Deprivation of protection for aquatic hyphomycetes is disturbing because they are key players in freshwater ecosystems across the globe. To attain a more holistic conservation paradigm for biodiversity in freshwaters, it is necessary to broaden our ecological perception of microfungi, mainly in aquatic hyphomycetes. A considerable groundwork still needs to be accomplished in progressing towards conserving aquatic hyphomycetes. Overcoming the paucity of information regarding the rare and endangered species, biogeography and above all, a global biodiversity database, would be a significant contribution in the initiation of an overarching conservation strategy for aquatic hyphomycetes. Being aware that the biodiversity decline in freshwaters is alarming, here we seek to explore why biodiversity data of aquatic hyphomycetes are missing. This article closely examines the threats to the biodiversity of aquatic hyphomycetes and freshwater ecosystems. Moving forward, we advocate a structured approach to gaining a thorough understanding to embrace aquatic hyphomycetes biodiversity into the conservation strategies. Including aquatic hyphomycetes in the conservation objectives may attract more funding opportunities for global surveys to initiate a fungal inclusive conservation era. Fungal conservation ventures can profit from interdisciplinary collaborations and cutting-edge science and technology, leading to informed decision making for biodiversity assessment and management.

Aquatic fungi, especially aquatic hyphomycetes, are promising bioindicators for assessing the health and integrity of freshwater ecosystems. Their sensitivity to a wide range of environmental stressors, coupled with their essential roles in ecological processes such as organic matter decomposition and nutrient cycling, establish them as important tools for monitoring ecological disturbances. By examining aquatic fungal responses at various biological levels—from molecular mechanisms to ecosystem dynamics—ecologists are able to uncover valuable information about the functioning of freshwater habitats. Despite challenges such as the complexity of fungal communities and knowledge gaps, the prospects for using aquatic fungi as bioindicators are encouraging. Advancing research and technological innovations are expected to refine our understanding of the ecological roles of aquatic fungi and enhance their use in detecting impacts on freshwater ecosystems. The inclusion of these organisms in environmental monitoring programmes alongside other bioindicators could significantly improve our ability to detect and mitigate the effects of both natural and anthropogenic environmental changes, leading to more effective conservation strategies.

Co-contamination of freshwaters by nanoplastics (NPs; ≤ 1 μm) and metals is an emerging concern. Aquatic hyphomycetes play a crucial role as primary decomposers in these ecosystems. However, concurrent impacts of NPs and metals on the cellular and physiological activities of these fungi remain poorly understood. Here, the effects of environmentally realistic concentrations of two types of polystyrene (PS) NPs (bare and -COOH; up to 25 μg L^-1) and copper (Cu; up to 50 μg L^-1) individually and all possible combinations (NPs types and Cu) on Articulospora tetracladia, a prevalent aquatic hyphomycete, were investigated. Endpoints measured were intracellular reactive oxygen species accumulation, plasma membrane disruption and fungal growth. The results suggest that functionalised (-COOH) NPs enhance Cu adsorption, as revealed by spectroscopic analyses. Notably, NPs, Cu and their co-exposure to A. tetracladia can lead to ROS accumulation and plasma membrane disruption. In most cases, exposure to treatments containing -COOH NPs with Cu showed greater cellular response and suppressed fungal growth. By contrast, exposure to Cu individually showed stimulatory effects on fungal growth. Overall, this study provides novel insight that functionalisation of NPs facilitates metal adsorption, thus modulating the impacts of metals on aquatic fungi.

Nanoplastics (NPs) are an emerging concern in freshwater ecosystems due to their persistence and potential to interact with persistent pollutants, such as metals. These combined stressors threaten freshwater ecosystems functioning, where leaf litter decomposition, primarily driven by aquatic hyphomycetes, supports energy transfer to higher trophic levels. A microcosm experiment was conducted to assess the joint impacts of polystyrene NPs (bare and carboxylated) at environmentally relevant (0.25 and 2.5 µg L⁻¹) and elevated (25 and 250 µg L⁻¹) concentrations in reference and metal-polluted stream waters. Fungal biomass, aquatic hyphomycetes sporulation and community composition, microbial leaf litter decomposition, as well as invertebrate feeding behaviour were quantified. Carboxylated NPs showed greater aggregation and surface alterations than bare NPs. Fungal biomass and sporulation declined significantly at 2.5 µg L⁻¹, with carboxylated NPs exerting stronger effects. Non-metric multidimensional scaling (NMDS) revealed clear shifts in fungal community structure across two water types (reference and metal-polluted) and NP concentrations. Metal pollution alone reduced decomposition by 17 %, with reductions reaching up to 24 % when combined with NPs, particularly carboxylated NPs. Invertebrate feeding was reduced by 27 % under metal pollution alone, with maximum inhibition (47 %) observed at the highest NP concentration, although NP type did not significantly alter feeding rates. Together, these results demonstrate that NPs, especially carboxylated forms, exacerbate the ecological impacts of metal pollution, impairing microbial processes and detritivore feeding. These findings underscore the importance of considering NPs surface chemistry and multiple stressors interactions in ecological risk assessments of polluted freshwater systems.