Molecular Microbiology Research 2024, Vol.14, No.3, 131-140 http://microbescipublisher.com/index.php/mmr 132 and pollutant degradation, and assess the potential of microbial indicators for monitoring and managing water quality. Understanding the dynamic interactions between microbial communities and their aquatic environments is essential for developing effective strategies to preserve and enhance water quality in the face of ongoing environmental challenges. 2 Overview of Microbial Decomposers 2.1 Types of microbial decomposers In aquatic systems, the primary microbial decomposers are bacteria and fungi. Bacteria are often the main decomposers in the pelagic zones of lakes and oceans, where they act as primary mineralizers (Wurzbacher et al., 2014). Fungi, on the other hand, dominate the decomposition of organic matter in streams and wetlands, and they are also active in lakes (Wurzbacher et al., 2014). Aquatic hyphomycetes, a group of fungi, are particularly important in freshwater ecosystems for their ability to produce extracellular enzymes that break down complex molecules in leaf litter (Mariz et al., 2021). Additionally, microbial communities associated with submerged detritus often include a mix of autotrophic and heterotrophic microbes, such as algae, protozoa, and fungi, which interact to enhance decomposition processes (Kuehn et al., 2014). 2.2 Characteristics of aquatic microbes Aquatic microbes exhibit a range of characteristics that enable them to thrive in diverse environments. For instance, aquatic hyphomycetes can assimilate nutrients from stream water and immobilize them in decomposing leaf litter, thereby increasing its nutritional value for higher trophic levels (Mariz et al., 2021). The gut microbiome of freshwater isopods like Asellus aquaticus also demonstrates the complexity and robustness of microbial communities, with distinct microbiomes in different habitats and digestive organs. These microbes are closely related to lignocellulose degradation, highlighting their role in breaking down plant material (Liao et al., 2023). Furthermore, microbial eukaryotes in freshwater environments show high molecular diversity, with groups like Amoebozoa, Viridiplantae, and Cryptophyta being particularly diverse (Debroas et al., 2017). 2.3 Microbial diversity in aquatic environments The diversity of microbial decomposers in aquatic environments is vast and varies significantly across different habitats. For example, bacterial communities in freshwater, intertidal wetland, and marine sediments show distinct taxonomic compositions, with freshwater sediments having the highest diversity (Wanget al., 2012). Fungal communities also exhibit significant diversity, with different species playing central roles in decomposition processes. The interactions between fungi and bacteria can further influence microbial diversity and ecosystem functioning, as bacteria can promote fungal diversity and stimulate colonization (Baudy et al., 2021). Additionally, the necrobiome of decomposing fish reveals a strong succession of microbial communities, with specific bacteria dominating at different stages of decomposition (Lobb et al., 2020). This succession highlights the dynamic nature of microbial communities and their functional roles in nutrient cycling. 3 Mechanisms of Decomposition in Aquatic Systems 3.1 Breakdown of organic matter The breakdown of organic matter in aquatic systems is a fundamental process driven by microbial activity. Microbes, including bacteria and fungi, play a crucial role in decomposing both terrestrial and aquatic organic materials. For instance, bacteria from the family Burkholderiaceae have been identified as key decomposers of leaf litter and polystyrene in freshwater environments, highlighting their versatility in breaking down both natural and synthetic polymers (Vesamäki et al., 2022). Additionally, aquatic hyphomycetes are significant contributors to the decomposition of leaf litter in freshwater ecosystems, facilitating the turnover of organic matter and supporting detrital food webs (Pimentão et al., 2019). In marine environments, diverse microbial communities, including Cloacimonetes and Marinimicrobia, are responsible for degrading dissolved organic matter (DOM) and protein extracts, particularly under anoxic conditions (Suominen et al., 2019).
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