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A. A. Zhamaletdinov A. N. Shevtsov E. P. Velikhov A. A. Skorokhodov V. E. Kolesnikov T. G. Korotkova P. A. Ryazantsev B. V. Efimov V. V. Kolobov M. B. Barannik P. I. Prokopchuk V. N. Selivanov Yu. A. Kopytenko E. A. Kopytenko V. S. Ismagilov M. S. Petrishchev P. A. Sergushin P. E. Tereshchenko B. V. Samsonov M. A. Birulya M. Yu. Smirnov T. Korja Yu. M. Yampolski A. V. Koloskov N. A. Baru S. V. Poljakov A. V. Shchennikov G. I. Druzhin W. Jozwiak J. Reda Yu. G. Shchors 《Izvestiya Atmospheric and Oceanic Physics》2015,51(8):826-857
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Dominant amphipods of Posidonia oceanica seagrass meadows display considerable trophic diversity 下载免费PDF全文
Loïc N. Michel Patrick Dauby Sylvie Gobert Martin Graeve Fabienne Nyssen Nicolas Thelen Gilles Lepoint 《Marine Ecology》2015,36(4):969-981
Gut content examination and trophic markers (fatty acids, stable isotopes of C and N) were combined to delineate the diet of the dominant species of amphipods from Mediterranean Posidonia oceanica seagrass meadows and to highlight trophic diversity among this community. Our results indicate that, although all dominant species heavily relied on macroalgal epiphytes, considerable interspecific dietary differences existed. Carbon stable isotope ratios notably showed that some of the amphipod species favored grazing on epiphytes from leaves or litter fragments (Apherusa chiereghinii, Aora spinicornis, Gammarus aequicauda), while others such as Dexamine spiniventris preferred epiphytes from rhizomes. The remaining amphipods (Caprella acanthifera, Ampithoe helleri and Gammarella fucicola) readily consumed both groups. In addition, SIAR modeling suggested that most species had a mixed diet, and relied on several food items. Fatty acid analysis and gut contents revealed that contributions of microepiphytic diatoms and of benthic and suspended particulate organic matter to the diet of amphipods were anecdotal. None of the examined species seemed to graze on their seagrass host [low 18:2(n‐6) and 18:3(n‐3) fatty acids contents], but Gammarus aequicauda partly relied on seagrass leaf detritus, as demonstrated by the lesser 13C‐depletion of their tissues. Overall, our findings suggest that amphipods, because of their importance in the transfer of organic matter from primary producers and detritus to higher rank consumers, are key items in P. oceanica‐associated food webs. 相似文献
416.
The major drawback of Ka band, operating frequency of the AltiKa altimeter on board SARAL, is its sensitivity to atmospheric liquid water. Even light rain or heavy clouds can strongly attenuate the signal and distort the signal leading to erroneous geophysical parameters estimates. A good detection of the samples affected by atmospheric liquid water is crucial. As AltiKa operates at a single frequency, a new technique based on the detection by a Matching Pursuit algorithm of short scale variations of the slope of the echo waveform plateau has been developed and implemented prelaunch in the ground segment. As the parameterization of the detection algorithm was defined using Jason-1 data, the parameters were re-estimated during the cal-val phase, during which the algorithm was also updated. The measured sensor signal-to-noise ratio is significantly better than planned, the data loss due to attenuation by rain is significantly smaller than expected (<0.1%). For cycles 2 to 9, the flag detects about 9% of 1Hz data, 5.5% as rainy and 3.5 % as backscatter bloom (or sigma0 bloom). The results of the flagging process are compared to independent rain data from microwave radiometers to evaluate its performances in term of detection and false alarms. 相似文献
417.
