Zeev Reiss

Primary production in a desert-enclosed sea— the Gulf of Elat (Aqaba), Red Sea

Abstract Chlorophyll a , primary production, nutrient levels, and microphytoplankton abundances were determined during 1976 and 1977 in the northern basin of the Gulf of Elat (Aqaba). During most of the year (April–November) the photic zone extends to great depth (170 m) and is oligotrophic (chl. a 16 to 54 mg m −2 , primary production 200 to 900 mg C m −2 day −1 ). During winter (mainly December to March) the upper waters are much more productive (chl. a 33 to 70 mg m −2 , primary production 690 to 1,120 mg C m −2 day −1 ). The seasonal pattern is also expressed in the depth-distribution of these parameters. Overall the gulf is moderately productive, averaging 160 g C m −2 year −1 . The biological characteristics are closely related to nutrient distribution in the water column. Nutrient distribution is determined by the circulation regime in the gulf, which is stratified in summer and mixed in winter. Phytoplankton blooms following peaks of the NO 2 + NO 3 − N and of N/P ratios suggest that nitrogen is the major limiting factor. There is also an increase in productivity from the open waters towards the coral reef, as well as from the northern to the southern basin at the approaches to the more productive Red Sea proper.

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

Abstract 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.

Late Quaternary Paleoceanography of the Gulf of Aqaba (Elat), Red Sea☆

Abstract The quantitative distribution of planktonic foraminifera, pteropods, and coccolithophorids, as well as oxygen-isotope variations were analyzed in four deep-sea cores from the Gulf of Aqaba (Elat) and the northernmost Red Sea. The core record covers about 150,000 yr. Detailed stratigraphic subdivision is facilitated by combining all calcareous plankton groups. Time-stratigraphic correlation and dating beyond the radiocarbon range are possible by comparison of the oxygen-isotope curves. During the glacial maximum salinity rose to more than 50‰, while winter temperature of the upper waters fell by at least 4°C compared to the present. The rise in salinity can be accounted for by sea-strait dynamics and lowering of sea level. The Gulf of Aqaba and the Red Sea were continuously connected through the Straits of Tiran, and there is no indication of desiccation during the glacial maximum.

Upper Cretaceous high-resolution multiple stratigraphy, northern margin of the Arabian platform, central Israel

Abstract Nineteen columnar sections of pelagic sediments, from outcrops and boreholes across central Israel, deposited at relatively moderate rates on the outer shelf and the continental slope of the Arabian margin, were correlated using lithological and electric-log markers, calcareous nannofossils, planktic and benthic foraminifera, ostracods and ammonites. Thirty-seven local correlatable datum levels, from Upper Coniacian to the end of the Cretaceous, were recognized, of which 30 are based on diagnostic fossils of Tethyan significance. These datum levels include first (FA) and/or last (LA) appearances of 13 nannofossils, 14 planktic and 9 benthic foraminifera, 5 ostracod zones and 4 ammonites, as well as 10 lithological markers of chalks, marls, cherts, phosphorites and dark bituminous shales. The biostratigraphic planes do not cross lithological boundaries and therefore both are considered synchronous events. The datum levels are used for a biostratigraphic zonation, a lithostratigraphic subdivision and a chronostratigraphic interpretation. The multi-disciplinary correlations provide a powerful high-resolution stratigraphic tool for further quantitative basin analysis and for the study of global events.

The foraminiferal genera Pararotalia, Neorotalia , and Calcarina : taxonomic revision

-. 1977. Calcareous Algae. Developments in Palaeontology and Stratigraphy, 4. Elsevier, New York, 185 p. ., N. P. JAMES, AND R. N. GINSBURG. 1974. The puzzling Paleozoic phylloid algae--Holocene answer in squamariacean calcareous red algae. American Association of Petroleum Geologists, Annual Meeting, 2:82-83. ZHANG YUN. 1989. Multicellular thallophytes with differentiated tissues from late Proterozoic phosphate rocks of South China. Lethaia, 22:113-132.

Salinity tolerance or marine organisms deduced from Red Sea Quaternary record

Abstract The oxygen-isotopic record and microfossils from deep-sea cores raised in the hypersaline (41‰ salinity) Gulf of Aqaba indicate that during Late Quaternary glacial time salinity rose considerably due to sea-level fall and strait-dynamics, reaching values of more than 50‰ during the last Glacial maximum about 18 Ka B.P. The salinity-dependent sequence of disappearance of various species of foraminifera, pteropods and coccolithophorids can be used to determine upper salinity tolerance limits of different taxa. Only the pteropod Creseis acicula and various benthonic foraminifera are able to withstand high salinities like those during the last glacial maximum.

Partitions and Fistulose Chamberlets in Textulariina

Representatives of the genera Spirotextularia, Plotnikovina, Siphoniferoides and Sahulia possess fistulose chamberlets, formed by the outer pavement and separated from the main chamber lumen by a partition which is always perforated by parapores in both solid-walled and in paraporous genera. In some species fistulose chamberlets are replaced during ontogeny by elongated chamber lobes. In certain species of Sahulia irregular cavities are produced between paraporous wall and pavement. Lobes and cavities probably serve the same function as fistulose chamberlets. Forms with fistulose chamberlets appeared during the Cretaceous and seem characteristic of well-oxygenated, warm, normal to hypersaline marine environments. The function of parapores and of the chamberlets is unknown; it may be connected with uptake of dissolved organic matter by diffusion.

Living gephyrocapsa protohuxleyi McIntyre in the gulf of Elat ('AQABA)

Abstract Coccolithophore assemblages in the Gulf of Elat contain living Geopyrocapsa protohuxleyi hitherto assumed to have been extinct at least since 75, 000 years B.P.

150,000 Years Gulf of Aqaba

Intensive studies of numerous deep-sea cores from the Red Sea proper have elucidated its paleoceanographic history during the Late Quaternary and have thereby significantly contributed to the reconstruction of regional Pleistocene-Holocene paleoclimates in this arid-semi-arid area (Degens and Ross 1969, Deuser et al. 1976, Herman 1968, Rosenberg-Herman 1965). Indeed, the Red Sea has been regarded as a “natural laboratory” for investigating changes in partly restricted marine environments (Berggren 1969).

Benthic Foraminifera: Response to Environment

As pointed out in the previous chapter, the response of each benthic species to the abiotic and biotic conditions in its environment is a specific one, reflected by its particular life history. An attempt is made in the following to summarize and integrate in situ observations, experimental evidence and assumptions based on circumstantial evidence separately for each species or for (informal) groups of species of benthic Foraminifera living in the Gulf of Aqaba.