Radiolarian assemblages in the eastern tropical Atlantic: patterns in the plankton and in sediment trap samples

JOURNAL

OF

K?&Kz

ELSEVIER

Journal of Marine Systems 8 (1996) 31-51

Radiolarian assemblages in the eastern tropical Atlantic: patterns in the plankton and in sediment trap samples D. Boltovskoy a,*, H. Oberhgnsli b, G. Wefer ’ a Departamento de Ciencias Biol&icas, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and CONICET, Buenos Aires, Argentina b Max-Planck-lnstitut fir Chemie, Abt. Biogeochemie, Postfach 3060, D-55020 Maitu, Germany ’ Fachbereich Geowissenschaften, Klagenfutier Strasse, Universitiit Bremen, 28359 Bremen, Germany

1428

Received 25 January 1995; accepted 20 June 1995

Abstract Polycystine Radiolaria were studied in 40 Multinet (63 pm) plankton samples collected in February-March 1988 in the eastern tropical Atlantic (10”N to 17”S), from depths ranging between 0 and 300 m. A total of 148 taxa were recorded, most of them accounting for very low proportions of the individuals identified. The geographic distribution of polycystine assemblages throughout the area was relatively homogeneous and quite unpatterned; no clear associations with latitude, surface temperature, salinity or chlorophyll a were found. On the other hand, several radiolarians showed fairly distinct vertical profiles, allowing identification of forms preferring the uppermost 25-50 m, forms peaking at 50 to 150 m, and forms with highest percentage contributions below 150 m. Comparison of this planktonic collection with a similar survey carried out in 1983 in the same area indicates good overall agreement. In contrast, radiolarian compositions in sediment trap samples deployed at 853 and 2195 m in close vicinity with some of the plankton stations surveyed are totally different. Subsurface advection of shells produced at higher latitudes and integration of low radiolarian abundances over large depth-intervals are the most likely cause of the inconsistencies.

1. Introduction During the last decades polycystine fossil assemblages have been intensively used for paleoecological reconstructions Wing, 1977; Moore et al., 1981; Boltovskoy, 1991, 1992). However, because plankton-based studies on the distribution of these protists are extremely scarce and fragmentary, species-specific distributional ranges and the corresponding inferred ecological settings are * Corresponding author. 0924-7963/96/$15.00

0 1996

SSDZO924-7963(95)00038-O

almost exclusively derived from surface sediment materials. Although, in principle, surface sediment-based patterns do fulfill some of the requirements of the methods utilized when deciphering past oceanographic conditions from present-day distributions on the bottom, the assumptions involved present some potential pitfalls. The significance of these drawbacks is especially important if assemblages on the ocean floor do or did not reflect adequately fauna1 makeups in the plankton (Boltovskoy, i988, 1994; Kling and Boltovskoy, 1995). The very few surveys that drew

Elsevier Science B.V. All rights reserved

D. Boltovskoy et al. /Journal

32

of Marine Systems 8 (1996) 31-51

detailed comparisons between polycystine assemblages in the water-column and in the underlying sediments found some major disagreements, and these were usually attributed to the effects of selective dissolution (see reviews in Boltovskoy, 1988, 1994) which, in the case of polycystines, occurs almost exclusively after settling on the sea-floor (Takahashi and Honjo, 1983). On the other hand, comparisons between the upper-layer plankton (where presumably most of the sinking populations are engendered), and accumulation in sediment traps at intermediate depths, above the bottom (where polycystine dissolution is still negligible) to our knowledge have not been carried out with Radiolaria. This paper presents such a comparison on the basis of tropical materials concluding that the remarkable differences observed, which cannot be attributed to selective dissolution, seem to be associated with problems in our interpretation of polycystine quantitative vertical distribution profiles, as well as with significant distortions in the assumed modes of downward flux.

in the eastern tropical Atlantic, between 10”N and 17% (see Table 1 and Fig. 1). Temperature, salinity and chlorophyll a values were obtained at 5 m depth. Samples were fixed onboard with HgCl,; in the laboratory l/2 of each sample was ashed and the cleaned residue used for foraminiferal (Oberhinsli et al., 1992) and radiolarian (this work) analyses. Polycystine counts and identifications were based on these dry residues pretreated with hydrochloric acid and mounted in permanent slides with Depex mounting medium. Because the nets were not provided with flowmetering devices, data on absolute radiolarian concentrations throughout the water-column are unavailable. Thus, conclusions are based on relative (percentage) abundance relationships between species, based on counts of approx. RIO-300 radiolarians per sample (Table 1). Cluster analyses of samples and stations were performed using Pearson’s r correlation coefficient and the Unweighted Pair-Group Arithmetic Average clustering algorithm (UPGMA, cf. Sneath and Sokal, 1973). Specific diversity values were calculated according to Shannon-Wiener’s formula (Shannon and Weaver, 1949).

2. Material and methods 3. Results and discussion

Plankton samples were collected by means of vertical tows with an opening-closing Multinet system (Hydrobios Co., Kiel), provided with 63 pm-mesh nets (METEOR cruise M6/6, 23 February to 21 March, 1988; Wefer et al., 19881,

3.1. Radiolarian dWibution pattern The samples surveyed yielded a total of 148 polycystine taxa (Appendix); this number com-

Table 1 Station list and numbers of radiolarian individuals identified per sample Station

1016-l 1026-l 1037-3 1038-4 1039-2 1041-2 1042-2 1043-3 1044-2 1047-2

Position

Date (1988)

Latitude

Longitude

11”45.23’s 17”lO.lS’S 13”08.99’S 06”27.38’S 06Y2.38’S 03=28.76’S 02”49.53’S 00”01.05’s OO”37.46’N 09”57.69’N

ll”41.7’E 08’54.36’E 00”08.54’E 00”12.69’E oo”52.46’W 07”36.28’W 08”54.08’W 09”57.54’W 09=‘40.69’W 22”20.36’W

a Sample barren of Radiolaria

Feb. 25 Feb. 29 Mar. 7 Mar. 9 Mar. 10 Mar. 12 Mar. 12 Mar. 13 Mar. 14 Mar. 18

Towing depths (m) O-25 25-50 50-100 Radiolarian individuals identified a a B a

71 125 421 367 37 137 189 86

a a

205 361 117 115 23

a

B

loo-150 47 a

a

68 441 353 420 169 44 182 110

162 267 209 366 120 135 133 199

150-300 411 382 423 344 430 127 436 235 181 437

D. Boltovskoy et al. /Journal

of Marine Systems 8 (1996) 31-51

pares favorably with previous investigations in tropical and subtropical areas in general that attempted to identify all polycystines (rather than selected subsets of their taxocoenoses) (e.g., Boltovskoy and Jankilevich, 1985; Boltovskoy and Riedel, 1987; Kling and Boltovskoy, 1995), and in the eastern equatorial Atlantic in particular

2oow

r

100

33

(Boltovskoy et al., 1993a; Boltovskoy et al., in press). Due to the obscure taxonomic status of several morphotypes, especially in the poorly known families Litheliidae, Pyloniidae and Plagoniidae, various presumably different forms were lumped into loosely defined categories at supraspecific levels. Very few radiolarians, how-

00

20”E

100

l200N

CB ,*

0

100

104

l

1044/2 1043/3 --Il 1042/2 1041/2 . 1039/2=.

