Hypothesized seasonal progression of P. antarctica in the Southern Ocean.

Phaeocystis antarctica

• The role of Phaeocystis in global carbon cycling
• The Phaeocystis genus
• Strains of P. antarctica to be used for genome sequencing
• Methods
• Further reading

The role of Phaeocystis in global carbon cycling:

The Phaeocystis genus contributes approximately 10% of annual global marine primary production, equivalent to 4 billion metric tons of carbon annually. Given that up to 50% of this carbon is in the form of polysaccharide gels, 2 billion tons of polysaccharide gels is produced by Phaeocystis sp. each year. The polymer gels released after blooms of Phaeocystis are dispersed into the dissolved organic carbon (DOC) pool, serve as attachment sites for bacteria and protists, and sediment into the deep ocean, affecting the cycling of organic matter. Because DOC constitutes a large carbon pool (700 x 10¹⁵ g C) of similar magnitude to the atmospheric CO₂ pool (750 x 10¹⁵ g C), understanding the cycling and reactivity of its various components and sources has implications for the global carbon cycle and carbon sequestration.

Sites of most frequent bloom occurrences of P. pouchetii (blue circles), P. globosa (red circles) and P. antarctica (yellow circles).

The Phaeocystis genus:

The Phaeocystis genus belongs to the prymnesiophytes and to the larger division of Haptophyta. The haptophytes, classified as chromist algae, branched from the red algae about 1300 million years ago (Ma) through a secondary red algal endosymbiotic event. Subsequently, the chromist algae radiated into 3 groups, the cryptophytes, stramenopiles and the haptophytes. In today's ocean, haptophytes are clearly distinct from other phytoplankton clades, clustering between green algae/terrestrial plants, and the golden-brown stramenopiles which include the bacillariophycea (diatoms) and the pelagophycea¹ . The largest Phaeocystis blooms are from the Northern and Southern Polar seas where P. pouchetii and P. antarctica bloom, respectively, and in Belgian/Dutch coastal waters where P. globosa blooms² . The P. antarctica haplotypes are more closely related to P. pouchetii than P. globosa which blooms in temperate and warm waters³ .

P. antarctica CCMP1871

Strains of P. antarctica to be used for genome sequencing:

P. antarctica strain CCMP1374 was isolated from McMurdo Sound near the ice in the Ross Sea and strain P. antarctica CCMP1871 was isolated from the open ocean in the Southern Bellingshausen Sea. Both strains are available to the research community from the Provasoli-Guillard National Center for Culture of Marine Phytoplankton (CCMP, http://ccmp.bigelow.org/) as xenic cultures. We have rendered both these strains axenic and will supply them upon request. The diploid genome size of each strain is estimated to be 160 Mbp and the GC content 54% based on measurements by flow cytometry⁴. Currently, the level of polymorphism and the repeat structure of the genomes are not known.

Axenic P. antarctica growing in liquid and on solid media

Methods

Coming soon!

Further reading:

1. Bhattacharya D, Yoon HS, Hackett JD (2004) Photosynthetic eukaryotes unite: endosymbiosis connects the dots. Bioessays 26:50-60
2. Schoemann V, Becquevort S, Stefels J, Rousseau W, Lancelot C (2005) Phaeocystis blooms in the global ocean and their controlling mechanisms: a review. Journal of Sea Research 53:43-66
3. Lange M, Chen YQ, Medlin LK (2002) 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
4. Vaulot D, Birrien JL, Marie D, Casotti R, Veldhuis MJW, Kraay GW, Chretiennotdinet MJ (1994) Morphology, Ploidy, Pigment Composition, and Genome Size of Cultured Strains of Phaeocystis (Prymnesiophyceae). Journal of Phycology 30:1022-1035