Arctic | Climate and Oceanography
Distributions of dinoflagellate cysts and diatoms in surface sediments of the Chukchi Sea in relation to the upper water masses Presenter: Vera Pospelova , vpospe@umn.edu, University of Minnesota, Department of Earth & Environmental Sciences
Maria S. Obrezkova , obrezkova@poi.dvo.ru, V.I. Il’ichev Pacific Oceanological Institute Alexander N. Kolesnik , aiaks1986@mail.ru, V.I. Il’ichev Pacific Oceanological Institute
Dinoflagellate cyst and diatom analyses were performed on 22 surface sediment samples from the Chukchi Sea to document their geographical distributions in one of the most understudied sections of the Arctic Ocean and to examine the influence of upper water masses on these two major groups of phytoplankton. Total concentrations vary from 0.9 to 5.9 x 106 valves g-1 for diatoms and from 0.8 to 12.5 x 103 cysts g-1 for organic-walled dinoflagellate cysts, with the highest values for both groups observed in the southern part of the Chukchi Sea and away from the Bering Strait. The most abundant diatoms are Paralia sulcata , Thalassiosira antarctica , Thalassiosira nordenskioeldii , and Chaetoceros spp. , whereas cysts of autotrophic Alexandrium spp ., Operculodinium centrocarpum (sensu Wall and Dale 1966), and heterotrophic Islandinium minutum and Brigantedinium spp . were most common in dinoflagellate cyst assemblages. Statistical analysis identified three major dinoflagellate cyst and diatom clusters: 1. Sites influenced by the Alaska Coastal Current in the eastern part of the Chukchi Sea are characterized by high abundances of Paralia sulcata and Operculodinium centrocarpum ; 2. The western part and Herald Canyon in the northwestern part of the Chukchi Sea are distinguished by Chaetoceros spp. , T. antarctica and cysts of Alexandrium spp . and affected by the Siberian Coastal Current and Bering Shelf Water; and 3. Assemblages in the southern part of the Chukchi Sea have noticeable abundances of Thalassiosira nordenskioeldii , cryophilic group of diatoms and heterotrophic Islandinium minutum . This work revealed the potential applicability of the combined use of diatoms and dinoflagellate cysts for reconstructions of past dynamic water mass changes in the Chukchi Sea.
Alaska Marine Science Symposium 2023 66
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