Impact of aquaculture mode on harmful dinoflagellate dynamics in abalone farming

Although aquaculture areas are believed to be more susceptible to harmful algal blooms (HABs), which cause significant ecological damage and economic losses, the harmful dinoflagellate communities that occur at different stages of abalone aquaculture remain unknown, which hinders the control of HABs in its culture zones. In this study, we curated a comprehensive internal transcribed spacer (ITS) database for dinoflagellates (DinoSeq) and employed high-throughput sequencing to examine the community structure of harmful dinoflagellates across various stages of abalone aquaculture. Over the course of 1 year, we conducted 28 sampling voyages to assess the temporal dynamics of these communities under two distinct aquaculture modes in China: continuous aquaculture in Zhangpu and relay aquaculture in Lianjiang. Network analysis revealed variations in harmful dinoflagellate communities across the different stages of abalone aquaculture. Analysis of similarities showed that these variations were more strongly correlated with the aquaculture stage than with seasonal changes. Redundancy analysis showed that dissolved oxygen was the primary environmental factor. Compared with the continuous farming mode, the abundance of harmful dinoflagellates in the relay aquaculture mode exhibits a stronger correlation with the farming stage, with a higher contribution of deterministic processes to community assembly. As representative harmful dinoflagellate species, Alexandrium pacificum and Karenia mikimotoi are more abundant under relay aquaculture mode according to qPCR results. Furthermore, A. pacificum is the dominant species in both farming systems. Our findings provide a deep understanding of the response of harmful dinoflagellates to different aquaculture modes and the selection of abalone aquaculture mode.