Why Sequence Phaeocystis antarctica?

Phaeocystis is a group of important unicellular, photosynthetic, eukaryotic algae distributed throughout the world’s oceans. Representatives of this genus live in the open ocean as well as in sea ice. A unique attribute of Phaeocystis is its ability to form a floating colony with hundreds of cells embedded in a polysaccharide gel matrix that can multiply massively during blooms.

Diffraction interference contrast micrograph of P. antarctica colony with five cells embedded in a carbohydrate matrix. Photo courtesy Oliver Killian and Gry Mine Berg.

The polar algae Phaeocystis antarctica is a key member of the phytoplankton community in the Southern Ocean where it plays a major role in global carbon and sulfur cycles. It sequesters CO₂ efficiently over large geographical areas and is a major emitter of 3-dimethylsulphoniopropionate (DMSP), the precursor of dimethyl sulfide (DMS). Biogenic DMS is a highly volatile gas that contributes about 1.5x10¹³ grams of sulfur to the atmosphere annually. As such, P. Antarctica may be a source of sulfate aerosols that play an important part in cloud formation and potentially in climate regulation.

Although P. Antarctica has been investigated intensively for decades in cultures and in the field, important questions with respect to its life cycle and growth regime remain unanswered. Sequencing of the P. antarctica genome will provide long-awaited insights into processes that enable it to transition from solitary to colonial stages, to form massive blooms, and to transition from the water column to sea ice. Ultimately, a better understanding of the metabolic pathways present in this enigmatic organism may aid in forecasting its future distribution as global warming continues and ice cover diminishes in the Southern Ocean ecosystem.

Principal Investigators: Gry Mine Berg and Kevin R. Arrigo (Stanford Univ.) and Arthur R. Grossman (The Carnegie Inst.)