Spatial Distribution and Community Structure of Heterotrophic Protists in the Central Barents Sea of Arctic Ocean During Summer

Abstract

To investigate the spatial distribution and community structure of heterotrophic protists, we collected water samples at 23 stations of central Barents Sea in August, 2003. This study area was divided into three area with physico-chemical and chl-α distribution characteristics: AreaⅠ of warm Atlantic water mass, AreaⅢ of cold Arctic water mass and AreaⅡ of mixed water mass. Chl-α concentration ranged from 0.18 to 1.04 ㎍ℓ-1 and was highest in AreaⅠ. The nano-sized chl-α accounted for more than 80% of the total chl-α biomass in this study area. The contribution of nano-sized chl-α to total chl-α was higher in AreaⅠ than in AreaⅡ. Communities of heterotrophic protists were classified into three groups such as heterotrophic nanoflagellates(HNF), ciliates and heterotrophic dinoflagellates(HDF). During the study periods, carbon biomass of heterotrophic protists range from 11.3 to 38.7 ㎍Cℓ-1(average 21.0 ㎍Cℓ-1), and were highest in AreaⅠ and were lowest in AreaⅢ. The biomass of ciliates ranged from 4.2 to 19.3㎍Cℓ-1 and contributed 31.5-66.9% (average 48.1%) to the biomass of heterotrophic dinoflagellates biomass ranged from 5.7 to 18.4㎍Cℓ-1 and contributed 27.1 to 56.3% (average 42.8%) of heterotrophic protists. Heterotrophic dinoflagellates to heterotrophic protists biomass accounted fo about 50% in AreaⅢ. Heterotrophic nanoflagellate biomass ranged from 0.5 to 3.4㎍Cℓ-1 and contributed 3.2 to 19.6% (average 9.2%) of heterotrophic protists. Heterotrophic nanoflagellates to heterotrophic protists biomass accounted for more than 10% in AreaⅢ. These results indicate that the relative importance and structure of heterotrophic protists may vary according to water mass. Heterotrophic protists and phytoplankton biomass showed strong positive correlation in the study area The results suggest that heterotrophic protists are important consumers of phytoplankton, and protists might play a pivotal role in organic carbon cycling in the pelagic ecosystem of t