Parab Ashutosh Shankar, Ghose Mayukhmita, Manohar Cathrine Sumathi
Biological Oceanography Division, CSIR- National Institute of Oceanography, Dona Paula, Goa, India.
Biological Oceanography Division, CSIR- National Institute of Oceanography, Dona Paula, Goa, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India.
Mar Environ Res. 2025 Sep;210:107292. doi: 10.1016/j.marenvres.2025.107292. Epub 2025 Jun 16.
The eastern Arabian Sea (EAS) experiences seasonal nutrient availability and productivity shifts driven by the Indian monsoon, influencing microbial contributions to biogeochemical cycles. This study explores carbon, nitrogen and sulfur cycling using metagenome-assembled genomes (MAGs) from water samples collected at chlorophyll maxima (C-Max) depths during non-monsoon and monsoon seasons. A total of 49 high-quality MAGs were reconstructed from 12 metagenomic samples, including four novel lineages from the phyla Pseudomonadota and Bacteroidota. These MAGs revealed distinct seasonal shifts in microbial composition and function. During the non-monsoon season, microbial communities dominated by Idiomarina and Marinobacter showed increased gene abundance for C1 compound metabolism, nitrogen cycling and sulfur oxidation, processes essential for managing climate-active gases such as carbon dioxide (CO) and nitrous oxide (NO), while also preventing toxic sulfide accumulation. In contrast, monsoon conditions enhanced organic matter influx, promoting nitrogen retention pathways driven by Sinimarinibacterium and Oleibacter, raising concerns about potential nutrient buildup and localized hypoxia. Despite seasonal variations, functional redundancy ensured the stability of nutrient cycling processes. PERMANOVA analysis (p < 0.001) confirmed that microbial functional gene distribution was primarily shaped by taxonomic structure, with genus-level composition playing a dominant role. The study highlights microbial adaptability and resilience, ensuring ecosystem stability in the dynamic EAS environment. Understanding microbial processes at C-Max depths has enhanced our understanding of biogeochemical cycling in the EAS. Although focused on oxygenated depths, these findings offer insights relevant to microbial functions in the OMZ, reflecting the distinct environmental conditions of EASs.
阿拉伯海东部（EAS）受印度季风驱动，经历季节性的养分可用性和生产力变化，影响微生物对生物地球化学循环的贡献。本研究利用在非季风季节和季风季节叶绿素最大值（C-Max）深度采集的水样中的宏基因组组装基因组（MAGs），探索碳、氮和硫的循环。从12个宏基因组样本中重建了总共49个高质量的MAGs，包括来自假单胞菌门和拟杆菌门的四个新谱系。这些MAGs揭示了微生物组成和功能的明显季节性变化。在非季风季节，以嗜压嗜盐菌属和海杆菌属为主的微生物群落显示出C1化合物代谢、氮循环和硫氧化的基因丰度增加，这些过程对于管理诸如二氧化碳（CO）和一氧化二氮（N₂O）等气候活性气体至关重要，同时还能防止有毒硫化物的积累。相比之下，季风条件增强了有机物的流入，促进了由中华海杆菌属和油杆菌属驱动的氮保留途径，引发了对潜在养分积累和局部缺氧的担忧。尽管存在季节性变化，但功能冗余确保了养分循环过程的稳定性。PERMANOVA分析（p < 0.001）证实，微生物功能基因分布主要由分类结构决定，属水平的组成起主导作用。该研究突出了微生物的适应性和恢复力，确保了动态EAS环境中的生态系统稳定性。了解C-Max深度的微生物过程增强了我们对EAS中生物地球化学循环的理解。尽管该研究聚焦于含氧深度，但这些发现为缺氧区微生物功能提供了相关见解，反映了EAS独特的环境条件。
