Distribution of living coccolithophore assemblages in the Gulf of Elat ('Aqaba)

Marine Micropaleontology, 4 (1979): 197--223 ©Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands

197

DISTRIBUTION OF LIVING COCCOLITHOPHORE ASSEMBLAGES IN THE GULF OF ELAT ('AQABA)

AMOS WINTER, ZEEV REISS and BOAZ LUZ

Department of Geology, The Hebrew University o f Jerusalem, Jerusalem (Israel) (Approved May 22, 1978)

Abstract Winter, A., Reiss, Z. and Luz, B., 1979. Distribution of living coccolithophore assemblages in the Gulf of Elat ('Aqaba). Mar. Micropaleontol., 4: 197--223. The bathymetric and seasonal distribution of coccolithophores between surface and 400 m depth in the northern and southern Gulf of Elat was investigated. Fifty-two coccolithophore species, seven of them described for the first time, were identified from 84 water samples collected during 1975--1976. Most of the species recorded were found in surface waters. High salinities in the Gulf of Elat seem to prevent the entrance of many common pelagic species. Standing crop was highest at the surface, decreasing rapidly with depth, except in the samples collected in February which were more homogeneous. Seasonally, the standing crop reached a maximum value in December, remaining lower throughout the rest of the year. Three coccolithophore assemblages, correlatable with the seasonal patterns of hydrological conditions in the Gulf, were identified. Two species, Emiliania huxleyi and Gephyrocapsa ericsoni, appeared frequently in the Elat assemblages throughout the year. Standing crop is negatively correlated with insolation and is highest in November--December, comparable to that in the productive Equatorial Pacific. During the remainder of the year the lower standing crop approaches values known from the Transitional Zone of the Pacific. High species diversity (similar to the productive Equatorial Pacific) is correlated with high water temperature (summer) and low diversity (similar to that in the Transitional Zone of the Pacific) is characteristic of the relatively cool winter period. Judging from chlorophyll a data, coccolithophores constitute a major component of the phytoplankton and contribute greatly to primary production in the Gulf. The role of nutrient levels, which seem to be of importance for coccolithophores, is not yet well understood. This study should serve also interpretation of the paloceanography, on the basis of deep-sea cores, of tropical-subtropical regions like the Gulf of Elat.

Introduction

Coccolithophores are widely distributed throughout the photic and uppermost aphotic zones in the world's oceans, except in Polar regions (McIntyre et al., 1970}. Together with diatoms and dinoflagellates they constitute the major part of the phytoplankton in the marine environment. Coccoliths, the minute (1--25 #m) calcite plates secreted by coccolithophores, comprise up to 30% of the calcareous oozes on the ocean floor and up to

60% of deep-sea carbonates, deposited since the Jurassic (Bramlette, 1958; Black and Barnes, 1961; Noel, 1965; Berger and Roth, 1975). Owing to their rapid evolutionary rates (see Haq, 1973) they prove to be excellent stratigraphic indicators. [See McIntyre and B~ (1967) and Berger and Roth (1975) for references.] Relatively few studies have been undertaken on the distribution of living coccolithophores in the ocean. Published investigations have shown that cocc01ithophores are

198 frequently stratified in the water column and prefer subtropical-tropical waters. Highest diversity has been recorded in low to middle latitudes (McIntyre and B~, 1967; Okada and Honjo, 1973; Honjo and Okada, 1974) where they often dominate the biomass (Kimor and Wood, 1975). In boreal waters as~mblages are usually dominated by one species, i.e. Emiliania huxleyi whose concentration of 3.5 × 10 T cells per liter has been recorded in the Oslo Fjord (Braarud, 1945). Biogeographic coccolithophore provinces have been recognized on the basis of changes in their distribution which seem to be influenced by current systems, temperature, light, and depth of mixed layer (Okada and Honjo, 1973). The use of coccolithophores for the reconstruction of ancient marine environments is now being undertaken by a number of workers. They have shown coccoliths to be excellent paleoenvironmental indicators for the Quaternary (McIntyre and B~, 1967; McIntyre et al., 1967; Boudreaux and Hay, 1969; Berger and Roth, 1975; Ruddiman and McIntyre, 1976) and paleoclimatic indicators in the Cenozoic (see e.g. Haq and Lohmann, 1976). Very little is known concerning the biology of coccolithophores (Berger, 1976). Research is complicated by the intricate life cycle of most species (Deflandre, 1952) and polymorphic character of their coccoliths (Okada and McIntyre, 1977). In the absence of firstorder criteria, distribution patterns of coccolithophores must be correlated empirically with ecological factors. Interpretation of such correlations is facilitated by studying environments in which many ecological factors show minimal variability. The Gulf of Elat is especially interesting in this respect because of its particular geological, hydrological and biological features. Comprising part of the Syrian--African Rift System (Freund, 1965), the Gulf has extremely steep shores and submarine slopes. It is 170 km long, 14--26 km wide and up to 1,830 m deep and is separated by a narrow, 252 m deep sill at the Straits of Tiran. The Gulf is thus unique in that it pos-

sesses pelagic characteristics cios~ to ~h~, land. The high evaporation rates due ~(', the ~ot and arid climate of the region lead to inflow of water over the 250 m deep silt of Tirai~ from the Red Sea (against the prevailing northerly winds), as well as rapid mixing of the water column to great depths. As a result, the waters are warm (21 -27°C), highly salir~e (41°/00) and highly oxygenated (4--6 mt i-:i throughout the year (Klinker et al., .l 97{~;). The Gulf is extremely nutrient-poor and is comparable with the least produc.tive regiot~s in the ocean. Phosphate values range from 0 . 0 3 - 0 . 2 5 pg-at 1TM and nitrate from 0.07 to 2.0 pg-at. 1-~ Biomass values are als(,~ relatively low (see Klinker et al., 1978). Seasonal and bathymetric fluctuations are weakly expressed in the Gulf. Thermocline, halocline and pycnocline in the Gulf are a o t as pronounced as in the open ocean. Nevertheless, two hydrological seasons are discerned (Klinker et al., 1976): the "winter" season from January to March is characterized~ particularly in the northern part of the Gulf, by a water mass with nearly uniform temperature and salinity values at all depths. During this season the surface water temperatures of approximately 21°C are the coldest recorded for the entire Red Sea. The " s u m m e r " season spans the months of April to O c t o b e r During this period a stratification of the up.~ per 150 m of water results in a weak thermocline ( 2 7 - 2 2 ° C ) which rests above a more uniform, cooler water b o d y of max. 20.9°(;. Previous investigations on the plankton m the Gulf of Elat have been carried out by Kimor (1973) and Kimor and Golandsky (1977) on microplankton communities, es -~ pecially blue-green algae, tintinnids, diatoms and dinoflagellates, as well as on sediments; by Reiss et al. (1974) on foraminiferida, by Almogi-Labin and Reiss (1977) on pteropods; and by Schmidt (1972, 1973) on hydroids. Other than a short survey of the calcareous nannoplankton by Mikkelsen (1973), the present investigation is the first one of the quantitative and qualitative aspects of the

199 coccolithophores in the Gulf of Elat. The purpose of the present study is to contribute to the knowledge of coccolithophore t a x o n o m y , distribution, and their dependence upon ecologically important parameters, and thus to a better understanding of ecological, paleoceanographical, and biostratigraphic patterns. Research was conducted within the multidisciplinary framework of the Data Collecting Program in the Gulf of Elat (DCPE) (Klinker et al., 1975, 1976, 1978), which provided the physical, chemical and biological data. Material, m e t h o d s and techniques Water samples were taken aboard the R.V. from DCPE station A (29°31'N,

Arnona

34°57'E, see Fig. 1) five times throughout the period from December, 1975 to November, 1976. In November, 1975 a single surface sample was taken. Collections were made at depths of 0, 25, 50, 100, 150, 200, 300, and 400 m. In addition, samples were collected at these depths from DCPE station G (28°07'N, 34 ° 30'E) during February and April, 1976. Ten liters of sea water were collected from each depth by means of a Hydrobios TNP bottle and were brought as soon as possible to the laboratory on shore. There the water was prefiltered (65 ~m) and then passed through Millipore filters of 47 mm diameter with a nominal pore size of 0.8 gm. A suction of less than 5 $ was applied. After this process, the filters were rinsed with approximately 20 ml of tap water (see McIntyre and B~, 1967), dried at 25°C for a few hours and placed in plastic bags until further use. Standing crop per liter of water was computed by counting the number of cells on a section of the filter corresponding to 100 ml of seawater. This m e t h o d closely followed that described by Okada and Honjo (1975). C o m m u n i t y structure was analyzed by viewing a portion of the filter coated with gold with a "Stereoscan S-10" microscope. When samples were especially rich in individuals, a m i n i m u m of 300 specimens were counted and identified. Otherwise, as m a n y specimens as possible were counted and identified. Occasionally, a small area of the filter was photographed at a magnification of 1000 X with the SEM. Negatives were then viewed with a simple stereo-microscope at low magnification. Standing crop was c o m p u t e d by converting the number of cells per negative area to cells per liter. This technique also permitted the identification of larger coccolithophore species. T a x o n o m i c notes

Fig. 1. Location map of DCPE water sampling stations.

