Molecular Microbiology Research 2024, Vol.14, No.3, 131-140 http://microbescipublisher.com/index.php/mmr 133 3.2 Nutrient recycling and mineralization Nutrient recycling and mineralization are critical processes in aquatic ecosystems, ensuring the availability of essential nutrients for primary production. Microbial mineralization of organic compounds, such as lignin and cellulose, is essential for carbon recycling in food webs (Vesamäki et al., 2022). In coral reef ecosystems, microbial processes are central to the transformation and recycling of DOM, which acts as a key currency in nutrient cycling and ecosystem stability (Nelson et al., 2022). The presence of specific microbial taxa, such as Dechloromonas and Pseudomonas, in benthic environments further underscores the role of microbes in nutrient cycling, particularly in the presence of stressors like E. coli (Gu et al., 2021). These microbes contribute to the biogeochemical balance by mediating the turnover of nitrogen and other essential elements. 3.3 Microbial enzymes and their functions Microbial enzymes are pivotal in the decomposition process, facilitating the breakdown of complex organic molecules into simpler compounds that can be assimilated by other organisms. In the decomposition of fish tissues, for example, the presence of hemolytic toxin genes in Aeromonas veronii suggests that these enzymes play a role in host cell lysis during early stages of decomposition (Lobb et al., 2020). Similarly, in oligotrophic streams, the performance of fungal decomposers, including their respiration, biomass accrual, and sporulation rates, is influenced by the quality of leaf litter, which in turn affects the enzymatic activity involved in decomposition (Pérez et al., 2021). The enzymatic capabilities of microbial communities in the Black Sea's sulphidic zone also highlight their role in organic matter degradation, particularly under anoxic conditions where streamlined microorganisms like Parcubacteria and Woesearchaeota exhibit high activity (Suominen et al., 2019). 4 Impact on Water Quality 4.1 Removal of organic pollutants Microorganisms are essential in the degradation and recycling of organic pollutants in aquatic systems. They naturally control the flux of nutrients and degrade anthropogenic contaminants, thereby maintaining the ecological balance (Ribeiro et al., 2019). The use of high-throughput molecular technologies has shown that microbial communities can respond to extreme pollution conditions, such as oil spills, by altering their structure and function to degrade pollutants more effectively (Michán et al., 2021) (Figure 1). Additionally, metagenomic approaches have revealed new metabolic pathways in microbes that are crucial for the breakdown of organic pollutants, further highlighting their importance in water quality management (Grossart et al., 2019). 4.2 Reduction of eutrophication Eutrophication, caused by excessive nutrient inputs, leads to harmful algal blooms and oxygen depletion in water bodies. Microbial communities play a significant role in mitigating eutrophication by participating in nutrient cycling processes. For instance, bacteria and archaea are involved in nitrogen cycling, which helps in the removal of excess nutrients from the water (Sehnal et al., 2021). The presence and diversity of microbial communities can serve as bioindicators for monitoring eutrophication levels and implementing timely interventions (Sagova-Mareckova et al., 2020). Moreover, submerged macrophytes recruit unique microbial communities that drive functional zonation, aiding in the efficient conversion of nutrients and reducing the risk of eutrophication (Zhu et al., 2021). 4.3 Maintenance of oxygen levels The maintenance of oxygen levels in aquatic systems is vital for the survival of aerobic organisms. Microbial communities contribute to this by participating in oxygen production and consumption processes. Photosynthetic microorganisms, such as cyanobacteria, produce oxygen as a byproduct of photosynthesis, thereby replenishing oxygen levels in the water (Sehnal et al., 2021). Conversely, microbial respiration processes consume oxygen, but the balance between these activities is crucial for maintaining stable oxygen levels. The resilience of microbial communities in adapting to environmental changes ensures the continuous regulation of oxygen levels, even under stress conditions (Mamidala et al., 2021). Understanding the dynamic relationship between aquatic microbiota and their environment is essential for monitoring and managing oxygen levels in aquatic ecosystems (Michán et al., 2021; Sehnal et al., 2021).
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