraints in shaping both biomass and composition of phytoplankton. This is especially true in winter. In addition, the results were compared to the outcomes of the PEG model, since a plasticity\ud in the structure of phytoplankton much greater than that reported in this widely acknowledged model has been recorded in the data set used. This high variability found in this study in relation to physical constraints might also explain the different patterns of phytoplankton growth observed from Northern temperate to Mediterranean lakes as well as those occurring in shallow and deep lakes