Phytoplankton variability in Admiralty Bay, King George Island, South Shetland Islands: six years of monitoring

• Main Authors: Elżbieta E. Kopczyńska, Zakład Biologii Antarktyki Pan
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2005
• Subjects: Key words; Antarctica; King George Island; coastal zone; phytoplankton; Admiralty Bay; Bransfield Strait; South Shetland Islands; Antarc*
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.622.9891; http://www.polar.pan.pl/ppr29/PPR29-117.pdf

summer peaks (maxima 4.0–5.2×106 cells l−1) associated with small variations in low atmo− spheric pressure, and low velocity winds. They were dominated by nano−sized (<20 μm) flagellates and picoplankton (~2 μm). The prevalent nanoflagellates were either Prasino− phyceae, Cryptophyceae, or Prymnesiophyceae. Diatoms were next in abundance. Of the seven spring−summer diatom blooms, five had initiated at the shore (maximum 9.8×105 cells l−1; November 1998). They were significantly greater than in the open water, and did not spread into the bay centre. Two observed open water blooms did not reach the shore. Di− atoms formed up to 44 % of the total cells in the period 1996–98; they only formed <5 % in 2003–05. Shore and open water populations differed by diatom dominance structure. Pennates (Fragilariopsis spp., F. cylindrus, Pseudo−nitzschia spp.), and benthic species were prevalent at the shore; centrics (Thalassiosira spp., Chaetoceros socialis) were most common offshore. In 2003–05 diatoms were relatively impoverished in Chaetoceros spp. and the larger (>20 μm) Fragilariopsis spp. Nano−sized Thalassiosira spp. were the winter dominants. Diatom species dominance structure may change at each of the two sites within a month (e.g. shore site: F. cylindrus dominant in October ’98; T. gravida in November ’98). Dinoflagellates showed summer increases associated with diatom blooms. Variations in phytoplankton cell concentrations, the species structures between the shore and open wa− ters, and between seasons appear to be related to physical factors: changes in wind velocity and direction, inflow of waters from the Bransfield Strait, ice melting and changes in atmo− spheric pressure.