Effects of drilling cuttings on the behaviour of the Norway lobster Nephrops norvegicus     

C.A Richardson 《Marine pollution bulletin》1984,15(5):170-174

Small quantities of drilling cuttings (100 g/250 cm²) were found to affect both the survival and general behaviour of Nephrops norvegicus held in experimental aquaria. In one experiment volatile hydrocarbons released from the cuttings caused a significant decrease (p < 0.05) in the beat of the exopodite on the third maxilliped. Flicking rates of the antennule and the time taken to identify and capture food introduced into the tanks were unaffected by exposure to cuttings. When the water flow through the tanks was interrupted for 12 h, 58% of animals died after exposure to the highest concentration of cuttings but those at the lower concentrations survived. After the water flow was restored the remaining survivors showed disorientated behaviour and uncoordinated movements which lasted for about 36 h. In this condition animals will be more vulnerable to predators. This unnatural behaviour may have serious implications for natural populations exposed to cuttings discharge in the close vicinity of offshore drilling platforms.  相似文献   

Correspondence regarding Symposium on Ice and Climate Modeling     

H. Richardson 《Climatic change》1982,4(3):323-323

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Geochemical signature of historical mining: Fowey Estuary, Cornwall, UK     

Duncan Pirrie  Matthew R. Power  Paul D. Wheeler  Andy Cundy  Colin Bridges  Graham Davey 《Journal of Geochemical Exploration》2002,76(1)

Geochemical analyses of intertidal sediments from the northern part of the Fowey Estuary, Cornwall, UK, reveal a clear pulse in Sn concentration in sediments which predate 1880. Sn concentrations at the base of the cores increase rapidly to peak values of 1200 ppm and then decrease to values of 200 ppm at the present-day sediment surface. The mineralogy of the sediments is consistent with an origin from the release of mine waste from tin streaming and smelt products into the estuary. Further to the south, the down-core geochemistry of the estuary sediments is uniform with values of typically 400 ppm. This is interpreted as due to the natural reworking of the recognised pulse in particulate mine waste seen to the north.  相似文献   

Placement of sensors/actuators on civil structures using genetic algorithms     

Makola M. Abdullah  Andy Richardson  Jameel Hanif 《地震工程与结构动力学》2001,30(8):1167-1184

The optimal design and placement of controllers at discrete locations is an important problem that will have impact on the control of civil engineering structures. Though algorithms exist for the placement of sensor/actuator systems on continuous structures, the placement of controllers on discrete civil structures is a very difficult problem. Because of the nature of civil structures, it is not possible to place sensors and actuators at any location in the structure. This usually creates a non‐linear constrained mixed integer problem that can be very difficult to solve. Using genetic algorithms in conjunction with gradient‐based optimization techniques will allow for the simultaneous placement and design of an effective structural control system. The introduction of algorithms based on genetic search procedures should increase the rate of convergence and thus reduce the computational time for solving the difficult control problem. The newly proposed method of simultaneously placing sensors/actuators will be compared to a commonly used method of sensors/actuators placement where sensors/actuators are placed sequentially. The savings in terms of energy requirements and cost will be discussed. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

Multiple thread flow and channel bifurcation in a braided river: Brahmaputra–Jamuna River, Bangladesh     

W. Roy Richardson  Colin R. Thorne 《Geomorphology》2001,38(3-4)

Considerable progress has been made recently in characterising the patterns displayed by the anabranches of braided rivers. However, the physical processes of sediment scour, transfer and deposition that govern the generation and evolution of anabranch channels remain largely unexplained. Direct measurement of three-dimensional flow fields and morphological evolution of the anabranches in the braided Brahmaputra–Jamuna River, Bangladesh, were undertaken to investigate the interactions between fluvial processes and anabranch morphology. These data were used to elucidate the circumstances leading to the bifurcation of a single channel, which is a topic of fundamental importance to understanding the physical processes responsible for braiding. Results indicate that division of the velocity field into multiple threads within a single channel precedes a division in the cross-sectional morphology of the channel and appears to be a necessary prerequisite for development of a bifurcation. An empirical relationship was established to discriminate between channels with single and multi-thread velocity fields, based on the depth-to-width ratio and specific energy of the flow at a representative channel cross-section. This function requires further validation, but could be used to predict the conditions under which a single channel is likely to bifurcate to produce two anabranches.  相似文献   

Decomposition rates of purple loosestrife (Lythrum salicaria) and Lyngbyei’s sedge (Carex lyngbyei) in the Fraser River estuary     

Jeff A. Grout  Colin D. Levings  John S. Richardson 《Estuaries and Coasts》1997,20(1):96-102