Fifty-two m o d e m coccolithophore taxa recognized in the Gulf of Elat are listed below, followed by brief remarks on some of them.

200 COCCOLITHACEAE Kamptner, 1928 Crenalithus? sp. (Plate I, 1) Emiliania huxleyi (Lohmann), 1902 (Plate I, 2 -5) Gephyrocapsa ericsoni McIntyre and B6, 1967 (Plate

1,6) G. oceanica Kamptner, 1943 (Plate I, 7 9) G. cf. G. ornata Heimdal, 1973 (Plate I, 10) G. protohuxleyi McIntyre, 1970 (Plate I, 11 ) G. oceanica--E, huxleyi dimorphic (Plate I, 12)

Genus? sp. ? (Plate II, 1) Oolithotus fragilis (Lohmann) subsp, cavurn Okada and McIntyre, 1977 (Plate II, 2) Umbilicosphaera sibogae (Weber-Van Bosse), 1901 (Plate II, 3) HELICOSPHAERACEAE Black, 1971, emend. Jafar and Martini, 1975 Helicosphaera carteri (Wallich), 1877 (Plate II, 4)

RHABDOSPHAERACEAE Lemmermann, in Brandt and Apstein, 1908 Acanthoica cf. A. acathifera Lohmann, 1913 (Plate

II, 5)

S. S. S. S.

prolongata Gran ex Lohmann, 1913 (Plate IV. 4) pulchra Lohmann, 1902 (Plate IV, 5) rotula Okada and McIntyre, 1977 (Plate IV, 6) variabilis (Halldal and Markali), 1955 (Plate IV,

7 8) S. sp. A (Plate IV, 9) CALYPTROSPHAERACEAE Boudreaux and Hay, 1969 Calyptrosphaera catillifera (Kamptner), 1937 (Plate

IV, 10) (7. oblonga Lohmann, 1902 (Plate IV, 11) C. pirus Kamptner, 1941 (Plate IV, 12)

C. sp. A (Plate V, 1) Corisphaera arethusae Kamptner, 1941 (Plate V, 2) C. aff. C. gracilis Kamptner, 1937 (Plate V, 3) Helladosphaera cornifera (Schiller), 1913 (Plate V, 4! Homozygosphaera quadriperforata (Kamptner), 1937

(Plate V, 5) H. wettsteini (Kamptner), 1937 (Plate V, 6) Sphaeroealyptra bannockii Borsetti and (?ati, :197~

(Plate V, 7) S. hasleana (Gaarder), 1962 (Plate V, 8) S. quadridentata (Schiller), 1913 (Plate V, 9) Zygosphaera divergens Halldal and Markati, ~95i:,

A. aculeata Kamptner, 1941 (Plate II, 6) Anthosphaera quatricornu (Schiller), 1914 (Plate II,

(Plate V, 10)

7)

(Plate V, 11 )

A. robusta (Lohmann), 1902 (Plate II, 8) Discosphaera tubifera (Murray and Blackman), 1898

Thoracosphaera? sp. A (Plate V, 12)

(Plate II, 9) Rhabdosphaera clavigera Murray and Blackman~ 1898

(Plate II, 10) R. longistylis Schiller, 1925 (Plate II, 11 ) Umbellosphaera irregularis Paasche, 1955 (Plate II,

Thoracosphaera

cf. T. heimi

( Lohmann ~, 1919

C r e n a l i t h u s ? sp. (Plate 1, 1). T h e single slightly e n c r u s t e d s p e c i m e n possesses pla. coliths with high p r o t r u d i n g walls e x t e n d i n g f r o m the collar.

12) U. tenuis (Kamptner), 1937 (Plate III, 1--2)

SYRACOSPHAERACEAE Lemmermann, in Brandt and Apstein, 1908 Anoplosolenia

brasiliensis (Lohmann), 1919 (Plate

III, 3) Calciopappus caudatus Gaarder and Ramsfjell, 1954

(Plate III, 4) Halopappus cf. H. adriaticus Schiller, 1914 (Plate

III, 5) Ophiaster formosus Gran, 1912 (Plate III, 6) O. hydroideus (Lohmann), 1903 (Plate III, 7) Michaelsarsia sp. Borsetti and Cati, 1976 (Plate III,

8) Syracosphaera corolla Lecal, 1966 (Plate III, 9) S. corrugis Okada and McIntyre, 1977 (Plate III, 10) S. elatensis Winter, n.sp. (Plate III, 11--13) S. exigua Okada and MeIntyre, 1977 (Plate IV, 1) S. mediterranea Lohmann, 1902 (Plate IV, 2) S. pirus Halldal and Markali, 1955 (Plate IV, 3)

( L o h m a n n ) (Plate {. 2 6 J ; Hay and Mohler, in H a y et al. ( 1 9 6 7 , p. 447, pl. 10, figs. 1 - 2 ; pl. 11, figs. 1--2). E. h u x l e y i has been f o u n d with up t o three layers of coccoliths. T h e relative w i d t h o f the central area in t h e Elat specimens is occasionally greater (Plate I, 5) t h a n the n o r m (Plate I, 3) b u t usually smaller (Plate I, 2) t h a n that rec o r d e d b y various authors. In the Elat material t h e r e exists a significant c o r r e l a t i o n b e t w e e n central area s t r u c t u r e and season: w i n t e r specimens (Plate I, 4) possess central areas in which the e l e m e n t s are partially fused, until a solid p a v e m e n t is c r e a t e d t o w a r d s the m i d d l e o f the central area. S u m m e r specimens (Plate I, 3) have cribrate t o comb-like central areas. ( C o m p a r e the c o r r e l a t i o n b e t w e e n m o r p h o l o Emiliania huxleyi

201 gy and latitude recorded by McIntyre and B~, 1967.) Few specimens are encrusted. Their distribution is definitely n o t correlatable with depth, b u t on the other hand, most of these specimens originate from the January collection at station G. Despite the low nitrogen content of the waters of the Gulf, (Klinker et al., in press) there are almost no malformed specimens, as the case appears to be in N-deficient (or in neritic) environments (Okada and Honjo, 1975).

(Plate I, 10); Heimdal, (1973, pp. 71 - 7 2 , 74, text-figs. 1 - 5 ) . The single specimen found bears tooth-like protrusions characteristic of G. ornata. Heimdal (1973) reports that the bridge crossing the central area of G. ornata is "sometimes separated" as is the case in the Elat specimen. Unlike the specimens described by Heimdal, the Elat specimen has wide, tapering bridge elements extending over the central area at a high angle to the longitudinal axis of the placolith.

Gephyrocapsa ericsoni McIntyre and B~ (Plate I, 6); McIntyre and B~ (1967, p. 571, pl. 10; pl. 12, fig. b). Coccosphere diameter of most specimens examined is slightly below the minimum value of 3.1 p m given by McIntyre and B~ (1967).

Gephyrocapsa protohuxleyi McIntyre (Plate I, 11); McIntyre (1970, pp. 1 8 7 - 1 9 0 , text-figs. a~g). Living specimens of this species hitherto regarded as extinct since 75,000 B.P. were recorded from the Gulf of Elat by Winter et al. (1978). The possibility that the interelement spacings are a result of dissolution effects is excluded. This is supported by the fact that the Elat specimens possess smooth, rounded element edges which bear no resemblance to G. ericsoni specimens which are in the process of dissolution (Burns, 1977). In addition, the Elat waters are saturated with respect to CaCO3 (Reiss et al., 1974) and thus dissolution seems unlikely.

Gephyrocapsa oceanica Kamptner (Plate I, 7--9); Gaarder and Hasle (1971, p. 533, textfig. 6 d - f ) . Placoliths of this species possess a large central collar and a thick bridge, placing the Elat specimens in the second of the three groups described and figured by Okada and McIntyre (1977). None of the specimen bears an additional bridge, c o m m o n on coccospheres from the Pacific and Atlantic. An interesting feature of G. oceanica is that most of the Elat specimens have been found in clusters (Plate I, 8). Burns (1977) has also described this p h e n o m e n o n as a salient feature of G. oceanica, p h e n o t y p e B, which however, is not present in the Elat material. The February surface coccolithophore collection contained many specimens of G. oceanica where apparent etching had separated the seams between the unit crystals (Plate I, 9). This p h e n o m e n o n has previously been reported by Honjo (1975) for placoliths collected from great depths, b u t not from the surface. Since no CaCO3 dissolution seems to occur in the Gulf of Elat (Reiss et al., 1974) the possibility is not excluded that etching is due to the processes of digestion of coccolithophores by other organisms. Gephyrocapsa

sp.

cf.

G. ornata

Heimdal

G. Oceanica -E. huxleyi "dimorphic" (Plate I, 12); Clocchiatti (1971, pp. 318--321, textfigs. 1--2). The rare dimorphic coccospheres from 400 m, Station G, Feb., 1976) bear placoliths of both E. huxleyi and G. oceanica and cannot be attributed according to present taxonomic criteria to either of these taxa. They definitely support close affinities between Emiliania and Gephyrocapsa. (see also McIntyre, 1970). For a summary of various theories pertaining to dimorphism between Gephyrocapsa oceanica and Emiliania huxleyi, see Clocchiatti (1971). The possibility is not excluded that actually dithecatism of Emiliania is involved.

