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Antarctic Research Series



  • Ecology—Research—Antarctica—Antarctic Peninsula Region

Index Terms

  • 4855 Oceanography: Biological and Chemical: Plankton
  • 4815 Oceanography: Biological and Chemical: Ecosystems, structure and dynamics
  • 4850 Oceanography: Biological and Chemical: Organic marine chemistry



Phytoplankton: Quantitative and qualitative assessments

R. R. Bidigare, J. L. Iriarte, S.-H. Kang, D. Karentz, M. E. Ondrusek, and G. A. Fryxell

The standing stock of phytoplankton and its physiological condition can be estimated using several methods or combinations of methods. In this chapter the stress is on comparisons of those methods in detecting recently observed phytoplankton patterns west of the Antarctic Peninsula: size fractionation, cell counts, chlorophyll a and other pigments, and photoprotective mycosporine-like amino acids. Fractionated chl a for nano-phytoplankton (<25 μm) and net phytoplankton (≥25 μm) size classes was measured at 11 stations around Livingston Island, South Shetland Islands (Antarctica) from the XXVI Chilean Expedition to the South Shetland Islands during February 1990, onboard of M/N Capitán Luis Alcázar. The biomass of phytoplankton within the study area was variable, with the highest contribution by net phytoplankton found in coastal waters of the South Shetland Islands, and the highest contribution of nanophytoplankton found in Drake Passage waters. During austral spring 1990, a collaborative investigation (named Icecolors ′90) was undertaken to directly measure the effects of ozone diminution and ultraviolet (UV) radiation on Southern Ocean phytoplankton. HPLC pigment analyses were carried out on suspended particle samples collected along four north south transects (T1–4) in the Bellingshausen Sea. Elevated chl a levels were measured at the edge of the marginal ice zone (MIZ), which was located at ca. 64.4°S during Icecolors ′90. Accessory pigment distributions documented that the phytoplankton sampled at the ice edge during the first three transects was dominated by Phaeocystis spp. in colonial form. Pigment patterns observed at the edge of the MIZ on the fourth transect revealed that the Phaeocystis-dominated phytoplankton community was replaced by a diatom-dominated phytoplankton community. The diatom cells were more abundant and were distributed ubiquitously in the open water within 150 km from the ice edge, while P. spp. cells were mainly restricted in distribution to within 50 km of the ice edge. More than 60 phytoplankton species were found. Natural samples and algal cultures were also screened for mycosporine-like amino acids (MAAs) during Icecolors ′90 to determine if these pigments represent a “potential” UV protection mechanism. The quantitatively important MAAs detected in suspended particulate samples have been identified as porphyra-334, shinorine, and palythine. A fourth MAA has been tentatively identified as mycosporine glycineivaline based on its absorption and chromatographic properties. The field measurements and culture study confirm previous suggestions that the pronounced UVB (ultraviolet-B = 280–320 nm waveband absorption peak measured in Antarctic suspended particulate matter and Phaeocystis is attributable to MAAs. Dramatic temporal changes in Phaeocystis were observed, and Phaeocystis seems to be more sensitive to environmental changes such as light (UVB) and physical conditions.

Citation: Bidigare, R. R., J. L. Iriarte, S.-H. Kang, D. Karentz, M. E. Ondrusek, and G. A. Fryxell (1996), Phytoplankton: Quantitative and qualitative assessments, in Foundations for Ecological Research West of the Antarctic Peninsula, Antarct. Res. Ser., vol. 70, edited by E. E. Hofmann, R. M. Ross, and L. B. Quetin, pp. 173–198, AGU, Washington, D. C., doi:10.1029/AR070p0173.

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