It is known from the Antarctic Peninsula, McMurdo Sound, the Ross Sea, South Georgia, Victoria Land and various subarctic islands.

These pigments give the seaweed a greater ability to utilise blue light in the dim sub-ice environment.

[4] In some locations such as at Cape Evans on Ross Island, P. antarctica is the main primary producer at depths between 10 and 30 m (30 and 100 ft).

Although the alga contains secondary metabolites which make it distasteful to herbivores, research has shown that polychaete worms and amphipods consume it to some extent, and the beds of drifting seaweed may help provide continuity of food supply for them during the dark Antarctic winter.

The species found attached or associated with the alga include the limpet Iothia emarginuloides, the amphipod Paramoera walkeri, various polychaete worms, and the Antarctic sea urchin.