00

GBN3 #

103814 100

200s 0 ;;nldkn *

samples (1988)

!Sec≠t~trp,~~x$ngs Boltovskoy& U&a,

A

(1988-l 990)

in press

Plankton samtIes (April 1983) Dworetzky 8 MO ey. 1987

Fig. 1. Geographic distribution of the samples and main surface currents in the area (inset; mainly based on Gorshkov, and triangle denote location of collections discussed in text.

1977). Stars

D. Boltovskoy et al. /Journal of Marine Systems 8 (1996) 31-51

2 $ .-E

3

5 Z

Correlation (Pearson’s r) 0.00 t

0.50

#

$

1.00 i 1016-l

100-150

1036-4

O-25

1036-4

25-50

1043-3

O-25

1044-2

50-100

1041-2

100-150

1044-2

O-25

1042-2

25-50

1043.3

50-100

1047-2 1016-l

25.50 150300

1044-2

150300

1041-2

150-300

1043-3

2550

1047-2

O-25

1042-2

O-25

1039.2

O-25

1043.3

150-300

1043.3

loo-150

1044.2

100-150

1026.1

150900

1037-3

50-100

10379

100-150

1037-3

150.300

1038-4

50-100

1039-2

50-100

1036-4

100-150

1039.2

100-150

1039.2

150-300

1042.2

100-150

1042.2

50-100

1041-2

O-25

1041.2

50-100

1042-2

150-300

1041-2

2550

1036-l

150-300

1047.2

100-150

1047-2

50-100

1047.2

160-300

1037-3

O-25

D. Boltovskoy et al. /Journal

ever, were represented by abundant populations: only 30 species exceeded 5% of the overall assemblage in any one sample. Spumellarians were overwhelmingly dominant over the Nassellarians (mean: 91%; range: 65 to lOO%), with Spongodiscidae being the most abundant family WCtyocoryne profunda, Spongodiscus resurgens, Spongaster tetras, Euchitonia elegans /fircata; mean: 50% of all polycystines). The geographic distribution of species (and, presumably, of individuals), was remarkably unpatterned throughout the area of the survey. Fig. 2 illustrates fauna1 similarities between all samples investigated, as revealed by a cluster analsyis of the 30 most abundant radiolarians. Shaded areas in the cluster identify faunistically relatively homogeneous groups of samples. The geographic distribution of the corresponding sites (Fig. 3) does not seem to suggest any clear pattern. Panels on the right-hand side of Fig. 2 allow visually assessing homogeneities in the geographic and oceanographic settings of the fauna1 assemblages compared. Variations in geographic location, surface temperature, salinity and chlorophyll a between sample groups are roughly as large as within them, suggesting that none of these parameters exerted a discernible influence on the fauna1 makeups of the samples. Sample group C seems to be the only one fairly circumscribed to locations slightly south of the equator, characterized by high temperatures and salinities, and by variable but generally below-average chlorophyll a concentrations at 5 m (Fig. 2). The numbers of polycystines recorded in group C samples (mean: 299) were somewhat higher than those found in the rest of the collection (mean: 178), which might be indicative of enhanced in situ radiolarian concentrations. These richer samples yielded higher specific diversities than the rest of the collection (4.36 vs. 3.63, respectively), noticeably higher percentages of some of the radiolarian species and families often associated with high

of Marine Systems 8 (1996) 31-51

35

productivity

areas (e.g. various morphotypes of calvata, Plagoniidae, Theoperidae, Nassellaria in general, etc.), and consistently lower numbers of several characteristically warm water and/or oligotrophic forms ( Acrosphaera

Arachnocorallium

murrayana, Collosphaera macropora, Dictyocoryne profunda / truncatum, Didymocyrtis tetrathalamus, Euchitonia elegans /furcata, Siphonosphaera martensi, Siphonosphaera polysiphonia, Spongaster tetras tetras, etc.)

As opposed to geographic location, depth of tow influenced the distribution patterns of at least some radiolarian species rather clearly. Fig. 4 illustrates the vertical profiles for the 20 most abundant polycystine species recorded; these radiolarians accounted for approximately 2/3 of all the shells identified. Although station-to-station species-specific patterns varied noticeably, in general terms roughly 3 groups can be identified: (1) Species peaking in the top 25 or 50 m (Dictvocoryne profunda, Euchitonia elegans / furcata, Spongaster tetras tetraq Didymocyrtis tetrathalamus, Octopyle stenozona); (2) Species peaking at 50 to 150 m (Spongodiscus resurgens, Spongotrochus glacialis, Stylodictya multispina, Styptosphaera spumacea); (3) Species with maximum percentage contributions below 150 m (Stylochlamydium asteriscus, Larcopyle butschlii, Stylodictya aculeata, Lamprocyclas maritalis, Spongocore cylindrica, Spongopyle setosa). These results are generally consistent with pre-

vious information on the depth-distribution of radiolarian species in open-ocean areas (e.g. Kling, 1979; Dworetzky and Morley, 1987; Kling and Boltovskoy, 1995). Not surprisingly, radiolarians with highest relative values in the topmost layers are characteristic of warm oligotrophic waters, while many of those that dwell deeper in the water-column usually prefer cooler areas (e.g. Boltovskoy, 1991, 1992). Also specific diversities varied generally with

Fig. 2. Fauna1 similarities between all the samples analyzed as revealed by a cluster analysis based on the 30 most abundant polycystine species (Pearson’s r correlation and UPGMA, cf. Sneath and Sokal, 1973). Panels on the right-hand side illustrate latitude and various oceanographic properties of the corresponding sites. See Fig. 3 for geographic distribution of samples included in groups A-C.

