In situ impact of petrochemicals on the photosynthesis of the seagrass Zostera capricorni

We used photosynthetic activity (measured as chlorophyll a fluorescence) and photosynthetic pigment concentrations to assess the effect of pulsed exposures of aged crude oil (Champion Crude), dispersant (VDC) and an oil+dispersant mixture on the seagrass Zostera capricorni Aschers in laboratory and field experiments, using custom-made chambers. Samples were exposed for 10 h to 0.25% and 0.1% concentrations of aged crude oil and dispersant as well as mixtures of 0.25% oil+0.05% dispersant and 0.1% oil+0.02% dispersant. During this time and for the subsequent four day recovery period, the maximum and effective quantum yields of photosystem II (Fv/Fm and DeltaF/Fm' respectively) were measured. In the laboratory experiments, both values declined in response to oil exposure and remained low during the recovery period. Dispersant exposure caused a decline in both values during the recovery period, while the mixture of aged crude oil+dispersant had little impact on both quantum yields. In situ samples were less sensitive than laboratory samples, showing no photosynthetic impact due to dispersant and oil+dispersant mixture. Despite an initial decline in DeltaF/Fm', in situ oil-exposed samples recovered by the end of the experiment. Chlorophyll pigment analysis showed only limited ongoing impact in both laboratory and field situations. This study suggests that laboratory experiments may overestimate the ongoing impact of petrochemicals on seagrass whilst the dispersant VDC can reduce the impact of oil on seagrass photosynthesis.     

Nutrient loss and water quality under extensive grazing in the upper Burdekin river catchment, North Queensland

Increased sediment and nutrient losses resulting from unsustainable grazing management in the Burdekin River catchment are major threats to water quality in the Great Barrier Reef Lagoon. To test the effects of grazing management on soil and nutrient loss, five 1 ha mini-catchments were established in 1999 under different grazing strategies on a sedimentary landscape near Charters Towers. Reference samples were also collected from watercourses in the Burdekin catchment during major flow events. Soil and nutrient loss were relatively low across all grazing strategies due to a combination of good cover, low slope and low rainfall intensities. Total soil loss varied from 3 to 20 kg ha(-1) per event while losses of N and P ranged from 10 to 1900 g ha(-1) and from 1 to 71 g ha(-1) per event respectively. Water quality of runoff was considered moderate across all strategies with relatively low levels of total suspended sediment (range: 8-1409 mg l(-1)), total N (range: 101-4000 microg l(-1)) and total P (range: 14-609 microg l(-1)). However, treatment differences are likely to emerge with time as the impacts of the different grazing strategies on land condition become more apparent. Samples collected opportunistically from rivers and creeks during flow events displayed significantly higher levels of total suspended sediment (range: 10-6010 mg l(-1)), total N (range: 650-6350 microg l(-1)) and total P (range: 50-1500 microg l(-1)) than those collected at the grazing trial. These differences can largely be attributed to variation in slope, geology and cover between the grazing trial and different catchments. In particular, watercourses draining hillier, grano-diorite landscapes with low cover had markedly higher sediment and nutrient loads compared to those draining flatter, sedimentary landscapes. These preliminary data suggest that on relatively flat, sedimentary landscapes, extensive cattle grazing is compatible with achieving water quality targets, provided high levels of ground cover are maintained. In contrast, sediment and nutrient loss under grazing on more erodable land types is cause for serious concern. Long-term empirical research and monitoring will be essential to quantify the impacts of changed land management on water quality in the spatially and temporally variable Burdekin River catchment.     

Thomson Thick X-Ray Absorption in a Broad Absorption Line Quasar, PG 0946+301

We present results of new ASCA observations of the low-luminosity active galactic nucleus (LLAGN) NGC 4579 obtained on 1998 December 18 and 28, and we report on the detection of variability of an iron K emission line. The X-ray luminosities in the 2-10 keV band for the two observations are nearly identical (LX approximately 2x1041 ergs s(-1)), but they are approximately 35% larger than that measured in 1995 July by Terashima et al. An Fe K emission line is detected at 6.39+/-0.09 keV (source rest frame), which is lower than the line energy 6.73+0.13-0.12 keV in the 1995 observation. If we fit the Fe lines with a blend of two Gaussians centered at 6.39 and 6.73 keV, the intensity of the 6.7 keV line decreases, while the intensity of the 6.4 keV line increases, within an interval of 3.5 yr. This variability rules out thermal plasmas in the host galaxy as the origin of the ionized Fe line in this LLAGN. The detection and variability of the 6.4 keV line indicates that cold matter subtends a large solid angle viewed from the nucleus and that it is located within approximately 1 pc from the nucleus. It could be identified with an optically thick standard accretion disk. If this is the case, a standard accretion disk is present at the Eddington ratio of Lbol/LEdd approximately 2x10-3. A broad disk-line profile is not clearly seen, and the structure of the innermost part of accretion disk remains unclear.     

