Correction: Research progress on biot-mercury interactions in the periphyton: environmental processes, ecological effects and restoration applications

Mercury (Hg) is a widespread global pollutant, found throughout the natural environment, posing a health threat to millions of people worldwide. In 2010, the World Health Organization identified mercury as one of the top ten chemicals of major concern for public health (Zhang, 2022). Once mercury enters the ecosystem, its extremely low biodegradability means it can remain in environmental media for decades, accumulating over time and causing irreversible organ damage and cognitive impairments in those exposed. Mercury naturally occurs in the Earth's crust and is mainly released into the surface environment through natural geological processes such as rock weathering and volcanic eruptions. Human activities are also the primary source of mercury release, with key contributors including the steel, cement, gold, non-ferrous metal smelting, chlorine-alkali industries, and sectors directly involved in mercury production (Pavithra et al., 2023).Mercury is an element that exists in multiple forms, commonly known as quicksilver. It can be classified into three main types: elemental mercury (metal), inorganic mercury (such as the highly toxic mercury chloride), and organic mercury (such as the extremely toxic methylmercury). Different forms of mercury exhibit significant differences in toxicity and can severely damage critical human organs, including the central nervous system, digestive tract, immune system, lungs, kidneys, skin, and eyes. In aquatic systems, mercury exists in organic, inorganic, and elemental forms (Zhang, 2023). In the atmosphere, mercury is mostly found in its elemental form, with divalent mercury being the most common oxidation state of the elemental mercury. Mercury is typically released into the environment in its inorganic form, while methylmercury (MeHg) is one of the most neurotoxic substances and predominates in fish. This occurs because inorganic mercury is transformed into methylmercury through various biological and abiological processes in aquatic environments. While microbial methylation is the dominant pathway, abiological processes, such as the photochemical degradation of methylmercury, also significantly influence its environmental cycling and persistence (Donovan et al., 2016). Thus, mercury methylation is a crucial step in the mercury environmental cycle, and it determines the toxicological consequences of mercury release (Wu et al., 2024). Methylmercury has a higher bioavailability than both elemental and inorganic mercury, and it can diffuse from cells and be adsorbed by benthic organisms. These benthic organisms can include zooplankton, small fish, and other small organisms or nonliving entities. Through the food chain, mercury accumulates biologically and is passed on to predators at the top of the food chain (Donadt et al., 2021;Minet et al., 2022). Additionally, studies on wetlands have shown that the production and accumulation of methylmercury are significantly present in floating mats of large aquatic plants (such as Eichhornia crassipes) and waterlogged forest soils in tropical regions (Murphy and Guentzel, 2022).Compared to other metals, mercury is much harder to degrade in ecosystems. Remediation of mercury will typically involve processes like immobilization or removal (Mu, 2023). Techniques such as oxidation, reduction, and adsorption can remove mercury from contaminated sites and also convert harmful mercury into less toxic forms (Veeraswamy et al., 2024). Therefore, understanding the mechanisms behind mercury production and accumulation is crucial. It is urgent to find safe and effective ways to control mercury pollution, protecting both the environment and human health.Periphyton is a microbial community made up of various organisms, including algae, bacteria, fungi, animals, and both organic and inorganic debris. These organisms attach together to organic or inorganic substrates (Zhao et al., 2023), held together by extracellular polymeric substances (EPS) secreted by the matrix. EPS is widely present in various aquatic systems and forms the basis of the food web in aquatic ecosystems. As the main component of surrounding organisms, EPS is a crucial source of carbon and energy that helps maintain the integrity of the periphyton community and enhances microbial activity, including that of mercury methylating bacteria (Xiang et al., 2022). Crucially, the same EPS matrix that supports the periphyton community also governs its interaction with environmental contaminants.Periphyton, as a bioaccumulator or a sensitive receptor of environmental pollutants (Shahzad et al., 2025), has been shown to play a critical role in binding and adsorbing heavy metals due to the various functional groups (such as carboxyl, phospho, amine, sulfhydryl, hydroxyl, etc.) in its EPS (Wang L. et al., 2020).Given the escalating severity of mercury pollution, understanding its biogeochemical cycling in critical environmental compartments is paramount. Periphyton, a ubiquitous and complex microbial-algal consortium, represents such a compartment where the fate of mercury is decisively shaped. This community not only efficiently concentrates and adsorbs mercury ions via its