Genus? sp. ? (Plate II, 1). One coccosphere having encrusted placoliths with "I"-shaped elements and occasionally one or two bridges perpendicular or at an angle to the longitudi(text continued on p. 206)

202 PLATE I (p. 203) All figures on Plates I--IV are scanning electron micrographs. Scale bar equals 1 pm unless otherwise indicated. Nr. refers to water sample (first letter: station; following digits: year, month, day; last two digits: sample number). Neg. refers to SEM negative deposited in the Department of Geology, Hebrew University.

1. Crenalithus? sp. Note the very high protruding walls extending from the collar of the placoliths. Nr. G760 12101a (25 m); Neg. E15-08. 2--5. Emiliania huxleyi (Lohmann). 2. Slightly encrusted specimen with small central area. Nr. G76012107 (400 m); Neg, E49-34. 3. Typical "summer" specimen with cribrate to combqike central area. Nr. A76080910 (0 m); Neg. H29-20. 4. Typical "winter" specimens possessing partially fused to nearly solid central area. Nr. A75120924 (0 m); Neg. A87-5. 5. Partially mal-formed coccosphere showing wider than average central area. Nr. A75120924 (0 m); Neg. A87-21. 6. Gephyrocapsa ericsoni McIntyre and Be. Nr. A76112601 (0 m); Neg. F68-27. 7--9. Gephyrocapsa oceanica Kamptner. 7. Placolith with wide central collar and bridge. Nr. A75120924 (0 m); Neg. E42-01. 8. Cluster formation typical of this species in the Gulf of Elan. Note E. huxleyi in upper left corner and G. ericsoni in lower right corner. Nr. A76020226a (0 m); Neg. H29-3(~. Bar = 10 ~m. 9. Placolith exhibiting apparent etching between unit crystal, common in February assemblage. Nr. A76020226a (0 m); Neg. H24-8. 10. Gephyrocapsa sp. cf. G. ornata Heimdal. Specimen with tooth-like protrusions characteristic of G. ornata but having different bridge element arrangement. Nr. A76020230 (150 m); Neg. D32-7. 11. Gephyrocapsa protohuxleyi McIntyre. Coccosphere with cribrate central area. Nr. 76080910 (0 m); Neg. 519-14. 12. Dimorphic G. oceanica--E, huxleyi. Unique coccosphere bearing placoliths of both E. huxleyi and G. oceanica. Nr. G76012103 (100 m); Neg. E27-01. PLATE II (p. 204) 1. Genus? Species? Encrusted placoliths with "I" shaped elements and one element bridge crossing the central area. Nr. G76020234 ( 4 0 0 m ) ; Neg, E05-8. 2. Oolithotus fragilis (Lohmann) subsp, cavum Okada and McIntyre. Note curved sature lines and holes in central area characteristic of the subspecies. Nr. A75120924 (0 m); Neg. A86-11. 3. Umbilicosphaera sibogae (Weber-van Bosses). Nr. A75120924 (0 m); Neg. F60-28. 4. Helicosphae ra carteri (Wallich). Nr. A75120924 (0 m); Neg. F80-08. 5. Acanthoica cf. A. acathifera Lohmann. Coccosphere bearing simple cyrtolith exhibiting higher than normal central parts. Nr. A7608910 (0 m); Neg, F81-12. G Acanthoica aculeata Kamptner. Proximal and distal view of cyrtoliths. Nr. A76080910 (0 m); Neg. F60-25L. Bar = 2 ~m. 7. Anthosphaera quatricornu (Schiller). Labiatiform cyrtolith with trapazoidal appendix (side view) and elliptical outline as seen from above. Nr. A75120924 (0 m); Neg. A97-22. 8. Anthosphaera robusta (Lohmann). Specimen showing characteristic parallel sides of double-lipped appendix as seen from above. Nr. A75112001 (0 m); Neg. F68-30. 9. Discosphaera tubifera (Murray and Blackman). Salpingform cyrtoiiths with trumpet-shaped appendix. Nr. A76112606 (200 m); Neg. F60-34. 10. Rhabdosphaera clavigera Murray and Blackman. Cyrtolith w i t h appendix ending in four vanes arranged around a central spine. Nr. A76080912 (50 m); Neg. H92-15. 11. Rhabdosphaera longistylis Schiller. Dimorphic partially broken coccosphere showing simple oval cyrtoliths and helatoform cyrtoliths with club-shaped appendix. Nr. A76080910 (0 m); Neg. E3928. Bar = 2 urn. 12. Umbellosphaera irregutaris Paasche. Partially broken macro- and micrococcoliths. Nr. A76112601 (0 m); Neg. F60-26. PLATE III (p. 205) 1---2. Umbellosphaera tenuis (Kamptner). 1. Macrococcolith showing clearly defined radial ribs with frequent knoblike protrusions between them. Nr, A76080910 (0 m); Neg. 541-10. 2. Maerocoecoliths of a different o> namentation with main radial ribs discontinuous towards the periphery and knoblike protrusions less common. Nr. A76080910 (0 m); Neg. 541-8. 3. Anoplosolenia brasiliensis (Lohmann). Complete spineless coccosphere bearing scapholite-type coccoliths. Nr. G76012101a (25 m); Neg. E15-11. Bar = 3 urn. 4. Calciopappus caudatus Gaarder and Ramsfjell. Coccosphere with characteristic bayonet-like polar apical spines. Nr. A75120925 (50 m); Neg. COO-29, 5. Halopappus of. H. adriaticus Schiller. "Naked" coccolithophore with membranous sheath and apical spines possessing a circular base. Nr. G76012106 (300 m); Neg. E41-11. Bar = 3 um. 6. Ophiaster f o r m o sus Gran. Specimen bearing articulate arms formed by short, broad links. Nr. A75120925 (50 m); Neg. COO-27 7. Ophiaster hydroideus (Lohmann, 1913). Specimen bearing articulate arms consisting of long narrow links. Nr. A75120924 (0 m); Neg. 541-19. 8. Michaelsarsia? sp. Borsetti and Cati. Dimorphie coccosphere with whorl coccoliths and temur-shaped spines. Nr. A75120924 (0 m); Neg. H24-18, Bar = 2 um. 9. Syracosphaera corolla Lecal. Broken dimorphic coccosphere showing ordinary incomplete caneoliths and larger elliptical coccoliths. Nr. A76112601 (0 m); Neg. E63-03. 10. Syracosphaera corrugis Okada and McIntyre. Complete coccosphere exhibiting ditheeatism with dimorphic endotheca. Nr. A76080910 (0 m); Neg. E60-22. 11 13. Syracosphaera elatensis Winter n. sp. 11. Coccosphere exhibiting ditheeatism; complete endothecal caneoliths and asymmetrical cyrtoliths. Nr. A75120924 (0 m); Neg. A97-19. 12. Coccosphere showing endothecal caneoliths. Holotype. N r A75120924 (0 m); Neg. A87-7. 13. Dimorphic endotheca with helatoform caneoliths. Nr. A75120924 (0 mi: Neg. 541-20. Bar = 5 urn.

203 PLATE I

2

3

4

6

10

9

8

7

.

.

.

.

.

.

11

'

'

12

'

204 P L A T E I1

1

2

I

3

205 P L A T E III

3

4

5

6

7

8

9

11

.....

12

lo

"--

13

..........

206 hal axis of the central area occurs in the present material. The bridges are formed of one element. The presence of bridges excludes the specimen from Emiliania which it resembles by the shape of the distal elements. The fact that the bridges are composed of one element excludes it also from Gephyrocapsa. More material and further study is required to establish the significance of this apparently hitherto undescribed type.

Oolithotus fragilis (Lohmann) subsp, cavum Okada and McIntyre (Plate II, 2); Okada and McIntyre (1977, p. 11, pl. 4, figs. 4--5). No typical O. fragilis occur with this subspecies in the present material, emphasizing the significance of separating the two forms (Okada and McIntyre, 1977). Helicosphaera carteri (Wallich) (Plate II, 4); Jafar and Martini {1975, pp. 381--390, pl. 1, figs. 1, 4--5). The single specimen resembles closely the scanning electron micrograph published by Borsetti and Cati (1972) as Helicosphaera carteri. Acanthoica cf. A. acanthifera Lohmann (Plate II, 5); Borsetti and Cati (1972, pp. 3 9 7 - 3 9 8 , pl. 39, fig. la--b). The single Elat specimen in the summer 1976 surface assemblage resembles the coccosphere figured by Borsetti and Cati (1972). The same number of radially arranged lamellae are present. The simple cyrtoliths, however, are smaller in width {1.2 p m ) than the norm (2.1 pln) and have a much higher central part than that depicted by Borsetti and Cati. No styliform cyrtotiths were found on the broken ('occosphere. Umbellosphaera tenuis Kamptner (Plate III, 1 - 2 ) ; Paasche, in Markali and Paasche (1955, p. 96, pls. 1--2); Borsetti and Cati {1972, pp. 4 0 6 - 4 0 7 , pt. 53, fig. 3; pl. 54, figs. 1--2). Both the macro- and micro-coccoliths of this species exhibit a variation in ornamentation of the distal shield. In some cases the long, radial main ribs are clearly defined and ex-

tend continuously from the centeJ' ~o the periphery of the coccolith. The areas be-tween these ribs are covered by short ribs. parallel to each other and at an angle to the main strips. Knob-like protrusions are frequent, particularly in the short ribs (Plate [II~ 1). In other cases the main radial ribs are often discontinuous towards the periphery, while the intercalary, short ribs are more ir regular and at a lesser angle to the main ribs. Knobs are less c o m m o n {Plate III, 2k

