The influence of sea ice concentration on phytoplankton community structure in the Chukchi and East Siberian Seas.

Abstract

To understand the influence of sea ice retreat on the phytoplankton community distribution in the rapidly warming Arctic Ocean, the field surveys were conducted in August 2012 and 2015 in the Chukchi and East Siberian Seas. Pigment analysis and chemical taxonomy were used to enumerate major phytoplankton groups. The average sea ice concentration in August 2012 was lowest since the sea ice observations from 1979, with higher sea surface temperature. The deeper mixed layer depth (MLD) and higher surface nitrate concentrations were due to exposure of the sea surface to wind in August 2012. The euphotic depth and subsurface chlorophyll maximum layer were deeper in August 2015 than those in August 2012. Even though a little difference of the average of phytoplankton biomass between two periods, phytoplankton community structure dramatically different during two study periods. Small phytoflagellate groups, prymnesiophytes, prasinophytes, dinoflagellates, cryptophytes, were dominated in phytoplankton biomass in August 2012, while the diatoms predominated in the study area in August 2015. Several environmental factors were found to affect the interannual variation of phytoplankton community structure in the surface layer of the Chukchi and East Siberian Seas, but they appeared to be controlled mainly by deeper MLD and seeding from sea ice caused by sea ice retreat and extend, respectively. Furthermore, underwater light conditions might be one of the influential factors for phytoplankton distribution in the subsurface layer of this area.