Radiolaria Polycystina
Vertical profiles

Vertical profiles of total radiolarian abundance in tropical and subtropical waters indicate that the bulk of their populations is usually located in the upper 50-100 m (Petrushevskaya, 1971b; Renz, 1976; Dworetzky and Morley, 1987; Kling, 1979; Kling and Boltovskoy, 1995; Abelmann and Gowing, 1997; see the panels A-C, F, and G of figurevertical distribution patterns). Quite often several discrete maxima are recorded, one at or near the surface, and a second one between 50 and 100 m (Petrushevskaya, 1971b; Kling and Boltovskoy, 1995). In the Antarctic, however, peak abundances seem to be associated with the Warm Deep Water and occur deeper, at 200-400 m (Petrushevskaya, 1967; Boltovskoy and Alder, 1992; Abelmann and Gowing, 1997; see panels D and E of figurevertical distribution patterns).

Many radiolarian species occupy discrete depth intervals of the water column. Kling and Boltovskoy (1995), on the basis of a series of plankton tows in the upper 2000 m in the eastern subtropical Pacific defined the following characteristic layers: (1) surface (with maxima at 0 m, 25 m, 0 and 50 m, 50 m, or 0 and 100 m), (2) subsurface (maximum at 100 m), (3) deep (maxima at 200 m, 200 and 300 m, or 300 m), and (4) species peaking below 300 m. Roughly similar zonations were established by other authors as well (e.g., Renz, 1976; Dworetzky and Morley, 1987; Kling, 1979). Worldwide depth zonations, however, cannot be defined in terms of fixed depths because the distribution of radiolarian species is related to water masses which move vertically as well as horizontally. For example, in the eastern subtropical Pacific inshore and oceanic 0-25 m waters can host a typically warm-water assemblage associated with the Central Water which is advected coastward by the Southern California Eddy, while midway between these two sites the same depths are inhabited by a conspicuously different, colder-water assemblage associated with the cooler waters of the California Current (Kling and Boltovskoy, 1995). Many cold water radiolarians that inhabit the upper layers at high latitudes submerge with their corresponding water masses and can be found at depth in mid- and low-latitude areas (Kling, 1976; Boltovskoy, 1988; Steineck and Casey, 1990). Siphocampe arachnea (Siphocampe arachnea;Siphocampe arachnea 2), for example, is a dominant component of surface Pacific Arctic and Subarctic plankton; in the central north Pacific it peaks at 100-300 m, and at 300-1000 m in the subtropical eastern Pacific (Boltovskoy, 1994).

Changes in the proportions of presumably living polycystine cells with depth have been assessed in a few studies. Boltovskoy et al. (1993a), based on extensive sediment trap data, concluded that numbers of live specimens decrease drastically downwards (e.g., aprox. 100% at 0 m, 50-60% at 100 m, 20-40% at 200 m, 10-20% at 500 m, 5% at 1000 m; see panel H of figurevertical distribution patterns). These results generally agreee with other studies (e.g., Petrushevskaya, 1971a; Kling and Boltovskoy, 1995). On the other hand, Abelmann and Gowing (1997) estimated much higher proportions of living cells at comparable levels in the water column: over 90% at 100-200 m, around 70% at 300-500 m. It should be noticed that staining techniques, which are usually applied for these estimates, do not adequately differentiate between live and dead cells (see RaPo. 2 Provenance and collection of materials), for which reason it is probable that concentrations of living specimens below 50-100 m are systematically overestimated in such surveys (Boltovskoy et al., 1993a; see panel H of figurevertical distribution patterns).

As with geographic patterns, data on the depths at which the various species peak listed in Table RaPo (see at the bottom of this page) have been compiled from reports on different oceanic areas. It is anticipated that they are generally valid for subtropical and tropical environments worldwide; at higher latitudes, however, some deep species may occur closer to the surface, while in the Antarctic the bulk of the asssemblages seems to occupy deeper layers (see above).

Geographic and vertical distributions of polycystines are gathered in Table RaPo — alphabetically arranged and devided in seven parts: [Table RaPo (A-B);Table RaPo (C);Table RaPo (D-H);Table RaPo (L-O);Table RaPo (P);Table RaPo (S-Spo);Table RaPo (Sti-Z)].