Distribution And Environmental Significance Of Living Benthic Foraminifera In The Contemporary Sediment Of Bohai Sea And North Yellow Sea

In this study, firstly, we investigated the living (stained) and dead(thanatocoenoses) benthic foraminiferal assemblages collected from the surfacesediment samples from the Bohai Sea (BS) and the northern Yellow Sea (NYS). Thesamples were collected from different seasons-50samples in May (spring) and46samples in November (autumn).（1）Our benthic foraminiferal fauna analysis on these samples shows four livingassemblages in May and three in November, indicating a sensitive response toseasonal environmental changes where the fauna live in the modern setting in the BSand NYS.（2）Our redundancy analysis (RDA) between the living assemblages and theircorresponding environmental parameters indicates that in spring, the abundances ofAstrononion tasmanensis, Nonionella stella and Bulimina sp. have positivecorrelations with increased water depth, density, salinity, and negative correlationswith increased FLOUR (chlorophyll). The abundances of Buccella frigid andVerneuilinulla advena have are positively correlated with increased dissolved oxygen(DO) and negatively correlated with the increases of temperature. The abundances ofCribrononion subincertum are positively correlated with increased turbidity (TURB)and temperature, but negatively correlated with increased DO. In autumn, there is apositive correlation between the abundances of V. advena and increased salinity.Protelphidium tuberculatum, Ammonia beccarii (vars.) abundances, however, havenegative correlations with salinity. During the autumn, the benthic foraminiferaspecies P. tuberculatum was noticeably expanded and the dominance areas occupiedby E. magellanicum and C. subincertum were significantly reduced in the BS, and inthe southern coast of the Liaodong Peninsula, the dominant B. frigida in the spring was replaced by V. advena in the autumn. The seasonal shifting of benthicforaminferal species are local responses to the combined changes in temperature,salinity, TURB, and DO in the BS and NYS, and also to the more intensifiedautumn/winter intrusion of the Yellow Sea Warm Current (YSWC).（3） The dead assemblages of benthic foraminifera, which are used toreconstruct paleoenvironments, experienced considerable destruction of agglutinatedassemblages. We found that such species V. advena, Trochammina sp., Ammoscalariasp., and Polskiammina asiatica are not existed in the dead assemblages possibly dueto the postmortem, taphonomic processes in the BS and NYS. We should take thenotion that the considerable destruction of agglutinated species in dead assemblagesmay bias slightly our estimation for paleoenvironmental parameters in the uses ofbenthic foraminifera fossil shells.After that we analysis two short cores collected from station B24（in NYS） andstation B42（in BS） for qualitative and quantitative research and analysis the benthicforaminifera assemblages, combined with210Pb dating measurement data and RDAresults.And discussed the changes in recent decades of marine environmental in thestudy area.