Diving down the reefs? Intensive diving tourism threatens the reefs of the northern Red Sea     

Hasler H  Ott JA 《Marine pollution bulletin》2008,56(10):1788-1794

Intensive recreational SCUBA diving threatens coral reef ecosystems. The reefs at Dahab, South Sinai, Egypt, are among the world’s most dived (>30,000 dives y⁻¹). We compared frequently dived sites to sites with no or little diving. Benthic communities and condition of corals were examined by the point intercept sampling method in the reef crest zone (3 m) and reef slope zone (12 m). Additionally, the abundance of corallivorous and herbivorous fish was estimated based on the visual census method. Sediments traps recorded the sedimentation rates caused by SCUBA divers. Zones subject to intensive SCUBA diving showed a significantly higher number of broken and damaged corals and significantly lower coral cover. Reef crest coral communities were significantly more affected than those of the reef slope: 95% of the broken colonies were branching ones. No effect of diving on the abundance of corallivorous and herbivorous fish was evident. At heavily used dive sites, diver-related sedimentation rates significantly decreased with increasing distance from the entrance, indicating poor buoyancy regulation at the initial phase of the dive. The results show a high negative impact of current SCUBA diving intensities on coral communities and coral condition. Corallivorous and herbivorous fishes are apparently not yet affected, but are endangered if coral cover decline continues. Reducing the number of dives per year, ecologically sustainable dive plans for individual sites, and reinforcing the environmental education of both dive guides and recreational divers are essential to conserve the ecological and the aesthetic qualities of these dive sites.  相似文献   

Habitat Selection and Ecology of Two Speleophilic Gobiid Fishes(Pisces: Gobiidae) from the Western Mediterranean Sea     

Jürgen Herler  Robert A. Patzner  Harald Ahnelt&  Helge Hilgers 《Marine Ecology》1999,20(1):49-62

The life habits and microhabitat selection of speleophilic gobiid fishes were investigated on the Balearic Island of Ibiza (western Mediterranean Sea). Corcyrogobius liechtensteini (Kolombatović, 1891) was the most frequent species within submarine crevices, cavities and caves. Didogobius splechtnai Ahnelt & Patzner, 1995 co-occurred with C. liechtensteini in several cases but showed a clear spatial separation based on a different microhabitat preference. The microhabitat selection of both species was confirmed by habitat-choice experiments in anaquarium. Corcyrogobius liechtensteini was frequent in depths between 5 m and 25 m and attained abundances of 14.2 individuals · m⁻². This species inhabited the ceilings and upper parts of the walls within the caves. D. splechtnai was mainly found between 7 m and 11 m and showed abundances of approximately 2 indivi-duals · m⁻². This species occupied the fine sediment bottoms in the innermost parts of crevices and caves. The growth and the maximum age of both species were determined by length-frequency distributions. The overall sex ratio from catches of three different years are given for C. liechtensteini .  相似文献   

The stellar populations of early-type galaxies in the Fornax cluster     

Harald Kuntschner 《Monthly notices of the Royal Astronomical Society》2000,315(1):184-208

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Evaluation of energy balance closure adjustment methods by independent evapotranspiration estimates from lysimeters and hydrological simulations          下载免费PDF全文

Matthias Mauder  Sandra Genzel  Jin Fu  Ralf Kiese  Mohsen Soltani  Rainer Steinbrecher  Matthias Zeeman  Tirtha Banerjee  Frederik De Roo  Harald Kunstmann 《水文研究》2018,32(1):39-50

Non‐closure of the surface energy balance is a frequently observed phenomenon of hydrometeorological field measurements, when using the eddy‐covariance method, which can be ascribed to an underestimation of the turbulent fluxes. Several approaches have been proposed in order to adjust the measured fluxes for this apparent systematic error. However, there are uncertainties about partitioning of the energy balance residual between the sensible and latent heat flux and whether such a correction should be applied on 30‐min data or longer time scales. The data for this study originate from two grassland sites in southern Germany, where measurements from weighable lysimeters are available as reference. The adjusted evapotranspiration rates are also compared with joint energy and water balance simulations using a physically based distributed hydrological model. We evaluate two adjustment methods: the first one preserves the Bowen ratio and the correction factor is determined on a daily basis. The second one attributes a smaller portion of the residual energy to the latent heat flux than to the sensible heat flux for closing the energy balance for every 30‐min flux integration interval. Both methods lead to an improved agreement of the eddy‐covariance based fluxes with the independent lysimeter estimates and the physically based model simulations. The first method results in a better comparability of evapotranspiration rates, and the second method leads to a smaller overall bias. These results are similar between both sites despite considerable differences in terrain complexity and grassland management. Moreover, we found that a daily adjustment factor leads to less scatter than a complete partitioning of the residual for every half‐hour time interval. The vertical temperature gradient in the surface layer and friction velocity were identified as important predictors for a potential future parameterisation of the energy balance residual.  相似文献   

