Distribution characteristics of benthic foraminifera in surface sediments of Zhanjiang Bay - Leizhou Bay and its environmental significance

Benthic foraminifera from the surface sediments were sampled at 89 points in June 2020 in the Zhanjiang Bay - Leizhou Bay, Guangxi, SW China, and analyzed. A total of 103 species from 52 genus were identified, including 64 species from 37 genus with hyaline tests, 13 species from 10 genus with agglutinated tests, and 26 species from 5 genus with porcelaneous tests. The abundance of benthic foraminifera was characterized by an increase from inner bay to outer bay. Four assemblages were recognized based on Q-type factor analysis. AssemblagesⅠ, Florilus scaphus - Pseudorotalia gaimardi, was dominated by warm water species, indicating the shallow water environment of the inland shelf, which was obviously influenced by the South China Sea warm current. Assemblages Ⅱ, Nonion belridgense - Hemirotalia foraminulosa - Elphidium macellum, was mainly a saltwater species, which reflected a shallow water environment with significantly increased salinity in ocean-land transition zone. Assemblages Ⅲ, Hanzawaia convexa - Rosalina bradyi, was dominated by shallow-water species, indicating the shallow water environment of inland shelf affected by coastal current and South China Sea warm current. Assemblages Ⅳ, Neoconorbina terquemi - Ammonia beccarii, consisted mainly of eurysaline species, reflecting the coastal environment that obviously affected by the coastal current. A comprehensive analysis on various factors on the distribution of benthic foraminiferal assemblages showed that bottom water temperature and water depth are main impact factors on the distribution of benthic foraminifera assemblages in the study area. In addition, the distribution of benthic foraminifera is also influenced by ocean current and substrate type.