Seasonal and interannual changes in planktic foraminiferal fluxes and species composition in Guaymas Basin, Gulf of California

Abstract

Abstract Paleoclimate records based on planktic foraminifera shells are reliant upon an understanding of how populations respond to annual and interannual changes in surface hydrography. In particular, annual and interannual flux variability would be expected to impact the interpretation of geochemical proxies from foraminifera shells. A seven-year time series from Guaymas Basin, Gulf of California reveals a seasonal progression of foraminiferal species flux, with faunal assemblages characteristic of winter, summer, and fall conditions. Observations of flux along with remotely sensed sea surface temperatures and previously published oxygen isotope data are used here to assess the range of environmental conditions each species would be expected to represent in the fossil record. We find that both species abundances and phenology are altered during negative El Nino Southern Oscillation (ENSO) phases, as occurred over the course of the study period. This observation is used in conjunction with published δ18O data to subsample fluxes in simulation of assemblages collected and analyzed by standard paleontological methods. This approach indicates that during periods more influenced by El Nino conditions, Globigerina bulloides would record warmer conditions, while Neogloboquadrina dutertrei would reflect cooler conditions.