The Stubenberg meteorite—An LL6 chondrite fragmental breccia recovered soon after precise prediction of the strewn field          下载免费PDF全文

Addi Bischoff  Jean‐Alix Barrat  Kerstin Bauer  Christoph Burkhardt  Henner Busemann  Samuel Ebert  Michael Gonsior  Janina Hakenmüller  Jakub Haloda  Dennis Harries  Dieter Heinlein  Harald Hiesinger  Rupert Hochleitner  Viktor Hoffmann  Melanie Kaliwoda  Matthias Laubenstein  Colin Maden  Matthias M. M. Meier  Andreas Morlok  Andreas Pack  Alexander Ruf  Philippe Schmitt‐Kopplin  Maria Schönbächler  Robert C. J. Steele  Pavel Spurný  Karl Wimmer 《Meteoritics & planetary science》2017,52(8):1683-1703

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Investigating the shock histories of lunar meteorites Miller Range 090034, 090070, and 090075 using petrography,geochemistry, and micro‐FTIR spectroscopy          下载免费PDF全文

Dayl J. P. Martin  John F. Pernet‐Fisher  Katherine H. Joy  Roy A. Wogelius  Andreas Morlok  Harald Hiesinger 《Meteoritics & planetary science》2017,52(6):1103-1124

Fourier transform infrared (FTIR) spectroscopy and cathodoluminescence (CL) imaging techniques, combined with electron microprobe analyses, have been used to determine the physical state of feldspathic phases that have been subject to varying levels of shock in the grouped lunar meteorites Miller Range 090034, 090070, and 090075. Six feldspathic phases have been identified based on spectral, textural, and chemical properties. A specific infrared wavelength band ratio (1064/932 cm^?1 equivalent to 9.40/10.73 μm), chosen because it can distinguish between some of the feldspathic phases, can be used to estimate the pressure regimes experienced by these phases. In addition, FTIR spatial mapping capabilities allow for visual comparison of variably shocked phases within the samples. By comparing spectral and compositional data, the origin and shock history of this lunar meteorite group has been determined, with each of the shocked feldspathic phases being related to events in its geological evolution. As such, we highlight that FTIR spectroscopy can be easily employed to identify shocked feldspathic phases in lunar samples; estimate peak shock pressures; and when compared with chemical data, can be used to investigate their shock histories.  相似文献   

Physical and biological characteristics of the pelagic system across Fram Strait to Kongsfjorden   总被引：1，自引：1，他引：1  

Haakon Hop  Stig Falk-Petersen  Harald Svendsen  Slawek Kwasniewski  Vladimir Pavlov  Olga Pavlova  Janne E. Sreide 《Progress in Oceanography》2006,71(2-4):182

