 |
| Titel |
Picoplankton diversity in the South-East Pacific Ocean from cultures |
| VerfasserIn |
F. Gall, F. Rigaut-Jalabert, D. Marie, L. Garczarek, M. Viprey, A. Gobet, D. Vaulot |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1726-4170
|
| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 5, no. 1 ; Nr. 5, no. 1 (2008-02-15), S.203-214 |
| Datensatznummer |
250002237
|
| Publikation (Nr.) |
 copernicus.org/bg-5-203-2008.pdf |
|
|
|
|
|
| Zusammenfassung |
In late 2004, the BIOSOPE cruise sailed between the equatorial influenced
waters off the Marquesas Islands and the nutrient enriched waters of the
Chilean upwelling. Along the way, it explored the Southeast Pacific gyre
centred around Easter Island, which is probably the most oligotrophic
oceanic region on earth. During this cruise, we undertook a vigorous effort
to isolate novel photosynthetic picoplanktonic eukaryotes. Two strategies
were attempted on board: enrichment of filtered samples with culture medium
and sorting of specific populations by flow cytometry based on size and
chlorophyll fluorescence. Over 1900 pre-cultures were started and then
further purified by flow cytometry, serial dilution or pipette isolation to
yield a total of 212 strains. These strains were characterized
morphologically and for more than 50% of them, genetically, through
partial sequencing of the 18 S rRNA gene.
Among the characterized strains, the largest number belongs to stramenopiles
(Heterokontophyta) with a record of 38 strains belonging to the species
Pelagomonas calceolata (Pelagophyceae). Strains from the recently described genera Bolidomonas and
Florenciella have been re-isolated for the first time since their description. Two other
abundant groups are the Chlorophyta, especially Prasinophyceae, and the
Haptophyta, especially the genera Phaeocystis and Emiliania. A limited number of heterotrophic
flagellates have also been isolated, all of them belonging to groups
containing known species. Finally, over a dozen of unicellular cyanobacterial
Synechococcus strains have been obtained, some forming unusual short chains.
Overall our strategy was quite successful since it allowed us to isolate a
large number of picoplankton strains. Still it failed in two respects.
First, apparently very few novel taxa have been obtained. One set of strains
is related to Prasinoderma coloniale (Prasinococcales, Prasinophyceae) but their sequences are
sufficiently different from the latter to probably belong to a new genus or
species. The sequences of two other strains, unfortunately later lost, were
phylogenetically affiliated to stramenopile environmental sequences,
probably corresponding to a new algal class. Second, very few strains have
been obtained from the very oligotrophic central gyre itself. In order to be
successful, future work in similar waters should probably combine flow
cytometry sorting with culture media and cultivation approaches specifically
developed for oligotrophic water species. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|