Planktonic foraminifera from the M124 cruise plankton multinets (Subtropical South Atlantic)

Temperature appears to be the best predictor of species composition of planktonic foraminifera communities, making it possible to use their fossil assemblages to reconstruct sea surface temperature (SST) variation in the past. However, the role of other environmental factors potentially modulating the spatial and vertical distribution of planktonic foraminifera species is poorly understood. This is especially relevant for environmental factors affecting the subsurface habitat. If such factors play a role, changes in the abundance of subsurface-dwelling species may not solely reflect SST variation. In order to constrain the effect of subsurface parameters on species composition, we here characterize the vertical distribution of living planktonic foraminifera community across an E-W transect through the subtropical South Atlantic Ocean, where SST variability was small but the subsurface water mass structure changed dramatically. Four planktonic foraminifera communities could be identified across the top 700 m of the transect. Gyre and Agulhas Leakage surface faunas were predominantly composed of Globigerinoides ruber, Globigerinoides tenellus, Trilobatus sacculifer, Globoturborotalita rubescens, Globigerinella calida, Tenuitella iota and Globigerinita glutinata, and only differed in terms of relative abundances (community composition). Upwelling fauna was dominated by Neogloboquadrina pachyderma, Neogloboquadrina incompta, Globorotalia crassaformis and Globorotalia inflata. Thermocline fauna was dominated by Tenuitella fleisheri, Globorotalia truncatulinoides and Globorotalia scitula in the west, and by G. scitula in the east. The largest part of the standing stock was consistently found in the surface layer, but SST was not the main predictor of species composition, neither for the depth-integrated fauna across the stations nor at individual depth layers. Instead, we identified a pattern of vertical stacking of different parameters controlling species composition, reflecting different aspects of the pelagic habitat. Whereas productivity appears to dominate in the mixed layer (0 - 60 m), physical properties (temperature, salinity) become important at intermediate depths and in the subsurface, a complex combination of factors including oxygen concentration is required to explain the assemblage composition. These results indicate that the seemingly straightforward relationship between assemblage composition and SST in sedimentary assemblages reflects vertically and seasonally integrated processes that are only indirectly linked to SST. It also implies that fossil assemblages of planktonic foraminifera should also contain a signature of subsurface processes, which could be used for paleoceanographic reconstructions. The data consists of concentration values (individues.m-3) of planktonic foraminifera identified to specific level. The methodology was made on counting census of > 100 µm specimens. The first and second data sheets comprise the total (living and dead) analyzed foraminifera. The third and the fourth data sheets do not comprise dead specimens, the living fauna was separated in adults (third sheet) and pre-adults (fourth sheet) specimens. Pre-adults comprise juveniles and neanic specimens.