The microbiotest battery as an important component in the assessment of snowmelt toxicity in urban watercourses—preliminary studies

The aim of the study was to use a battery of biotests composed of producers (Selenastrum capricornutum, Sorghum saccharatum, Lepidium sativum, and Sinapis alba), consumers (Thamnocephalus platyurus), and decomposers (Tetrahymena thermophila) to evaluate the toxicity of snowmelt and winter storm water samples. The toxicity of the samples collected in the winter period December to February (2010–2011), in one of the largest agglomerations in Poland, the city of Lodz, was compared to that of storm water samples taken under similar conditions in June. The most toxic snowmelt samples were found to be high acute hazard (class IV), while the remaining samples were rated as slight acute hazard (class II). L. sativum (in the Phytotox test) was the most sensitive test organism, giving 27 % of all toxic responses, followed by S. capricornutum with 23 % of all responses. T. thermophila was the least sensitive, with only 2 % of all toxic responses. The greatest range of toxicity was demonstrated by samples from the single family house catchment: no acute hazard (class I) to high acute hazard (class IV

Bacteria homologus to Aeromonas capable of microcystin degradation

Water blooms dominated by cyanobacteria are capable of producing hepatotoxins known as microcystins. These toxins are dangerous to people and to the environment. Therefore, for a better understanding of the biological termination of this increasingly common phenomenon, bacteria with the potential to degrade cyanobacteria-derived hepatotoxins and the degradative activity of culturable bacteria were studied. Based on the presence of the mlrA gene, bacteria with a homology to the Sphingopyxis and Stenotrophomonas genera were identified as those presenting potential for microcystins degradation directly in the water samples from the Sulejów Reservoir (SU, Central Poland). However, this biodegrading potential has not been confirmed in in vitro experiments. The degrading activity of the culturable isolates from the water studied was determined in more than 30 bacterial mixes. An analysis of the biodegradation of the microcystin-LR (MC-LR) together with an analysis of the phylogenetic affiliation of bacteria demonstrated for the first time that bacteria homologous to the Aeromonas genus were able to degrade the mentioned hepatotoxin, although the mlrA gene was not amplified. The maximal removal efficiency of MC-LR was 48%. This study demonstrates a new aspect of interactions between the microcystin-containing cyanobacteria and bacteria from the Aeromonas genus.The authors would like to acknowledge the European Cooperation in Science and Technology, COST Action ES 1105 “CYANOCOST - Cyanobacterial blooms and toxins in water resources: Occurrence, impacts and management” for adding value to this study through networking and knowledge sharing with European experts and researchers in the field. The Sulejów Reservoir is a part of the Polish National Long- Term Ecosystem Research Network and the European LTER site

Data Descriptor : A European Multi Lake Survey dataset of environmental variables, phytoplankton pigments and cyanotoxins

Under ongoing climate change and increasing anthropogenic activity, which continuously challenge ecosystem resilience, an in-depth understanding of ecological processes is urgently needed. Lakes, as providers of numerous ecosystem services, face multiple stressors that threaten their functioning. Harmful cyanobacterial blooms are a persistent problem resulting from nutrient pollution and climate-change induced stressors, like poor transparency, increased water temperature and enhanced stratification. Consistency in data collection and analysis methods is necessary to achieve fully comparable datasets and for statistical validity, avoiding issues linked to disparate data sources. The European Multi Lake Survey (EMLS) in summer 2015 was an initiative among scientists from 27 countries to collect and analyse lake physical, chemical and biological variables in a fully standardized manner. This database includes in-situ lake variables along with nutrient, pigment and cyanotoxin data of 369 lakes in Europe, which were centrally analysed in dedicated laboratories. Publishing the EMLS methods and dataset might inspire similar initiatives to study across large geographic areas that will contribute to better understanding lake responses in a changing environment.Peer reviewe

Stratification strength and light climate explain variation in chlorophyll a at the continental scale in a European multilake survey in a heatwave summer

To determine the drivers of phytoplankton biomass, we collected standardized morphometric, physical, and biological data in 230 lakes across the Mediterranean, Continental, and Boreal climatic zones of the European continent. Multilinear regression models tested on this snapshot of mostly eutrophic lakes (median total phosphorus [TP] = 0.06 and total nitrogen [TN] = 0.7 mg L−1), and its subsets (2 depth types and 3 climatic zones), show that light climate and stratification strength were the most significant explanatory variables for chlorophyll a (Chl a) variance. TN was a significant predictor for phytoplankton biomass for shallow and continental lakes, while TP never appeared as an explanatory variable, suggesting that under high TP, light, which partially controls stratification strength, becomes limiting for phytoplankton development. Mediterranean lakes were the warmest yet most weakly stratified and had significantly less Chl a than Boreal lakes, where the temperature anomaly from the long-term average, during a summer heatwave was the highest (+4°C) and showed a significant, exponential relationship with stratification strength. This European survey represents a summer snapshot of phytoplankton biomass and its drivers, and lends support that light and stratification metrics, which are both affected by climate change, are better predictors for phytoplankton biomass in nutrient-rich lakes than nutrient concentrations and surface temperature