Using litter bag experiments in the Fraser River estuary in British Columbia, we tested for differences in the relative decomposition rates between leaves of purple loosestrife (Lythrum salicaria), an introduced exotic and a native sedge (Carex lyngbyei). The difference in the mean decay rate coefficient for the two species was significantly defferent (p<0.01) and the coefficient for purple loosestrife (0.0110 d^?1) was nearly four times higher than for Lyngbyei's sedge (0.0028 d^?1). This is the first estimate of the decay rate coefficient for purple loosestrife from an estuary. The rapid decay rate of loosestrife leaves suggests that they supply detritus to the ecosystem in autumn whereas the much slower decay rate of sedge implies that it supplies detritus throughout the winter and early spring. Consumer organisms important in juvenile salmon food webs appear to be adapted to take advantage of the detritus provided in these seasons. The findings have implications for habitat management because purple loosestrife has recently invaded estuaries of the northeast Pacific and may be outcompeting native sedges important in detrital-based food webs.  相似文献   

Variability in in situ shear strength of gassy muds     

K. B. Briggs  Michael D. Richardson 《Geo-Marine Letters》1996,16(3):189-195

Torque measurements are made by divers with a vane apparatus to a sediment depth of 136 cm in the high-porosity, gassy sediments of Eckernförde Bay. Corrected shear strength values calculated from torque measurements are quite variable in the Eckernförde Bay sediments, varying from less than 0.5 kPa in the top 10 cm of sediment to 4–5 kPa at 136 cm sediment depth. Variability increases markedly below 60 cm sediment depth, probably because of the presence of methane gas bubbles within the sediment fabric.  相似文献   

Using continuous plankton recorder data     

A.J. Richardson  A.W. Walne  T.D. Jonas  D.W. Sims  M. Witt 《Progress in Oceanography》2006,68(1):27-74

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The Distribution of Talitrid Amphipods (Crustacea) on a Salt Marsh in Southern Tasmania, in relation to Vegetation and Substratum     

A. M. M. Richardson  M. E. Mulcahy 《Estuarine, Coastal and Shelf Science》1996,43(6):801-817

Supralittoral and terrestrial talitrid amphipods were collected from a salt marsh in Southern Tasmania by pitfall trapping along transects from the mid-tidal level to above the high-tide mark, and by hand collecting from sites chosen to represent the full range from salt marsh to terrestrial vegetation. At each site, the cover of all major plant species was recorded, and soil samples were collected from which soil moisture, organic content and salinity were measured.Eight talitrid species from four ecological groups were collected; one palustral species, one beachflea, three coastal landhoppers and three eastern forest landhoppers. There was substantial overlap in the distributions of these groups. The undescribed beachflea had the widest distribution, from the wettest, most saline sites to theSchoenus nitenstussock grassland at the extreme high-tide mark. The palustral species,Eorchestia palustris, overlapped substantially with the beachflea, but was found within a narrower band of salinities (though not in the most saline sites) and in more poorly-drained sites than the beachflea. Coastal landhoppers,Austrotroides maritimus,Keratroides rexand an undescribed species ofTasmanorchestia, were found mainly in theS. nitenstussock grassland, where they overlapped with forest landhoppers,Keratroides vulgaris,Mysticotalitrus tasmaniaeandM. cryptus, which were found mainly in non-saltmarsh terrestrial sites, well above the high-tide mark.These distributions are discussed in terms of the likelihood that salt marshes provided the route by which talitrid amphipods colonized land. There is no reason from these data to reject salt marshes as the route to land, and it is suggested that they are a more likely route than via rocky or sandy shores.  相似文献   

An overview of SAX99: acoustic measurements   总被引：5，自引：0，他引：5  

Thorsos  E.I. Williams  K.L. Chotiros  N.P. Christoff  J.T. Commander  K.W. Greenlaw  C.F. Holliday  D.V. Jackson  D.R. Lopes  J.L. McGehee  D.E. Piper  J.E. Richardson  M.D. Dajun Tang 《Oceanic Engineering, IEEE Journal of》2001,26(1):4-25

A high-frequency acoustic experiment was performed at a site 2 km from shore on the Florida Panhandle near Fort Walton Beach in water of 18-19 m depth. The goal of the experiment was, for high-frequency acoustic fields (mostly In the 10-300-kHz range), to quantify backscattering from the seafloor sediment, penetration into the sediment, and propagation within the sediment. In addition, spheres and other objects were used to gather data on acoustic detection of buried objects. The high-frequency acoustic interaction with the medium sand sediment was investigated at grazing angles both above and below the critical angle of about 30°. Detailed characterizations of the upper seafloor physical properties were made to aid in quantifying the acoustic interaction with the seafloor. Biological processes within the seabed and the water column were also investigated with the goal of understanding their impact on acoustic properties. This paper summarizes the topics that motivated the experiment, outlines the scope of the measurements done, and presents preliminary acoustics results  相似文献