Contributions of the net, nano- and picoplankton to the phytoplankton standing crop and primary productivity in the Southern Ocean

• Published in: Journal of Plankton Research
• Main Authors: Weber, Larry H., El-Sayed, Sayed Z.
• Format: Text
• Language: English
• Published: Oxford University Press 1987
• Subjects: Articles; Antarctic; Southern Ocean; The Antarctic; Drake Passage; Bransfield Strait; Indian; Antarctic Ocean; Elephant Island; Antarc*
• Online Access: http://plankt.oxfordjournals.org/cgi/content/short/9/5/973; https://doi.org/10.1093/plankt/9.5.973

The Southern Ocean phytoplankton community is largely dominated by nanoplankton (cells which will pass a 20-μm mesh), as demonstrated by numerous size-fractionated measurements of both chlorophyll a and carbon uptake rates. Furthermore, in agreement with findings from lower and temperate latitudes, a significant portion of the photoautotrophs in the Antarctic Ocean are in the picoplanktcm (< l-μm) size range. The relative proportions of nano- and picoplankton are highly variable both in space and time. In the vicinity of Elephant Island, Drake Passage and the Bransfield Strait (western Atlantic sector), the contribution of nanoplankton to integrated water column chlorophyll a was 39–98% (mean = 76% for 39 stations). In the western Indian sector of the Antarctic, 31–92% (mean = 64% for 69 stations) of the chlorophyll was in the nanoplankton size fraction. Picoplankton accounted for 5–74% (mean = 40% for six stations) and 7–42% (mean = 15% for 14 stations) of the chlorophyll a in the Drake Passage/Bransfidd Strait region and in the Indian sector respectively. Size-fractionated measurements of carbon uptake in the Indian Ocean sector revealed that nanoplankton accounted for 16–92% (mean = 53% for 26 stations), and picoplankton for 0–32% (mean = 8% for seven stations) of the primary production. The fact that the Southern Ocean phytoplankton are dominated by cells in the nano- and picoplankton size ranges has far-reaching ecological implications. The classical food chain (diatoms–krill–whales) may thus represent only a fraction of the energy flow within the Antarctic marine ecosystem.