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171.
Environmental monitoring is performed on seafloor communities since these organisms are relatively stationary and integrate the environmental conditions over many years. Standard practices involve sampling by grab. Epifaunal taxa, often missed by grab sampling, are likely to have different ecological functions. We investigate how current environmental assessments represent the benthic community as a whole by comparing taxonomic and functional components sampled by grabs and epibenthic trawls. Faunal communities sampled by trawl (filtrating or predator, epifauna) and grab (infaunal, detrivore) differs widely by sampling distinct functional components, and these may be expected to respond to different human-induced stressors. Neither component appears to be a good surrogate for the community as a whole. We suggest a benthic monitoring by combining both techniques. Sustainable ecosystem functioning is intimately tied to the health of both components of the benthic community, and is recognized as an important goal by signatories of the Convention on Biological Diversity. 相似文献
172.
The legacy of multiple marine transgressions is preserved in a complex morphology of ridges, mounds and reefs on the Carnarvon continental shelf, Western Australia. High-resolution multibeam sonar mapping, underwater photography and sampling across a 280 km2 area seaward of the Ningaloo Coast World Heritage Area shows that these raised features provide hardground habitat for modern coral and sponge communities. Prominent among these features is a 20 m high and 15 km long shore-parallel ridge at 60 m water depth. This ridge preserves the largely unaltered form of a fringing reef and is interpreted as the predecessor to modern Ningaloo Reef. Landward of the drowned reef, the inner shelf is covered by hundreds of mounds (bommies) up to 5 m high and linear ridges up to 1.5 km long and 16 m high. The ridges are uniformly oriented to the north-northeast and several converge at their landward limit. On the basis of their shape and alignment, these ridges are interpreted as relict long-walled parabolic dunes. Their preservation is attributed to cementation of calcareous sands to form aeolianite, prior to the post-glacial marine transgression. Some dune ridges abut areas of reef that rise to sea level and are highly irregular in outline but maintain a broad shore-parallel trend. These are tentatively interpreted as Last Interglacial in age. The mid-shelf and outer shelf are mostly sediment covered with relatively low densities of epibenthic biota and have patches of low-profile ridges that may also be relict reef shorelines. An evolutionary model for the Carnarvon shelf is proposed that relates the formation of drowned fringing reefs and aeolian dunes to Late Quaternary eustatic sea level. 相似文献
173.
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176.
Using a Diamond Anvil Cell combined with micro Raman spectroscopy,the quantitative relations among Raman shifts,pressure and temperature were obtained for the vibration of O-H in H2O-NaCl,C-O in CO32-,S-O in SO42- and C-H in n-heptane-cyclohexane.Based on the quantitative relationships obtained,it is possible to determine the inner pressure for single fluid inclusions and to further determine the isochore of the systems.It is not only helpful to obtain the forming temperatures and pressures of the enclosing minerals,but also to be able to provide information concerning the chemical compositions of the fluid inclusions. 相似文献
177.
This paper examines an apparent ‘early stage’ governance transformation in the Tam Giang Lagoon, Vietnam. In this context, the role of key policy windows for innovative governance practice is assessed (e.g., changes to Land and Fisheries Laws). Also examined is the emergence of recent initiatives to catalyze a wider shift in governance practice in the region, including the formation of co-management institutional networks that contribute to trust building and learning, and the allocation of collective territorial use rights for fisheries. While these changes are consistent with experiences in other coastal marine contexts, the paper shows that place-based and longitudinal research is necessary to explain and predict the conditions and incentives that catalyze governance shifts. Differences between a governance change and more fundamental transformation are difficult to discern using point-in-time analysis. Moreover, the results show that current declines in ecological conditions in the lagoon may not be reversed by changes to access rights or the emergence of co-management. Rather, these governance changes may simply help to stabilize the situation and buy time until other livelihood opportunities arise. Assessments of governance transformation thus need to be linked to ecological outcomes (i.e., reversing degradation of coastal marine systems, avoiding biophysical tipping points) which may not be easily identified in the short-term. Despite uncertainty, the emergence of policy windows, evidence of institutional innovation, and small-scale rights allocation experiments, all suggest important shifts in the trajectory of governance are underway in the Tam Giang Lagoon. 相似文献
178.
《Geoforum》2015
As human codings of animals are often simultaneously legal and spatial, it may be useful to bring together the animal geographies literature and scholarship on legal geography. Through a case study set in southwest Finland, we explore the emergent and fraught entanglements of wolves, humans and sheep, characterizing the attempts at the regulation of the wolf as entailing tense biopolitical calculations between the contradictory legal imperatives of biodiversity and biosecurity. Under the former, the wolf must be made to live; under the latter, it may need to die. These are worked out in and productive of two territorial configurations: the everyday spaces of encounter (real or imagined) between wolf and human, and the propertied territories of sheep farming. While human imperatives and anxieties are clearly central to these spatializations, we also seek to give the wolf its due, noting its important role in the making of legal territories. The coproduction of law and space, we conclude, offers important ethical lessons for humans in their relations to the wolf, as well as directing us to the need for more capacious thinking regarding territory. 相似文献
179.
基于航空重力测量的基本数学模型,详细分析了航空重力测量的系统误差来源.大致可将系统误差分为三类,即停机坪重力基准值、比力初值的观测误差,格值、交叉耦合系数、摆杆尺度因子的标定误差和水平加速度改正的模型化误差等.然后,对每类系统误差的量级及其补偿方法进行了研究,指出水平加速度改正是引起系统误差的主要因素之一.大同、哈尔滨和渤海湾航空重力测量的实测数据分析均表明,在各项系统误差尤其是水平加速度改正得到有效补偿后,航空重力与地面(或船测)参考值的系统误差将小于1×10-5m·s-2. 相似文献
180.
Jane M. Chewings Cliff B. Atkins Gavin B. Dunbar Nicholas R. Golledge 《Sedimentology》2014,61(6):1535-1557
Aeolian sand and dust in polar regions are transported offshore over sea ice and released to the ocean during summer melt. This process has long been considered an important contributor to polar sea floor sedimentation and as a source of bioavailable iron that triggers vast phytoplankton blooms. Reported here are aeolian sediment dispersal patterns and accumulation rates varying between 0·2 g m?2 yr?1 and 55 g m?2 yr?1 over 3000 km2 of sea ice in McMurdo Sound, south‐west Ross Sea, adjacent to the largest ice free area in Antarctica. Sediment distribution and the abundance of southern McMurdo Volcanic Group‐derived glass, show that most sediment originates from the McMurdo Ice Shelf and nearby coastal outcrops. Almost no sediment is derived from the extensive ice free areas of the McMurdo Dry Valleys due to winnowed surficial layers shielding sand‐sized and silt‐sized material from wind erosion and because of the imposing topographic barrier of the north‐south aligned piedmont glaciers. Southerly winds of intermediate strength (ca 20 m sec?1) are primarily responsible for transporting sediment northwards and offshore. The results presented here indicate that sand‐sized sediment does not travel more than ca 5 km offshore, but very‐fine sand and silt grains can travel >100 km from source. For sites >10 km from the coast, the mass accumulation rate is relatively uniform (1·14 ± 0·57 g m?2 yr?1), three orders of magnitude above estimated global atmospheric dust values for the region. This uniformity represents a sea floor sedimentation rate of only 0·2 cm kyr?1, well below the rates of >9 cm kyr?1 reported for biogenic‐dominated sedimentation measured over much of the Ross Sea. These results show that, even for this region of high‐windblown sediment flux, aeolian processes are only a minor contributor to sea floor sedimentation, excepting areas proximal to coastal sources. 相似文献