Per- and polyfluoroalkyl substances (PFAS) are persistent organic pollutants with bioaccumulative, biomagnifying and toxic potential, and largely unknown fate and health effects in terrestrial wildlife. In a contaminated area, we studied PFAS in a terrestrial food web including soil, mushrooms, berries, and wild-living herbivores (bank vole and two ungulate species) and a specialized predator (Tengmalm’s owl). In addition, in voles, we studied potential PFAS-induced liver damage and infection with a zoonotic pathogen. Concentrations of PFAS in vole livers were among the highest reported in terrestrial wildlife. Results suggest biomagnification of PFAS from soil, mushrooms, and berries to bank voles, from mushrooms to ungulates and from voles to the owl. Most vole livers showed diffuse cytoplasmic granulation, ranging from mild to severe, as well as mild and variable hepatocellular hypertrophy. We found high prevalence of Orthohantavirus puumalaense infection in bank voles, highlighting the possibility of PFAS-induced infection susceptibility. Our study supports that terrestrial wildlife magnifies PFAS from the environment and highlights largely unexplored yet worrying effects on wildlife health.

Methylmercury (MeHg) is the most important and the most abundant organic Hg pollutant in the aquatic ecosystem that can affect human health through biomagnification. It is the most toxic organic Hg form, which occurs naturally and by human-induced contamination in water and is further biomagnified in the aquatic food web. MeHg is the only Hg form that accumulates in living organisms and is able to cross the blood–brain barrier, presenting an enormous health risk. Anthropogenic activity increases eutrophication of coastal waters worldwide, which promotes algae blooms. Microalgae, as primary producers, are especially sensitive to MeHg exposure in water and are an important entrance point for MeHg into the aquatic food web. MeHg assimilated by microalgae is further transferred to fish, wildlife and, eventually, humans as final consumers. MeHg biomagnifies and bioaccumulates in living organisms and has serious negative health effects on humans, especially newborns and children. Knowledge of the microalgae–MeHg interaction at the bottom of the food web provides key insights into the control and prevention of MeHg exposure in humans and wildlife. This review aims to summarize recent findings in the literature on the microalgae–MeHg interaction, which can be used to predict MeHg transfer and toxicity in the aquatic food web.

Methylmercury (MeHg) is a potent neurotoxin commonly found in aquatic environments and primarily formed by microbial methylation of inorganic divalent mercury (Hg(II)) under anoxic conditions. Recent evidence, however, points to the production of MeHg also in oxic pelagic waters, but the magnitude and the drivers for this process remain unclear. Here, we performed a controlled experiment testing the hypothesis that inputs of terrestrial dissolved organic matter (tDOM) to coastal waters enhance MeHg formation via increased bacterial activity. Natural brackish seawater from a coastal area of the Baltic Sea was exposed to environmentally relevant levels of Hg(II) and additions of tDOM according to climate change scenarios. MeHg formation was observed to be coupled to elevated bacterial production rates, which, in turn, was linked to input levels of tDOM. The increased MeHg formation was, however, not coupled to any specific change in bacterial taxonomic composition nor to an increased abundance of known Hg(II) methylation genes. Instead, we found that the abundance of genes for the overall bacterial carbon metabolism was higher under increased tDOM additions. The findings of this study may have important ecological implications in a changing global climate by pointing to the risk of increased exposure of MeHg to pelagic biota.

Flocculation is a widely utilized separation technique in colloid chemistry, the chemical industry, and wastewater treatment. However, its application in microalgal biomass production and downstream processing remains limited. Biomass harvesting represents a significant cost factor in large‐scale microalgae production, with the separation of biomass from the liquid medium accounting for up to one‐third of total production expenses. The use of flocculants as a pre‐treatment step has emerged as a promising approach to reducing these costs. Laboratory‐scale flocculation is commonly employed to optimize flocculant dosage and assess strain‐specific flocculation efficiencies. Meanwhile, pilot‐scale flocculation, when applied before centrifugation, provides critical insights into the applicability of specific flocculant–strain combinations and their impact on yield and biomass quality. Numerous studies have investigated the flocculation behavior of various microalgal strains using a wide range of chemically distinct flocculants at the laboratory scale. This review highlights recent advancements in microalgal flocculation as a pre‐centrifugation strategy and outlines future perspectives for achieving cost‐effective, large‐scale microalgal biomass production as a globally viable resource.

Green microalgae are widely used as model organisms in ecotoxicology due to their sensitivity to environmental stressors and their critical role in aquatic ecosystems as primary producers at the bottom of the food web. Pulse-Amplitude Modulated (PAM) chlorophyll fluorometry is a non-destructive, rapid and informative method for assessing photosynthetic efficiency and culture health, particularly through parameters such as the maximum photochemical activity of PSII (F_v/F_m) and effective PSII activity (Φ_PSII). Despite the growing number of studies utilizing PAM as an indicator rather than as a direct tool to evaluate microalgal stress responses, there remains a lack of standardized, accessible data for these key photosynthetic indicators. In this review, we analyze 38 sources, including 35 original research articles and 3 foundational references, to compile and compare reported values of F_v/F_m and Φ_PSII across various green microalgae species exposed to a wide range of chemical and environmental stressors. We highlight species-specific differences in sensitivity, identify underrepresented contaminants such as ionic liquids and artificial sweeteners, and emphasize the need for systematic numerical reporting in future research. PAM is an excellent and reliable technique for rapidly assessing culture health of green microalgae and their photosynthetic performance in various culture conditions and the vast array of chemical and physical stressors.