36

D. Boltovskoy et al. /Journal

O-25 m

25-50

m

of Marine Systems 8 (I 9%) 31-51

i 50-100 m

H 100-150 m

R

i 150-300 m

Fig. 3. Geographic distribution of the samples included in groups A-C in Fig. 2. Columns give approximate position of stations involved; shadings represent towing depths of samples grouped.

depth, showing lowest values between O-25 and 50-100 m, and increasing more or less sharply at 100-150 and 150-300 m (Fig. 5). Interestingly, one station, 1041-2, showed the opposite pattern, with specific diversity values clearly decreasing toward the bottom (Fig. 5). Analysis of the vertical profiles illustrates in Fig. 4 also point at sharp differences between station 1041-2 and the rest of the sites; these dissimilarities are summarized in the lower panel of Fig. 5. Many of the taxa which occupied the uppermost 25-50 m throughout the area, including Dictyocoryne profinda, Euchitonia elegans/furcata, Spongaster tetras tetras and Spongosphaera streptacantha , peaked below 150 m at station 1041-2; whereas several deeper-water radiolarians at most of the, stations (e.g. Stylochlamydium aster&us, Larcopyle butschlii, Lamprocyclas maritalis, S)ongocore cylindrica) showed

major peaks near the surface at station 1041-2 (see Fig. 4 and lower panel of Fig. 5). Thus, it seems as though the “normal” vertical pattern was inverted at this locale, with deeper species dwelling preferably near the surface, and

surface-layer ones sinking toward the bottom. We hypothesize that this anomaly could reflect a circumscribed upwelling cell of deep waters from the Equatorial Undercurrent and/or the South Equatorial Counter Current, such as those described by McPhaden (1984) and by Hastenrath and Merle (1987) (surface water temperatures at 1041-1, however, were not lower than those at neighboring stations). High proportions of surface-water species at depth at station 1041-2, in turn, are more difficult to explain in hydrographic terms, yet the fact of our dealing with percentage values (rather than with absolute abundance figures) can bias perception of distribution patterns because of the closed systems these transformations generate. Indeed, when percentage values are used, changes in the (absolute) abundance of the deep species alone affect not only their own share of the overall assemblage, but also that of all other species, including the surface ones. Thus, one can envision that reduced proportions of these deep radiolarians at 150-300 m at station 1041-2 are responsible for the high relative abun-

Fig. 4. Vertical profiles for the 20 most abundant radiolarian taxa recorded. Dendrogram at left shows similarity between specific vertical distribution patterns (as indicated by correlation values between their percentage abundances at the 5 depth layers of the 8 stations), most homogeneous groups of patterns are hachured (vertical profile panels not indented). Black scale bars at top of panels are 10%. Data for 25-50 m at stations 1037-3, 1039-2 and 1044-2 are interpolated values.

D. Boltovskoy et al. /Journal

Stations

of Marine Systems 8 (1996) 31-51

D. Boltovskoyet al./Joumul of Marine Systems8 (19%) 31-51

38

O-25 m 25-50 m

50-I 00 m x E 4 2

100-I

50 m

@

150-300

m 2.2

2.6

3.0

Polycystine

-

3.4

specific

3.8

diversity

4.2

4.6

5.0

(Shannon-Wiener)

Station 1041-2

,

20% ,

O-25 m 25-50m 50-100 m lOO-150m 150-300

m

O-25 m 25-50 m 50-100 m loo-150

m -

150-300

m

Mean for all other stations of upper panel

20%1

Fig. 5. Top panel: specific diversities (Shannon and Weaver, 1949) of the polycystine assemblages identified as a function of sample depth. Bottom panel: comparison of the vertical profiles of the 20 species illustrated in Fig. 4 (left-to-right sequence reproduces top-to-bottom sequence in Fig. 4) at station 1041-2 and at all other stations (mean values for each depth-interval) included in the top panel.

D. Boltovskoy et al. /Journal

dances of surface taxa at these depths, rather than actual increases in the absolute abundances of the latter. 3.2. Comparison with previous surveys of plankton and sediment trap collections Dworetzky and Morley (1987) reported the analysis of radiolarians recorded in two vertically stratified tows (O-200 m) carried out in the area of our stations 1038-4 and 1039-2 (see Fig. 1) in April 1983. Based on their illustrations and species-definition list (rather than on names solely), we established the equivalences between 26 of their 28 taxa identified to species level with our own identifications and compared the relative (percentage) abundances of these taxa in the two databases (i.e., mean values for their 2 tows, 15 samples, and our stations 1038-4 and 1039-2).

of Marine Systems 8 (19%) 31-51

39

The agreement is generally good, insofar as for 23 of the 26 taxa considered differences in mean percentage abundance were below 5% (Fig. 6). Collosphaerids and some other typically warm water, surface species (e.g. Octopyle stenozona) represent higher proportions of overall radiolarian numbers in the collection of Dworetzky and Morley (1987) (= Tetrapyle octacantha therein), which can be attributed to the fact that their tows were shallower than ours and had a denser coverage of the surface (O-50 m) strata. In both datasets the 26 species used accounted for sizable proportions of total Radiolaria (approx. 40 to 60%). Also vertical distribution patterns show some clear similarities between the two collections. Dictyocoryne profunda ( = Hymeniastrum euclidis), Euchitonia elegans / furcata (= Euchitonia spp.), Spongaster tetras and Didymocyrtis tetrathalamus dwelled preferably in the up-

11 5 2

-z

10 9

-

Sta. 1038-4 & 1039-2

A

4: s5 3 6

4 3

2

2

B

’ 0

Fig. 6. Comparison of the mean percentage abundances of radiolarian species recorded by Dworetzky and Morley (1987) at approx. 5”S, 0”lO’W CO-202 m) in April 1983, with our results for the nearby stations 1038-4 and 1039-2.

NASSELLARIA

SPUMELLARIA

Artostrobiidae

Cannobotryidae

Pterocorythidae Spyrida

Theoperidae

Plagoniidae

Collosphaeridae

Coccodiscidae

Litheliidae

Actinommidae

Pyioniidae

Spongodiscidae

CBN3

SED. TRAP

Stas. 1042-2,

1043-3

PLANKTON

Percentage Of 0

z_

Cl31

Sta. 1047-2

PLANKTON

4 d ‘A CD

SED. TRAP

b-l

total polycystines

D. Boltovskoy et al. /Journal

Boltovskoy et al. (in press) and Boltovskoy et al. (1993a) studied the radiolarians retrieved in two time-series sediment trap collections deployed at 21”N, 2O”W (13 samples, 22.3.1988 to 8.3.1989, trap-depth: 2195 m; CBl site), and at 2”N, 11“W (22 samples, 1.3.1989 to 16.3.1990, trap-depth: 853 m; GBN3 site; see Wefer and Fischer, 1993). These moorings were located in the vicinity of our samples 1047-2, and 1042-2, 1043-3, respectively (see Fig. 1). Comparison of the proportions of various radiolarian taxa in these collections is illustrated in Fig. 7, which clearly points at striking differences. Nassellarians represented ca. 80-90% in both sediment trap collections, and below 10% in the plankton samples. The Plagoniidae, overwhelmingly dominant in the sediment traps, are barely present in the O-300 m plankton, where spongodiscids account for over 50% of the radiolarian shells. Only traces of the most abundant plankton-sample species are recorded in the traps, and viceversa (Fig. 7). The impressive differences found are numerically illustrated by data summarized in Fig. 8; relative species contributions are very similar in both sediment trap collections dealt with (Pearson’s r correlation coefficient: 0.9601, and there is also a large degree of similarity between upper-layer (O-25 m> and deep (150-300 m) \

:

!

