Growth and herbivory by heterotrophic dinoflagellates in the Southern ocean, studied by microcosm experiments

• Published in: Marine biology Vol. 109; no. 3; pp. 397 - 405
• Main Authors: BJORNSEN, P. K, KUPARINEN, J
• Format: Journal Article
• Language: English
• Published: Heidelberg Springer 01-10-1991; Berlin
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Fundamental and applied biological sciences. Psychology; Gymnodinium; Marine; Sea water ecosystems; Synecology; Southern Ocean; PSW, Weddell Sea; Marine environment; Trophic chain; Phytophagous; Growth; Algae; Microbial biomass; Thallophyta
• ISSN: 0025-3162; 1432-1793
• DOI: 10.1007/BF01313505

Growth and herbivory of heterotrophic dinoflagellates (Gymnodinium sp.) from the Weddell Sea and the Weddell/Scotia Confluence were studied in 1988 in 100-liter microcosms. The microcosms were screened through 200- mu m or 20- mu m mesh nets and incubated for 12 d at 1 degree C under artificial light. Mean cell volume of dinoflagellates was 1000 to 1500 mu m super(3), and that of their phytoplankton prey 360 to 430 mu m super(3). Dinoflagellate growth rate followed a Holling type II functional response, with a maximum growth rate of 0.3/d and half-saturation food concentrations of 1.0 mu g chlorophyll a/l, 50 mu g C/l, or 1500 cells/ml. Carbon budgets based on super(14)CO sub(2) assimilation and biomasses of phytoplankton and heterotrophic dinoflagellates suggested a balance between phytoplankton grazing loss and dinoflagellate consumption, assuming a dinoflagellate carbon conversion efficiency of 40%. Applying this to the functional response yielded estimates of maximum ingestion rate (0.8 mu g C/ mu g C/d, or 6 pg C dinoflagellate super(-1)/h) and maximum clearance (0.8 to 1.2 x 10 super(5) body volumes/h, or 80 to 120 nl/ind./h).