卫星云图模式识别小波分形特征量分析

本文采用小波分析中的小波包函数对卫星云图进行分解和小波包系数重构，并结合分形分数维计算，提取卫星云图的分数维，分析不同类型的云系分数维的主要特征，来实现卫星云图的模式识别。     

21世纪地质调查所的作用

地质调查所的建立最初是为了从事地质测图（与实际地质工作有关的，如采矿、建筑和运输）。尽管有些地调所已把重点放在更加基础的地质工作上，但测图仍然是地调所的主要工作，很多地调所已更加注重市场，部分原因是为了适应政府经费的缩减。技术的进步也将影响地调所从事调查研究工作的方式。国家地质调查所将来的工作也将受到广泛的社会经济趋势的影响。２１世纪地质调查所工作的重点将依赖于国家关注资源开发、工业发展、人口高度     

Statistical power of non-parametric tests: a quick guide for designing sampling strategies

The importance of considering statistical power in marine pollution studies is unequivocal. However, the vast majority of ecological literature on power analysis focuses on parametric rather than non-parametric tests. This note describes a Monte Carlo simulation method for estimating the power of non-parametric tests. The method is illustrated using ordinal data.     

Improvement of the sediment ecosystem following diversion of an intertidal sewage outfall at the Fraser river estuary,Canada, with emphasis on Corophium salmonis (Amphipoda)

Primary treated sewage effluent from the city of Vancouver, Canada was deposited directly onto the intertidal ecosystem of Sturgeon bank, Fraser river estuary between 1962 and 1988. In response to the degraded sediment conditions an azoic zone developed near the discharge outfall. Effluent discharges into the intertidal zone were almost completely stopped in 1988 with the construction of a submerged outfall. Our studies, conducted between 1994 and 1996, showed considerable improvement in the environment of the mudflat ecosystem, including increased dissolved oxygen, decreased sediment chlorophyll, decreased organic material in the sediment, reduced heavy metals in surficial sediment and increased grain size. The amphipod Corophium salmonis, important in the food web for juvenile salmon and other fish species, recolonized the previously azoic location. At reference stations, C. salmonis density was similar to that observed in previous surveys two decades earlier. Our data strongly suggest that improvement or sediment conditions near the former sewage outfall was a major factor enabling colonization by C. salmonis.     

Demographic response to rural restructuring and counterurbanisation in South Australia, 1981-1991

"Using South Australia as a case study, this paper seeks to trace and demonstrate two processes (counterurbanisation and rural restructuring) whose effects overlap to differentiate and characterise the population geography of...two zones, separated by a transition along the outer fringe of Adelaide's urban field.... In the demographic core zone [rural restructuring] has been partly offset by continued counterurbanisation, resulting in demographic mixing and rural dilution. The 1981-91 population growth in rural communities is shown to be more a function of population density at the outset of the period than of initial population size. Demographic growth...is shown to conform to a simple unidimensional scale, allowing the production of a clear, easily interpretable typology of rural demographic change with few non-conforming statistical areas. At a local level within individual rural communities, demographic decline is shown to be accompanied by increased concentration of the population into small towns, while demographic growth is associated with deconcentration."     

Exposure to 2,4-decadienal negatively impacts upon marine invertebrate larval fitness

Diatoms liberate volatile, biologically active unsaturated aldehydes following cell damage, which negatively impact upon invertebrate reproductive processes such as fertilization, embryogenesis and larval survival. 2,4-Decadienal is frequently identified among the aldehydes produced and is one of the more biologically active. The majority of studies which have examined the toxic effects of diatom aldehydes to invertebrate reproduction have scored egg production and/or hatching success as indicators of biological impacts. There are very few studies which have dealt specifically with the impacts of diatom-derived aldehydes on larval fitness. Larval stages of the polychaetes Arenicola marina and Nereis virens and the echinoderms Asterias rubens and Psammechinus miliaris exposed to 2,4-decadienal at sub 1 microg ml(-1) concentrations suffered reduced survival over the incubation period (day 1-8 post fertilization) with detectable differences for the polychates at a concentration of 0.005 and 0.01-0.1 microg ml(-1) for the echinoderms. Susceptibility of larval N. virens was investigated using stage specific 24 h exposures at 2,4-decadienal concentrations up to 1.5 microg ml(-1). A clear stage specific effect was found, with earlier larval stages most vulnerable. Nectochaete larvae (9-10 d) showed no reduction in survival at the concentrations assayed. Fluctuating asymmetry (FA), defined as random deviations from perfect bilateral symmetry, was used to analyse fitness of larval P. miliaris exposed to 2,4-decadienal at concentrations of 0.1, 0.5 and 1 microg ml(-1). The degree and frequency of asymmetrical development increased with increasing 2,4-decadienal concentration. Equally, as FA increased larval survival decreased. These results provide further support for the teratogenic nature of 2,4-decadienal and its negative impact on invertebrate larval fitness.