2195 m

Fig. 8. Correlation values for mean percentage radiolarian compositions in the plankton samples (O-25 m, and 150-300 m tows only), and in sediment trap samples retrieved at nearby locations (cf. Fig. 1).

of Marine Systems 8 (19%) 31-51

41

plankton-sample radiolarian inventories (r = 0.758). In contrast, plankton and sediment trap percentage data are totally uncorrelated (r = 0.004 to 0.059), which testifies to the remarkable uncoupling of these two collections. Although the attributes of planktonic populations that are recorded by collections of plankton samples differ from the ones that are logged by time-series sediment traps (e.g. Boltovskoy, 1994), the differences illustrated in Fig. 7 seem to go far beyond what one could anticipate, to the point that the two data sets seem to be recording two widely different communities. Since all samples were processed by the same person, we rule out any effects of heterogeneous identification or counting procedures. On the other hand, methodological differences in collection and preparation techniques may have influenced this comparison to a certain extent. For example, plankton materials were collected with a 63 pmmesh net, while sediment trap samples were sieved with a 15 pm-mesh screen; total nassellarian numbers illustrated in Fig. 7 include about 50% of juvenile Nassellaria 40-60 pm in size, many of which would have been missed by the coarse plankton nets used. However, even excluding juvenile nassellarians from the yields of sediment trap samples (thus lowering the share of Nassellaria in these materials to 55-58%), leaves a 40-50% abundance difference between sediment traps and plankton samples which cannot be accounted for by methodological artifacts. Differences in the proportions of plagoniids, which are generally represented by rather small-shelled individuals, could also be partially attributed to mesh-size inconsistencies, but spongodiscids are usually large and easily identifiable, even in their early growth stages (at least at the family-level, cf. Boltovskoy et al., 1993b), which precludes the possibility of their having been underrepresented in the sediment traps. Thus, although mesh-size most probably played a significant role in the comparison drawn, we contend that it only accounts for a restricted fraction of the differences observed, the sizable remainder reflecting real dissimilarities in the ways ecological and distributional trends are perceived by these two sampling techniques. The

42

D. Boltovskoy

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time-integrative nature of sediment trap materials (and, conversely, the snapshot-type picture conveyed by plankton samples) is of minor concern in this particular case because seasonal differences in radiolarian specific make-ups are extremely low in the area of our survey (Boltovskoy et al., 1993a; Boltovskoy et al., in press). The key to the differences reviewed should probably be sought in the vertical distribution patterns of living radiolarian assemblages and the concomitant fluxes of sedimenting shells. Assuming steady-state conditions and negligible effects of year-to-year variations, the main source of difference between sediment-trap and plankton-sample materials is depth of retrieval of the organisms (O-300 m for the plankton, vs. ca. 850 and 2200 m for the sediment traps). Because O-300 m populations can only go down upon death, and since dissolution of polycystine shells

of Marine Systems 8 (1996) 31-51

before reaching the depths of the traps is most probably insignificant (e.g. Milliman and Takahashi, in press), either strong selective destruction (by grazing?) of radiolarian skeletons produced near the surface occurs somewhere between 300 and 800 m, or a major source of the assemblages intercepted by the traps is located away from the surface, below 300 m, or in a geographically different area. Deeper plankton assemblages (150-300 m) are not more similar to the corresponding sediment trap faunas than plankton retrieved at O-25 m (Fig. 81, which suggests that whatever distorting factors are at play, they are most active below 300 m. Several alternative (or complementary) scenarios can be envisioned which can account for the large dissimilarities described (Fig. 9): (1) Selective destructive grazing by particleconsuming zooplankton exerts more pressure on

Fig. 9. Hypothetical mechanisms than could account for the remarkable differences in radiolarian assemblages retrieved in plankton and in sediment trap samples at closely spaced locations. See text for detailed explanation of the probable effects schematically represented (numbered I through 5).

D. Boltovskoy et al. /Journal of Marine Systems 8 (19%) 31-51

the species missing in the sediment trap samples, thus decreasing their effective output rates (I). In Antarctic waters, for example, over 90% of the radiolarians produced above 400 m may be destroyed by grazing between 400 and 900 m (Boltovskoy and Alder, 1992). Evidences of selective grazing, which in turn facilitates subsequent dissolution, have been reported for a variety of microplanktonic groups and environments (e.g. Gersonde and Wefer, 1987; Sancetta, 1989; Samtleben and Bickert, 1990). However, in tropical areas highest concentrations of zooplanktonic grazers are usually located above 300 m (Vinogradov, 19681, which conflicts with drastic compositional changes occurring below this level. Furthermore, it has long been known that vulnerability to destruction by grazing is closely associated with robustness of the test; most of the radiolarians which show significantly higher abundances in the plankton than in the traps posess rather solid shells with abundant and tightly organized skeletal material (like the Spongodiscidae). We therefore conclude that selective destructive grazing does not play a major role in engendering the dissimilarities described. (2) Near surface populations can be carried away by surface and subsurface currents eventually settling elsewhere, rather than significantly contributing to the traps and sediments located directly below the given site (2). Although the locales in question are effectively characterized by active and complex surface and subsurface currents (Bubnov, 1960; Moroshkin et al., 1970; see Fig. 11, our collection comes from a rather large area where no major changes in radiolarian assemblage composition were recorded. Assuming that the average sinking speed of a radiolarian shell is around 50 to 150 m d-i (Takahashi and Honjo, 19831, it would take l-3 weeks for an individual dead at 0 m to reach the trap depth of 800 m; in terms of horizontal displacement, under normal oceanic conditions this cannot represent a distance of more than 100 to 600 km, which is negligible at the spatial scale of the sampling design used. (3) Radiolarians recorded by the trap samples are mostly contributed by organisms produced elsewhere, either at or near the surface or at

