Response of the protozooplankton assemblage during the European Iron Fertilization Experiment (EIFEX) in the Antarctic circumpolar current
|Author(s)||Assmy Philipp1, 2, Cisewski Boris3, Henjes Joachim4, Klaas Christine2, Montresor Marina5, Smetacek Victor2|
|Affiliation(s)||1 : Norwegian Polar Res Inst, Fram Ctr, N-9296 Tromso, Norway.
2 : Alfred Wegener Inst Helmholtz Ctr Polar & Marine, D-27570 Bremerhaven, Germany.
3 : Thunen Inst Sea Fisheries, D-22767 Hamburg, Germany.
4 : IMARE Inst Marine Resources Gmbh, D-27570 Bremerhaven, Germany.
5 : Stn Zool A Dohrn, I-80121 Naples, Italy.
|Source||Journal Of Plankton Research (0142-7873) (Oxford Univ Press), 2014-09 , Vol. 36 , N. 5 , P. 1175-1189|
|WOS© Times Cited||8|
|Keyword(s)||protozoa, rhizaria, sarcodines, Southern Ocean, top-down control|
|Abstract||Ocean iron fertilization experiments enable the quantitative study of processes shaping the structure and functioning of pelagic ecosystems following perturbation under in situ conditions. EIFEX was conducted within a stationary eddy adjacent to the Antarctic Polar Front over 38 days in February/March 2004 and induced a massive diatom bloom. Here, we present the responses in abundance and biomass of all identifiable protozooplankton taxa (heterotrophic protists ranging from 2 to 500 mm) during the bloom. Acantharia, dinoflagellates and ciliates together contributed >90% of protozooplankton biomass in the upper 100 m throughout the experiment with heterotrophic nanoflagellates, nassellaria, spumellaria, phaeodaria, foraminifera and the taxopodidean Sticholonche zanclea providing the remainder. Total protozooplankton biomass increased slightly from 1.0 to 1.3 g C m(-2) within the fertilized patch and remained at 0.7+0.04 g C m(-2) outside it. However, distinct trends in population build-up or decline were observed within the dominant taxa in each group. In general, smaller less-defended groups such as aloricate ciliates and athecate dinoflagellates declined, whereas the biomass of large, spiny and armoured groups, in particular acantharia, large tintinnids and thecate dinoflagellates increased inside the patch. We attribute the higher accumulation rates of defended taxa to selective, heavy grazing pressure by the large stocks of copepods. Of the defended taxa, acantharia had the lowest mortality rates and the highest biomass. Large stocks of tintinnid loricae in the deep water column identify this group as a relevant contributor to deep organic carbon export. Highest accumulation rates (0.11 day(-1)) were recorded in S. zanclea.|