Spatio-temporal Variability of Coupling between Ice Retreat and Phytoplankton Blooms in the Southern Ocean

Polar organisms are adapted to the strong seasonality of environmental conditions. A small timing mismatch among biological and environmental events could potentially have significant consequences for the entire food web. Phytoplankton blooms in the marginal ice zone (MIZ) and coastal polynyas of the Antarctic develop in a narrow growth window due to the constraints of multiple environmental factors (e.g., light, ice, mixing). Changes in sea ice coverage and ice retreat timing can directly affect the timing and magnitude of primary production in the region. So far, the spatio-temporal patterns of phytoplankton blooms and their links to environment have not been fully examined, limiting our ability to interpret the past, present and future of Antarctic ecosystems. In this study, we use the available satellite datasets of sea ice and ocean color to assess the links between sea ice and phytoplankton. Our results suggest that the timing of ice retreat has a strong impact on the timing of phytoplankton blooms over most of the Antarctic: earlier ice retreat is generally associated with earlier onset of phytoplankton bloom. However, there is also significant spatial variability in the coupling of these events: phytoplankton blooms in the northern MIZ edge and the eastern Antarctic polynyas are likely to decouple with sea ice retreat due to the distinct strong water-column mixing regime. Underlying mechanisms for the variability and potential implications for higher trophic levels (e.g., seabirds) in the Antarctic ecosystem are discussed.