extracellular polymers but also hosts a dynamic microbial consortium that actively transforms them. For instance, sulfate-reducing bacteria (SRB), known mercury methylators found within periphyton, see their composition and methylation rates influenced by the community's nutrient status (Gambardella et al., 2025;Leclerc et al., 2021). Interestingly, under certain conditions, methanogens can emerge as the primary methylators, working synergistically with other microorganisms in this process (Lei et al., 2021). This intricate interplay between adsorption and microbial transformation within periphyton establishes it as a pivotal micro-ecosystem governing mercury speciation, bioavailability, and risk in aquatic environments.As the economy and society continue to develop, the increasing emissions of mercury and its compounds from human activities are making mercury pollution more severe. Periphyton, located at the lowest trophic level in the ecosystem, is a highly dynamic micro-ecological environment composed of algae, archaea, bacteria, fungi, microorganisms, and organic and inorganic substances. The extracellular polymers it secretes not only concentrate and adsorb mercury but also have a high potential for mercury methylation. As primary producers in the ecosystem, periphyton serves as the primary food source for small consumers, contributing more than half of the primary production in the ecosystem. By studying the interactions between periphyton and mercury from a microbial ecology perspective, we can gain further insight into the biological mechanisms and clarify how periphyton adsorbs and transforms different bioavailable forms of mercury. The high methylation potential within periphyton and its important role in the food chain of aquatic ecosystems highlight its significance for research on and removal of methylmercury pollution. Therefore, further understanding of the migration and transformation mechanisms of mercury under the influence of periphyton is essential for mercury pollution prevention and control.To establish a robust evidence base for this review, a systematic literature search was conducted focusing on studies from the year 2000 onward. Primary databases, including Web of Science and Google Scholar, were utilized with targeted keywords such as "mercury biosorption," "periphyton," "extracellular polymeric substances (EPS)," alongside specific terms for "bacteria," "fungi," and "algae." The synthesis prioritizes peer-reviewed studies that provide quantitative adsorption capacities and elucidate binding mechanisms, which directly inform the following discussion structured around the three key microbial constituents of periphyton: bacteria, fungi, and algae.The mercury biosorption capability of periphyton is largely dependent on the chemical makeup of its microbial constituents and their extracellular polymeric substances (EPS). Cell surfaces and the EPS matrix are rich in polysaccharides, proteins, and lipids, which offer a multitude of functional groups including amino, carboxyl, and thiol groups for effective complexation with metal ions like mercury. This structural and compositional diversity underpins the high affinity and selectivity of periphyton for various mercury species, forming the basis for its remarkable adsorption capacity. This is corroborated by research indicating that the EPS matrix is rich in these components and displays significant biological activity, with its organic components containing diverse metalbinding functional groups such as amino, carboxyl, thiol, phosphate, and sulfhydryl (Balíková et al., 2022). Since the 21st century, the bioadsorption potential of microorganisms for metals has become a focus of attention due to its broad applicability and environmental adaptability (Zhou et al., 2023). Consequently,The selection of bioadsorption materials for mercury has mainly focused on algae, bacteria, and fungi.Compelling evidence exists for bacterial biosorption, which often hinges on specific functional groups and demonstrates high remediation potential. Studies on bacteria have shown that the thiol group (-SH) on the surface of sulfate-reducing bacteria binds with Hg(II), promoting the adsorption and methylation process of Hg(II) by these bacteria (Thomas et al., 2020). Notably, Research on mucilaginous Bacillus as a that it has adsorption for Hg(II), with a adsorption of et al., 2022). In studies the adsorption of Hg(II) by Bacillus the was to the adsorption of on Hg(II) at the et al., 2023). understanding of environmental further how the of ions in different the mercury adsorption of Bacillus and sulfate-reducing bacteria et al., 2021). the broad applicability of this the and extracellular polymers of bacterial that the on the surfaces and EPS of these Bacillus and have potential as for mercury (Zhao et al., from like exhibit adsorption and Studies on have shown that can adsorb et adsorption at with a of et al., 2020). et that and its potential in et al., biosorption is by significant capacities and in its high mercury due to its functional with adsorption under et al., 2024). Additionally, et found that its mercury in and its applicability in et al., bioadsorption of mercury periphyton is by a of mechanisms, by the diverse functional groups within extracellular polymeric substances (EPS) and on microbial