An evaluation of controls on planktonic foraminiferal Sr/Ca : comparison of water column and core-top data from a North Atlantic transect

Abstract

Sr/Ca in planktonic foraminifera recovered from the water column over 0-800 m along a meridional transect in the North Atlantic Ocean from 30° to 60°N were compared with data from core-top samples on the same transect and with in situ temperatures determined from water column CTD profiles. Species belonging to the globorotaliid genus show significant variability in Sr/Ca from place to place, whereas non-globorotaliid species show no significant variability. This variability for the globorotaliid species in core-top samples has already been shown to covary with calcification temperature derived from δ¹⁸O, but it also covaries with bottom depth (symptomatic of a dissolution artifact). These alternatives are distinguishable from the water column data for which the globorotaliid species show a small temperature dependence of 0.025 mmol/mol/°C within the range 5-15°C. However, temperature dependence is not supported by glacial-interglacial differences in Sr/Ca for globorotaliid and non-globorotaliid species, and at least from this perspective, a [CO₃²⁻] influence seems more likely.