Climate induced shifts in the phytoplankton community biomass and community structure along the West Antarctic Peninsula

The West Antarctic Peninsula (WAP) is experiencing some of the most rapid climate change on Earth as evidenced by the fastest winter warming on the planet, dramatic declines in sea ice, and documented shifts in the secondary and higher trophic levels.  One lacking component to the unraveling the drivers of the ecosystem shifts was to what degree there were accompanying shifts in the primary producers that might translate the physical changes into the higher trophic levels. Our group has been focused on this problem using data collected as part of the Palmer LTER.  A retrospective analysis of the ocean color satellite data from the SeaWiFS and CZCS suggest that there have been significant shifts in the phytoplankton biomass within the LTER sampling region over the last 40 years.  In the northern regions, the absolute amount of chlorophyll has declined which is associated with the declines in sea ice, the increase of wind intensity and cloud cover. This would suggest an increase in the overall light limitation of the phytoplankton.  In the southern portion of the grid, the phytoplankton biomass appears to have increased.  This increase is hypothesized to largely reflect the declines in the absolute amount of fast and annual sea ice present in the system.  Additionally there appears to have been a shift in the phytoplankton community structure from diatoms to flagellated cryptomonad communities in the northern sections of the WAP.  These community shifts represent a fundamental shift in the size spectrum of the phytoplankton communities. These shifts in absolute concentration and composition represent fundamental shifts in the WAP food web that can link the observed shifts in the physical and higher trophic levels in the WAP.