Marine sinking particles serve as hotspots for microbial colonization and activity, with diverse microbes co-consuming particulate organic matter (POM) to recover essential nutrients. However, the interaction patterns between such diverse and complex microbial communities and its possible impact on the marine biological carbon pump (BCP) remains unclear. Here we analyze snapshots of microbial community composition on marine particles with different particle sizes collected during the Malaspina 2010 Expedition and found that the diversity of particle-attached microbial communities and microbial networks stability showed a negative transition pattern as a function of particle size. Large particles harbor low complexity microbial networks and less microbial diversity and have a low abundance of carbon mineralization genes due to strong homogeneous selection and weak dispersal limitation lead to ecological overlap of large particle-attached microbes, enhancing the negative interspecies interactions proportion and exclude other species. Weak dispersal limitation leads to the detaching of microbes from fast-sinking particles also further intensifying the loss of microbial diversity. Based on the ecological pattern of negative microbial interaction and loss of microbial diversity within and between particle communities, we proposed the hypothesis of "large particle eutrophication" and demonstrated the dynamic ecological selection strategy of particle-attached microbial communities during particle export. Our hypothesis of "large particle eutrophication" highlights the important but underestimated role of particle-attached microbial interactions in determining the dynamics of particle-associated community composition. Future studies linking microbial interactions to the efficiency of the biological carbon pump, with a focus on physiological and ecological processes of individual particle, will be important for understanding the microbial interactions involved in particle degradation across different ages and/or sources.
 

Marine sinking particles,bacterial community composition,networks stability,microbial interactions