Sensitivity of planktic foraminifera to sea surface temperature and export production as derived from sediment trap data

Abstract

Planktic foraminiferal flux data from time-series sediment trap observations have been compiled from 42 sites across the world's oceans, comprising a variety of oceanographic settings. To analyze species sensitivity to environmental parameters, distributional and optimum ranges are derived by relating fluxes and relative abundances of the following seven species to sea surface temperature (SST) and export production normalized to 1000 m water depth: Globigerinoides ruber (white and pink), G. sacculifer, Globigerinella siphonifera, Globigerina bulloides and Neogloboquadrina pachyderma (dextral and sinistral coiling varieties). Of the warm-water species, G. ruber (white) and G. sacculifer exhibit the widest SST tolerance range (9.7/9.8–31°C), followed by G. siphonifera (11.9–31°C), while G. ruber (pink) shows the narrowest SST range (16.4–29.6°C). G. bulloides and N. pachyderma (dex.) cover almost the whole SST range, N. pachyderma (dex.) exhibiting a clear preference for mid-temperatures, while the distribution pattern of G. bulloides is polymodal due to different genetic types comprised in this morphologically defined category. The polar–subpolar species N. pachyderma (sin.) is absent at SSTs above 23.7°C. The change in dominance of right- over left-coiled N. pachyderma is observed at 9°C. Derived optimum ranges for all species are in good agreement with previous plankton tow and laboratory studies, while lower temperature limits for G. ruber (white) and G. sacculifer might be several degrees lower than previously reported. With the exception of the morphospecies G. bulloides, SST has a significant effect on all investigated species. However, it seems to be a governing factor for species fluxes only at the edges of the thermal tolerance range. The influence of export production on planktic foraminiferal fluxes and relative abundances is not as pronounced. Highest relative abundances of the symbiont-bearing and thus light-dependent species G. ruber, G. sacculifer and G. siphonifera are restricted to oligotrophic and mesotrophic conditions, even though high fluxes can be observed at high export productions as well. In contrast, the asymbiotic species G. bulloides and N. pachyderma (dex.), depending more on food, reach high fluxes and relative abundances even at very high rates of export production, where they can easily outnumber the symbiotic species. Within the joint space of both SST and export production, N. pachyderma (sin.) yielded high fluxes and relative abundances coinciding mostly with medium to high export productivities.