VERTICAL DISTRIBUTION OF THE SPECIES (Figures 230-236)
Although our database covers a large number of plankton tows (1854), summarization of this informantion is strongly hindered by the fact that radiolarian vertical density profiles in the plankton are affected by many variables, both environmental (e.g., latitude and longitude, season) and methodological (plankton net mesh size, sieve mesh size, preparation procedures), which complicate comparisons across surveys.
For species with reasonably abundant information, we reviewed vertical distribution patterns from two different perspectives: (a) The depth of maximum abundance of the taxon ("Vertical abundance profiles of individual species,"
Figures 230-234); and (b) the species that dominate the radiolarian assemblage at different depth layers in warm and cold waters ("Dominant species at different depths,"
Figures 235, 236).
For category (a) the information in the figures of vertical distribution of selected species was derived as follows:
1. We selected the 857 plankton tows with absolute cell concentrations per unit water filtered;
2. within each series of vertical plankton tows from the same location (450 series in total), absolute abundances were pooled and averaged for the following depth intervals: 0-50 m, 50-150 m, 150-500 m, 500-1000 m, and 1000-5000 m;
3. each of these series of 5 values (in numbers of shells per unit volume filtered) was transformed to percentages. Thus, for each geographic location and each species considered we derived the proportions of individuals recovered from the various depth intervals; (4) for each species, these percentages were averaged across all geographic sites.
For category (b) we selected the 50 species with highest numbers of records in the 857 plankton samples available. Proportions of each of these in the overall polycystine assemblage were averaged for the same 5 depth intervals as above and for samples obtained in warm waters (mean annual water temperature at 10 m >12°C, according to
Antonov et al. 1998a,
1998c), and samples obtained in cold waters of the northern hemisphere (mean annual water temperature at 10 m <12°C). A similar data set for the southern hemisphere was too small to yield meaningful information.
NOTE: Please see sidebar for list of vertical distribution of species.