Comparison of genetic diversity and ecophysiological performance in the colony-forming polar prymnesiophyte species
Phaeocystis antarctica and Phaeocystis pouchetii
The prymnesiophyte
Phaeocystis is a cosmopolitan, ecologically important and bloom-forming genus of the phytoplankton containing
two colony-forming cold water species:
P. pouchetii in the Arctic and
P. antarctica in the Southern Ocean.
Fig. 1: Left: Overview showing the main ocean currents in the Southern Ocean; ACC (Antarctic Circumpolar Current), thin white arrows close to
the coast line show the Antarctic Coastal Current, (
Map modified after Rintoul S, Hughes C, Olbers D, 2001. The Antarctic Circumpolar Current
System. In: Siedler G, Church J and Gould J (eds). Ocean Circulation and Climate. Academic Press, New York, p 271-302) Right: Overview showing
the main ocean currents and water transport in the Arctic Ocean; Polar cold Water = blue arrow, Atlantic warm Water = red arrow. (
Map taken from
http://www.whoi.edu/cms/images/oceanus/GlobeCurrentsMap_550_47170.jpg)
In the past, the morphology of the genus
Phaeocystis has led to much taxonomic confusion assigning a species name to the similar
colony stages. Traditional methods for taxonomy, such as microscopy for phytoplankton, need high expertise and proper identification of
phytoplankton smaller than 20 µm is often impossible. Furthermore the lack of morphological characters makes the delimitation of species
difficult for most microalgae. Therefore molecular techniques have become a valuable additional tool during the past decades to study
the genus
Phaeocystis by providing the possibility to identify phytoplankton even down to species level, regardless of their sizes and
developmental stages.
Fig. 2: Different
P. antarctica morphotypes (developmental stages) a) flagellates, b) new cell stage, c) overview of various colony
stages, d) young colony, e) middle-sized colony and f) large colony. (Scale bar for a, b, d = 20 µm; c = 50 µm, e, f = 100 µm, photos
taken by F. Hinz and S. Gäbler-Schwarz)
Molecular biological analyses of the ribosomal RNA (rRNA) and ITS (Internal Transcribed Spacer) sequences indicated substantial inter- and
intraspecific diversity, the possibility of a species complex in
P. pouchetii and tried to trace the biogeographic history
of
P. antarctica strains in Antarctic coastal waters. Based on these results, a detailed analysis of the population structure of both
polar species is intended to link genetic data to environmental parameters as well as to ecophysiological response patterns. In a
previous DFG project (ME 1480,
Estimation of genetic diversity in the colony forming polar prymnesiophyte spezies Phaeocystis antarctica),
microsatellites, short, repetitive sequences that are highly polymorphic, for P. antarctica were designed and successfully applied.
We are now able to study the genetic diversity inside populations from different locations and the gene flow between them. The same approach
is also planned for
P. pouchetii although microsatellites have still to be developed if applicability tests with markers designed
for
P. antarctica fail.
Fig. 3: Different
P. pouchetii morphotypes, photos taken by E. Bauernfeind and Y. Okolodkov)
Selected clones of both
Phaeocystis species with large genetic differences will be comparatively studied in terms of photosynthesis
and growth under different abiotic conditions to outline the respective optima and tolerance limits. The main goal is to experimentally
evaluate whether genetic differences are reflected in different ecophysiological response patterns which could well explain specific biogeographic
distribution patterns. Moreover, this new approach offers for the first time the opportunity to relate population genetics to predicted climatic
changes in both Polar Regions.
Scientists
Victor Smetacek, Steffi Gäbler-Schwarz, Helga Mehl
Alfred-Wegener-Institute Bremerhaven
Ulf Karsten, Rhena Schumann, Juliane Buss
Universität Rostock
Research areas
Southern Ocean, Northern Atlantic and Pacific
Publications
Edvardsen B, Eikrem W, Green JC, Andersen RA, Moonvan der Staay S, Medlin LK, 2000. Phylogenetic reconstructions of the Haptophyta
inferred from 18S ribosomal DNA sequences and available morphological data. Phycologia, 39:19-35.
Gäbler-Schwarz S, Davidson A, Assmy P, Chen J, Henjes J, Lunau M, Nöthig EM, Medlin LK. A new cell stage in the haploid-diploid life
cycle of the colony-forming haptophyte Phaeocystis antarctica and its ecological implications. J. Phycol. submitted.
Gäbler-Schwarz S, Beszteri B, Gindulis JS, Hinz F, Nöthig EM, Wesche C, Kirst GO, Medlin LK. Responses of Different Antarctic Genotypes
of Phaeocystis antarctica to three salinities: Evidence for Ecosystem Resilience. Marine Ecology Progress Series. submitted.
Gäbler-Schwarz S, Leese F, Evans KM, Medlin LK (in prep.) Genetic structure and diversity of Phaeocystis antarctica assessed by
fast-evolving microsatellite.
Gäbler-Schwarz S, Evans KM, Hayes PK, Medlin LK (in prep.). PRIMER NOTE: Microsatellite markers for the polar prymnesiophyte species
Phaeocystis antarctica.
Gäbler S, Hayes PK, Medlin LK, 2007. Methods used to reveal genetic diversity in the colony forming prymnesiophytes Phaeocystis
antarctica, P. globosa and P. pouchetii – preliminary results. Biogeochemistry, 83:19-27.
Kraemer L, Beszteri B, Gäbler-Schwarz S, Held C, Leese F, Mayer C, Pohlmann K, Frickenhaus S, 2009. STAMP: Extensions to the STADEN
sequence analysis package for high throughput interactive microsatellite marker design. BMC
Bioinformatics, 10:41, doi:10.1186/1471-2105-10-41
Lange M, Chen Y, Medlin LK, 2002a. Molecular genetic delineation of Phaeocystis species (Prymnesiophyceae). using coding and
non-coding regions of nuclear and plastid genomes. European Journal of Phycology, 37:77-92.
Lange M, Medlin LK, 2002b. Design and Testing of ITS probes for distinguishing Phaeocystis species, Protist, 153:275-282
Medlin LK, Lange M, Baumann MEM, 1994. Genetic differentiation among three-colony-forming species of Phaeocystis further
evidence for the phylogeny of the Prymnesiophyta. Phycologia 33/3:199-212.
Medlin LK, Zingone A, 2007. A taxonomic review of the genus Phaeocystis. Biogeochemistry, 83:3-18.
Tang KW, Smith WO Jr, Shields AR, Elliott DT, 2009. Survival and recovery of Phaeocystis antarctica (Prymnesiophyceae) from prolonged darkness
and freezing. Proceedings of the Royal Society B 276:81-90.
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Research funding organisation
German Research Foundation
Project number: SM 22/11, KA 899/18
Funding period: 17/11/2009 – 16/11/2011
