Award: PLR-1043593

Using autonomous gas measurements and incubations with collected water samples, we studied photosynthesis and respiration by phytoplankton in the Western Antarctic Peninsula during the Austral summer 2012-2013.  Our observations captured the development and disappearance of a massive phytoplankton bloom in early spring, following retreat of the sea ice. During this spring bloom, which accounted for more than half of the seasonal gross primary production, the phytoplankton grew extremely rapidly, despite the low ambient temperature.  The photosynthetic activity was so intense that the ambient concentration of carbon dioxide (CO₂) in surface water declined to a small fraction of its normal value near equilibrium with the atmosphere.

 

Detailed oceanographic and physiological studies revealed some of the key conditions and mechanisms responsible for the rapid growth of the phytoplankton despite the very cold conditions (0-5ºC) encountered in high latitude waters.  The development of the phytoplankton bloom was facilitated by low concentration of grazing organisms in early spring and long daylight hours, which allowed extended photosynthetic activity.  Key physiological adaptations of cold-water phytoplankton include low respiration rates during daylight hours and high concentrations of the cellular proteins that are responsible for photosynthetic activity and cannot be modified for rapid activity at low temperature.

 

These results ameliorate our understanding of the high biological productivity of high latitude oceans which sustain a highly effective food chain, from phytoplankton to krill and marine mammals. They also provide new insight into the possible effects of CO₂-induced global change on polar ecosystems.

Last Modified: 08/04/2015
Modified by: Francois M Morel