Anoplosolenia brasiliensis (Lohmann~ tPlate tII, 3); Deflandre (1952, p. 458, text-figs. 356D--E); Halldal and Markali (1955, p. 14. pl. 26). This species is identified on the basis of lack of spines and the apparent identity in characters of scapholites with the specimens figured by Kling (1975) and by BOF setti and Cati (1972). Calciopappus caudatus Gaarder and Ramsfjell {Plate III, 4); Gaarder and Ramsfjell {1954. p. 155, text-fig. 1a--b). Specimens available are identified as Calciopappus caudatus on the basis of the characteristic bayonet-like tip and split base of their polar apical spines. Halopappus cf. H. adriaticus Schiller (Plate III, 5); Deflandre (1952, p. 455, text-fig, 352E). The specimen from 300 m, station G. Jan. 1976, resembles that depicted by De ftandre (1952) as Halopappus adriaticus by having no coccoliths and having apical sprees possessing a circular base. The membrane sheath illustrated by Deflandre is also present. On the other hand, the alternating projections on the spines are no~ shown on Deflandre's drawing. Ophiaster formosa Gran (Plate III, 6); Gran (1912, p. 331, fig. 239, 2); Gaarder~ 1967. p 185, pl. 1, fig. C, pl. 3, figs. B, E). Ophiaster hydroideus (Lohmann) {Plate III, 7); Gaarder (1967, pp. 1 8 4 - 1 8 5 , pl. 1, figs. A--B; pl. 2; pl. 3, figs. A, C--D: pl. 4). Findings

207 from the Elat collection support the distinction b y Gaarder (1967) of two different species of Ophiaster. Those with articulate arms consisting of long narrow links have been placed in the species hydroideus, while those specimens bearing articulate arms formed by short, broad links have been placed in formosa.

Michaelsarsia? sp. Borsetti and Cati (Plate III, 8); Borsetti and Cati (1976, p. 216, pl. 15, figs. 1 - 8 ) . Referring to Deflandre's (1952) definition (p. 454) and to Borsetti and Cati (1976), the Elat specimens are attributed to Michaelsarsia. General remarks on Syracosphaera In a recent publication by Gaarder and Heimdal (1977) on "A revision of the genus Syracosphaera Lohman (Coccolithineae)" the genus Syracosphaera is emended and various species previously included in it are attributed to the new genera Caneosphaera and Coronosphaera. This new subdivision is based mainly on the presence or absence of two layers of coccoliths (dithecatism), on the presence or absence of centripetal widening of the proximal ring, and on the width of the distal rim. Using these criteria Syracosphaera mediterranea is removed to Coronosphaera while Syracosphaera molischi is transferred by Gaarder and Heimdal (1977) to Caneosphaera. However, since S. molischi has been shown to exhibit dithecatism (Okada and McIntyre, 1977) this species cannot be included in Caneosphaera and should remain in Syracosphaera. Moreover, in the present authors' opinion the specimens figured by Gaarder and Heimdal ( 1 9 7 7 ) a s Caneosphaera molischi (pls. 7 and 8) belong to more than one species. Thus, pl. 7, figs. 41 and 42 are most probably S. molischi, although in the absence of exothecal cyrtoliths positive identification is difficult. The specimens on pl. 8, figs. 49a--b are most probably Syracosphaera corrugis, a species with a much more simple central area and a less acute angle between the two distal shields than S. molischi and

which rarely exhibits dithecatism (see Okada and McIntyre, 1977, pl. 8, figs. 3 and 6, as well as the present paper, Plate III, 10). The speciment figured as C. molischi by Gaarder and Heimdal (1977, pl. 7, fig. 43) may in fact belong -- because of the strong ribbing of the distal shield - to Syracosphaera exigua (see Okada and McIntyre, 1977, pl. 8, figs. 1 0 - 1 1 , as well as the present paper, Plate IV, 1). Gaarder and Heimdal also include in C. molischi specimens (pl. 7, figs. 44 46) which differ from this latter species by the protrusions of the inner wall of the distal shield into the central area (a specific character not recognized as valid by Gaarder and {-Ieimdal) and which strongly resemble Syra. cosphaera elatensis sp. nov. On the other hand, the taxonomic validity of the protrusions is supported by (1) the morphological differences between the exothecal cyrtoliths in S. molischi and in S. elatensis and (2) the biogeographical distribution of these two forms (see present paper). Although S. elatensis is very c o m m o n in the Gulf of 'Aqaba no S. molischi occurs in it.

Syracosphaera elatensis Winter n. sp. (Plate III, 11--13). Derivation of name: From the town of Elat. _Diagnosis: Coccosphaera ab sphaeroidale ad ellipsoidale, dithecata, endotheca dimorpha, coccosphaera habens circa 30---80 caueolithos, magnitudo ab 7 ad 8 pm. Coccolithi endothecales: (a) Caneolithi completi, ab ovi~ formibus ad ellipsoidales, habentes clipeum distale plenumque angustum, interdum latius. Superficies clipei maxime plicatur. Area centralis formatur 19--32 lamellis, positis circa structuram centralem plerumque in fasciculis irregularibus ab 5--8. De latere parietis clipei distalis elementa digitiformia. Aegentia partem quartam ad dimidium areae centralis intro protrudent; elementa clipeorum distalium plurala quam protruberationes et sine correlatione; (b) caneolithi helatoformes cum processu centrali ab 1.5 p m alto. Caneolithi completi et helatoformes ab 1.9 ad 3.5 t~m

208 longi et ab 1.2 ad 2.1 /am lati. C o c c o l i t h i exothecales: semirotundi, cyrtholiti asymmetri e t area centralis m a g n a . C l i p e u m m a r g i n a l e p l e r u m q u e f o r m a t u r 2 cyclis e l e m e n t o r u m . C y c l o s i n t e r i o r f o r m a t u r e l e m e n t i s paucis brevibus i n t r o p r o t r u d e n t i b u s ; c y c l o s e x t e r i o r f o r m a t i s 15 - 2 0 e l e m e n t i s ovoideis, elongatis et a t t e n u a t i s in p a r t e latiore clipei. M a g n i t u d o ab 2 - 2 . 8 / a m .

Description o f coccosphere: Spherical to ellipsoidal c o c c o s p h e r e , e x h i b i t i n g d i t h e c a t i s m ; d i m o r p h i c e n d o t h e c a . C o c c o s p h e r e consisting of approximately 30-80 c a n e o l i t h s . Size ranges f r o m 7 to 8 / a m . Description o f coccoliths: E n d o t h e c a l c o c c o liths: (a) Oval to elliptical, c o m p l e t e c a n e o liths w i t h distal shield t h a t is m o s t l y n a r r o w , b u t on ,. o c c a s i o n relatively wide. S u r f a c e o f shield is v e r y s t r o n g l y c o r r u g a t e d , Central area o f shield c o n s t r u c t e d o f s h o r t , fingerlike e l e m e n t s p r o t r u d e freely i n w a r d . T h e p r o t r u s i o n s are irregularly s p a c e d a n d are n o t e x t e n s i o n s o f t h e distal shield e l e m e n t s ; t h e r e are m a n y m o r e distal shield e l e m e n t s t h a n p r o t r u s i o n s a n d no c o r r e l a t i o n exists b e t w e e n t h e m . (b) H e l a t o f o r m c a n e o l i t h s w i t h a c e n t r a l p r o c e s s averaging 1.5 /am in

height. C o m p l e t e and h e l a t o f o r m c a n e o t i t h s m e a s u r e f r o m 1.9 t o 3.5 p m in length and f r o m 1.2 t o 2.1 p m m w i d t h . E x o t h e c M c o c c o l i t h s : semicircular, a s y m m e t r i c a l c y r t o liths with large c e n t r a l area. Marginal shiekt is usually f o r m e d b y t w o cycles of elemenLs. I n n e r cycle is c o n s t r u c t e d of few s h o r t and i n w a r d l y p r o t r u d i n g e l e m e n t s . O u t e r cycle f o r m e d b y 1 5 - - 2 0 egg-shaped e l e m e n t s whi¢.h b e c o m e longer a n d t h i n n e r over ~,he wider p a r t o f the shield. Size ranges f r o m 2 - 2 . 8 pm.