et al., et al., 2020). processes include chemical complexation with carboxyl, hydroxyl, and thiol and which synergistically to mercury adsorption of periphyton mercury typically occurs in key extracellular adsorption and accumulation The adsorption the surface and The is an process where metal ions are the via chemical This is by significantly but is crucial for the of in periphyton have which are into and The is composed of a made up of multiple of including polysaccharides, and while the mainly of The composition of the on the of the The extracellular is rich in extracellular mainly of and (such as and released by For the of like polysaccharides, proteins, and et al., 2021). These organisms provide and functional groups such as amino, hydroxyl, phosphate, and which can with metal an important role in the adsorption of mercury ions by the of and which in with heavy metals et al., 2022). that the of in the periphyton community in the of its a large specific surface This for the of functional that these groups can efficiently to the the with metal that typically of heavy metal ions can be on the surface of cells et al., 2022). This adsorption process is mainly to the extracellular (EPS) commonly found on the surface of periphyton and the of various functional such as phosphate, carboxyl, thiol, and in the the adsorption functional groups can release through on to adsorb metal functional groups on other with metal ions through the of to establish adsorption et al., chemical adsorption of periphyton for mercury (Hg) is a complex the of extracellular polymers (EPS) in the microbial surface functional and polymers are the components of mercury composed of polysaccharides, proteins, and The functional groups for mercury adsorption mainly include and which into under conditions, Hg(II) via and forming or of high affinity for and the of the containing thiol groups (-SH) in EPS (such as and directly Hg(II), forming In the level enhances the to with Hg(II) through groups to the chemical complexation and mechanisms adsorption a for mercury by This process occurs through and While typically in binding to chemical in biological systems, studies its significant by research on that methylmercury removal via with a of and within that groups and this through and et al., This chemical of mercury adsorption by periphyton and the role of functional in Science the critical role that the of EPS in sites for the of mercury, the and forming an of the adsorption of the adsorption mechanisms in is by a of environmental the of the EPS matrix which these mechanisms, can be influenced by The key governing adsorption and transformation are in of the is a key in the adsorption of heavy metals by It not only the surface complexation sites of the but also significantly the chemical and of the heavy metal In the of for Hg(II) et al., functional groups like amino, carboxyl, and significantly of mercury by bacteria, fungi, and in energy and process can be for or exhibit a for on the bacterial adsorption for Hg(II) found that at low and in the of Hg(II) adsorption its from to at at higher the in these were less The also that the was to the adsorption of Hg(II), that the adsorption of Hg(II) is by the surface of the For the from to the adsorption of Hg(II) In the of Hg(II) as such as and further its state et al., adsorption of Hg(II) is highly dependent on For instance, increasing Hg(II) as the from to with under to et al., This is by the surface under the surface is a that Hg(II) et al., 2020). As the of functional groups carboxyl, a metal was as a for Hg(II) et al., it was found that Hg(II) adsorption as the from to The that under the surface a which is for the adsorption of Hg(II) of the bioadsorption be an important for the mechanisms of microorganisms in metal mechanisms are to be influenced by as the processes for bioadsorption are within the of and chemical The of significantly with the of For instance, in studies of as a for Hg(II), the bioadsorption to be largely a broad a in binding was at et al., In studies on often a For instance, the biosorption of Hg(II) has been to be an where the adsorption is by as by et al., directly adsorption environmental potential a influence on mercury by periphyton through its control over Mercury the process of forming neurotoxic methylmercury (MeHg) from inorganic mercury, is by potential in such as soils and in directly the microbial and biogeochemical that this that can significantly key the oxidation of into under higher conditions, which sulfate-reducing bacteria and methylation et al., 2022). the in under these and The role of is further by studies that bioavailability and methylation in as the of et al., influence of on methylation is ecosystems. In and bacteria are identified as primary methylators, with with (Zhao et al., 2024). significantly the composition of methylating microbial For in mercury methylation under specific how the dominant methylators in different et al., by governing the microbial synthesis of potential as a pivotal environmental the speciation, and adsorption of mercury within periphyton a ubiquitous microbial in aquatic systems et al., represents a complex consortium of algae, bacteria, and other microorganisms in a matrix of extracellular polymeric substances (EPS). This the and of this critical community