B.M. Mwashote W.C. Burnett J. Chanton I.R. Santos N. Dimova P.W. Swarzenski 《Estuarine, Coastal and Shelf Science》2010
Submarine groundwater discharge (SGD) assessments were conducted both in the laboratory and at a field site in the northeastern Gulf of Mexico, using a continuous heat-type automated seepage meter (seepmeter). The functioning of the seepmeter is based on measurements of a temperature gradient in the water between downstream and upstream positions in its flow pipe. The device has the potential of providing long-term, high-resolution measurements of SGD. Using a simple inexpensive laboratory set-up, we have shown that connecting an extension cable to the seepmeter has a negligible effect on its measuring capability. Similarly, the observed influence of very low temperature (≤3 °C) on seepmeter measurements can be accounted for by conducting calibrations at such temperatures prior to field deployments. Compared to manual volumetric measurements, calibration experiments showed that at higher water flow rates (>28 cm day−1 or cm3 cm−2 day−1) an analog flowmeter overestimated flow rates by ≥7%. This was apparently due to flow resistance, turbulence and formation of air bubbles in the seepmeter water flow tubes. Salinity had no significant effect on the performance of the seepmeter. Calibration results from fresh water and sea water showed close agreement at a 95% confidence level significance between the data sets from the two media (R2 = 0.98). Comparatively, the seepmeter SGD measurements provided data that are comparable to manually-operated seepage meters, the radon geochemical tracer approach, and an electromagnetic (EM) seepage meter. 相似文献
418.
Land use/cover and mangrove spatial changes were assessed for ten sites and their sub-catchments in Southeast Queensland, Australia. Two time periods were involved: 1972–1990, a period of relatively high rainfall, and 1990–2004, which was significantly drier. Aerial photographs and Landsat satellite imagery were used to map the inter-tidal wetlands and classify the land use/cover in the sub-catchments. A Maximum Likelihood Classification was used to map three types of land cover: agriculture, built-up and plantation forest. Mangroves (mainly Avicennia marina) were the focus as they have been recorded over recent decades encroaching into salt marsh. The Mangrove-Salt marsh Interface (MSI) Index was developed to quantify the relative opportunity for mangroves to expand into salt marshes, based on the shared boundary between them. The index showed a consistent relationship with mangrove expansion and change. To address problems of high dimensionality and multi-collinearity of predictor variables, a Partial Least Squares Regression (PLSR) model was used. A key finding of this research was that the contribution of environmental variables to spatial changes in the mangroves was altered following a reduction in rainfall. For example, agriculture had more influence on mangrove expansion and change during the wet period than during the dry period. 相似文献
419.
C.R. German A.M. Thurnherr J. Knoery J.-L. Charlou P. Jean-Baptiste H.N. Edmonds 《Deep Sea Research Part I: Oceanographic Research Papers》2010,57(4):518-527
High-temperature hydrothermal activity occurs in all ocean basins and along ridge crests of all spreading rates. While it has long been recognized that the fluxes associated with such venting are large, precise quantification of their impact on ocean biogeochemistry has proved elusive. Here, we report a comprehensive study of heat, fluid and chemical fluxes from a single submarine hydrothermal field. To achieve this, we have exploited the integrating nature of the non-buoyant plume dispersing above the Rainbow hydrothermal field, a long-lived and tectonically hosted high-temperature vent site on the Mid-Atlantic Ridge. Our calculations yield heat and volume fluxes for high-temperature fluids exiting the seafloor of ~0.5 GW and 450 L s?1, together with accompanying chemical fluxes, for Fe, Mn and CH4 of ~10, ~1 and ~1 mol s?1, respectively. Accompanying fluxes for 25 additional chemical species that are associated with Fe-rich plume particles have also been calculated as they are transported away from the Rainbow vent site before settling to the seabed. High-temperature venting has been found to recur at least once every ~100 km along all slow-spreading ridges investigated to-date, with half of all known sites on the Mid-Atlantic Ridge occurring as long-lived and tectonically hosted systems. If these patterns persist along all slow- and ultraslow-spreading ridges, high-temperature venting of the kind reported here could account for ~50% of the on-axis hydrothermal heat flux along ~30,000 km of the ~55,000 km global ridge crest. 相似文献
420.
S. A. Sviridov N. A. Palshin V. A. Solovyev A. V. Zaretskiy A. A. Metal’nikov 《Oceanology》2010,50(1):139-147
A coastal observatory for long-term continuous measurements of oceanological parameters and real-time data transfer via the
Internet to remote users is described. The observatory was designed at the Shirshov Institute of Oceanology (SIO) and tested
at its southern branch (SB) in the Black Sea. The architecture, components, and design principles of the observatory are discussed
along with its application for solving problems of water dynamics in the coastal zone. Results of field tests are given. 相似文献