Spring phytoplankton onset after the ice break-up and sea-ice signature (Adélie Land, East Antarctica)

Abstract

The phytoplankton onset following the spring ice break-up in Adélie Land, East Antarctica, was studied along a short transect, from 400 m off the continent to 5 km offshore, during the austral summer of 2002. Eight days after the ice break-up, some large colonial and solitary diatom cells, known to be associated with land-fast ice and present in downward fluxes, were unable to adapt in ice-free waters, while some other solitary and short-colony forming taxa (e.g., Fragilariopsis curta, F. cylindrus) did develop. Pelagic species were becoming more abundant offshore, replacing the typical sympagic (ice-associated) taxa. Archaeomonad cysts, usually associated with sea ice, were recorded in the surface waters nearshore. Rough weather restricted the data set, but we were able to confirm that some microalgae may be reliable sea-ice indicators and that seeding by sea ice only concerns a few taxa in this coastal area of East Antarctica.

• Ice break-up
• phytoplankton
• sea-ice signature
• East Antarctica

Acknowledgements

We thank the over-wintering team members for their field assistance and fellowship during EPONTA programmes and the Astrolabe polar ship crew. We also thank Louise Oriol (Laboratoire d'Oceanographie Biologique de Banyuls, Banyuls-sur-Mer, France) for providing the nutrient data and Mélanie Simard (Institut des Sciences de la Mer, Université du Québec à Rimouski, Canada) for providing cell enumeration. We acknowledge Dr Leanne Armand and an anonymous reviewer for their valuable suggestions and the journal Antarctic Science for giving approval to reproduce Fig. 2i – k. We thank the Natural Sciences and Engineering Research Council of Canada and the Canadian Museum of Nature for research grants to Michel Poulin. Funds and logistic assistance in the field were supported by the Institut Polaire Français Paul-Émile Victor, Brest, France.