43

some depth, and advected laterally to the sediment trap sampling sites at mesopelagic depths (3). The lateral (usually equatorward) advection of organisms produced elsewhere has been documented for many pelagic taxa, and the effects of this displacement can strongly “contaminate” the corresponding sediments with shells different from those which are produced in the nearsurface, overlying waters (see detailed discussion in Boltovskoy, 1988, 1994). In the eastern equatorial Atlantic strong meridional currents have been described, with velocities up to 10 cm s-l as deep as 500 m (Moroshkin et al., 1970; Stramma and Peterson, 1989). In the case of the deepest trap here evaluated (2195 m), such velocities could, in principle, advect surface-layer organisms from distances not exceeding some 100-200 km. However, this figure assumes passive oblique sinking of dead individuals only, which is not necessarily the case. In effect, colder-water organisms can survive extended periods of time in deeper and cooler waters upon having been displaced into a warmer-water domain (Wiebe and Boyd, 1978). Thus, living cells can be subjected to lateral displacement on much broader scales than the ones inferred from regular, passive sinking of dead shells alone (Boltovskoy, 1988, 1994). Interestingly, most of the radiolarians “overrepresented” in the traps (as compared with the overlying plankton) are colder-water species, which supports the assumption that they have been produced at higher latitudes, most probably to the south of our sampling area. (4) While plankton samples record population biomass, the yields of sediment traps are an indicator of production (Deuser et al., 1983, 1990), which does not necessarily correlate with standing stock. Species with high densities but low reproduction rates would be abundant in planktonic materials, but might be scarce in the sediment trap that collects their output; whereas a sparsely distributed but fast reproducing organism is rare in the plankton but accumulates at high rates in the underlying trap (4). Most of the polycystine species that dominated the sediment trap assemblages have been recorded in the plankton samples at one time or another, but they mostly represented very low fractions of the

44

D. Boltovskoy

et al. /Journal

overall taxocoenoses. Unfortunately, almost nothing is known about the modes and frequencies of radiolarian reproduction (Anderson, 19831, let alone the reproductive rates of different radiolarian species. At any rate, since trap assemblages are dominated by generally colder- (and deeper) water species, and because for most marine animals colder-water representatives reproduce less frequently than their warm water counterparts, we do not think that differential output rates can explain the differences described. (5) Our plankton samples document the instantaneous standing stocks present in the upper 300 m, whereas the sediment trap materials involved integrate the production of 800 to 2000 m of water. Although upper-layer species are characteristically much more abundant than deepwater ones, the vertical ranges of the former are also significantly shorter than those of the latter. As shown by Kling and Boltovskoy (1995) in their study of O-2000 m radiolarian vertical profiles in the northeastern Pacific, species-specific absolute abundances are rather well coupled with the corresponding depth-ranges of maximum concentration. In other words, abundant forms are fairly circumscribed to short and shallow depth intervals, while the scarce ones (in terms of individuals per m3) occupy extended stretches of the watercolumn, often on the order of l-2 km. Thus, when a significant depth range is considered, the depth-integrated absolute numbers of these deeper species can exceed up to 10 times those of the more densely packed upper-layer ones (Kling and Boltovskoy, 1995). Integration of low abundances over large depth ranges could therefore have contributed to enhance the proportions of deeper radiolarians in the traps (5). As shown in Fig. 7, the deeper sediment traps record much higher proportions of nassellarians than the shallow plankton samples; this trend is consistent with some observations that reported considerably higher percentages of Nassellaria on the bottom, than in the overlying surface-layer plankton. For example, the average proportion of Nassellaria in the O-25 m plankton samples of Renz (1976) from the tropical Pacific was ca. 30%, while the corresponding surface sediments contained 50% of shells belonging to this order. This

of Marine Systems 8 (19%) 31-51

trend, however, is probably restricted to comparisons encompassing the entire water-column, including depths above 100-200 m and below 300400 m. Thus, the yields of our 150-300 m plankton samples are not more similar to trapped assemblages than those retrieved at O-25 m (Fig. 8). This interpretation agrees with the results of Takahashi and Honjo (19811, who found significant changes in nassellarian species composition between traps placed at 389 and at 988 m, as well as higher nassellarian fluxes at 3755 m than at 988 m. It is probable that 300-400 m constitutes an important threshold depth where the gradient of change in radiolarian abundance and specific composition steepens abruptly (Kling, 1979; Kling and Boltovskoy, 1995). The above discussions analyze the probable mechanisms which could be responsible for the remarkable compositional differences observed, but the answer to the problem remains open. A more comprehensive ad hoc survey, especially encompassing deeper plankton tows and shallower sediment trap deployments, would help address the questions raised, but it would probably not suffice for solving the riddle altogether. A major obstacle is the fact that, although homogenized through transformations into percentage data, as pointed out above the databases compared are expressions of different attributes of polycystine taxocoenoses: standing stock (plankton samples) vs. production and output rates (sediment trap samples). While it would be reasonable to assume that on broad scales the two parameters are generally positively correlated, different species may have quite dissimilar standing stock vs. production ratios. Unfortunately, the information needed in order to establish the relationship between these two attributes is unavailable even for the polycystines as a group, .let alone for individual species. We do not know how these organisms reproduce, what their life-span is, or how many offspring per reproductive event are produced (Anderson, 1983). Another crucial drawback is the lack of reliable information on the depth-distribution of radiolarian species. We suggest that studies of the vertical distribution patterns of shelled organisms, having borrowed some interpretational

D. Boltovskoy et al. /Journal

premises from work carried out with plankton (mostly soft-bodied) in general, tend to overlook the fact that shelled species are present both at the level of their living vertical range, and from there all the way down to the bottom. Very few of the studies dealing with the vertical distribution of Radiolaria attempted to differentiate dead from living organisms (traditionally, by means of staining the cytoplasm; e.g. Petrushevskaya, 1971a). However, even counting stained and unstained specimens separately does not solve the problem because we ignore how long it takes for a dead protoplasm to disappear by decomposition; since the time in question could largely exceed what it takes a shell to reach a 5000-6000 m bottom (cf. Boltovskoy and Lena, 1970; Takahashi and Honjo, 19831, separating these two categories is no guarantee of adequately discriminating living assemblages from dead, sedimenting shells. Despite these unsolved uncertainties, the fact itself of vast dissimilarities between assemblage compositions in the plankton and in the traps represents a major obstacle for paleoecologic interpretations based on fossil remains. As shown by Boltovskoy et al. (1993b), surface sediment radiolarian assemblages at the GBN3 site (Fig. 1) are very similar to those recorded in the corresponding trap samples, and therefore very different from the living fauna at O-300 m described in this study. In other words, contrary to the generally assumed premise that the sediments are an adequate indicator of the plankton in the overlying near-surface layer of water, and by extension of the environmental settings which characterize that area, our results show that specific compositions in the plankton and in the sediments can be as different as those which characterize areas thousands of kilometers apart. For example, comparison of radiolarian fauna1 similarities between an equatorial sample and a series of samples located at increasing distances to the south of the former (surface sediments studied by Boltovskoy, 1987) shows that correlation values as low as the ones found for the planktonic vs. the sediment trap materials discussed (0.004 to 0.059, cf. Fig. 8) are equivalent to those between equatorial and Antarctic assemblages! Admittedly, this assess-

