Microbial degradation of various types of dissolved organic matter in aquatic ecosystems and its influencing factors

Interactions between chemodiverse dissolved organic matter(DOM)and biodiverse microbes are governed by a myriad of intrinsic and extrinsic factors which are not well understood.Here,we update and bridge the gap of this interdisciplinary theme comprehensively.At an ecosystem level,aquatic ecosystems dominated by algae-sourced DOM(e.g.,eutrophic lake or coastal upwelling areas)harbor more biolabile DOM,such as directly assimilable monomers and readily hydrolysable biopolymers.However,other ecosystems prevailed by DOM supply from soil and vascular plants(e.g.,river or wetland)have more biorefractory DOM,such as low molecular weight(LMW)residue of aliphatic C skeletons and geopolymers.A variety of heterotrophic bacteria,archaea,fungi,phagotrophic protists,and even photoautotrophic phytoplankton shows genomic and/or culturing experimental evidence of being able to process a diverse type of organics.The various biodegradable organics have different chemical structures and chemical bonds such as carbohydrates,amino acids,proteins,lignins,lipids,carboxylic acids,humic acids,hydrocarbons,and nanoplastics.Meanwhile,bio-production of metabolism intermediates and/or biorefractory organics(e.g.,carboxyl-rich alicyclic molecules,CRAM)is observed despite general decay of bulk dissolved organic carbon(DOC)during bioassay experiments.In particular,emerging evidence shows that archaea contribute significantly to biomass in the marine mesopelagic zone and subsurface environments and their abundance often increases with depth in sediments.Furthermore,not only intrinsic factors(e.g.,DOM composition and structure),but also extrinsic ones(e.g.,sunlight and dissolved oxygen)play important roles in interplays between DOM and microbes.

海洋负排放的生态工程方案

在未来30~40年内实现“碳中和”目标已成世界范围内共识,但亟需全人类共同努力以应对日益严重的气候变化威胁.实现这一宏伟目标的基本途径,一是减少人为向大气排放的二氧化碳,二是增加碳汇或负排放,即从大气中去除二氧化碳.本文提出海洋负排放的生态工程方案,旨在呼吁加强利用海洋环境中的碳汇潜力,同时倡议建立一个多国共同参与的国际大科学计划,以促进海洋负排放相关技术途径与实施方案的研发,综合考虑驱动不同形式碳汇(无机/有机、生物/非生物、颗粒态/溶解态)的生态与生物地球化学过程和机制.本文重点关注旨在揭示生物泵(BP)、微型生物碳泵(MCP)、微生物诱导碳酸盐沉积(MICP)之间相互作用的变革性机制研究,特别是提高富营养化河口、低氧和缺氧水域、珊瑚礁生态系统以及水产养殖区的碳汇潜能.海洋负排放生态工程对实现碳汇并减轻环境压力具有重要意义.