Calcification response of a key phytoplankton family to millennial-scale environmental change.
Coccolithophores are single-celled photosynthesizing marine algae, responsible for half of the calcification in the surface ocean, and exert a strong influence on the distribution of carbon among global reservoirs, and thus Earth's climate. Calcification in the surface ocean decreases the buffering capacity of seawater for CO2, whilst photosynthetic carbon fixation has the opposite effect. Experiments in culture have suggested that coccolithophore calcification decreases under high CO2concentrations ([CO2(aq)]) constituting a negative feedback. However, the extent to which these results are representative of natural populations, and of the response over more than a few hundred generations is unclear. Here we describe and apply a novel rationale for size-normalizing the mass of the calcite plates produced by the most abundant family of coccolithophores, the Noëlaerhabdaceae. On average, ancient populations subjected to coupled gradual increases in [CO2(aq)] and temperature over a few million generations in a natural environment become relatively more highly calcified, implying a positive climatic feedback. We hypothesize that this is the result of selection manifest in natural populations over millennial timescales, so has necessarily eluded laboratory experiments.
Department of Earth Sciences, University of Oxford, South Parks Road, Oxford, OX1 3AN, UK.
H L O
HL
McClelland
CEREGE CNRS-IRD-Aix Marseille Univ, Avenue Louis Philibert, BP80 13545 Aix en Provence cedex 04, France.
N
N
Barbarin
CEREGE CNRS-IRD-Aix Marseille Univ, Avenue Louis Philibert, BP80 13545 Aix en Provence cedex 04, France.
L
L
Beaufort
Department of Earth Sciences, University of Oxford, South Parks Road, Oxford, OX1 3AN, UK.
M
M
Hermoso
Consiglio Nazionale delle Ricerche, Istituto per la Dinamica dei Processi Ambientali(CNR-IDPA), c/o Universita' Ca' Foscari Venezia, Via Torino 155, Mestre Venice I-30172, Italy.|Godwin Laboratory for Palaeoclimate Research, Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, UK.
P
P
Ferretti
Godwin Laboratory for Palaeoclimate Research, Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, UK.
M
M
Greaves
Department of Earth Sciences, University of Oxford, South Parks Road, Oxford, OX1 3AN, UK.
R E M
RE
Rickaby
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