Growth of the coccolithophore <i>Emiliania huxleyi</i> in light- and nutrient-limited batch reactors: relevance for the BIOSOPE deep ecological niche of coccolithophores
Coccolithophores are unicellular calcifying marine algae that play an important role in the oceanic carbon cycle via their cellular processes of photosynthesis (a CO<sub>2</sub> sink) and calcification (a CO<sub>2</sub> source). In contrast to the well-studied, surface-water...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-11-01
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| Series: | Biogeosciences |
| Online Access: | http://www.biogeosciences.net/13/5983/2016/bg-13-5983-2016.pdf |
| Summary: | Coccolithophores are unicellular calcifying marine algae that play an
important role in the oceanic carbon cycle via their cellular processes of
photosynthesis (a CO<sub>2</sub> sink) and calcification (a CO<sub>2</sub> source). In
contrast to the well-studied, surface-water coccolithophore blooms visible
from satellites, the lower photic zone is a poorly known but potentially
important ecological niche for coccolithophores in terms of primary
production and carbon export to the deep ocean. In this study, the
physiological responses of an <i>Emiliania huxleyi</i> strain to conditions
simulating the deep niche in the oligotrophic gyres along the BIOSOPE
transect in the South Pacific Gyre were investigated. We carried out batch
culture experiments with an <i>E. huxleyi</i> strain isolated from the
BIOSOPE transect, reproducing the in situ conditions of light and nutrient
(nitrate and phosphate) limitation. By simulating coccolithophore growth
using an internal stores (Droop) model, we were able to constrain fundamental
physiological parameters for this <i>E. huxleyi</i> strain. We show that
simple batch experiments, in conjunction with physiological modelling, can
provide reliable estimates of fundamental physiological parameters for
<i>E. huxleyi</i> that are usually obtained experimentally in more
time-consuming and costly chemostat experiments. The combination of culture
experiments, physiological modelling and in situ data from the BIOSOPE cruise
show that <i>E. huxleyi</i> growth in the deep BIOSOPE niche is limited
by availability of light and nitrate. This study contributes more widely to
the understanding of <i>E. huxleyi</i> physiology and behaviour in a
low-light and oligotrophic environment of the ocean. |
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| ISSN: | 1726-4170 1726-4189 |