Remarks: This n e w species differs f r o m ,~. molischi G r a n b y its c a n e o l i t h s possessing p r o t r u s i o n s w h i c h are n o t e x t e n s i o n s of distal shield e l e m e n t s , b y its slightly d i f f e r e n t e x o t h e c a l c y r t o l i t h s a n d central area. It is similar to S. protrudens O k a d a and Mcint y r e in having internally e x t e n d i n g p r o t r u sions b u t it is unlike it in a n y o t h e r w a y . Occurrence: C o m m o n t h r o u g h o u t the y e a r , 1975--1976. Itolotype: Plate I l l , 12 f r o m s a m p l e no. A 7 5 1 2 0 9 2 4 SEM negative n u m b e r : A 8 7 - 7 Paratypes: Plate I I I , 11, 13 f r o m s a m p l e n o A 7 5 1 2 0 9 2 4 SEM negative n u m b e r s : A 9 7 - 1 9 a n d 541-20.

PLATE IV

1. Syracosphaera exigua Okada and McIntyre. Proximal and distal views of endothecal complete coccoliths. Nr. A76112605 (150 m); Neg. F60-27. 2. Syracosphaera mediterranea Lohmann. Endothecal incomplete caneoliths. Nr. A76080910 (0 m); Neg. H29-11. 3. Syracosphaera pirus Halldal and Markali. Broken coccosphere showing dithecatism with endotheca dimorphism. Arrow points to exothecal cyrtoliths. Nr. A76080910 (0 m ) Neg. H29-33. 4. Syracosphaeraprolongata Gran ex Lohmann. Exothecal circular cyrtoliths. Note short knob like structures. Nr. A76112601 (0 m); Neg. 519-9. 5. Syracosphaera pulchra Lohmann. Partially broken coccosphere consisting of endothecal caneoliths. Nr. G76012101a (25 m); Neg. E15-10. 6. Syracosphaera rotula Okada and McIntyre. Partially disintegrated endothecal complete caneolith and exothecal circular cyrtolith of a dithec~ cate coccosphere. Nr. A76112603 (50 m); Neg. F61-09. 7--8. Syracosphaera variabilis (Halldal and Markali). 7. Complete coccosphere showing incomplete endothecal caneoliths. Nr. A76080910 (0 m); Neg. H29-34. 8~ Complete coccosphere showing dithecatism and composed mostly of simple, circular exothecal cyrtoliths. Arrow points to endothecal caneolith. Nr. A76020232 (300 m); Neg. D81-7. 9. Syracosphaera sp. A. Broken cocosphere showing ordinary caneoliths, helatoform caneoliths and exothecal cyrtoliths. Nr. A76112605 (150 m); Neg. F60-22. 10. Calyptrosphaera catillifera (Kamptner). Calyptroform holococcolith. Nr. A76080910 (0 m); Neg. F81-18. 11. Calyptrosphaera oblonga Lohmann. Nr. A76080910 (0 m); Neg. 541-7. 12. Calyptrosphaera pirus Kamptner. Somewhat disintegrated holococcolith. Nr. A76080910 (0 m); Neg. H21-I 4

209 PLATE

IV

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210

Syracosphaera prolongata Gran ex Lohmann (Plate IV, 4); Okada and McIntyre 1977, p. 26, pl. 7, figs. 2 - 3 ) . One interesting feature is the short knob-like structures, protruding outwards from each sinistrally radiating element of the marginal shield, seemingly as extensions of each of the approximately thirty radiating arms.

Syracosphaera pulchra Lohmann (Plate IV, 5); Okada and McIntyre (:[977, p. 27, pl. 10, figs. 11--12). Exothecal cyrtoliths are much rarer in the Elat material than endothecal caneoliths (Plate IV, 5).

Syracosphaera variabilis (Halldal and Markali) (Plate IV, 7--8); Okada and McIntyre (1977, p. 27, pl. 9, figs. 7--8). Exothecal cyrtoliths (Plate IV, 8) were present a t station A in winter, 1976; endothecal caneoliths (Plate IV, 7) in summer, 1976.

Syracosphaera sp. A (Plate IV, 9). The single Elat specimen shows dithecatism with dimorphic endotheca.

Description of coccoliths: EndQthecal coccoliths oval to elliptical, complete carmoliths with no central structure. Central area constructed of approximately 36 lameltar elements. Distal shield e x t r e m e l y narrow and raised, its surface decorated by thin ridges created by imbricated elements, Each element

of the shield corresponds to one lamellar element of the central area. Caneoliths measure approximately 3:0 pm in length and 1.6 g m in width. Helatoform central process {P1. IV, 9) is long, reaching a height of 1.0 p m and ending in a four-pointed structure. Exothecal coccOliths are thimble-shaped cyrtoliths with a circular to oval profile ir~ distal view and a trapezoidal lateral profile. Marginal shield consists of two rings. Upper ring sloping towards central area at an acute angle from lower ring, Both rings decorated by imbricate elements. Approximately 36 long radiating elements (strands) connect a small, smooth central area (bottom of thimble) to short, knob-like processes in lower ring of marginal shield. These processes are similar to those found on the exotheca of S. rotula. Height of exotheca approximately 4 g m width of central area approximately 2 p m width of upper marginal ring approximately 3.2 Urn. Occurrence: November, 1976, station A a~: 150 m.

Calyptrosphaera sp. A (Plate V, 1). No complete coccosphere was observed. Description of coccoliths: Coccoliths are calyptroform holococcoliths with 4--6 rings of microcrystals slightly tapering in height towards the center. Outer layer o f rings one microcrystal higher than normal. Inter-spaced in an irregular pattern are c r y s t a l knobs

PLATE V

1. Calyptrosphaera sp. A. Note microcrystal knobs usually found at the periphery of holococcolith. Nr. A76080910 (0 m); Neg. H23-33. 2. Corisphaera arethusae ~ p t n e r . Nr. A76080910 (0 m); Neg. H2i,14 3. Coris~ phaera aff. C. gracilis Kamptner. Specimens lacking distinct holes. Nr. A760809t0 (0 rn); Neg. H29-24~ 4. Helladosphaera cornifera (Schiller). Nr. A76080910 (0 m); Neg. F81,11. 5. Homozygosphaera quatriperforata (Karnptner). Probable organic strands s u r r o ~ i n g coccolith. Nr. A76080910 (0 m); Neg. F05-29. 6. Hornozy~ gosphaera wettsteini (Kamptner). Note variation in number of archs in the center. Nr, A75120924a (25 m); Neg. B68-09. Bar = 2 urn, 7. Sphaerocalyptra hagleana (Gaarder). Nr. A76080910 (0 ra); Neg. E60,26, Bar = 2 urn. 8. Sphaerocalyptra bannoekii Borsetti and Cati, iNr. A76080910 (0 rn); Neg. H21-15. 9. Sphaerocalyp tra quadridentata (Schiller), Nr. A76080910 (0 m); Neg, H29-35. 10. Zygosphaera divergens Hal!dal andMarka~ li. Broken coccosphere formed o f d ~ o r m and z y g o ~ holococcoliths. Nr, A76112601 (0 rn); Neg. F60,35. 11. Thoracosphaera cf. T. heimi (Lohrnann), Nr. A75120924 (0 rn); Neg. A86-10. i2. Thoracosphaera sp. A. Nr. A75120927 (150 rn); Neg. B08-09.

211

PLATE V

2

3

4

5

6

7

8

9

10

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1 1

212 numbering from 7 to 11 and usually found at coccolith periphery. Calyptrotith size ranges from 1.6 to 2 p m in length and from ] to 1.8 p m in width. Occurrence: Rare at station A in summer assemblage.

Corisphaera arethusae Kamptner (Plate V, 2); Borsetti and Cati (1972, p. 408, p!. 48, figs. 3a--b}. The rare Elat specimens are almost identical to that illustrated and described by Borsetti and Cati (1972, pl, 48, fig. 3a--b), unlike those specimens pictured by Okada and McIntyre (1977, pl. 13, fig. 6) and by Gaarder (1962, pl. 3) [see also Okada and Honjo (1977) for remarks on the specimen figured b y K a m p t n e r ] . Corisphaera aff. C. gracilis Kamptner (Plate V, 3); Borsetti and Cati (1976, p. 218, pl. 15, fig. 11). Our rare summer specimens lack the distinct larger holes of typical C: gracilis and thus correspond closely to the species figured by Borsetti and Cati (1976) as C. aff. gracilis. Homozygosphaera

wettsteini (Kamptner} (Plate V, 6); Halldal and Markali (1955, p. 9, pl. 5, figs. 1--4). Some of the zygoform holococcoliths possess only four arches in the center, i.e. less than the number of five to seven reported by Halldal and Markali. Sphaerocalyptra bannockii Borsetti and Cati (Plate V, 7); Borsetti and Cati (1976, p. 212, pl. 13, figs. 4--6). While most of the distally protruding walls are perpendicular to the long axis as figured by Borsetti and Cati {1976), some of the protruding walls of the Elat specimen are parallel to the long axis of the calyptroform holococcoliths.

Thoracosphaera

cf. T. heimi (Lohmann) (Plate V, 11}; Kamptner (1954, pp. 40--42, figs. 41--42). Identification is based on Cohen (1964) and Boudreaux and Hay {1969) whose illustration and description of T. heirni resemble the Elat specimen.

