The CRISTA/MAHRSI experiment on board a space shuttle was accompanied by a broad campaign of rocket, balloon and ground-based measurements. Supporting lower ionospheric ground-based measurements were run in Europe and Eastern Asia between 1 October–30 November, 1994. Results of comparisons with long ionospheric data series together with short-term comparisons inside the interval October-November, 1994, showed that the upper middle atmosphere (h =80–100 km) at middle latitudes of the Northern Hemisphere in the interval of the CRISTA/MAHRSI experiment (4–12 November, 1994) was very close to its expected climatological state. In other words, the average results of the experiment can be used as climatological data, at least for the given area/altitudes. The role of solar/geomagnetic and “meteorological” control of the lower ionosphere is investigated and compared with the results of MAP/WINE, MAC/SINE and DYANA campaigns. The effects of both solar/geomagnetic and global meteorological factors on the lower ionosphere are found to be weak during autumn 1994 compared to those in MAP/WINE and DYANA winters, and they are even slightly weaker than those in MAP/SINE summer. The comparison of the four campaigns suggests the following overall pattern: in winter the lower ionosphere at northern middle latitudes appears to be fairly well “meteorologically” controlled with a very weak solar influence. In summer, solar influence is somewhat stronger and dominates the weak “meteorological” influence, but the overall solar/meteorological control is weaker than in winter. In autumn we find the weakest overall solar/meteorological control, local effects evidently dominate. 相似文献
Perceived changes in the culture of sponge science and sponge conferences served as motivation for an evaluation of the sponge science community and research, over time and at present. Observed changes included a decrease in proceedings publications on sponge fossils and freshwater sponges, sponges from temperate environments, review papers and data syntheses, frequency of aquarium studies, and number of species investigated per publication. Publications on recent sponges, hexactinellids, calcareans, marine, Indo‐Pacific and warm‐water sponges increased, as well as the number of authors per publication and the proportion of field studies. Studies at the level of specimens and ultrastructure were gradually replaced by molecular approaches, but studies at the community level remained stable. The five sub‐disciplines morphology/taxonomy, phylogeny/evolution, physiology, ecology and faunistics also retained about equal proportions over time. Conference publications related to taxonomy, phylogeny and biodiversity prevailed, whereas those on management and conservation were rare, possibly because studies on sponge recovery, survival and mortality were also scarce. The community of sponge scientists has grown and become more diverse over time, presently representing 72 nations. The gender distribution evened out since the first sponge conference and presently favours women at early and men at late career stages. Although stated research interests are generally dominated by physiology and ecology, taxonomy and evolution are favoured after retirement. Sponge science has become more dynamic, but maybe also more competitive and less inclusive. We now face the dual challenge of safeguarding against the loss of some sub‐disciplines, and fostering the collaborative, helpful culture characteristic of sponge science. 相似文献
In this study we compared reproductive characteristics and steroid hormone levels in the non-indigenous scleractinian coral, Oculina patagonica, inhabiting contaminated vs. uncontaminated reference sites along the Israeli Mediterranean coast. Our results indicate significantly higher steroid levels in both seawater and coral tissue samples from contaminated sites as compared to reference sites, suggesting that corals tend to accumulate steroids from the surrounding waters. Despite their higher steroid levels, corals from the contaminated sites showed reproductive potential comparable to those of the reference sites. Interestingly, a clear distinction could be seen between corals exposed to pollution for long vs. short durations, with the latter showing a failure to complete gametogenesis. This suggests that reproduction in O. patagonica is susceptible to acute rather than chronic stress. The involvement of adjustment/adaptation processes may explain this species tolerance, and may reflect the ability of O. patagonica to successfully invade new areas in the Mediterranean Sea. 相似文献
The Helsinki Commission (HELCOM) Baltic Sea Action Plan, adopted by the coastal countries of the Baltic Sea and the European Community in November 2007, is a regional intergovernmental programme of measures for the protection and management of the marine environment explicitly based on the Ecosystem Approach. The Action Plan is structured around a set of Ecological Objectives used to define indicators and targets, including effect-based nutrient input ceilings, and to monitor implementation. The Action Plan strongly links Baltic marine environmental concerns to important socio-economic fields such as agriculture and fisheries and promotes cross-sectoral tools including marine spatial planning. Due to complementarities with the European Union (EU) Marine Strategy Framework Directive, the Action Plan is in essence a pilot for this process without neglecting the important role of the Russian Federation - the only Baltic coastal country not a member of the EU. 相似文献
We investigate winter Arctic Amplification (AA) on synoptic timescales and at regional scales using a daily version of the Arctic Amplification Index (AAI) and examine causes on a synoptic scale. The persistence, frequency and intensity of high AAI events show significant increases over the Arctic. Similarly, low AAI events are decreasing in frequency, persistence and intensity. In both cases, there are regional variations in these trends, in terms of significance and timing. Significant trends in increasing persistence, frequency and intensity of high AAI events in winter are concentrated in the period 2000–2009, with few significant trends before and after this. There are some decreases in sea-ice concentration in response to synoptic-scale AA events and these AA events can contribute to the decadal trends in AA found in other studies. A sectoral analysis of the Arctic indicates that in the Beaufort–Chukchi and East Siberian–Laptev Seas, synoptic scale high AAI events can be driven by tropical teleconnections while in other Arctic sectors, it is the intrusion of moisture-transporting synoptic cyclones into the Arctic that is most important in synoptic-scale AA. The presence of Rossby wave breaking during high AAI events is indicative of forcing from lower latitudes, modulated by variations in the jet stream. An important conclusion is that the increased persistence, frequency and intensity of synoptic-scale high AAI events make significant contributions to the interannual trend in AA.
