Microphytoplankton assemblages in the waters surrounding South Georgia, Antarctica during austral summer 1994 |
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Authors: | P W Froneman E A Pakhomov R K Laubscher |
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Institution: | (1) Southern Ocean Group, Department of Zoology and Entomology, Rhodes University, Box 94, Grahamstown, 6140, South Africa, ZA |
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Abstract: | The composition and distribution of microphytoplankton assemblages in the vicinity of South Georgia were examined during
a krill survey conducted during voyage 119 the RV Africana in austral summer (January/February) 1994. Microphytoplankton distribution was studied at 83 stations along a zig-zag transect
in the waters surrounding South Georgia. Oceanographic and zooplankton data suggest that conditions were anomalous during
the investigation, in that sub-Antarctic surface waters had probably been advected southwards and were present around the
island. The two most widely distributed species were Corethron criophilum and Eucampia antarctica, which were recorded at all stations sampled. Also well-represented amongst the microphytoplankton assemblages were temperate,
neritic species such as Chaetoceros atlanticus, Proboscia alata and Odontella weissflogii. This can probably be related to the intrusion of sub-Antarctic surface waters unusually far south. Cluster and ordination
analysis identified three distinct groupings of stations in the waters surrounding the islands. These were found to the east,
west and north of the islands. The diatom groupings identified during this investigation broadly correspond to three water
masses previously described in the vicinity of South Georgia. Despite the anomalous hydrographical conditions that existed
during the investigation, the differences in phytoplankton were negligible when compared to normal years. Small mesoscale
features are, however, important in imposing biogeographic patterns on microphytoplankton.
Received: 21 February 1996 / Accepted: 3 November 1996 |
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