Effects of sediment on fish communities in East Cape streams,North Island,New Zealand     

J. Richardson  I. G. Jowett 《新西兰海洋与淡水研究杂志》2013,47(2):431-442

We examined the effects of sediment on fish communities at 38 sites in the East Cape region of New Zealand. Many streams in this region are subject to high sediment loads, a natural situation that has been exacerbated by the conversion of native forest to pasture. The fish community consisted of diadromous native species common throughout New Zealand that require access to and from the sea. We found that site altitude and distance inland were important factors in determining the abundance and composition of the fish community. We used four measures as indices of sediment load: suspended sediment concentration, median substrate size, substrate stability, and the ratio of the wetted width to the width of the active (non‐vegetated) stream channel. Although all indices were correlated, the ratio of wetted width to width of active channel was most closely related to fish abundance and diversity. Fish abundance and diversity reduced as sediment load increased among streams, with up to nine fish species in streams with low sediment loads and only two species in streams with high sediment loads. In‐stream habitat also varied with sediment load; as load increased, depth and substrate size decreased and velocity increased. These results suggest that activities that increase sediment loads in rivers will have a negative impact on native fish communities in New Zealand.  相似文献   

Setting new thermal standards for transitional and coastal (TraC) waters     

Wither A  Bamber R  Colclough S  Dyer K  Elliott M  Holmes P  Jenner H  Taylor C  Turnpenny A 《Marine pollution bulletin》2012,64(8):1564-1579

The construction of a new generation of coastal power stations in the UK and other western European countries has highlighted the absence of robust standards for thermal discharges to transitional and coastal waters. The proposed discharge volumes are greater than hitherto, yet there has been little independent critical examination of their potential impact, whilst much of the existing guidance has been adapted from freshwater practice. This review considers the available knowledge on the tolerance and behaviour of fish and other marine biota to heated effluents. Appropriate ways are suggested of grouping fish species to reflect their sensitivity to thermal effects. The plethora of existing standards are considered and their validity assessed in a framework of predicted seawater temperature rise. Those species or groups of organisms most likely to be affected are identified and finally specific recommendations for thermal standards consistent with long term sustainability are proposed.  相似文献   

Commonwealth Urban Policy in Australia: the case of inner urban regeneration in Sydney, 1973–75     

Kristian Ruming  Andy Tice  Robert Freestone 《The Australian geographer》2010,41(4):447-467

Urban regeneration has intermittently been identified within Commonwealth policy circles as central to the functioning of Australian cities since the 1940s. This paper adds to existing knowledge by exploring the role of the Commonwealth Department of Urban and Regional Development (DURD) in the 1970s in facilitating a series of urban regeneration projects in Sydney. Drawing upon ministerial correspondence and minutes recently out of confidential embargo, the genesis of a holistic urban regeneration agenda is explored. The paper traces the approaches to Commonwealth intervention at a time marked by disillusionment with the comprehensive redevelopment paradigm. It explores the relationships and tensions apparent between and within different levels of government in establishing a Commonwealth presence, focusing on three inner city neighbourhoods: Waterloo, Glebe and Woolloomooloo. The significance of the interventions is considered to lie primarily in the pioneering of an all-of-government approach to urban governance.  相似文献   

Evidence for ecosystem engineering in a lentic habitat by tadpoles of the western toad     

Sylvia L. R. Wood  John S. Richardson 《Aquatic Sciences - Research Across Boundaries》2010,72(4):499-508

A number of aquatic organisms have demonstrated an ability to modulate sediment deposition in tropical and temperate stream systems, but little is known about the impact of similar benthic grazing processes in temperate pond systems. Using exclosure experiments in mesocosms, we used tadpoles of the western toad (Anaxyrus boreas) to investigate two questions: (1) can grazing activities of tadpoles of the western toad in ponds reduce sediment accrual on grazing surfaces (e.g. via bioturbation or ingestion); and (2) do these grazing activities contribute to enhanced periphyton biomass and chlorophyll a content of benthic matter. Mesocosms received pulses of fine sediment weekly over 8 weeks to simulate allochthonous surface inputs following rainstorms. Accumulated sediment and periphyton matter on exposed and grazing-restricted substrate surfaces were measured weekly. Tadpole grazing activity significantly reduced the standing stock of periphyton on open grazing surfaces by 80% in controls. Under sediment-additions, tadpoles effectively removed settled particulate matter from exposed grazing surfaces, but no corresponding increase in periphyton biomass was observed. These results suggest that tadpoles can impact the dynamics of sediment distribution in ponds as well as streams, providing support for a role as “ecosystem engineers” in these habitats.  相似文献   

The new carbon economy: constitution,governance and contestation edited by Peter Newell , Maxwell Boykoff and Emily Boyd (eds), Wiley‐Blackwell,Oxford, 2012. 208 pp. ISBN 978‐1‐4443‐5022‐7.     