The speciation of aqueous dissolved sulfur was determined in hydrothermal waters in Iceland. The waters sampled included hot springs, acid-sulfate pools and mud pots, sub-boiling well discharges and two-phase wells. The water temperatures ranged from 4 to 210 °C, the pHT was between 2.20 and 9.30 at the discharge temperature and the SO4 and Cl concentrations were 0.020-52.7 and <0.01-10.0 mmol kg−1, respectively. The analyses were carried out on-site within ∼10 min of sampling using ion chromatography (IC) for sulfate (SO42−), thiosulfate (S2O32−) and polythionates (SxO62−) and titration and/or colorimetry for total dissolved sulfide (S2−). Sulfite (SO32−) could also be determined in a few cases using IC. Alternatively, for few samples in remote locations the sulfur oxyanions were stabilized on a resin on site following elution and analysis by IC in the laboratory. Dissolved sulfate and with few exceptions also S2− were detected in all samples with concentrations of 0.02-52.7 mmol kg−1 and <1-4100 μmol kg−1, respectively. Thiosulfate was detected in 49 samples of the 73 analyzed with concentrations in the range of <1-394 μmol kg−1 (S-equivalents). Sulfite was detected in few samples with concentrations in the range of <1-3 μmol kg−1. Thiosulfate and SO32− were not detected in <100 °C well waters and S2O32− was observed only at low concentrations (<1-8 μmol kg−1) in ∼200 °C well waters. In alkaline and neutral pH hot springs, S2O32− was present in significant concentrations sometimes corresponding to up to 23% of total dissolved sulfur (STOT). In steam-heated acid-sulfate waters, S2O32− was not a significant sulfur species. The results demonstrate that S2O32− and SO32− do not occur in the deeper parts of <150 °C hydrothermal systems and only in trace concentrations in ∼200-300 °C systems. Upon ascent to the surface and mixing with oxygenated ground and surface waters and/or dissolution of atmospheric O2, S2− is degassed and oxidized to SO32− and S2O32− and eventually to SO42− at pH >8. In near-neutral hydrothermal waters the oxidation of S2− and the interaction of S2− and S0 resulting in the formation of Sx2− are considered important. At lower pH values the reactions seemed to proceed relatively rapidly to SO42− and the sulfur chemistry of acid-sulfate pools was dominated by SO42−, which corresponded to >99% of STOT. The results suggest that the aqueous speciation of sulfur in natural hydrothermal waters is dynamic and both kinetically and source-controlled and cannot be estimated from thermodynamic speciation calculations. 相似文献
Using observations with the ALOMAR SOUSY radar near Andenes (69.3°N, 16.0°E) from 1994 until 1997 polar mesosphere summer echoes (PMSE) have been investigated in dependence on geomagnetic K indices derived at the Auroral Observatory Tromsø (69.66°N, 18.94°E). During night-time and morning hours a significant correlation between the signal-to-noise ratio (SNR) of the radar results and the geomagnetic K indices could be detected with a maximum correlation near midnight. The correlation becomes markedly smaller in the afternoon and early evening hours with a minimum near 17 UT. This diurnal variation is in reasonable agreement with riometer absorption at Ivalo (68.55°N, 27.28°E) and can be explained by the diurnal variation of ionization due to precipitating high energetic particles. Therefore, a part of the diurnal PMSE variation is caused by this particle precipitation. The variability of the solar EUV variation, however, has no significant influence on the PMSE during the observation period. 相似文献