Distribution of dinoflagellate cysts in surface sediments from the East Siberian and Chukchi Seas and their relation to the prevailing hydrographical conditions

Abstract

Twenty-two surface sediment samples from the East Siberian and Chukchi Seas, Pacific Arctic Ocean sector were investigated to determine the distribution, abundance and species composition of resting stages of dinoflagellates (dinoflagellate cysts). This study is the first to document the distribution of the dinoflagellate cysts in the area. A clearly distinguishable distribution pattern was observed in species diversity, concentration and taxa dominance varying along inner-shelf to outer-shelf gradient. The data presented here also reveal a clear longitudinal trend in the dinoflagellate cyst distribution such that subdivision into two domains is possible. The first, the Chukchi Sea area, is characterized by higher numbers and diversity of dinoflagellate cysts, with the assemblages dominated by Operculodinium centrocarpum, Pentapharsodinium dalei and Spiniferites elongatus. The second, the East Siberian Sea area, is characterized by high occurrence of the RBSC-type cysts that are brown in color with a distinct spheroidal and process-bearing shape. A particular note is for the recently described species, Islandinium minutum subsp. barbatum subsp. nov., which shows rather restricted distribution pattern in the shallow East Siberian Sea shelf area. This result tentatively suggests a potential use of dinoflagellate cysts in providing retrospective information on the long-term changes in the phytoplankton community in the study area. Our study also highlights the importance of further investigation to identify the main environmental drivers of the dinoflagellate cyst distribution patterns, several regional and in situ environmental parameters in the East Siberian and Chukchi Seas.