Andy Reisinger 《New Zealand geographer》2013,69(1):79-80

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A model for the demise of large, glacial Lake Ojibway, Ontario and Quebec     

Justin S. Stroup  Thomas V. Lowell  Andy Breckenridge 《Journal of Paleolimnology》2013,50(1):105-121

Large glacial lakes modulated the return of meltwater to the ocean during deglaciation, and their drainage may have initiated global climate change. Yet few records of their drainage come from observations within their basins. Sediment cores from nine lakes along a 240-km transect from northwestern Quebec to northeastern Ontario cover a portion of former Lake Ojibway and provide a stratigraphy of the terminal phase of this large glacial lake. Magnetic susceptibility, density, grain size, X-ray fluorescence chemistry and X-ray diffraction data were used to characterize stratigraphic changes within the basin. The basal sequence consists of till and rhythmites, with ice-proximal debris flows overlain by varves. The varves thin up-section and become unrecognizable, which indicates decreased deposition rates. This fine-grained sediment forms the matrix of a clay-pebble conglomerate. The clay-pebbles are ice-rafted debris (IRD). The IRD flux was probably constant, whereas the sedimentation rate of the finer-grained matrix decreased. The end of IRD marks the cessation of icebergs in the lake and is the best indication for drainage of the glacial lake. The conglomerate is capped by laminated to massive gray silt deposited after lake drainage and marks the transition to organic-rich, post-glacial lakes. Such sequences place drainage into the broader context of deglaciation.  相似文献   

Shocks and sheaths in the heliosphere     

John D. Richardson 《Journal of Atmospheric and Solar》2011,73(11-12):1385-1389

This paper compares three kinds of shocks and sheaths; the bow shock and magnetosheaths of planets, interplanetary coronal mass ejection (ICME) shocks and sheaths, and the termination shock and heliosheath. We compare the energy balance across these shocks, fluctuations in the sheaths, asymmetries, and shock evolution. All three shocks and sheaths display asymmetries imposed by outside magnetic fields. Energy balance is often achieved through reflection of ions of the shocks, but in some cases no reflected ions are observed. The shocks may have similar small scale fluctuations which drive density changes in the sheaths.  相似文献   

Using FTIR spectroscopy to characterise the soil mineralogy and geochemistry of cryoconite from Aldegondabreen glacier,Svalbard     

Harry Langford  Andy Hodson  Steve Banwart 《Applied Geochemistry》2011

Mineralogical and geochemical diversity in cryoconite granules from Aldegondabreen glacier was investigated using FTIR spectroscopy. Results suggest that the technique is an effective tool for investigating mineralogy and identifying spatial differences in geochemistry, based upon characteristic spectral signatures.  相似文献   

Development of Specimen Curing Procedures that Account for the Influence of Effective Stress During Curing on the Strength of Cemented Mine Backfill   总被引：2，自引：1，他引：1  

Martin Fahey  Matthew Helinski  Andy Fourie 《Geotechnical and Geological Engineering》2011,29(5):709-723

Paste backfill used to provide ground support in underground mining is generated from full-stream tailings and is almost always placed underground with cement. For the backfill, both the rate of strength development and the final strength are important considerations for design, particularly when the backfill is subsequently exposed in the stope-mining sequence. There is strong evidence that strengths measured on specimens obtained from coring the in situ cemented backfill are much greater than laboratory-cured specimens with the same cement content. The paper reviews some of the experimental evidence showing that one of the major reasons for the different strength is the difference in effective stress acting on the backfill during curing. Laboratory specimens are (almost) always cured under zero total stress, so no effective stress develops. In contrast, backfill in a stope may cure under high effective stress, which develops due to either “conventional” consolidation in free-draining backfills, or to the so-called “self-desiccation” mechanism in fine-grained fills. Evidence is presented showing how the final strength is affected by applying stress to specimens at different stages of curing and at different rates. It is shown that a fully-coupled analysis of the filling behaviour is required to determine the appropriate effective stress regime to apply in curing laboratory specimens, where “fully-coupled” in this context means taking account of the interaction of consolidation/drainage rate, filling rate and cement hydration rate. Curing protocols for laboratory specimens are proposed, which would ensure that the strengths obtained are representative of in situ conditions.  相似文献   

A geomorphological mapping approach for the assessment of seabed geohazards and risk     

Gayle Hough  Jennifer Green  Paul Fish  Andy Mills  Roger Moore 《Marine Geophysical Researches》2011,32(1-2):151-162

Exploration and development of offshore hydrocarbon resources has advanced into remote deepwater regions over the last decade and poses significant technical challenges for the design and installation of wells and facilities at extreme water depths. Seafloor and shallow subsurface processes and conditions in these areas are complex and generally poorly understood, and the geohazards to development are larger scale and fundamentally different to those encountered onshore; consequently the geohazard risk to deepwater development projects is potentially significant and requires careful evaluation and mitigation during the front-end planning and engineering design stages of projects. There are no established industry standards or methods for the assessment of geohazards and engineering-quality geophysical data at the scale of development. The paper describes an integrated and systematic map-based approach for the assessment and mitigation of seabed geohazards and risk to proposed deepwater development. The approach employs a multi-disciplinary team working with engineering-quality field calibrated data to accurately map and assess seafloor ground conditions and ensure that development proposals are not exposed to intolerable geohazard risk. The approach taken is very similar to the practice of establishing geological models for land-based engineering projects, in which the complete geological history of the site is used to characterise and predict the performance of the ground. Such an approach is routine for major projects on land but so far does not seem to be common practice in the offshore industry. The paper illustrates the seafloor geomophological mapping approach developed. The products are being used to optimise development layouts to avoid geohazards where possible and to support site-specific engineering design of facilities based on a detailed understanding of the potential geohazard loadings and associated risk.  相似文献