Seasonal organization of tintinnid community by temperature preference and LOD size-class in a subtropical brackish embayment

Abstract

Most annual studies of tintinnid and phytoplankton in coastal habitats are influenced by alien species introduced by water masses exchange, and therefore cannot be used as direct evidence for exploring the mechanism of annual succession in indigenous community. For brackish communities, very limited annual studies exist because of the difficulty of conducting stable sampling in the transition between freshwater and seawater. The special topography of Xiangshan Bay isolates the external water mass and provides a suitable habitat for exploring the annual succession mechanism of the brackish tintinnid community. In this study, samples were collected from seven stations in Tie Harbor, Xiangshan Bay (East China Sea) during 10 months from 2022 to 2023. A total of 23 tintinnid species of five genera were identified throughout the year. These tintinnid species can be clustered into four seasonal groups, winter, summer, autumn and spring-autumn, with three temperature preferences. The Lorica Oral Diameter (LOD) size-class of each tintinnid species, which determines the food item size of tintinnid, separated their different ecological niches within each seasonal group. The seasonal succession of tintinnid community in Xiangshan Bay was organized by both temperature preference and LOD size of the tintinnid species.