under mercury mercury periphyton significant in their and chemical activities and 2022). The mainly as certain or to their processes and within the The of mercury on the and of periphyton directly from the toxicity of mercury and its Research that mercury the of and its also as mercury (Zhao et al., 2021). of in a environment that both mercury and pollution to a in the from the of pollution et al., and mechanisms of periphyton are to the and of in the environment to mercury exhibit under mercury with their Studies have that are to high of mercury their and are significantly the mercury toxicity For a high to mercury the of mercury methylation et al., the to in containing mercury Research demonstrates that under Hg(II) to elemental via both surface adsorption and further it into such as and These mechanisms its persistence in aquatic et al., 2022). In the of at higher mercury is severely and its is Therefore, under mercury pollution, and and are influenced by their to mercury and complex the influence of mercury, the composition of cells the of certain while other components remain For and remain under with significant in the of proteins, and exhibit to and research (Wu et al., 2023), as mercury the production a with mercury the level of accumulates a highly significant while the significantly and a on mercury These that the dynamic of component is to and to with environments. Research that the demonstrates under mercury (Hg) Hg(II) is activities et al., Mercury by binding to functional groups on the surface and the adaptability to environments. involve not only but also of mercury as mercury but the significantly between their of these has become an important research in this to the conducted by et al., mercury the of within periphyton that mercury significantly the photochemical of to a of by a in photochemical indicating of the under conditions, cells a by to a of energy and further damage to the that while mercury not the or of key such as and its were in compositional of extracellular polymeric substances (EPS). in the of the in the EPS of a potential of to heavy metal This the complexation and of mercury ions by functional groups and within EPS et al., play a key role in the biogeochemical cycling of mercury, in its adsorption and For instance, adsorbs Hg(II) from Studies have shown a significant between mercury in cells and various including activity, and et al., 2023). This how mercury and how this accumulation can their their on the a that mercury organic has been shown to mercury methylation under in the of This is because components are to the methylation in mercury or in and microbial the in sulfate-reducing bacteria has been identified as a key in to mercury and methylation under conditions, the influence of on mercury (Wang et al., also the of which in elemental cycling in Research that to high production in with a significant from in to These of diffuse from the into and (Zhao et al., high can influence and bioavailability in the the of methylmercury (MeHg) pollution, in systems, are being For instance, the potential for methylmercury production in from plants can be by elemental This and by mercury bioavailability and through bioavailable Hg(II) to and promoting the of with the et al., 2024). This a to pollution, which be for by Mercury transformation by methylation by microorganisms, bacteria, is the most common for methylmercury and et al., et al., 2022). bacteria involved in mercury sulfate-reducing bacteria (SRB), bacteria, bacteria, and other and et al., et al., 2022). The of methylmercury is influenced by various environmental which the and of different methylating microbial such as and that specific For instance, sulfate-reducing bacteria typically and methylation in environments. In is bacteria and methanogens become more methylators, with their being influenced by and the for like and the of organic further the bioavailability of Hg(II) to these microorganisms et al., et al., et al., 2021). the complex and interplay of these environmental further research is to clarify the and methylation mechanisms these microbial studies have that sulfate-reducing bacteria (SRB), bacteria and bacteria are the key microorganisms for mercury methylation. these over the which is essential for mercury methylation. The within this a functional are to those of involved in to et al., 2020). main role is to efficiently convert the toxic Hg(II) into the highly toxic and the a which is for the of the et al., natural the microbial methylation of mercury is by the microbial of These processes are and the dynamic of in the environment and a critical role in the global mercury The of degradation via photochemical and via microbial transformation and with microbial transformation being degrade through which can be into major and oxidation et al., 2020). The is by and sulfate-reducing bacteria (SRB), which complex biological oxidation to convert into less toxic Hg(II) is with the and by microorganisms et al., The can efficiently the more Hg(II) and the further Hg(II) ions into the highly This process not only the toxicity of but also the of from cells and its into the atmosphere, effective mercury release et al., are the most group in mercury methylation with their to the conditions, energy through reduction, and which the methylation of The key the