525 research outputs found

    Diet of two Antarctic dragonfish (Pisces: Bathydraconidae) from the Indian sector of the Southern Ocean

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    The diet of Cygnodraco mawsoni Waite 1916 and Gymnodraco acuticeps Boulenger 1902 (Pisces: Bathydraconidae) was studied in the Cooperation and Cosmonaut seas in the depth range 200ā€“400 m during the summer 1988. Stomach content analysis showed that both species are piscivorous predators but with different feeding habits. Cygnodraco mawsoni fed mostly on young notothenioid fish, regularly complementing these with pelagic, Euphausia superba, and benthic crustaceans, such as amphipod gammarids and mysids. In contrast, G. acuticeps relied mostly on mesopelagic fish of the family Myctophidae. Although C. mawsoni and G. acuticeps occupy similar depths in the Cosmonaut Sea, different feeding habits appear to limit the probability of interspecific competition for food

    Stabilization of class-B broad-area lasers emission by external optical injection

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    We theoretically examine the effect of external optical injection on the spatio-temporal dynamics of class-B broad-area lasers. We demonstrate that optical injection can efficiently stabilize the intrinsic transverse instabilities in such lasers associated with both the boundaries of the pumping area and with the bulk nonlinearities of the active medium. Stabilizing action of optical injection is shown to be closely related to the suppression of inherent relaxation oscillations behavior.Comment: 8 pages, 7 figure

    Studying the impact of ocean eddies on the ecosystem of the Prince Edward Islands: DEIMEC ll

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    The Dynamics of Eddy Impacts on Marionā€™s Ecosystem Study (DEIMEC) programme was begun in 2002 with the aim of understanding the importance of the oceanic, upstream environment to the ecosystem of the Prince Edward Islands. This island group consists of two small volcanic islands and provides many opportunities for studying ecological and evolutionary processes, for monitoring ecological changes in relation to global climate change and for conserving a unique component of the planetā€™s biological diversity

    Surface distribution of microphytoplankton of the south-west Indian Ocean along a repeat transect between Cape Town and the Prince Edward Islands

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    Surface chlorophyll-a (chl-a) concentrations, microphytoplankton (>20 Ī¼m) species composition and distribution along a repeat transect between Cape Town and the Prince Edward Islands were investigated in early austral autumn (April/May) 1996. Samples were collected at approximately 30 nautical mile intervals for the analysis of size-fractionated chl-a and the identification and enumeration of microphytoplankton species. Peaks in total chl-a (>1 Ī¼g 1 [superscript -1]) were recorded at the Subtropical Convergence (STC), at the Sub-Antarctic Front (SAF) and in the waters surrounding the Prince Edward Islands. In addition, a minor peak in chl-a concentration was recorded in the continental shelf waters. At stations where elevated chl-a concentrations were recorded, microphytoplankton generally formed a substantial contribution (-10%) to total chlorophyll. Outside these regions, total chlorophyll concentrations were lower (95% of the total. Microphytoplankton species composition along both transects were dominated by chain-forming species of the genera Chaetoceros (mainly C. neglectum, C. peruvianus and C. constrictus), Nitzschia spp. and Pseudoeunotia doliolus. Cluster and ordination analysis based on species composition identified five distinct microphytoplankton assemblages, which were closely associated with the different water masses in the region between Cape Town and the Prince Edward Islands. The microphytoplankton species composition and biogeographic zones identified during this investigation are in general agreement with similar studies conducted in the south-west Indian Ocean during the austral summer, which suggests that there are little seasonal trends in both the microphytoplankton species composition and biogeographic zonation

    Prince Edward Islands' offshore oceanographic study: report of research cruise April-May 1997

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    preprintFocuses on the preliminary results of the second cruise of the Marion Island Oceanographic Study designed to provide oceanological observations off Prince Edward Islands from April 25 to May 28, 1997. Physical and chemical oceanographic results; Surface seawater temperature; Total chlorophyll-a distribution

    Variability in pH, fCO2, oxygen and flux of CO2 in the surface water along a transect in the Atlantic sector of the Southern Ocean

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    Underway sampling and measurements of pH, fCO2, oxygen and Chlorophyll a (Chl a) were performed in the surface waters from Cape Town (South Africa) to Queen Maud Land (Antarctica) in the Atlantic sector of the Southern Ocean during the austral summer 1997/1998. From direct measurements of these parameters and from calculated fCO2 the oceanic carbon dioxide system was studied and related to hydrological and biological parameters. fCO2 was in general undersaturated relative to the atmosphere and showed a large variability with values ranging from 313 to 377 Ī¼atm with a mean value of 346Ā±13 Ī¼atm. The undersaturation was more pronounced in areas associated with fronts where high Chl a and high pH in situ values were observed. Using shipboard wind speed data, estimates of the CO2 flux were made along the transect and during three mesoscale surveys on the northward return transect in the area of the Spring Ice Edge (SIE), the Winter Ice Edge (WIE) and in the Antarctic Polar Front (APF). The undersaturation observed during the transect caused the ocean to act as a sink for CO2 with a mean seaā€“air flux for the entire transect of āˆ’3Ā±5 mmol māˆ’2 dāˆ’1 with a large variability between āˆ’20 mmol māˆ’2 dāˆ’1 (oceanic uptake) to 1.3 mmol māˆ’2 dāˆ’1 (oceanic source). The lowest fCO2 values (largest oceanic uptake of CO2) were found at the southern boundary of the APF at 53Ā°S, which coincided with a supersaturation in oxygen and high pH values. Oxygen concentrations were measured from 50Ā°S to 63Ā°S and varied between 324 and 359 Ī¼mol kgāˆ’1 with a mean value of 347Ā±9 Ī¼mol kgāˆ’1. In general only small deviations from equilibrium oxygen saturation were observed (mean value=99Ā±2%). However, in the SIE oxygen was clearly undersaturated, probably an effect of upwelling of oxygen poor deep water which had not yet been compensated for by biological production. Three weeks later, the ice edge had retreated in the SIE region and the Chl a concentration had increased three-fold, suggesting the start of a phytoplankton bloom. This was also seen in the oxygen concentration which had increased and showed supersaturation. This coincided with an increased oceanic uptake of CO2 in the SIE during the mesoscale survey
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