T92 Foraminifera: Barometers of the Biotic and Abiotic World II

Tuesday, 6 November 2001
1:30 PM - 5:30 PM

THE INFLUENCE OF PRIMARY PRODUCTIVITY AND SEASONALITY OF PRODUCTIVITY ON DEEP-SEA BENTHIC FORAMINIFERA

Paper number: T92-2
Program: Technical Sessions
Time: 1:30 PM – 5:30 PM

Authors

Abstract

The effect of spatial and temporal variability of primary productivity on the d13 C of North Atlantic deep-sea benthic foraminifera has been investigated in two related studies. The first study is based on living (Rose Bengal stained) specimens of Hoeglundina elegans collected over a one-year interval at a 3010m site south of Nantucket Island. Carbon isotopic data taken over a 10-month interval (March, May, July, October, 1996, January, 1997) were compared with an 11.5-month time-series of organic carbon from a sediment trap to assess the effect of variation of organic carbon flux. The d13 C data show a 0.3‰ lower mean value following an organic carbon maximum resulting from a spring phytoplankton bloom. This change is suggested to be due to the presence of a phytodetritus layer on the seafloor and the subsequent depletion of d13 C in the porewaters within the phytodetritus.

In a related study, the d13 C of Holocene benthic foraminifera from 45 core tops from 0-62oN in the Atlantic were studied and compared with satellite-derived primary productivity and seasonality. The d13 C of Epistominella exigua show a ~ 1‰ decrease over 60 degrees of latitude, with the data correlating with overlying primary productivity, organic carbon flux, and seasonality. This significant depletion of d13 C of E. exigua is attributed to the seasonal presence of phytodetritus over a large portion of the North Atlantic. No relationships were found between the d13 C of Planulina wuellerstorfi and primary productivity, organic carbon flux, or seasonality. These observations demonstrate that (i) variation in the spatial and temporal pattern of organic carbon affects the d13 C of certain deep-sea taxa, (ii) carbon isotopic data of E. exigua may be potentially useful in reconstructing organic carbon flux and primary productivity, and (iii) the d13 C of P. wuellerstorfiin the North Atlantic is unaffected by organic carbon flux and reflects the d13 C of the bottom waters.