of Marine Systems 8 (1996) 31-51

45

ment has to be taken with caution because actual ecological affinities of the species covered by the analyses are not weighted; in other words, the numeric expressions used ignore the fact that in one case most of the taxa compared, while effectively different, still are all mostly tropical and subtropical in nature (Fig. 81, whereas in the other (Boltovskoy’s, 1987 data) the northernmost sample contains tropical species exclusively, and the southernmost one hosts only cold-water radiolarians. Although very significant differences in radiolarian assemblage compositions in the plankton and in the sediments seem to be the rule, rather than the exception (Renz, 1976; Boltovskoy, 1988, 1994; Boltovskoy and Riedel, 1987), we cannot ignore the possibility that such striking dissimilarities as those found in this region at different levels in the water-column are a local phenomenon. Some of the very few surveys that had adequate coverage of strata both above and below 300-400 m found rather homogeneous radiolarian assemblages throughout all depths sampled. For example, in Kling and Boltovskoy’s (1995) collection of vertically stratified tows from the northeastern Pacific, correlation values between O-25 m assemblages and those retrieved down to 1000 to 2000 meters are mostly above 0.9. On the other hand, in a similar survey carried out farther north by Kling (1979), fauna1 compositions along the water column were much less homogeneous. Nevertheless, as noted above plankton-tow data indicate standing stocks, whose comparison with the measurement of interest to paleoecological studies: accumulation rates, presents serious difficulties.

Acknowledgements This study was supported by grants from the University of Buenos Aires (UBA EX-059), from the Consejo National de Investigaciones Cientificas y TCcnicas, Argentina (CONICET, PID-BID 3661, and by the Deutsche Forschungsgemeinschaft through Sonderforschungsbereich 261 of the University of Bremen, Contribution N” 87.

D. Boltovskoy et al. / Joumul of Marine Systems 8 (I 9%)

46

Appendix A Taxa are sorted in alphabetical order. First set of square brackets gives a recent bibliographic reference to the species and/or comments on its identification; second set of square brackets gives its average percentage contribution in the collection investigated. Species Acunthodesmia vinculutu (Mueller) [Boltovskoy and Riedel, 19871 LO.361 Acanthosphaeru uctinotu (Haeckel) [Boltovskoy and Riedel, 19801 [0.03] Acunthosphaeru corlocu (Popofsky) [Boltovskoy and Riedel, 19801 [O.Ol] Acunthosphueru dodecustylu Mast [Boltovskoy and Riedel, 19801 [0.13] Acrobotrys sp. B [Boltovskoy and Riedel, 19871

ma Acrosphueru murruyunu (Haeckel) [Nigrini and

Moore, 19791 fO.361 Acrosphueru spinosu (Haeckel, 1860) [Boltovskoy and Riedel, 19801 [1.04] Actinommu unturcticum (Haeckel) [Nigrini and Moore, 19791 LO.071 Actinomma arcudophotum Haeckel [Nigrini and Moore, 19791 LO.091 Actinomma kptodetmum (Jorgensen) [Nigrini and Moore, 19791 LO.151 Actinommu sol [Boltovskoy and Riedel, 1980; Includes forms similar to Thecosphueru inermis (Haeckel)] [0.881 Actinommu sp. 1 [3 concentric shells, lo-15 3-bladed spines, outer shell with regular circular pores with hexagonal frames, 14-18 pores on the equator] [0.351 Actinommid sp. A [Boltovskoy and Riedel, 19871 to.061 Actinosphueru sp. [Probably conspecific with Actinosphueru ucunthophoru (Popofsky), in Takahashi, 19811 10.051 Amphirhopulum ypsilon Haeckel [Nigrini and Moore, 19791 IO.191 Amphispyks reticuluta (Ehrenberg) [Boltovskoy and Riedel, 19871 10.161 Androspyris rumosu (Haeckel) [Takahashi, 19811 [O.Ol] Anthocyrtidium ophirense (Ehrenberg) [Nigrini and Moore, 19791 [0.31]

31-51

Anthocyrtidium zungueburicum (Ehrenberg) [Nigrini and Moore, 19791 [0.05] Aruchnocorallium culvatu a [Boltovskoy and Riedel, 1987, as Aruchnocorullium calvutu group] [0.971 Aruchnocorullium culvutu b [Boltovskoy and Riedel, 1987, as Lithomelissu thorucites] [0.30] Aruchnocorullium culvutu d [Boltovskoy and Riedel, 1987, as Peridium sp. aff. P. laxum group] [0.561 Aruchnocorullium culvutu e [Boltovskoy and Riedel, 1987, as Peridium sp. and ?Trisulcus sp. aff. T. testudus] [0.141. Aruchnocorullium culvutu f [Boltovskoy and Riedel, 1987, as Lophophuena sp. aff. L. upiculata] [O.Ol]. Aruchnocorys circum textu Haeckel [Petrushevskaya, 1971bl [O.Ol]. Arachnosphaeru miryucunthu Haeckel [Takahashi, 19811 [0.06]. Botryocephulinu armutu Petrushevskaya [Boltovskoy and Riedel, 19871 [0.03]. Botryocyrtis scutum (Harting) [Nigrini and Moore, 19791 [0.34]. Botryopyle dictyocephulus Haeckel [Boltovskoy and Riedel, 19871 [O.Ol]. Botryostrobus uuritus / uustrulis (Ehrenberg) [Boltovskoy and Vrba, 19891 [0.14]. Culocyclas monumenturn Haeckel [Haeckel, 18871 [O.Oll. Cqvocunium sp. A [Boltovskoy and Riedel, 19871 [O.Oll. Curposphueru ucunthophoru (Popofsky) [Boltovskoy and Riedel, 19871 [0.04]. Cephulospyris plutybursu Haeckel [Petrushevskaya, 1971bl [O.OO]. Cenosphueru spp. [Various single-shelled actinommids of poorIy defined morphology] [0.03]. Cluuixoccus ubietinus Haeckel [Haeckel, 18871 [O.Ol]. Cludococcus cervicornis Haeckel [Boltovskoy and Riedel, 19871 [0.053. Cludococcus sp. 1 [Roughly similar to Cladococcus cervicomis Haeckel, but with shorter and less ramified spines, and large, irregular pores] [O.Oll. Cluthrocorys teuscheri Haeckel [Boltovskoy and Riedel, 19871 [0.14].

D. Boltovskoy et al. /Journal

Collosphaera

Reshetnjak,

huxleyi

Muller

[Strelkov

and

19711 [0.05].

Collosphaera macropora Popofslq [Strelkov and

Reshetnjak,

19711 [0.251.