Thoracosphaera sp. A (Plate V, ]2). The single Elat specimen from 300 m, Station A, Dec. 1975, is tentatively placed in the genus Thoracosphaera because of its resemblance to other forms previously described. Further taxonomic work should clarify its taxonomic position. Seasonal and bathymetrical distribution of coccolithophores

Standing crop The two most conspicuous features regarding number of specimens found at the same depths throughout the year and within the upper 400 m in the water column during one sampling period, were the unimodal yearly distribution of the standing crop and the general decrease in cell density with depth (Fig. 2). Usually cell count per liter was highest in the upper 50 m. However, during February, cells were evenly distributed throughout the column (Fig. 3). N u m b e r of cells in the water column ~100 cm 2 X 200 m; unit column} was calculated following Honjo and Okada's (1974) method, and were then compared to their results. The abundance of cells was greatest during early December, 1975 when a distinct peak occurred at all sampled depths. Close to 16.8 X 103 cells 1-1 were recorded from the surface while the unit wa~er column contained 27 × 108 individuals. These figures represent a high density of coccolithophores and compare to the highest ones recorded by Honjo and Okada (1974) in the productive Equatorial Pacific. A steep decrease in cell density ensued during the winter months, resulting in a scarcity of cells in May, 1976 at all depths. At the onset of summer a gradual increase of cell numbers occurred in the water column d o w n to 100 m depth, while below this level no appreciable increase in density was measured. On August 9, 1976 a maximum cell aggregation of 5.5 X 103 cells 1-' was measured at the surface. The unit water

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column contained 8.45 X 10 s coccolithophores. The numbers of August density in Elat are comparable to those recorded in the Pacific Transitional Zone (approximately 30-40 ° lat. N.) during late summer and early fall. An increase in cell density in the upper 25 m continued from August until the final sampling in November, 1976. Standing crop t h r o u g h o u t the water column sampled during this time was, however, well below that re-

corded nearly a year earlier. Surface water density was 1.25 X 104 cells 1TM and the unit water column contained 1.2 X 107 individuals.

Community structure Fifty-two coccolithophore species were identified from stations A and G in the Gulf of Elat during this investigation. Of these, 36

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and further characterized b y a n a b u n d a n c e of A. quatricornu, spine-producm~ S y r a ~ cosphaera spp., and scaDholite coccolith{> phores. Ten m i nor species are no[ c o m m o n to these m ont hs (Fig. 2). A profusion ~ff holococcolith coccospheres, and d~e appearance of m a n y Syracosphaera s p p , 4:. teuuis and R. longistylis characterized the summer (August, 1976) assemblage. The tram sitional, November, 1976 assemblage had elements of both summer and winter species. The occurrence of the different species a~ the surface and their percentage distribution is presented in Fig. 4.

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Fig. 3. Number of coccospheres per liter of water in the upper 400 m at station A, Gulf of Elat during five sampling periods of the year 1975--1976

have been r eco r d e d so far f r om both the Pacific and Atlantic Oceans (Okada and McIntyre, 1977), 3 from the Pacific only and 3 exclusively f r o m the Mediterranean Sea. Seven species seem to be endemic to the Gulf of Elat, while the distribution of three others is u n k n o w n . Of the 33 species identified by Mikkelsen (1973) f r om the Gulf, 26 have been acco u n ted for during this survey. The m o s t i m p o r t a n t o f those n o t observed in the waters o f the Gulf, are Gephyrocapsa carribeanica (Boudreaux and Hay) (possibly misidentified by Mikkelsen), and Cyclococcolithus leptoporus (Murray and Blackman). Most species collected f r om the Gulf of Elat were present in surface waters and, in general, c o m m u n i t y structure at greater depths reflected th a t of the surface (Fig. 2). Three major c o c c o l i t h o p h o r e assemblages were discernable t h r o u g h o u t the year. The N o v e m b e r 1975, D e c e m b e r 1975 and February, 1976 ( " w i n t e r " ) assemblages were d o m i n a t e d b y E. huxleyi and G. ericsoni

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Nov 26, '~;'6

iv} i'-\~ i

Fig. 4. Percentage distribution o f surface c o c c o l i t h o p h o r e species in the G u l f o f Elat, station A. N o t e change in c o m m u n i t y structure and diversity with increase in temperature in the A u g u s t assemblage. ( N = n u m b e r o f s p e c i m e n s c o u n t e d in the SEM~ S = n u m b e r o f species present; H' = diversity i n d e x in natural bels ( H o n j o and Okada, 1 9 7 4 ) ; o = --::1% "~

215

Species diversity

Discussion

For comparative purposes diversity was determined by the same m e t h o d as that used by Honjo and Okada {1974) for coccolithophores of the Pacific. The diversity index H' (in natural bels), is that of Shannon and Weaver (1963) with Basharin's modification (1959) quoted from Pielou (1966) for a type B collection:

Comparison of the Elat nannoflora with those from other investigated regions, including the Red Sea, indicates that the Elat coccolithophore assemblage is unique in composition. The particular combination of E. h u x l e y i and G. e r i c s o n i (Table I), comprising about 60% of the annual Elat population, appears in the central north zone of the Pacific where the two species account for 50% of the total assemblage (Honjo and Okada, 1974).

8

/1# (natural bels) = - ~

Pi In Pi - - (S - - 1)/2N

i=l

where Pi is the proportion of the ith species in the population, S is the number of species, and N is the number of specimens in the sample. Diversity was only measured for surface samples. The highest species diversity, 2.47 natural bels, was recorded in the summer, and the lowest, 1.41 natural bels, in the transitional November assemblage. In winter months diversity increased only slightly to 1.64 natural bels. The very high diversity recorded in the summer is mostly due to the abundance of holococcolithophores which contributed 12 of the 36 species recorded during this period and to a decrease in dominance of E. h u x l e y i and G. ericsoni. S e d i m e n t assemblages

The coccoliths present in two sediment samples taken from 600 m at station A were examined. Other than the delicate holococcoliths which were rare, the majority of species f o u n d in the water column occur in the sediment. Most species, especially the resistant placoliths, were very well preserved and showed no dissolution effects (see Berger and Roth, 1975). Mikkelsen (1973) also f o u n d most of the species recognized in the water to occur in sediment samples. Although C. l e p t o p o r u s was well represented in these latter samples and is listed by Mikkelsen as a species found in the water column, it was entirely absent in all 84 water samples examined in this study.

TABLE I List of major coccolithophore species (more than 10% of the population) appearing between 0 and 400 m in the ~ulf of Elat November 20, 1975 E. huxleyi G. ericsoni G. oceanica

December 09, 1975 E. huxleyi G. ericsoni

Spine-producing Syracosphaeraceae February 02, 1976 E. huxleyi G. ericsoni G. oceanica

Spine-producing Syracosphaeraceae May 03, 1976 E. huxleyi G. ericsoni U. sibogae

August 09, 1976 E. huxleyi G. ericsoni G. protohuxleyi R. longistylis A. brasiliensis H. cornifera

November 26, 1976 E. huxleyi G. ericsoni

216

F

0

I

5O 30

j

N : 72 S :13

STATION A G u l f of Elat

i

Feb 2,1976

L ~ I :'d

l i ~ 4 7

i

I0 3O

iO

S :12 ~

'

50

N :306 S :16

~

tO 9O

Gulf of EIo ~" Jan21~197E .............. tS~[ATION R - 3 0 " Central RedSeo [ ~~_ Feb 1971 I ] ~

N : 287

s

:

STATION R 7

4

Soother°

]

Re~ Se<,

i

Feb 1971

ZO

J

50

IPd

i

i

3O

iO

I LZ~ .

.

.

.

.

.

.

.

.

.

.

.

.

J

Fig. 5. Comparison of percentage distribution of coccolithophore species in surface waters between the Gulf of Elat (1976) and the Red Sea (1971) during winter. The difference in community structure between the Gulf of Elat and the central Red Sea during this time is attributed to higher salinity in the Gulf and slightly higher temperature in the Red Sea. Dominance of G. oceanica in the southern Red Sea is related to neritic character of water. (N = number of specimens counted; S = number of species present.) Red Sea data from Okadaand Honjo (1975). Consideration of the remaining species comprising the assemblages in each region reveals that while the Pacific assemblage is f ur t her co m p o s ed of species c o m m o n in the world's oceans, the Elat assemblage conspicuously lacks o t h e r c o m m o n pelagic species. Especially n o t e w o r t h y in this respect is the absence o f p r o m i n e n t deep-water species, e.g. Florisphaera profunda Okada and H onj o and Thoracosphaera flabellata Halldal and Markali in the 1,800-m deep Gulf, but present in the Red Sea (Fig. 5), and the very rare occurrence o f Discosphaera tubifera, C. leptoporus, and Umbellosphaera irregularis, c o m m o n in the Pacific and the Atlantic. F u r t h e r m o r e , the

