Abstract
Abstract. The B/Ca ratio in calcareous marine species is
informative of past seawater CO32- concentrations, but scarce data
exist on B/Ca in coralline algae. Recent studies suggest influences of
temperature and growth rates on B/Ca, the effect of which could be critical
for the reconstructions of surface ocean pH and atmospheric pCO2. In
this paper, we present the first laser ablation inductively coupled plasma mass
spectrometry (LA-ICP-MS) analyses of Mg, Sr, Li, and B in
the coralline alga Lithothamnion corallioides collected from different geographic settings and depths
across the Mediterranean Sea and in the Atlantic Ocean. We produced the
first data on putative temperature proxies (Mg/Ca, Li/Ca, Sr/Ca, Mg/Li) and
B/Ca in a coralline algal species grown in different basins from across the
photic zone (12, 40, 45, and 66 m depth). We tested the B/Ca
correlation with temperature proxies and growth rates in order to evaluate
their possible effect on B incorporation. Our results suggested a growth
rate influence on B/Ca, which was evident in the sample with the lowest growth rate of
0.10 mm yr−1 (Pontian Isl., Italy; 66 m depth) and in Elba (Italy; 45 m depth), where the algal growth rate was the highest (0.14 mm yr−1). At these
two sites, the measured B/Ca was the lowest at 462.8 ± 49.2 µmol mol−1 and the highest at 757.7 ± 75.5 µmol mol−1, respectively. A positive
correlation between B/Ca and temperature proxies was found only in the
shallowest sample from Morlaix (Atlantic coast of France; 12 m depth), where
the amplitude of temperature variation (ΔT) was the highest (8.9 ∘C). Still, fluctuations in B/Ca did not mirror yearly seasonal
temperature oscillations as for Mg/Ca, Li/Ca, and Sr/Ca. We concluded that
growth rates, triggered by the different ΔT and light availability
across depth, affect the B incorporation in L. corallioides.
Subject
Earth-Surface Processes,Ecology, Evolution, Behavior and Systematics
Cited by
4 articles.
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