of the phytoplankton can firstly be described by the different
< 3 µm phytoplankton
As it was evidenced in most water masses,
|Phytoplankton biomass in terms of chlorophyll a is
principally represented by the < 3 µm fraction (picophytoplankton)
which contributed for more than 60% in many atoll lagoon (Charpy
and Blanchot 1998 and Sakka 2000).
The taxonomic composition of phytoplankton is still poorly
known. The picophytoplankton (was mainly composed of Synechococcus
whereas Prochlorococcus constituted only 5% of this size class (Charpy
>= 3 µm phytoplankton
Very few data are available on the composition of
phytoplankton of size higher than 3 µm. The taxonomic
composition of the nano and the microphytoplankton of Takapoto
atoll lagoon (table) given by Sournia and Ricard (1976) reveals a
predominance of three major groups (diatoms, dinoflagellates and
coccolithophorids). The diatoms were the most diversified group
whereas the dinoflagellates were the most abundant.
later, observations made in the same atoll by Loret
et al (2000) and Sakka
et al (2000) show a drastic change in the phytoplankton
composition. Indeed, mostly pico and nanophytoplankton were
observed, the latter being small phytoflagellates (table). The HPLC pigment analysis outlined the predominance,
in term of chlorophyll a, of picocyanobacteria and prymnesiophytes
whereas chlorophytes, diatoms and cryptophytes were the secondary
groups. The dinoflagellates were mostly heterotrophic as their
specific pigment, the peridinin, was not detected by the HPLC
investigation methods changed between 1976 and 1996.
|the absence of big phytoplankton
cells in the net samples performed in 1996 and 1997
evidences a shift of the phytoplankton community towards
the smaller sizes.
reason of this shift towards the
smaller sizes is not yet clearly understood. It could be
enticing to relate it to the development of pearl oyster farming.
page was based on :
Charpy L, Blanchot J (1998) Photosynthetic
picoplankton in French Polynesian atoll lagoons: estimation of
taxa contribution to biomass and production by flow cytometry.
Marine Ecology-Progress Series 162: 57-70
Delesalle B, Sakka A, Legendre L, Pages J, Charpy L, Loret P (2001) The
phytoplankton of Takapoto Atoll (Tuamotu Archipelago, French
Polynesia): time and space variability of biomass, primary
production and composition over 24 years. Aquatic Living Resources
Charpy (1996) Phytoplankton biomass and production in two Tuamotu
atoll lagoons (
Ecol. Prog. Ser. 145 (1996), pp. 133¯142
Charpy and J. Blanchot (1998) Photosynthetic picoplankton in
French Polynesian atoll lagoons: estimation of taxa contribution
to biomass and production by flow cytometry. Mar. Ecol. Prog.
Ser. 162 (1998), pp. 57¯70.
Loret (1999) Le régime alimentaire et la sélection des
particules chez l'huître perlière Pinctada margaritifera
dans le lagon de Takapoto (Tuamotu, Polynésie française). Thèse
de doctorat. , Université de Polynésie française,
Loret, A. Pastoureaud, C. Bacher and B. Delesalle (2000)
Phytoplankton composition and selective feeding of the pearl
oyster Pinctada margaritifera in the Takapoto lagoon (
): in situ
study using optical microscopy and HPLC pigment analysis. Mar.
Ecol. Prog. Ser. 199 (2000), pp. 55¯67.
Sakka (1999), Structure et dynamique de la communauté
planctonique dans le lagon de l'atoll de Takapoto (Archipel des
Tuamotu, Polynésie française). Thèse de doctorat. , Université
Laval, Québec (1999).
Sakka, L. Legendre, M. Gosselin and B. Delesalle (2000) Structure
of the oligotrophic planktonic food web under low grazing of
heterotrophic bacteria: Takapoto atoll,
. Mar. Ecol.
Prog. Ser. 197 (2000), pp. 1¯17.
Sournia and M. Ricard (1976) Données sur l'hydrobiologie et la
productivité du lagon d'un atoll fermé (Takapoto, îles Tuamotu).
Vie Milieu 26 (1976), pp. 243¯279.