presence in the Gulf of (.;. pr'ot~.huxlcyu hitherto t h o u g h t to have been extm~t since 75,000 B.P. (Winter et at., 1978k must also be considered. It might be argued that the nbsence ~i' some major pelagic species is d u u h:~ lhe Gulf's " n e r i t i e " character in so far that its waters are always in proxi m i t y to land. However, as pointed out by Okada and Honjo (1975), subtropical and tropical nerHic waters (e.g. the southern Red Sea) are dora inated by G. oceanica (See Fig. ;;i. l'h~,~ though, is not the case in the Gulf of Elat, indicating its pelagic nature. Nevertheless, the abundance of holococcoliths, indicanw~ of near-shore assemblages (Berger and [Loth> 1975) in the Gulf during August, 1976, should not exclude the possible imporLance of the p r o x i m i t y of the land to any part ~,i' the Gulf in influencing communiW structuru of coccolithophores. An explanation for the peculiar absence of the above-mentioned species may he the e x tremely high salinities (41°/00) in the Gulf as com pared to the open ocean. It appears that the higher salinity in the n o r t h e r n m o s t Red Sea and especially in the Gulf acts as an ecological filter barrier. Hence, stenohaline pelagic species and deep-water taxa not adapted to the inherent osmotic pressure conditions m the Gulf would be prevented from livin~ there. Kimor (1973) described a simdar barrier for planktonic organisms passing from the Gulf of Aden to the Red Sea with its higher salinity and warmer, deeper waters. It is suggested, therefore, that coccolithophores pass through two filter barriers before entering the Gulf of Elat. This may explain the presence of some species in the P~ed Sea and the Gulf of Aden and their absence m the Gulf of Elat, as well as the presence of certain species in the Gulf of Aden exclusively (Fig. 5). A comparison of species diversity and standing crop to ot her ecologically i m port ant parameters in the Gulf of Elat is presented in graphic f o r m in Fig. 6. An important result of this investigation is the significantly

217

1975 1976 1977 2 6 tN DI J IF IMIA!N,I d Id ',A ISIOINIDIJ IF IMI

."" ~ " "?~ _ _ ~" i IO~ ~olo for surfoce missirg

18 ~ , - . ~ . ~

DIVERSITY " INDEX

ibul diversily e~iremely low I I,Nr of species less t ' ~ thon 5 of 25mF3"fSURFACE~ "

--~-. . . .

F26 P

_~/WATER TEMPERATURE {-24

[-22

"\-~/ ~.,1000 t

800P

/

>" 600 4O0 "~

Ioo

~

6(?

"

~

/

7

COCCOLITHOPHORE

PRIMARY ~PRODUCTION//

•

"~--'°

/\

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~NDIJ F I M ! A I M I J iJ A IS I O I N I D I J IF iMI 1975 1976 1977

Fig. 6. Comparison of coccolithophore species diversity and standing crop to physical, biological and chemical parameters in the Gulf of Elat. Diversity is given in natural bels. Insolation is undepleted solar radiation for latitude 30°N (Neumann and Pierson, 1966). Graphs of parameters, except for diversity, temperature and insolation are derived by integration of in situ values in a photic column of 200 m. Primary production, chlorophyll and nutrients from Levanon et al. (in press).

high positive correlation between coccolithophore diversity and temperature in the surface water. The lack of any significant seasonal change in salinity and the poor correlation of species diversity, with hydrological parameters other than temperature, justify the conclusion that temperature fluctuation (although within a range of only 6 ° C) is the major ecological factor influencing the c o m m u n i t y structure in the Gulf. The fact that diversity seems to be closely related to temperature indicates that those coccolithophores living in the Gulf of Elat are ex-

tremely sensitive indicators of this parameter (see Fig. 3). For example, the most important hydrological event in the Gulf is the breakdown of the upperwater stratification resulting in the nearly uniform (21°C) structure. Following this event, a rapid increase in the dominance of G. ericsoni, G. oceanica and U. sibogae and the disappearance of many " s u m m e r " species occur (see Table I), decreasing diversity dramatically. The three species mentioned above which dominate the assemblage during the winter become increasingly less important as water temperatures reach above 25°C in early summer. In the summer there is a proliferation of species and an increase in species diversity. Temperature has also been shown to be an important ecological parameter for coccolithophores by other investigations. Temperature tolerance ranges for those species in Bermuda waters, where a seasonal record of coccolithophore assemblages has been kept, have been given by McIntyre and B6 (1967). Although the c o m m u n i t y structure in the Bermuda region and the Gulf of Elat differ possibly owing to the lower salinity around Bermuda, the temperature ranges of those species occurring in both regions are very close. At present, few data exist on seasonal fluctuations of c o m m u n i t y structure and temperature tolerances of coccolithophores in other regions. Nevertheless, it seems significant that the Bermuda and Elat ranges should correlate so well. While the Elat waters are better mixed and much more saline than those of Bermuda, ecological factors are common to both regions (Table II), in particular the clear water, similar temperature ranges, and low biological production. These common factors have also been described by Reiss et al. (1974) and Almogi-Labin and Reiss (1977). Thus, nutrient levels and light penetration may be, in addition to temperature and salinity, important factors affecting the distribution of coccolithophores. The high negative correlation between insolation and coccolithophore standing crop (Fig. 6) is significant. Photoinhibition may be

218

T A B L E II C o m p a r i s o n o f p h y s i c a l , c h e m i c a l a n d n u t r i e n t values f r o m B e r m u d a ( T o l d e r l u n d a n d B~, 1971 ) a n d Elat ( K l i n k e r et al., 1 9 7 6 , 1 9 7 8 ; n o t e t h a t t h e B e r m u d a a n d Elat ranges are similar e x c e p t for salinity

Temperature(°C) PO4 -P (ug/at. 1TM ) NO3 +NO2 -N(ug-at. 1TM ) O x y g e n ( m l l TM ) Salinity ( ° / 0 0 )

Elat (1974-~1976)

Bermuda (1971)

20.5 ~27.3 0 . 0 3 - - 0.25 0.07 ...... 2.0 3.75 .... 6.10 40.26-41.63

19.0 - 2 7 . 7 0.02 0.16 0.01--- 1.5 4 . 2 5 - - 5.50 36.1 - 3 6 . 7

T A B L E III C o m p a r i s o n o f t h e d i s t r i b u t i o n a n d a b u n a a n c e s o f t h e i m p o r t a n t coccolithopi~ore species in t h e G u l f o f Elat a n d in t h e Pacific ( O k a d a a n d M c I n t y r e , 1 9 7 7 ) ; n o t e t h a t the w i n t e r c o c c o l i t h o p h o r e assem~ blage in Elat has far m o r e " E q u a t o r i a l " e l e m e n t s t h a n t h e s u m m e r assemblage Species

Percent composit i o n in Elat

O c c u r r e n c e in Pacific z o n e s

A b u n d a n c e in Pacific

Equatorial--Subarctic not present Central--Transitional Equatorial--Central Kuroshio Current Central--Transitional Kuroshio Current

abundant occassional rare t o occassional occassional common to abundant rare

Equatorial Central--Transitional Transitional Equatorial--Subarctic Equatorial--Transitional

common occasional rare abundant occassional t o c o m m o n abundant to common

occasional common occasional to c o m m o n

S u m m e r ( A u g u s t 9, 1 9 7 6 ) ~

E. huxley i E. protohuxleyi H. cornifera H. q uadriperforata R. longistylis U. tenuis Z. divergens

16 8.5 12.5 9 17 17 5

Winter ( N o v e m b e r 20, 1 9 7 5 )

A. brasiliensis

2.5

A. quatricornu E. huxleyi G. erzcsoni

5 30 40

G. oceanica

12.5

O. fragilis subsp, cavum

1

Equatorial Central--Transitional Equatorial- -Central

Ophiast-er spp. U. sibogae H. wettsteini

2 4 1 --9

Equatorial--Transitional Equatorial--Transitional Equatorial--Transitional

common

common to abundant

O t h e r m i n o r c o m p o n e n t s of s u m m e r h o l o c o c c o l i t h o p h o r e assemblages are n o t f o u n d in E q u a t o rial zones.

219 sufficient to keep down the standing crop during summer months when light intensity is extremely high. Takahashi et al. {1971) noted that long exposure to high light intensities (such as prevalent in the Gulf) may increase photo-inhibition. In addition, the low nutrient values in the Gulf may even further increase the light inhibiting effect (Parsons and Takahashi, 1973). The combined effect of low nutrients and high light intensities prevalent in the Gulf result in low primary productivity and chlorophyll a values (Levanon et al., in press). The yearly cycles are very similar in both these parameters showing a bimodal pattern (Fig. 6). The peak exhibited in late spring may be due to Trichodesmium sp. (Kimor and Golandsky, 1977), a nitrogen-fixing blue-green alga which peaked in the Gulf a year earlier at this time. Based on the fact that standing crop and chlorophyll a peaks coincide in December, 1975, it is concluded that coccolithophores comprise the major part of the phytoplankton biomass at this time in the Gulf. This assertion is supported when considering the results obtained one year earlier by Kimor and Golandsky (1977), who found no other p h y t o p l a n k t o n peaks occurring at or around this time, immediately at the beginning of the " w i n t e r " season. Of all the p h y t o p l a n k t o n groups in the Gulf, it appears that the coccolithophores are the first to react to the changing seasonal, hydrological conditions in the Gulf. Since chlorophyll a is also indicative of primary productivity in the Gulf (taking into account the correlation of their values) the coccolithophores are one of the major primary producers in the oligotrophic Gulf of Elat. A major puzzle arising out of this investigation is the fact that for a short time at the beginning of the " w i n t e r " season, the standing crop is as high as that recorded by Okada and Honjo (1973) for the Equatorial Pacific and also comparable to that of upwelling areas (Berger, 1976) rich in nutrients. Con-