Collosphaera

tuberosa

Haeckel

[Nigrini and

Moore, 19791 [0.02]. Conarachnium

polyacanthum

(Popofsky)

[Takahashi, 19811 [O.Ol]. Cornutella projimda

Ehrenberg

[Nigrini and

Moore, 19791 [0.07]. Corocalyptra cervus Ehrenberg

[Boltovskoy and

Riedel, 19871 [0.16]. Corocalyptra columba (Haeckel) [Boltovskoy and Riedel, 19871 [0.061. Corocalyptra kruegeri Popofsky [Boltovskoy and Riedel, 19871 [0.02]. Corocalyptra sp. aff. C. danaes Haeckel [Boltovskoy and Riedel, 19871 [0.15]. Cromyechinus icosacanthus Haeckel [Haeckel, 18871 [O.Ol]. Cromyomma circumtatum Haeckel [Haeckel, 18871 [O.Ol]. Cubotholus spp. [Probably conspecific with Cubotholus sp. aff. C. orthoceras Haeckel, in Benson, 19661 [0.15]. Cyrtopera laguncula Haeckel [Petrushevskaya, 1971b, as Cyrtolagena lagunculal [O.Ol]. Dictyocephalus papillosus (Ehrenberg) [Petrushevskaya, 19671 [0.05]. Dictyocoryne projiuufa Ehrenberg [Nigrini and Moore, 1979; includes speciments similar to Dictyocoryne truncatum (Ehrenberg)] f15.331. Dictyophimus gracilipes Bailey [Boltovskoy and Riedel, 19871 [0.27]. Dictyophimus hirundo (Haeckel) [Nigrini and Moore, 19791 [0.02]. Dictyophimus sp. aff. D. gracilipes [similar to D. gracilipes Bailey, but thicker skeleton, stouter and shorter feet] [0.03]. Dictyophimus sp. 2 [See remarks on this species in Boltovskoy et al., 1993al [O.Ol]. Didymocyrtis tetrathalamus (Haeckel) [Boltovskoy and Riedel, 19871 [4.02]. Disolenia quadrata s.1. group [Includes specimens resembling Disolenia zanguebarica (Ehrenberg) and 5. polymorpha (Haeckel)] [0.45]. Druppatractus irregularis Popofsky [Boltovskoy and Riedel, 19871 LO.631.

of Marine Systems 8 (1996) 31-51

41

Euchitonia elegans /fircata Ehrenberg [Nigrini and Moore, 1979, specimens included under Euchitonia elegans (Ehrenberg) and E. furcata Ehrenberg] [4.18]. Eucyrtidium acuminatum (Ehrenberg) [Nigrini and Moore, 19791 [O.Ol]. Eucyrtidium

dictyopodium

siphonostomum

(Haeckel) [Petrushevskaya, 1971b; includes several morphologically similar forms] [0.02]. Eucyrtidium hexastichum (Haeckel) [Nigrini and Moore, 19791 [O.OSl. Heliaster hexagonium Hollande et Enjumet [Hollande and Enjumet, 19601 [0.12]. Heliodiscus aster&us Haeckel [Nigrini and Moore, 19791 [O.SO]. Heliosoma echinaster Haeckel [Boltovskoy and Riedel, 19871 [0.06]. Heliosphaera radiata Popofsky [Boltovskoy and Jankilevich, 19851 [0.03]. Helotholus histricosa Jorgensen [Boltovskoy and Riedel, 19871 [O.ll]. Hexacontium armatum / hostile Cleve [Boltovskoy and Riedel, 1987, as Hexacontium armatum and H. hostile] [1.69]. Hexacontium laevigatum Haeckel, 1887 [Boltovskoy and Riedel, 19871 [0.07]. Hexalonche aristarchi Haeckel [Boltovskoy and Riedel, 19801 [0.27]. Hexastylus sp. [The outer surface of the single shell is very similar to that ofsiphonosphaera martensi, with 6 stout, 3-bladed radial spines] [O.Oll. Hexastylus sp. 2 [Single sphere with 3(?) primary spines and large subregular pores] [0.04]. Lamprocyrtis hannai (Campbell and Clark) [Nigrini and Moore, 1979, asLamprocyrtis (?) hannai] [O.OOl. Lamprocyclas maritalis Haeckel [Nigrini and Moore, 1979, as Lamprocyclas maritalis polypora and L. m. ventricosa] [1.04]. Lampromitra coronata Haeckel [Haeckel, 18871

[O.Ol]. Lampromitra quadricuspis Haeckel [Boltovskoy and Riedel, 19871 [0.13]. Larcopyle buts&hi Dreyer [Boltovskoy and Riedel, 19871 [1.65]. Larcospyra quadrangula Haeckel [Boltovskoy and Riedel, 19871 [0.40].

48

D. Boltovskoy et al. /Journal of Marine Systems 8 (19%) 31-51

Larnacalpis sp. [Takahashi, 19811 [O.Ol]. Larnacalpis sp. aff. L. lentellipsis Haeckel [Haeckel, 18871 L10.261. Liosphaera sp. [2 spheres, outermost with large circular pores, 12-14 on the equator and bristleshaped spines; medullary shell with smaller circular pores] [0.91]. Lipmanella bombus (Haeckel) [Petrushevskaya, 1971b] [0.16]. L ipm an ella virchowii (H aeckel) [Petrushevskaya, 1971bl [0.03]. Litharachnium tentorium H aeckel [Petrushevskaya, 1971bl [0.36]. Lithelius nautiloides Popofsky [Petrushevskaya, 19671 [0.05]. Lithelius spp. [Various unidentified Litheliidae, similar to Lithelius sp. aff. L. alveolina Haeckel in Renz, 19761 [2.32]. Lithocyclia heteropora? Haeckel [Boltovskoy, 19871 [0.151. Lophophaena butschlii (Haeckel) [Boltovskoy and Riedel, 19871 [O.OO]. Lophophaena hispida (Ehrenberg) [Boltovskoy and Riedel, 19871 [0.21]. Lophospyris pentagona pentagona (Ehrenberg) [Boltovskoy and Riedel, 19871 [0.09]. Lophospyris/Phormospyris [Boltovskoy and Riedel, 19871 [0.19]. Neosemantis distephanus (Haeckel) [Petrushevskaya, 1971bl [0.051. Nephrospyris renilla Haeckel, 1887 [Boltovskoy and Riedel, 19871 [0.03]. Octopyle stenozona Haeckel [Nigrini and Moore, 1979, as 0. stenozona and Tetrapyle octacanthal L4.401. Pertpyramis circumtexta Haeckel [Nigrini and Moore, 19791 [0.04]. Peromelissa phalacra (Haeckel) [Boltovskoy and Riedel, 19871 [0.02]. Phormacantha hystrix (Jorgensen) [Boltovskoy and Riedel, 19871 KO.091. Phormospyris stabilis scaphipes Haeckel [Boltovskoy and Riedel, 19871 [0.03]. Phormostichoartus corbula (Harting) [Boltovskoy and Riedel, 19871 [0.06]. Plectopyramis sp. [0.02].

