Distinct adaptation strategies and functional potentials of abundant and rare prokaryotes across seasonal dynamics and long-term eutrophication in Xiangshan Bay.

Effects of coastal water eutrophication on prokaryotic communities have been intensively elucidated. However, an adaptation of abundant taxa (AT) and rare taxa (RT) of prokaryotes to long-term eutrophic conditions remains unclear. In this study, community compositions, co-occurrence patterns, assembly mechanisms, and functional potentials of AT and RT in a eutrophic bay were compared across four seasons. Alpha diversity indices of AT and RT exhibited opposite correlations with the eutrophication index. The community compositions of both AT and RT were significantly influenced by environmental factors, particularly temperature and nutrient availability. RT were observed to be more sensitive to eutrophication and showed stronger correlations with biotic factors. Both the assembly mechanisms of AT and RT were more strongly influenced by stochastic processes, but deterministic processes increased progressively in AT from spring to winter. The roles of AT and RT varied significantly in co-occurrence networks, with AT playing a more crucial role in spring and RT being more significant in winter. The functional potential of RT showed clearer seasonal patterns than AT, suggesting a more significant contribution of RT to functional redundancy. These findings highlight the divergence between AT and RT prokaryotes in response to eutrophication, enhancing our understanding of the mechanisms underlying microbial community succession in long-term eutrophic waters.