sidering the low nutrient values of the Gulf of Elat and the seemingly insignificant seasonal fluctuation of nutrients with respect to coccolithophores, it seems surprising that the Gulf of Elat supports such a large number of calcareous nannoplankton. Especially n o t e w o r t h y is the lack of any large decrease in nutrients during the coccolithophore bloom (Levanon et al., in press). As a whole, nutrient levels at the surface throughout the year do not fluctuate greatly in amplitude, while there is a successive appearance of p h y t o p l a n k t o n (Kimor and Golandsky, 1977) and zooplankton species (Z. Reiss, personal observation, 1977). One may speculate that in an area such as the Gulf, containing little phosphate and nitrate, the nutrients are passed around from one p h y t o p l a n k t o n comm u n i t y to another. This should explain why nutrients would never increase greatly at any given time of the year. Considering the latitudinal and water mass distribution of the species present in the Gulf and the Pacific it is n o t e w o r t h y that of the six major summer species present in the Gulf of Elat, four are n o t found in the Equatorial zone of the Pacific (see Okada and Honjo, 1973, for a description of zones): Z. divergens and R. longistylis are prevaient in the Kuroshio current, A. cornifera is present in Central to Transitional zones, and U. ~enuis is found mostly in cooler waters of the Central to Transitional zones of the Pacific (Table III). Of the remaining two species, H. quadriperforata has a wide latitudinal distribution, ranging from the Equatorial zone to the central north zone and G. protohuxleyi is, at present, restricted to the Gulf. On the other hand, the important win~er species in the Gulf of Elat are all present in the Equatorial regions. Especially revealing is H. wettsteiui which is the only holococcolithbearing species of the thirteen identified so far that occurs in the winter, but not in the summer assemblages in the Gulf. This species is found in the Equatorial to Transitional zones of the Pacific. Further evidence of the affinities of the winter assemblage to the

220 Equatorial zones are the species characterized by scapholiths which are abundant in the Elat winter and are also very c o m m o n in the Equatorial region. Hence, high-fertility dep e n d e n t relationship exists between the seasonal composition of the Elat flora and its distribution in the Pacific.

Summary and conclusions (1) The c o c c o l i t h o p h o r e standing crop distribution t h r o u g h o u t 1 9 7 5 - 1 9 7 6 exhibited a unimodal curve. The peak occurred in late fall, 1975 just after stratification conditions ended. Cell density decreased with depth e x c e p t during F e br uar y when the water column was well mixed. Species diversity was highest in the " s u m m e r " (August, 1976) remaining lower during the rest of the year. Coccolithophores constitute the major part of the p h y t o p l a n k t o n biomass and are i m p o r t a n t primary producers in the Gulf of Elat. (2) 52 m o d e r n c o c c o l i t h o p h o r e species were identified from the Gulf of Elat during the sampling period. Most of these species also appear in the Pacific and Atlantic. Seven taxa, however, have been thus far described only from the Gulf of Elat. Most of the species recorded were found in the surface water samples. Morphological changes of the central structure o f E. huxleyi and G. protohuxleyi in the Gulf seem to be seasonally d e p e n d e n t . A correlation between central structure m o r p h o l o g y and latitude has also been recorded in E. huxleyi in the Atlantic and Pacific. The Elat finding thus supports the suggestion that this p h e n o m e n o n may be of paleoecological significance. The occurrence of dimorphic G. oceanica---E, t~uxleyi specimens and of a placolith-bearing coccosphere possessing "I"-shaped elements in addition to a one or two element bridge, indicates the close relationship between Gephyrocapsa and Emiliania. Apparent etching o f G. oeeaniea has been observed in February samples in Elat. As no CaCO3 dissolution seems to occur in the Gulf (as evidenced by a b u n d a n t presence of aragonite pteropods in

sediments, it is suggested that etching may I~: a result of digestive processes of ~>redatovy organisms. (3) Three major coccolithoph~,r~ asse~:~: blages, closely related to the hvd~'oh)gi::ai events in the Gulf were d~scernabie t h r o u g h o u t the year. Two species. E. [mxievi av,d (; ericsoni dominate the c o m m u n i t y ~trt~(:t.m~~ t h r o u g h o u t the year except in ,\ugtlsi:~ 197(~ " s u m m e r " assemblages whe~ ~h% wor~:. nevertheless, c o m m o n . (4) High salinities in the Gulf as ..,~m:pared to the open ocean, act as a l)arri,.~: :~ ~na~y c o m m o n pelagic species which are ~:ot !'ou:~(~ in the Elat assemblages. (5) T em perat ure and species diversil.y s h o ~ significant correlation. T em perat ure i(fleran,:~ ~ ranges of species living in Elat and Bermuda waters are similar. Bermuda and Elat have many c o m m o n ecological factors, includin~ low primary p r o d u c t i o n values a~:d clea; water. This may indicate that nutrients a~d light penetration are i m port ant i':wtors ~. fluencing distribution and num ber ~.ff c,,)cc,:~ lithophores. (6) Standing crop values seem to 1~ advers~'~ ly affected by high insolation whih~ ~mtrie~! levels in the Gulf do not seem t~ ,:,,->rrelat-c. with seasonal c o c c o l i t h o p h o r e bloom,_-,. (7) The August, 1976 "summe~ ~ assem blage in the Gulf of Elat has less Equatoriai Pacific affinities than "w i nt er ~' (November, December, 1975; February. 19761 assem~ blages.

Acknowledgements The assistance of the staff of the SEM units of the Hebrew University and the Pale~ ontological Division, Geological Sul-~ey ot! Israel and of the "H. Steinitz" Marine Bi,) logical L a b o r a t o r y , Elat, in particular i Levanon, is gratefully acknowledged. B. ]taq (WHOI, Woods Hole, Mass., U.S.A.} ~n:d A McIntyre (LDGO, Palisades, N . Y , [7.S.A.~ have offered constructive criticism of the manuscript. Thanks are due to J. Winter fo.*" patiently typing the manuscript aT:~ i:o ~:

221

dalicz for preparing the plates. This publicat i o n is p a r t o f t h e s e n i o r a u t h o r ' s M a s t e r ' s -Fhesis in O c e a n o g r a p h y at the H e b r e w U n i v e r s i t y o f J e r u s a l e m . T h e s t u d y was s u p p o r t e d in part b y grant Nr. 0 1 5 . 6 4 5 3 f r o m the Israel N a t i o n a l A c a d e m y of Sciences and Humanities. References Almogi-Labin, A. and Reiss, Z., 1977. Quaternary pteropods from Israel. Rev. Esp. Micropaleontol., 9: 5--48. Berger, W.H., 1976. Biogenous deep sea sediments: production, preservation and interpretation. In: J.P. Riley and R. Chester (Editors), Chemical Oceanography, 5: 265--388. Berger, W.H. and Roth, P.H., 1975. Oceanic micropaleontology: progress and prospect. Rev. Geophys. Space Phys., 13: 561--585. Black, M. and Barnes, B., 1961. Coccoliths and discoasters from the floor of the South Atlantic Ocean. R. Microscop. Soc., J., 80: 137--147. Borsetti, A.M. and Cati, F., 1972. I1 nannoplancton calcareo vivente nel Tirreno centromeridionale. Giorn. Geol., 38: 395--414. Borsetti, A.M. and Cati, F., 1976. I1 nannoplancton calcareo vivente nel Tirreno centromeridionale, Parte II. Giorn. Geol., 40: 209--240. Boudreaux, J.E. and Hay, W.W., 1969. Calcareous n a n n o p l a n k t o n and biostratigraphy of the Late Pliocene-Pleistocene--Recent sediments in the Submarex cores. Rev. Esp. Micropaleontol., 1: 249---292. Braarud, T., 1945. Forurensing og selvrensing av sj~vann. Naturen, 7--8. Bramlette, M.N., 1958. Significance of coccolithophorids in calcium-carbonate deposition. Bull. Geol. Soc. Am., 69: 121--126. Burns, D.A., 1977. Phenotypes and dissolution morphotypes of the genus Gephyrocapsa Kamptner and Emiliania huxleyi (Lohmann). N . Z . J . Geol. Geophys., 20: 143--155. Clocchiatti, M., 1971. Sur l'existence de coccospheres portant des coccolithes de Gephyrocapsa oceanica et de Emiliania huxleyi (Coccolithophoridds). C. R. Acad. Sci. Paris, 273: 318--321. Cohen, C.L.D., 1964. Coccolithophorids from two Caribbean deep-sea cores. Micropaleontology, 10: 231--250. Deflandre, G., 1952. Classe des coccolithophoridds (Coccolithophoridae Lohmann, 1902). In: P.-P. Grass~ (Editor), Trait4 de Zoologie, 1. Masson, Paris, pp. 439--470. Freund, R., 1965. A model of the structural development of Israel and adjacent areas since Upper

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