Assessment of the morphological, genetic, and ecological diversity of coccolithophores along the BIOSOPE transect.

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Colomban de Vargas, Rutgers University, USA
Luc Beaufort, CNRS, CEREGE
Assessment of the morphological, genetic, and
ecological diversity of coccolithophores along
the BIOSOPE transect.
Overarching Goal
The Prymnesiophyceae are the most abundant
organisms of the nannoplankton (2-20 µm) in the
oligotrophic ocean, where they play a key role in
directing flows of biogeochemically and
climatically major elements and gasses.
Coccolithophores, (Prymnesiophyceae) are one of
the rare phytoplanktonic group to produce calcite
(40 to 50 of global CaCO3 production)
We propose 1 - to examine, using innovative
methods in molecular biology and microscopy, the
genetic and morphological diversity of
coccolithophores along the vertical and
horizontal ecological gradients covered during
the BIOSOPE cruise. 2- to quantify calcite
production by coccolithophores along the BIOSOPE
transect in order to establish relation between
organic production and calcite production at
specific level.
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Scientific Objectives
To estimate the coccolithophore diversity
(taxonomy, abundance) at the species level in
both the depth and biogeographic ecological
gradients covered by BIOSOPE.
To identify the genetic provinces of the key
coccolithophore taxa in the stratified
oligotrophic ocean, and compare the ecological
partitioning between the morphological and
genetic diversity.
To estimate the coccolithophore CaCO3 production
in the biogeographic areas covered by BIOSOPE,
and particularly in extreme oligotrophic
environments.
To estimate the ecological importance of naked
coccolithophores and other haptophytes in extreme
oligotrophy.
To analyze the global diversity of
nannoplanktonic eukaryotes along BIOSOPE
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Methods
All proposed methods are based on materiel
collected on different kind of filters
The morphological diversity of coccolithophores
will be analyzed using
SYRACO the SYsteme de Reconnaissance
Automatique de COccolithes, which will allow a
rapid 1000 individuals per minute- screening of
(1) the morphological taxonomy, (2) the abundance
of morphological species at each station and
depths, (3) the weight of individual coccoliths
and thus the production of CaCO3.
Scanning Electron Microscopy SEM will allow the
recognition of ultrastructural characters of the
skeleton that allow species distinction in the
biological, genetically defined species of
coccolithophore.
The genetic diversity of coccolithophores will be
analyzed using
DNA PCR, sequencing, RFLP The use of specific
DNA primers targetting different taxonomic levels
within the coccolithophores will allow to (1)
reconstruct a first, global phylogeny of the
tropical coccolithophores, (2) detect the cryptic
genetic diversity within the classical,
morphological species, (3) analyse the
biogeographic and depth partitioning of genetic
diversity within the most important taxa.
Fluorescence In Situ Hybridization FISH will
permit the identification of naked or
non-calcifying coccolithophores and other
haptophytes.
SSU rDNA clones librairies rDNA librairies will
allow a rapid survey of the nannoplanktonic
diversity present along BIOSOPE.
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Dollfus Beauffort, Neur. Net., 1999 Beaufort
Dollfus, Mar. Mic. In Press
150 individuals of species 1 150 individuals of
species 2 150 individuals of species 11 2500
non coccolith individuals
E. huxleyi
U. tenuis
SYRACO
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CaCO3, growth rate, PP
Stoll et al., 2002
Beaufort, unpublished data
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Sampling Strategy
We propose to examine 6 different depths at each
station 2 samples below the Deep Chlorophyll
Maximum (DCM) 1 in the DCM 1 just above the DCM 1
in the midle-photic zone 1 in the upper-photic
zone
For each depth, we will need 12 liters of sea
water to accommodate the following protocol
12 liters
2-4 l
8 l
Polycarbonate Membrane 0.8 µm
1 l
Cellulose acetate membrane
FISH
SYRACO
SEM
Genetics