Figure 1.
Map of annual integrated chlorophyll concentration (high values are indicated in green and red) showing the sampling locations of acantharian cysts from meso-and bathypelagic traps (red triangle), and surface plankton nets (pink diamond). Genetic sequences (V9 region of the 18Sr RNA gene) have been also obtained from the surface and mesopelagic (orange star). (Map obtained from OceanColor website: http://oceancolor.gsfc.nasa.gov/).
Table 1.
Sampling sites and equipment used.
Figure 2.
Phylogenetic placement of the cyst-forming Acantharia.
Molecular phylogeny obtained with Maximum Likelihood analysis based on a concatenated matrix of 18S and 28S rRNA sequences of Acantharia (104 taxa and 2386 bp-long, GTR+I+G model), including cysts (bold red font) and vegetative (bold blue font) specimens collected in plankton nets and sediment traps at different depths. Each picture of a cyst (column 1) is shown together with the vegetative stage (column 2) that shares the highest genetic similarity. PhyML bootstrap percentages based on 500 pseudo-replicates and Bayesian posterior probabilities (PP) are indicated at each node (above and below, respectively) when support values were higher than 60% and 0.8, respectively. Species name of each taxon and accession numbers are provided in Table S1.
Figure 3.
Vertical distribution of Acantharia based on 18S rRNA environmental sequences.
A) clone libraries obtained from previous studies in different oceanic regions; B) V9 tag sequences from the present study sampled in the Indian (station 65), Antarctic (station 85), Pacific (stations 98 to 102) and Atlantic Oceans (stations 68 to 78) from different size fractions (0.8–5 µm and 20–2000 µm). In the pie-charts, cyst-forming clades A, B and C are highlighted with a white circle, and clades representing <1% of the total acantharian sequences are not shown. For the mesopelagic zone, the sampling depth and the contribution of acantharian sequences to total protistan sequences are indicated below the pie-charts.
Figure 4.
Geographic variation of the strontium flux.
Strontium fluxes were measured in different sediment traps deployed across the Atlantic Ocean, in the Scotia Sea at 2000 m (St 7 and St 8; in 2008), and in the Northern and Southern subtropical gyres at 3000 m (2007–2010). Significant strontium fluxes are represented by a bar, from which the width is proportional to the collection period (around 14–31 days). Strontium concentrations for each sediment trap sample are shown in Figure S2.
Figure 5.
Hypothetical scenario of the life cycle in symbiotic and cyst-forming Acantharia with shallow and deep reproduction, respectively.