Marine Biology

, Volume 87, Issue 3, pp 289–296

Species-specific grazing rates of heterotrophic dinoflagellates in oceanic waters, measured with a dual-label radioisotope technique

  • E. J. Lessard
  • E. Swift

DOI: 10.1007/BF00397808

Cite this article as:
Lessard, E.J. & Swift, E. Mar. Biol. (1985) 87: 289. doi:10.1007/BF00397808


A dual-isotope method was developed to measure grazing rates and food preferences of individual species of heterotrophic dinoflagellates from natural populations, collected from the Slope, Gulf Stream, and Sargasso Sea and from a transect from Iceland to New England, in 1983. The isotope method measures the grazing rates of microzooplankton which cannot be separated in natural populations on the basis of size. Tritiated-thymidine and 14C-bicarbonate were used to label natural heterotrophic and autotrophic food, respectively. Nine oceanic dinoflagellate species in the genera Protoperidinium, Podolampas, and Diplopsalis fed on both heterotrophic and autotrophic food particles with clearance rates of 0.4 to 8.0 μl cell-1 h-1, based on 3H incorporation, and 0.0 to 28.3 μl cell-1 h-1, based on 14C incorporation. Two dinoflagellate species, Protoperidinium ovatum and Podolampas palmipes, fed only on 3H-labelled food particles. Several species of dinoflagellates fed on bacteria (<1 μm) which had been prelabelled with 3H-thymidine. The clearance rates of heterotrophic dinoflagellates and ciliates were similar and within the range of tintinnid ciliate clearance rates reported in the literature. As heterotrophic dinoflagellates and ciliates can have comparable abundances in oceanic waters, we conclude that heterotrophic dinoflagellates may have an equally important impact as microheterotrophic grazers of phytoplankton and bacteria in oceanic waters.

Copyright information

© Springer-Verlag 1985

Authors and Affiliations

  • E. J. Lessard
    • 1
  • E. Swift
    • 1
  1. 1.Graduate School of OceanographyUniversity of Rhode IslandKingstonUSA

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