Plegmosphaera pachyplegma Haeckel [Boltovskoy and Riedel, 19801 [0.06]. Prunulum coccymelium? Haeckel [Boltovskoy, 19871 [ 1.281. Pseudocubus obebcus Haeckel [Boltovskoy and Riedel, 19871 [0.02]. Pterocanium praetextum (Ehrenberg) [Boltovskoy and Riedel, 1987, as Pterocanium praettxtum eucogum and P. p. praetextum] [0.03]. Pterocanium trilobum (Haeckel) [Boltovskoy and Riedel, 19871 [0.29]. Pterocorys minythorax (Nigrini) [Boltovskoy and Riedel, 19871 [0.05]. Pterocyrtidium dogieli Petrushevskaya [Petrushevskaya, 1971bl [0.02]. Pylolena armata Haeckel [Boltovskoy and Riedel, 19871 [0.741. Pylospyra octopyle Haeckel [Boltovskoy and Riedel, 19801 [0.25]. Sethophormis rotula (Haeckel) [Petrushevskaya, 1971bl [0.021. Siphonosphaera martensi Brandt [Boltovskoy and Riedel, 19801 LO.851. Siphonosphaera polysiphonia Haeckel [Boltovskoy and Riedel, 19801 11.191. Solenosphaera chierchiae Brandt [Strelkov and Reshetnjak, 19711 [0.02]. Solenosphaera sp. aff. S. polysolenia Strelkov and Reshetnjak [Strelkov and Reshetnjak, 19711 [0.04]. Spongaster tetras Ehrenberg, 1860 irregulatis Nigrini, 1967 [Boltovskoy and Riedel, 19871 [O.Ol]. Spongaster tetras tetras Ehrenberg [Nigrini and Moore, 19791 [8.35]. S’ngocore cylindrica (Haeckel) [Boltovskoy and Riedel, 19871 [1.27]. Spongodictyon spongiosum (Muller) [Boltovskoy and Riedel, 19871 [0.45]. Spongodiscus resurgens Ehrenberg [Boltovskoy and Riedel, 19801 [9.22]. Spongoliva ellipsoides Popofsky [Boltovskoy and Riedel, 19871 [0.19]. Spongoplegma sp. [Similar to Octodendron cubocentron Haeckel, in Boltovskoy, 1987, but lacking radial spines] [0.02].

D. Boltovskoy et al. /Journal of Marine Systems8 (19%) 31-51

Spongopyle

setosa

Dreyer

[Boltovskoy

and

Riedel, 19801 L1.451. Spongosphaera

streptacantha

[Boltovskoy

Zygocircus

productus

[Petrushevskaya,

1971bl [0.15].

49

(H ertw ig)

and

Riedel, 19871 [0.97]. Spongotrochus glacialis [Boitovskoy and Riedel,

Appendix B

19801 14.241. Spongurus pylomaticus

Riedel [Riedel,

19581

10.041. Spongurus sp. [Petrushevskaya, 19671 LO.471. Spongums sp. aff. S. elliptica (Ehrenberg) [Benson, 1966, as Spongurus cf. elliptical [0.49]. Spyrocyrtis scalaris / cornutella Haeckel

[Boltovskoy and Riedel, 1987][0.13]. Staurosphaera sp. [Takahashi, 19811 [O.Ol]. Stichapilium bicorne Haeckel [Boltovskoy and Riedel, 19871 [0.02]. Stylochlamydium asteriscus Haeckel [Boltovskoy and Vrba, 1988; includes specimens resembling Stylochlamydium venustum (Bailey) in Boltovskoy and Riedel, 19801 [2.44]. Stylodictya aculeata Jorgensen [Boltovskoy and Vrba, 19881 [0.54]. Stylodictya multispina Haeckel [Boltovskoy and Vrba, 19881 [3.27]. Stylosphaera sp. 1 [Forms similar to Stylatractus spp. and Axoprunum stauraxonium in Nigrini and Moore, 19791 [0.31]. Styptosphaera spumacea Haeckel [Boltovskoy and Riedel, 19871 [0.52]. Tetraplecta pinigera Haeckel [Takahashi, 19811 [O.Ol]. Theocalyptra davisiana (Ehrenberg) [Boltovskoy and Riedel, 19871 [0.15]. Theocorys veneti Haeckel [Boltovskoy and Riedel, 19871 LO.021. Theocorythium trachelium (Ehrenberg) [Nigrini and Moore, 1979, as T. t. trachelium and T. t. dianael [0.171. Theophormis

callipilium Haeckel

[Takahashi,

Theopilium tricostatum (Haeckel)

[Boltovskoy

19811 [O.Oll. and Riedel, 19871 [0.081. Tholospyra cervicomis Haeckel [Takahashi and Honjo, 1981; highly polymorphic species group] 10.771. Z’%olospyr+ssp. [Various D-shaped rings] [0.56]. Triacartus undulatum (Popofsky) [Takahashi, 19811 io.031.

Families ACTINOMMIDAE [9.28] ARTOSTROBIDAE [0.27] CANNOBOTRYIDAE [0.32] CARPOCANIIDAE [O.Ol] COCCODISCIDAE [3.69] COLLOSPHAERIDAE [3.74] LITHELIIDAE [6.23] PHACODISCIDAE [0.43] PLAGONIIDAE [2.93] PTEROCORYTHIDAE [ 1.531 PYLONIIDAE [17.25] SPONGODISCIDAE [50.38] SPYRIDA [1.52] THEOPERIDAE [2.25] THOLONIDAE [0.16]

Appendix C Orders NASSELLARIA SPUMELLARIA

[9.34] [90.66]

References Anderson, O.R., 1983. Radiolaria. Springer, New York, pp. l-355. Benson, R.N., 1966. Recent Radiolaria from the Gulf of California. Ph. D. Thesis, Univ. Minnessota, pp. l-577. Boltovskoy, D., 1987. Sedimentary record of radiolarian biogeography in the equatorial to Antarctic western Pacific Ocean. Micropaleontology, 33: 267-281. Boltovskoy, D., 1988. Equatorward sedimentary shadows of near-surface oceanographic patterns. Speculations Sci. Technol., 11: 219-232. Boltovskoy, D., 1991. Holocene-upper Pleistocene radiolarian biogeography and paleoecology of the equatorial Pacific. Palaeogeogr., Palaeoclimatol., Palaeoecol., 86: 227-241. Boltovskoy, D., 1992. Current and productivity patters in the equatorial Pacific across the Last Glacial Maximum based on radiolarian east-west and downcore fauna1 gradients. Micropaleontology, 38: 397-413. Boltovskoy, D., 1994. The sedimentary record of pelagic biogeography. Prog. Oceanogr., 34: 135-160.

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