A method of error adjustment for marine gravity with application to Mean Dynamic Topography in the northern North Atlantic

International compilations of marine gravity, such as the International Gravity Bureau (BGI) contain tens of millions of point data. Lemoine et al. (The Development of the Joint NASA GSFC and the National Imagery and Mapping Agency (NIMA) Geopotential Model EGM96, NASA/TP-1998-206861) chose not to include any marine gravity in the construction of the global gravity model EGM96. Instead they used synthetic anomalies derived from altimetry, so that no independent information about Mean Dynamic Topography (MDT) can be deduced. Software has been developed not only to identify and correct those aspects of marine gravity data that are unreliable, but to do so in a way that can be applied to very large, ocean-wide data sets. First, we select only straight-line parts of ship-tracks and fit each one with a high-degree series of Chebyshev polynomials, whose misfit standard deviation is σ _line and measures the random error associated with point gravity data. Then, network adjustment determines how the gravity datum is offset for each survey. A free least squares adjustment minimises the gravity anomaly mismatch at line-crossing points, using σ _line to weight the estimate for each line. For a long, well crossed survey, the instrumental drift rate is also adjusted. For some 42,000 cross-over points in the northern Atlantic Ocean, network adjustment reduces the unweighted standard deviation of the cross-over errors from 4.03 to 1.58 mGal; when quality weighted, the statistic reduces from 1.32 to 0.39 mGal. The geodetic MDT is calculated combining the adjusted gravity anomalies and satellite altimetry, and a priori global ocean model through a new algorithm called the Iterative Combination Method. This paper reports a first demonstration that geodetic oceanography can characterise the details of basin wide ocean circulation with a resolution better than global ocean circulation models. The result matches regional models of ocean circulation from hydrography measurements (Geophys Res Lett 29:1896, 2002; J Geophys Res 108:3251, 2003).     

On the moisture-related buckling of marine composite panels using approximate analysis

A discussion is presented that highlights the growing utilization of composite structures for marine applications. Important to this trend is an understanding of the buckling response of marine panels under hygroscopic loads. Consideration are presented for the use of eigensensitivity analysis as a means of developing an approximate closed-form expression for computing the critical buckling response in the absense of an exact solutions     

海水网箱养殖鱼类越冬期的死亡原因及对策

在冬春季低水温期,海水网箱养殖的鱼类大批死亡造成了严重的经济损失。本文对死亡的原因进行了初步研究,结果表明:在一定的低水温环境下,这些鱼类虽然因冻伤而造成局部坏死,但维持生命的主要器官的机能仍处于基本正常状态;而患鱼继发感染细菌致病才是其死亡的主要原因。采取适当的越冬防寒措施可提高养殖海鱼在越冬期的成活率。     

Environmental pollution in the Gulf of Guinea--a regional approach

Environmental pollution in the Gulf of Guinea (GOG) coastal zone has caused eutrophication and oxygen depletion in the lagoon systems, particularly around the urban centres, resulting in decreased fish (reproduction) levels and waterborne diseases. A pollution sources assessment was undertaken by six countries in the region as a first step in defining a region-wide Environmental Management Plan. Results show that households produce 90% of solid waste. Industry, however, is responsible for substantial amounts of hazardous waste, specifically the Nigerian petroleum industry. The latter is also responsible for the spilling of large amounts of oil. BOD load from industrial effluents is slightly larger than domestic loads in the industrialised coastal zone. Wastewater treatment systems are either absent or inadequate. Apart from large-scale gas flaring in Nigeria, air pollution, in terms of COx, HC, NOx and SO2 emissions, is contributed mainly by traffic. Particulates, originate mainly from industries and domestic biomass burning.     

Quantifying Inputs of Pesticides to the Great Barrier Reef Marine Park – A Case Study in the Herbert River Catchment of North-East Queensland

The Great Barrier Reef Marine Park (GBRMP) is an ecosystem whose ecological features are recognized internationally. There is a need to evaluate the impacts of historical and contemporary changes in land use on the GBRMP. This paper quantifies pesticide inputs in the Herbert River catchment of North Queensland in the context of changes in land use over the last 100 years. We show that three major phases of rural land use and land cover change have occurred, with large areas of native vegetation converted to agricultural production. The increase in agricultural land has seen a corresponding increase in the area receiving pesticides. We present data showing application histories for organochlorine, organophosphate, phenoxy, triazine, urea, mercurial and azole group pesticides. While the fate of these pesticides in aquatic and marine systems is largely unknown, these trends pose a significant challenge for agricultural industries in complying with the principles of ecologically sustainable development (ESD).     

Colonization strategies of lithobiontic microorganisms on carbonate rocks

Biogenic weathering is caused by the action of lithobiontic organisms. Homogeneous carbonates are predominantly colonized by endolithic species that actively penetrate the rock substratum independent of already existing pores or fissures. The organisms construct a system of ducts and cavities by active dissolution of the substratum. A fresh, noncolonized surface is penetrated by algae and ascomycetes in the first and second year after exposure to the environment. The establishment of complex colonization patterns on and in the substratum by lichens takes several years. In spite of the primary deteriorative effect on their substratum by the organisms, long-term endolithic growth also involves mechanisms that stabilize and preserve the rock surface morphology. A tightly woven cellular network may strengthen the colonized stone. This feature is of importance when natural and building stone are affected by biogenic weathering phenomena.Special issue: Stone decay hazards     

Modelling the effects of Marine Protected Areas (MPAs) on the southern rock lobster (Jasus edwardsii) fishery of Victoria,Australia

Since 2002, 5.3% of the Victorian coastal waters have been declared as Marine Protected Areas (MPAs). These are aimed at safeguarding important marine habitats and species, significant natural features, and areas of cultural heritage and aesthetic value. However, MPAs impact the fishery for southern rock lobster (Jasus edwardsii), as total allowable catches (TACs) were previously set to allow the biomass to recover to pre‐specified target levels. The model on which assessments and risk analyses are based is extended to include the impact of MPAs. The MPAs and the area open to fishing are modelled as subpopulations with different levels of mortality and consequently different density and population size‐structure. A range for the probability of a lobster moving from a MPA to the fished area from 0 to 15% is considered, based on the results of tagging studies. The reduction of biomass available to the commercial fishery because of the introduction of MPAs is estimated to be 8% and 16% (Western and Eastern Zones) respectively. The results of a risk assessment show that if the current TACs are maintained, the time to increase the biomass available to the commercial fishery by 50% would be delayed 5–9 years in the Western Zone and 1–4 years in the Eastern Zone because of the impact of displaced effort. In contrast, spawning biomass in the Eastern Zone is currently below the agreed limit reference point, and the introduction of MPAs would enhance the rate of recovery, although only marginally initially, faster than the absence of the MPAs.     

海上地震勘探主要采集参数的选取与验证——以南海北部某调查区为例

采集参数选取的优劣直接关系到野外地震资料质量的高低。作者经过多年海上地震调查实践,总结了一套实用的采集参数选取原则与验证流程。首先结合南海北部某调查区以往的地震和地质资料分析,建立了典型的地震地质结构模型;根据现有调查设备的性能,利用专业软件Nucleus6.2模拟对采集参数选取的理论计算,比较不同采集参数组合的模拟结果,选择有利于调查任务的参数组合。对海上生产前模拟选用的采集参数组合做试验和验证,确定了最适合的参数作业。运用该套原则和流程精心设计,实验获得了高质量野外资料。