The Fram Strait is very important with regard to heat and mass exchange in the Arctic Ocean, and the large quantities of heat carried north by the West Spitsbergen Current (WSC) influence the climate in the Arctic region as a whole. A large volume of water and ice is transported through Fram Strait, with net water transport of 1.7–3.2 Sv southward in the East Greenland Current and a volume ice flux in the range of 0.06–0.11 Sv. The mean annual ice flux is about 866,000 km² yr⁻¹. The Kongsfjorden–Krossfjorden fjord system on the coast of Spitsbergen, or at the eastern extreme of Fram Strait, is mainly affected by the northbound transport of water in the WSC. Mixing processes on the shelf result in Transformed Atlantic Water in the fjords, and the advection of Atlantic water also carries boreal fauna into the fjords. The phytoplankton production is about 80 g C m⁻² yr⁻¹ in Fram Strait, and has been estimated both below and above this for Kongsfjorden. The zooplankton fauna is diverse, but dominated in terms of biomass by calanoid copepods, particularly Calanus glacialis and C. finmarchicus. Other important copepods include C. hyperboreus, Metridia longa and the smaller, more numerous Pseudocalanus (P. minutus and P. acuspes), Microcalanus (M. pusillus and M. pygmaeus) and Oithona similis. The most important species of other taxa appear to be the amphipods Themisto libellula and T. abyssorum, the euphausiids Thysanoessa inermis and T. longicaudata and the chaetognaths Sagitta elegans and Eukrohnia hamata. A comparison between the open ocean of Fram Strait and the restricted fjord system of Kongsfjorden–Krossfjorden can be made within limitations. The same species tend to dominate, but the Fram Strait zooplankton fauna differs by the presence of meso- and bathypelagic copepods. The seasonal and inter-annual variation in zooplankton is described for Kongsfjorden based on the record during July 1996–2002. The ice macrofauna is much less diverse, consisting of a handful of amphipod species and the polar cod. The ice-associated biomass transport of ice-amphipods was calculated, based on the ice area transport, at about 3.55 × 10⁶ ton wet weight per year or about 4.2 × 10⁵ t C yr⁻¹. This represents a large energy input to the Greenland Sea, but also a drain on the core population residing in the multi-year pack ice (MYI) in the Arctic Ocean. A continuous habitat loss of MYI due to climate warming will likely reduce dramatically the sympagic food source. The pelagic and sympagic food web structures were revealed by stable isotopes. The carbon sources of particulate organic matter (POM), being Ice-POM and Pelagic-POM, revealed different isotopic signals in the organisms of the food web, and also provided information about the sympagic–pelagic and pelagic–benthic couplings. The marine food web and energy pathways were further determined by fatty acid trophic markers, which to a large extent supported the stable isotope picture of the marine food web, although some discrepancies were noted, particularly with regard to predator–prey relationships of ctenophores and pteropods.  相似文献   

Colour–magnitude relations and spectral line strengths in the Coma cluster     

A. I. Terlevich  Harald Kuntschner  R. G. Bower  N. Caldwell  R. M. Sharples 《Monthly notices of the Royal Astronomical Society》1999,310(2):445-452

We use the C₂4668, Fe4383, H γ _A and H δ _A spectral absorption line indices, together with U - and V -band photometry of 101 galaxies in the Coma cluster, to investigate how mean age and metal abundance correlate with galaxy luminosity. In particular, we use the line index measurements to address the origin of the colour–magnitude relation (CMR). We find that the CMR in Coma is driven primarily by a luminosity–metallicity correlation. We additionally show evidence for a relation between age and luminosity, in the direction predicted by the semi-analytic hierarchical clustering models of Kauffmann & Charlot, but this is only present in the C₂4668 index models, and could be an effect of the lack of non-solar abundance ratios in the Worthey models used.
By comparing deviations from the CMR with deviations in absorption index from analogous 'index–magnitude' relations, we find that colour deviations bluewards of the mean relation are strongly correlated with the hydrogen Balmer line series absorption. We show that the properties of these blue galaxies are consistent with the presence of a young stellar population in the galaxies, rather than with a reduced metallicity.  相似文献   

Scenario-based seismic hazard analysis using spectral element method in northeastern Pakistan     

Khan  Saad  van der Meijde  Mark  van der Werff  Harald  Shafique  Muhammad 《Natural Hazards》2020,103(2):2131-2144

Natural Hazards - Seismic hazard analysis is carried out in this study by estimating ground motion for hypothetical earthquakes in the area of Muzaffarabad, Pakistan, with the MT solution of the...  相似文献   

晚震旦世至早寒武世扬子地台北缘碳同位素研究   总被引：6，自引：0，他引：6  

郭庆军  刘丛强  Harald Strauss  Tatiana Goldberg 《地球学报》2004,25(2):151-156

震旦-寒武交变期是地史上一个重大转折期,亦是一个具有特殊意义的过渡时期。运用碳同位素地球化学方法,探讨扬子地台北缘四川南江地区晚震旦世-早寒武世交变期,碳同位素地球化学异常与环境变化和生物演化的相互联系。南江剖面沉积岩有机碳同位素组成在-35．8‰～-30．1‰间变化;碳酸盐碳同位素组成从-3．5‰～ 0．5‰。在灯影组顶部、牛蹄塘组下部和上部,变化的碳、硫同位素组成和不同的黄铁矿与有机碳含量反映了有机碳埋藏量和环境的变化。下寒武统富有机碳和黄铁矿的黑色页岩沉积,暗示了早寒武世早期缺氧环境的存在。  相似文献