Among them, the compounds produced by some species of microalgae and fungi represent a threat not only for the ecosystems and the species that live in them, but also for human health and food safety through the consumption of contaminated food (i.e. aquatic organisms or stored food) and exposure to water (drinking or through recreational activities). Environmental conditions are one of the main drivers of microalgae proliferation; it is quite likely that the forecasted climate change and water shortages will have a dramatic impact on harmful algae blooms (HABs) dynamics, toxin production and availability of drinking water. In addition the internationalization of food and feed trade has increased the storage and packaging of many goods but favoring fungi growth. Additionally, the number of natural toxins keeps on increasing, with new ones produced by microorganisms or metabolites produced by other organisms after uptaking the toxins. Research, monitoring and management on natural toxins demand a multidisciplinary and interdisciplinary approach, in order to monitor, prevent and eventually solve the challenges they pose to ecosystems, human health and economy. Impacts of HABs and fungal toxins can be found worldwide in fresh and marine waters. Examples of their relevance and impact in Europe are the re-construction of Lake Karla (listed in the network of the Greek protected areas as a vital aquatic ecosystem in terms of biodiversity, currently the completion of its re-construction is facing many episodes of fish mortality attributed to HABs) and the detection of Gambierdiscus sp (described in Canary Islands, Madeira and the Mediterranean, this dinoflagellate genus is responsible of the production of Ciguatera Fish Poisoning – CFP – toxins; the potency of the European strains and the potenial transfer of the toxins through food webs is yet to be determined). In European marine waters, HABs and associated toxins under current regulation are regularly monitored. However, some emerging toxins not yet regulated, such as cyclic imines and the microalgae that produce them should be more carefully evaluated in order to better understand their distribution and the real hazard they represent. Presentations in this session will include, but not be limited to: 1) new or emerging toxins: origin, detection and regulatory challenges; 2) ecotoxicological studies, defining biological, chemical and physical factors influencing the occurrence and control of HABs and toxic fungi; 3) comparative toxicology; 4) bioaccumulation of toxic compounds in organism, food webs or ecosystems; 5) sensory and analytical approaches for the early detection of HABs, fungi and the toxins they produce, including alternatives to animal testing; 6) studies on the effectiveness of HAB suppression and control technologies of HABs, fungi and the toxins they produce, including treatment alternatives; 7) economic and human health impacts of toxins and 8) regulatory needs, gaps and challenges.