group to through such as the in the methylmercury The with the is due to the high of the in like where the is higher than in other the methylation et al., are important group of bacteria, as essential as such as methylation through the The secreted by to increasing mercury Studies have shown that in the of production by with its directly to mercury ions et al., of from methylation rates to a highly methylating and play a significant role in the environment as major methylators of The is crucial for inorganic into methylmercury a key process in microbial environmental on for by the a has that the group for this methylation in methanogens is directly by the of a from the utilized by sulfate-reducing and bacteria et al., 2024). The the and methylation. methanogens due to for common such as production by In the of the in is significantly with in Studies found that mercury methylation was by a et al., but highly by These that than are the primary microorganisms in ecosystems and are with the most common mechanisms mainly include and photochemical Studies have shown that bacteria, such as degrade into and via the by the The further to the et al., 2022). In aquatic organic under through have shown that in with high the of can from to et al., et al., are a common in For it was that in in Science and trophic through research has shown that and to higher in the 2021). This is due to extracellular polymers by algae, which are rich in thiol groups of adsorbing mercury while microorganisms, forming a for mercury methylation (Lei et al., et al., 2021). Additionally, the of and microbial to the of microorganisms and mercury bioavailability, promoting mercury methylation et al., et al., of on mercury transformation significant environmental inorganic mercury methylation but in multiple species, with degradation rates to those of et al., This that in specific together with their extracellular and bacterial can as the that different aquatic functional role of periphyton in the mercury is between that of a and a of methylmercury This is by environmental that for microbial functional groups and their as a of under environmental that is systems, where the of establishes and organic These for sulfate-reducing and bacteria, of which the essential The of this methylating consortium is further by key a low potential and which establish a for the community to a of in by such as or specific In these the community often bacteria that the such as species, which the of to This microbial process can be by the of and the for the by organic and serves as the governing the between these functional By for dominant microbial functional it the critical between methylation and This determines the periphyton matrix as a of production or The pivotal role of periphyton microorganisms in mercury migration and in Science et of microbial and microorganisms to environmental have significant as and These include microorganisms to mercury (Hg) remediation at contaminated often focus on mechanisms like the mercury which pivotal for microbial mercury and its biogeochemical cycling et al., 2020). microbial remediation of mercury diverse mechanisms, a of biosorption, and et al., interactions with mercury involve and the removal of mercury ions microbial functional groups from components and extracellular polymeric substances (EPS) and 2020). to the and of mercury by microbial These concentrate mercury, making it to further and are critical The bacterial is a of a for mercury This that the and of mercury. the which toxic inorganic Hg(II) to significantly less toxic elemental mercury to For organic mercury, the which it to Hg(II) for et al., an effective immobilization This process microorganisms the of from metal This and into forms et al., diverse microbial both and are to and for mercury pollution that large species, such as and can also be to remove mercury from mercury with different and were in the and the was conducted over a The that significant mercury removal at these the that species, an for mercury of up to with a as high as This demonstrates that has potential in the remediation of aquatic mercury pollution et al., et the toxic of mercury on where was significantly as low as et al., small floating aquatic plants are as a key research in this to their and remarkable accumulation Research that can remediation For instance, and that and not only production to but also mercury and the role of in pollution et al., 2024). In species, et that mercury accumulation in high this under conditions, et al., 2023). on a in with heavy metal removal at for et al., 2020). potential for mercury group its mercury and a removal of up to Notably, plants and under mercury the of aquatic in mercury pollution et al., a ubiquitous microbial-algal consortium, and its extracellular polymeric substances (EPS) play pivotal and in the environmental fate of mercury, as and The functional groups of EPS to and In the within periphyton, the microbial mercury methylation and through the and methylmercury, which is within and with can in the food increasing and health the critical is to the quantitative between these interactions and the mercury This the of in dynamic systems and targeted with the remediation potential of in natural systems such as wetlands and These will provide more and for global mercury pollution