Articles | Volume 13, issue 18
Biogeosciences, 13, 5139–5150, 2016
Biogeosciences, 13, 5139–5150, 2016

Research article 16 Sep 2016

Research article | 16 Sep 2016

Seasonality in planktic foraminifera of the central California coastal upwelling region

Catherine V. Davis1,2, Tessa M. Hill1,2, Ann D. Russell2, Brian Gaylord1, and Jaime Jahncke3 Catherine V. Davis et al.
  • 1Bodega Marine Laboratory, University of California Davis, Bodega Bay, USA
  • 2Department of Earth and Planetary Science, University of California Davis, Davis, USA
  • 3Point Blue Conservation Sciences, Petaluma, USA

Abstract. The close association between planktic foraminiferal assemblages and local hydrography make foraminifera invaluable proxies for environmental conditions. Modern foraminiferal seasonality is important for interpreting fossil distributions and shell geochemistry as paleoclimate proxies. Understanding this seasonality in an active upwelling area is also critical for anticipating which species may be vulnerable to future changes in upwelling intensity and ocean acidification. Two years (2012–2014) of plankton tows, along with conductivity–temperature–depth profiles and carbonate chemistry measurements taken along the north-central California shelf, offer new insights into the seasonal dynamics of planktic foraminifera in a seasonal coastal upwelling regime. This study finds an upwelling affinity for Neogloboquadrina pachyderma as well as a seasonal and upwelling associated alternation between dominance of N. pachyderma and Neogloboquadrina incompta, consistent with previous observations. Globigerina bulloides, however, shows a strong affinity for non-upwelled waters, in contrast to findings in Southern California where the species is often associated with upwelling. We also find an apparent lunar periodicity in the abundances of all species and document the presence of foraminifera even at very low saturation states of calcite.

Short summary
We examine seasonality of planktic foraminifera in an upwelling area to identify species vulnerable to changes in upwelling and ocean acidification and improve interpretation of fossil foraminifera. Of species associated with upwelling on the central California shelf, some are consistent with observations elsewhere while some associations appear to be unique to the region. All species show lunar periodicity and we confirm the presence of foraminifera at very low saturation state of calcite.
Final-revised paper