Insight into how environmental change determines the production and distribution of cyanobacterial toxins is necessary for risk assessment. Management guidelines currently focus on hepatotoxins (microcystins). Increasing attention is given to other classes, such as neurotoxins (e.g., anatoxin-a) and cytotoxins (e.g., cylindrospermopsin) due to their potency. Most studies examine the relationship between individual toxin variants and environmental factors, such as nutrients, temperature and light. In summer 2015, we collected samples across Europe to investigate the effect of nutrient and temperature gradients on the variability of toxin production at a continental scale. Direct and indirect effects of temperature were the main drivers of the spatial distribution in the toxins produced by the cyanobacterial community, the toxin concentrations and toxin quota. Generalized linear models showed that a Toxin Diversity Index (TDI) increased with latitude, while it decreased with water stability. Increases in TDI were explained through a significant increase in toxin variants such as MC-YR, anatoxin and cylindrospermopsin, accompanied by a decreasing presence of MC-LR. While global warming continues, the direct and indirect effects of increased lake temperatures will drive changes in the distribution of cyanobacterial toxins in Europe, potentially promoting selection of a few highly toxic species or strains.

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.

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Invasive plant species can inhibit the growth of native plants by competing for resources as well as by secreting allelochemicals. Indigobush (Amorpha fruticosa L.), a deciduous shrub adaptable to a wide range of environmental conditions, was introduced into Europe as a decorative and valuable honey plant. In this study, we assayed the phytotoxic effect of aqueous leaf extracts (1, 3 and 5%) obtained from A. fruticosa leaves on seed germination and seedling growth of four important agricultural species (Trifolium pratense L. [cultivar "VIVA"], Medicago sativa L. [cultivar OS-100], Helianthus annuus L. [hybrid "Matej"] and Triticum aestivum L. [cultivar OS-Olimpija]). Five parameters were analyzed: germination percentage, mean germination time, germination index, fresh weight of seedling root and shoot. The phytotoxicity of A. fruticosa leaf extract was compared to that of juglone, a strong allelochemical that is known to inhibit growth of numerous plant species. The results demonstrate that A. fruticosa phytotoxicity is dependent on both the plant species tested and leaf extract concentration, with higher concentration extracts having stronger phytotoxicity. The highest concentration (5%) leaf extract caused similar inhibition of seed germination and seedling growth to that of juglone. The results of this study suggest that the rapid invasion of A. fruticosa in agricultural areas may have a negative impact on growth and yield of valuable forage and agricultural crops.

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