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741.
Both climate change and the North Atlantic Oscillation (NAO) may influence coastal systems by altering wave exposure. The effects of such climatic forcing are often coherent over relatively large geographic areas. Temporal trends in wave exposure at any particular shore are, however, the result of an interaction between site-specific fetch characteristics and changes in wind climate. This leads to contrasting trends in wave exposure at locations separated by no more than a few kilometres. Wave exposures were estimated at locations around a sea lough over 32 years to characterise these scales of variability. Locations separated by approximately 5 km had independent dynamics with respect to the temporal trend (correlation range −0.35 to 0.44) and to associations with the NAO (correlation range −0.18 to 0.40). Wave exposure can therefore be increasing for a section of shore while nearby areas have the opposite trend. Mean exposure at a location was not a good predictor of the temporal trend. More exposed sites were, however, sensitive to variations in the strength of the NAO. The reduction of large scale forcing to small-scale variability has implications for the detection and mitigation of potential climate change impacts. 相似文献
742.
H. L. Davies J. Lock D. L. Tiffin E. Honza Y. Okuda F. Murakami K. Kisimoto 《Geo-Marine Letters》1987,7(3):143-152
The anticlinal nappe which forms the Huon Peninsula and adjacent ranges extends offshore as the Huon Ridge. The frontal thrust of the nappe is the Ramu-Markham Fault (onshore) and a deformation front along the line of the Markham Canyon (offshore). The timing and geometry of the Finisterre arc-continent collision is controversial, and the origin of the Finsch Deep is unresolved. 相似文献
743.
Large-scale use of oil-based muds for drilling operations offshore can lead to high concentrations of aromatic hydrocarbons in the sediments close to these platforms. Fish were trawled from stations close to and distant from such platforms and the levels of hepatic aryl hydrocarbon hydroxylase (AHH) were determined in cod, haddock and whiting. These three species were caught in sufficient numbers to make reasonable preliminary data sets. The data for cod and haddock showed significantly higher levels of AHH in the livers of fish caught close to oil platforms than in those caught in areas away from oil activity, while whiting showed no such differences. A much larger sample number together with some measurement of enhanced cytochrome P-450 levels would be required to substantiate this trend, but these data are the first indications that the oil in the sediments around platforms may be biochemically available to fish in the area. 相似文献
744.
Heath Michael R; Boyle Peter R; Gislason Astthor; Gurney William S.C; Hay Stephen J; Head Erica J.H; Holmes Steven; Ingvarsdottir Anna; Jonasdottir Sigrun H; Lindeque Pennie; Pollard Raymond T; Rasmussen Jens; Richards Kelvin; Richardson Katherine; Smerdon Gary; Speirs Douglas 《ICES Journal of Marine Science》2004,61(4):698-708
745.
Acetylcholinesterase in mussel is potentially a useful biomarker of exposure to organophosphates (OP) in the marine environment. This study looked at cholinesterase activity in subcellular fractions of various tissues from the common mussel, Mytilus edulis. Measurement of enzyme rates demonstrated that although highest specific activity was found in foot 'mitochondrial' fraction, recovery of activity was very low. Gill 'microsomal' fraction had the second highest specific activity with a useful level of recovery and therefore was the most suitable tissue fraction for biomarker applications. Comparative studies of alternative alkylthiocholine substrates and competitive inhibitors suggest there is a single cholinesterase enzyme type present in this fraction. Inhibition of alkylcholine hydrolysis by BW284C51, specific to acetylcholinesterase in vertebrates, showed that cholinesterase activity in gill 'microsomal' fraction is inhibited by this compound but to a lesser extent than in vertebrate AChE. Inhibition of cholinesterase activity by azamethiphos in gill 'microsomal' fraction gave an IC50 of approximately 100 microM and showed both time and concentration dependence. However this indicates a lower potency compared to other animals and it is debatable whether mussel cholinesterase activity is useful as a biomarker of exposure in the field. 相似文献
746.
A new methodology for computing the gravitational effect of a spherical tesseroid has been devised and implemented. The methodology is based on the rotation from the global Earth-Centred Rotational reference frame to the local Earth-Centred P-Rotational reference frame, referred to the computation point P, and it requires knowledge of the height and the angular extension of each topographic column. After rotation, the gravitational effect of the tesseroid is computed via the effect of a sector of the spherical zonal band. In this respect, two possible procedures for handling the rotated tesseroids have been proposed and tested. The results obtained with the devised methodology are in good agreement with those derived by applying other existing methodologies. 相似文献
747.
748.
Relationships among chemical–physical features, total gross suspended organic matter, coverage of the seagrass Ruppia cirrhosa and its associated algal community in eight ponds of a saltworks system of western Sicily (Mediterranean Sea) were investigated in spring and summer 2004. All biological features varied both at different levels of seagrass coverage and between seasons. A low algal diversity (46 taxa, 14.75 ± 1.41 on average) was highlighted; algal coverage and species richness showed to be negatively correlated. Ruppia cirrhosa coverage was negatively correlated with algal coverage, but positively correlated with species richness. Moreover, a significant correlation among R. cirrhosa coverage, the availability of suspended matter in the water column and the chlorophyll a concentration was detected. 相似文献
749.
The sediment–water interface is usually marked by an increase in acoustic impedance and is therefore displayed in a seismic
section as a positive polarity reflection. Here, we use the term “seabed phase reversal” to describe areas of seafloor which
are instead expressed as a negative polarity reflection in seismic data. We describe in detail a number of examples of seafloor
phase reversals and use a simple one-dimensional geophysical model to test the hypothesis that they are the result of the
presence of gas within the seafloor sediment. Our examples are all related to seismically imaged mud volcanoes located within
the South Caspian Sea. Sections of phase-reversed seafloor at the summit area of these volcanoes have been mapped to reveal
the existence of seafloor mud pools (salses) and recently erupted mud flows which show a strong similarity to smaller-scale
features at onshore volcanoes in Azerbaijan. Synthetic geophysical modelling indicates that under the physical conditions
likely to occur when the seabed sediment is gas-bearing, the seafloor will be expressed as a strong negative polarity reflection.
Unlike other indicators of seafloor gas, such as pockmarks, which merely record the transient expulsion of fluids from sedimentary
basins, seafloor phase reversals indicate the presence of gas in marine sediment at the time of survey acquisition. They therefore
are of significance to engineering and site survey operations as well as the identification of biological communities and
gas flux calculations. 相似文献
750.
Gowlan BT McIntosh AD Davies IM Moffat CF Webster L 《Marine environmental research》2002,54(3-5):231-235
An aluminium smelter on the west coast of Scotland discharges an aqueous effluent containing polycyclic aromatic hydrocarbons (PAHs) at the head of Loch Leven. The loch also supports two mussel (Mytilus edulis) farms. Data are presented on burdens of PAHs in the soft tissues of mussels and the effect of these contaminants on glutathione S-transferase (GST) activity in mussel hepatopancreas. GST activity is shown to be correlated with total PAH burden and also with the concentrations of certain individual PAHs. These field data show that high molecular weight PAHs are closely correlated to GST activity, whereas low molecular weight PAHs are not. This suggests that 5- and 6-ring PAHs have a more pronounced role than 2- to 4-ring compounds in inducing GST activity in mussels from Loch Leven. It is proposed that it may be more appropriate to link GST activity with 5- and 6-ring compounds only, rather than with the total PAH burden. 相似文献