Planktonic foraminiferal faunal and stable isotopic indices of upwelling: a sediment trap study in the San Pedro Basin, Southern California Bight

Abstract

A planktonic foraminiferal faunal and stable isotopic study has been carried out on sediment trap samples collected in 1988 from the San Pedro Basin (Southern California Bight) in order to examine the response of this group of plankton to coastal upwelling. Hydrographic monitoring indicates that a period of upwelling occurred in the basin from late April to early June, with a brief spring bloom of planktonic foraminifera occurring prior to upwelling. The onset of upwelling resulted in a significant increase in total foraminiferal shell flux; the upwelling assemblage was initially dominated by Globigerina quinqueloba , with Globigerina bulloides dominating the latter half of upwelling. Following upwelling, the upper water column became thermally stratified and Neogloboquadrina dutertrei dominated the fauna. The observed pattern of faunal succession may be partly related to changes in food availability. Stable isotope analyses (δ 18 O and δ 13 C) of Neogloboquadrina pachyderma, N. dutertrei and G. bulloides indicate that all three species adjust their depth habitats in response to upwelling. Globigerina bulloides migrates from below the thermocline to the surface at the onset of upwelling. Both N. pachyderma and N. dutertrei appear to adjust their depth habitats in order to remain within specific temperature ranges.

Pliocene Changes in Tropical East Pacific Upper Ocean Stratification: Response to Tropical Gateways?

“…The distribution and abundance of planktonic foraminiferal species is strongly related to vertical variations in hydrographic parameters such as temperature, food availability, chlorophyll concentration, and light levels (e.g., Fairbanks et al, , 1982Curry et al, 1983;Ganssen and Sarnthein, 1983;Sautter and Thunell, 1991;Thunell and Sautter, 1992;Ortiz et al, 1995Ortiz et al, , 1996Ortiz et al, , 1997. These factors result in a predictable livingdepth range of different species that can be deciphered by the stable isotope composition of test calcite Ravelo et al, 1990;Ravelo and Fairbanks, 1992;Niebler et al, 1999) (Fig.…”

Deciphering isotopic signals of monsoon-induced upwelling in foraminifera from the Western Arabian sea sediment trap

“…Thunell and Sautter ( 1992) were able to assign a pre-upwelling, upwelling, or post-upwelling habitat to each of the species they studied based on the flux data, which had weekly resolution. Unfortunately, the Arabian Sea WAST data is bi-weekly, and thus does not resolve subtle changes in pre-, during, or post-upwelling timing.…”

Planktonic foraminifera in the sea of Okhotsk : population and stable isotopic analysis from a sediment trap

“…The seasonal change in equilibrium calcite 8 13 C values was calculated using the equation of Grossman (1982) as in Thunell and Sautter (1992):…”

“…commun. ), and the San Pedro Basin (Thunell & Sautter, 1992;Thunell, et al, 1994). This lack of correlation suggests that the trophic strategy of G. bulloides does not exclude diatoms.…”