Just out @ Biogeosciences
Impact of trace metal concentrations on coccolithophore growth and morphology: laboratory simulations of Cretaceous stress
Giulia Faucher, Linn Hoffmann, Lennart T. Bach, Cinzia Bottini, Elisabetta Erba, and Ulf Riebesell
The Cretaceous ocean witnessed intervals of profound perturbations such as volcanic input of large amounts of CO2, anoxia, eutrophication, and introduction of biologically relevant metals. Some of these extreme events were characterized by size reduction and/or morphological changes of a few calcareous nannofossil species. The correspondence between intervals of high trace metal concentrations and coccolith dwarfism suggests a negative effect of these elements on nannoplankton biocalcification process in past oceans. In order to verify this hypothesis, we explored the potential effect of a mixture of trace metals on growth and morphology of four living coccolithophore species, namely Emiliania huxleyi, Gephyrocapsa oceanica, Pleurochrysis carterae and Coccolithus pelagicus. These taxa are phylogenetically linked to the Mesozoic species showing dwarfism under excess metal concentrations. The trace metals tested were chosen to simulate the environmental stress identified in the geological record and upon known trace metal interaction with living coccolithophores algae.
Our laboratory experiments demonstrated that elevated trace metal concentrations not only affect coccolithophore algae production but, similarly to the fossil record, coccolith size and/or weight. Smaller coccoliths were detected in E. huxleyi and C. pelagicus, while coccoliths of G. oceanica showed a decrease in size only at the highest trace metal concentrations. P. carterae coccolith size was unresponsive for changing trace metal amounts. These differences among species allow to discriminate most- (P. carterae), intermediate- (E. huxleyi), and least- (C. pelagicus and G. oceanica) tolerant taxa. The fossil record and the experimental results converge on a selective response of coccolithophores to metal availability. These species-specific differences must be considered before morphological features of coccoliths are used to reconstruct paleo-chemical conditions.
READ IT HERE: http://www.biogeosciences-discuss.net/bg-2017-138/
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