Physical-biological drivers modulating phytoplankton seasonal succession along the Northern Antarctic Peninsula

The Northern Antarctic Peninsula (NAP) shows shifts in phytoplankton distribution and composition along its warming marine ecosystems. However, despite recent efforts to mechanistically understand these changes, little focus has been given to the phytoplankton seasonal succession, remaining uncertainties regarding to distribution patterns of emerging taxa along the NAP. To fill this gap, we collected phytoplankton (pigment and microscopy analysis) and physico-chemical datasets during spring and summer (November, February and March) of 2013/ 2014 and 2014/2015 off the NAP. Satellite measurements (sea surface temperature, sea ice concentration and chlorophyll-a) were used to extend the temporal coverage of analysis associated with the in situ sampling. We improved the quantification and distribution pattern of emerging taxa, such as dinoflagellates and cryptophytes, and described a contrasting seasonal behavior and distinct fundamental niche between centric and pennate diatoms. Cryptophytes and pennate diatoms preferentially occupied relatively shallower mixing layers compared with centric diatoms and dinoflagellates, suggesting differences between these groups in distribution and environment occupation over the phytoplankton seasonal succession. Under colder conditions, negative sea surface temperature anomalies were associated with positive anomalies of sea ice concentration and duration. Therefore, based on sea ice-phytoplankton growth relationship, large phytoplankton biomass accumulation was expected during the spring/summer of 2013/2014 and 2014/2015 along the NAP. However, there was a decoupling between sea ice concentration/duration and phytoplankton biomass, characterizing two seasonal periods of low biomass accumulation (negative chlorophyll-a anomalies), associated with the top-down control in the region. These results provide an improved mechanistic understanding on physical-biological drivers modulating phytoplankton seasonal succession along the Antarctic coastal waters.

Automated summary

The Northern Antarctic Peninsula is experiencing shifts in phytoplankton distribution and composition due to warming marine ecosystems. However, little attention has been given to the seasonal succession of phytoplankton and the distribution patterns of emerging taxa along the peninsula. In this study, we collected data on phytoplankton and physico-chemical variables during spring and summer seasons from 2013 to 2015. We found that emerging taxa, such as dinoflagellates and cryptophytes, had different distribution patterns and environmental preferences compared to centric and pennate diatoms. The relationship between sea ice concentration/duration and phytoplankton biomass was not consistent, suggesting the presence of top-down control on phytoplankton in the region.