Description: The presence of the cosmopolitan deep-sea coral Eguchipsammia fistula has recently been documented in the Red Sea, occurring in warm (〉20 °C), oxygen- and nutrient-limited habitats. We collected colonies of this species from the central Red Sea that successfully resided in aquaria for more than one year. During this period the corals were exposed to increased oxygen levels and nutrition ad libitum unlike in their natural habitat. Specimens of long-term reared E. fistula colonies were incubated for 24 h and calcification (G) as well as respiration rates (R) were measured. In comparison to on-board measurements of G and R rates on freshly collected specimens, we found that G was increased while R was decreased. E. fistula shows extensive tissue growth and polyp proliferation in aquaculture and can be kept at conditions that notably differ from its natural habitat. Its ability to cope with rapid and prolonged changes in regard to prevailing environmental conditions indicates a wide physiological plasticity. This may explain in part the cosmopolitan distribution of this species and emphasizes its value as a deep-sea coral model to study mechanisms of acclimation and adaptation.

Description: Late Quaternary sediments on the West African continental margin between 24°N and 15°N were studied with RV METEOR (1971) and VALDIVIA (1975). Cores on the shelf were taken with a 6-m-vibrocorer, in deeper water mainly with a 12 m Kastenlot corer. During Holocene, and up to the present time, more or less and climatic conditions north of the Senegal River area reduced terrigenous supply. Therefore, the biogenic-carbonate content exceeds about 50%. Wüstenquarz numbers (red + yellow quartz : white quartz x 100) are high (20 to mmore than 200), indicating eolian input. The Senegal River supplied fine grained, green colored, terrigenous material with some plant debris. During Würm, the Mediterranean climatic zone with winter rains was shifted more than 5° to the South and was reaching Banc d'Arguin (at about 20°N). Therefore, the terrigenous supply was increased in this northern part and consequently the carbonate content and the Wüstenquartz numbers dropped below 50% and 10, respectively. The arid zone was also shifted to the south; as a consequence, the Senegal River did not reach the sea, eolian supply diluted the biogenic carbonates, and increased Wüstenquartz numbers to more than 200. Eolian dunes covered parts of the shelf. Ratios of radiolarians/plankonic foraminifera and planktonic/benthonic organisms and sedimentation rates of organic carbon indicate stronger upwelling in the northern region. Turbidity currents were more frequent, eroding as much as a third of the material supplied ba pelagic sedimentation.

Description: Nutrient profiles in Southwest Pacific interstitial solutions suggest that in environments of oxic pelagic sedimentation microbially mediated nitrification is recognizable as a two-step process. During the first step partially oxidized nitrogenous intermediaries accumulate in distinctive ammonia and nitrite maxima along with nitrate. During the second step nitrification continues and all intermediate species are fully oxidized to nitrate. Both steps occur within a zone that corresponds in thickness to the biologically active surface layer. Similarly, experimental nitrogen regeneration from decomposition of plankton in seawater (VON BRAND and RAKESTRAW, 1941: VON BRAND et al., 1942) suggests that each step corresponds to a distinct reaction in the microbially mediated transformation of N-org → NH3 → NO2 → NO3. The resolution of distinct reaction zones in pore water nutrient profiles possibly depends on the nature and mode of supply of the organic matter undergoing nitrification or reflects the spatial succession downcore of microbial populations capable of deamination, ammonium oxidation and nitrite oxidation, respectively. Finally, stoichiometric ratios of nutrients in the free water column - here demonstrated on published data from Saanich Inlet - reflect the same two steps of nitrification as delineated by the dissolved pore water species. Future pore water studies should include dissolved oxygen measurements as well as accurate ∑CO2, PO4 and nitrogenous species profiles, to verify and better quantify these separate steps in nitrification mechanism of oxic pelagic sediments.

Description: Large euhedral crystals of calcium carbonate hexahydrate were recovered from a shelf basin of the Bransfield Strait, Antarctic Peninsula, at a water depth of 1950 meters and sub-zero bottom water temperatures. The chemistry, mineralogy, and stable isotope composition of this hydrated calcium carbonate phase, its environment of formation, and its mode of precipitation confirm the properties variously attributed to hypothetical precursors of the glendonites and thereby greatly expand their use in paleoceanographic interpretation.

Description: The vertical flux of biogenous organic matter to the sediment surface is a function of water depth and primary productivity; this relationship can be expressed empirically as: (1) org-Cflux = 5.9 · depth-0 616 · productivity Upon descent through the water column and prior to burial, biogenous detrital organic matter undergoes strong elemental fractionation by preferential removal of nitrogenous and P-containing organic compounds. At the water-sediment interface, a portion of the detritus is converted into biomass by benthic organisms, which concentrate nitrogen and phosphorus relative to carbon. These two processes are reflected in the elemental composition of sedimentary organic matter. A third process concentrates organic matter in sediments by sorption onto clays. This sorbed material is high in organic-N and devoid of organic-P; its relative abundance is high only in pelagic clays. The concentrations of each of the three forms of organic matter -detrital, biomass, and sorbed- can be calculated from the following expressions: (2) org-Csorb = 0.005 · Al2O3 (3) org-Cdetr = org-Ctota1 – org-Csorb - e · org-Ntotal / 1-2/f (4) org-Cbiom = org-Ctotal - org-Cdetr - org-Csorb where e and f are the C/N elemental weight ratios of biomass and detritus respectively

Description: In the sediments of the NW African continental margin the mainly biogenic carbonate constituents become increasingly diluted with terrigenous material as one approaches the coast, as indicated by the carbonate-C02 content, the Al20a/Si02-ratios, and the presence of ammonia fixed to alumino-silicates, predominantly to illites. In the northern area of investigation - off Cape Blanc and Cape Bojador - the terrigenous constituents are mainly quartz from the Sahara Desert, whereas in the south - off Senegal - more alumino-silicates as clay minerals are admixed with the carbonate constituents. The organic carbon content of the continental slope sediments off Senegal is higher than in samples of the continental rise or of the shelf, indicating optimal conditions for the preservation of organic matter as a result of high production and relatively rapid sedimentation. The zone of manganese-oxide enrichment follows the redox potential of + 330 m V from the surface (0-5 cm) into the sediments (20-30 cm deep) at 2000-3000 m and 3700 m of water depths, respectively. At shallower water depths, low redox potentials preclude deposition of manganese oxides and cause their mobilization from the sediments. About 1/3 of the total sedimentary Zn and 1/4 of the Cu is associated with the carbonate mineral fraction, probably in calcium phosphate overgrowths as a result of the mineralization of phosphorus-containing organic matter. Besides the precipitation of calcium phosphate, the mineralization of organic matter mediated by bacterial sulfate reduction also results in calcium carbonate precipitation and the exchange of ammonia for potassium on illites. Because of these simultaneous reactions, the depth distribution of all mineralization constituents in the interstitial water can be determined using the actual molar carbon-to-nitrogen-to-phosphorus ratios of the sedimentary organic matter. The amount of sulfide sulfur in this process indicates the predominance of bacterial sulfate reduction in the sediments off NW Africa. This process also preferentially decomposes nitrogen- and phosphorus-containing organic compounds so organic matter deficient in these elements is characteristic for the rapidly accumulating sediments. During the last glacial stage there were more biogenic carbonates and organic matter accumulating in the sedimcnts than today, indicating there was increased production of organic carbon compounds and more favorable conditions for their preservation. During the last interglacial times conditions were similar to those of today. This differentiation with time has also been observed in sediments from thc Argentine Basin and from the slope off South India indicating perhaps world-wide environmental changes throughout Late Quaternary times.