Importance of spawning location and timing to successful transport to nursery areas: a simulation study of Gulf of Alaska walleye pollock   总被引：2，自引：0，他引：2  

Hinckley  Sarah; Hermann  Albert J.; Mier  Kathy L.; Megrey  Bernard A. 《ICES Journal of Marine Science》2001,58(5):1042-1052

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Estimation of mackerel (Scomber scombrus L., 1758) and horse mackerel (Trachurus trachurus L., 1758) daily egg production outside the standard ICES survey area     

Dransfeld  Leonie; Dwane  Oonagh; Molloy  John; Gallagher  Sarah; Reid  Dave G. 《ICES Journal of Marine Science》2005,62(8):1705-1710

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Carbon stable isotopes in estuarine sediments and their utility as migration markers for nursery studies in the Firth of Forth and Forth Estuary, Scotland   总被引：2，自引：0，他引：2  

Julian Augley  Mark Huxham  Teresa F. Fernandes  Alastair R. Lyndon  Sarah Bury 《Estuarine, Coastal and Shelf Science》2007,72(4):648-656

The stable carbon isotope ratios (δ¹³C) of the organic fraction of intertidal sediments in the Forth Estuary and the Firth of Forth, Scotland, were measured to determine if terrestrially derived carbon was present in the estuarine sediments. It was hypothesised that differences in the inputs from marine vs. terrestrial sources to the organic carbon of estuarine and marine sediments, as well as differences in ambient seawater stable oxygen isotope (δ¹⁸O) ratios between the estuary and the Outer Firth, would allow the use of these two stable isotopes as habitat markers for juvenile plaice (Pleuronectes platessa), to allow determination of nursery habitats. Muddy and sandy sediments from the estuary and sandy sediments from the Outer Firth were sampled and δ¹³C measured. Juvenile plaice were caught at two estuarine sites and at two Outer Firth sites and otoliths were removed for δ¹³C and δ¹⁸O analysis. The sandy sediments in the estuary showed a strong gradient of δ¹³C enrichment with distance down the estuary, while the muddy sediments showed a much shallower gradient. δ¹³C and δ¹⁸O measured in the carbonate of juvenile plaice otoliths showed no clear difference between otoliths of fish caught at one of the estuarine sites and at the two Outer Firth sites. However, the isotope ratios of both carbon and oxygen in plaice otoliths from the other estuarine site showed the expected trend of depletion in the heavier isotopes. While the measurements recorded here did not conclusively distinguish between otoliths from juveniles caught in the estuarine site and those caught in the other three sites, they show that stable isotopes have potential to distinguish between estuarine habitats with terrestrial carbon inputs, and coastal marine habitats with predominantly marine carbon inputs.  相似文献   

Probing molecular-level transformations of dissolved organic matter: insights on photochemical degradation and protozoan modification of DOM from electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry     

Elizabeth B. Kujawinski  Rossana Del Vecchio  Neil V. Blough  Geoffrey C. Klein  Alan G. Marshall   《Marine Chemistry》2004,92(1-4):23

Molecular-level characterization of natural organic matter (NOM) has been elusive due to the inherent complexity of natural organic mixtures and to the fact that individual components are often polar and macromolecular. Electrospray ionization (ESI) is a “soft” ionization technique that ionizes polar compounds from aqueous solution prior to injection into a mass spectrometer. The highest resolution and mass accuracy of compounds within NOM have been achieved when ESI is combined with an ultrahigh-resolution mass spectrometer such as the Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS). With this technique, individual molecules within a variety of natural organic mixtures can be detected and their elemental composition can be determined. At low mass-to-charge (m/z) ratio, the resolution is high enough to assign exact molecular formulas allowing specific components of these mixtures to be identified. In addition to molecular identification, we can now use ESI FT-ICR MS to examine molecular-level changes in different organic mixtures as a function of relevant geo-processes, such as microbial alterations and photochemistry. Here we present the results from the application of ESI FT-ICR MS to two geochemical questions: (1) the effect of photoirradiation on the molecular composition of fulvic acids and (2) the role of protozoan grazers in the modification of DOM in aquatic systems.  相似文献   

Particle acceleration and the decay of soft X-ray non-thermal line broadening in solar flares     

David Alexander  Sarah A. Matthews 《Solar physics》1994,154(1):157-175

The relationship between the production of -ray emitting particles and non-thermal soft X-ray line broadening is investigated. A model of particle acceleration via the stochastic interaction with MHD turbulence is assumed and the time development of the wave energy density derived under the condition of energy conservation between waves and particles. The inferred numbers and energy distribution of accelerated protons for four -ray flares are used to define the wave energy density and its temporal development. The presence of Alfvén wave turbulence is considered as the source of the non-thermal motions in the ambient plasma. These motions are observed as excess widths in the soft X-ray line emission from these events. The decay of the waves via the particle acceleration process is compared with the observed decays of this non-thermal line broadening. Our results show that both the -ray emission and excess soft X-ray line widths in these flares can be explained by the single physical phenomenon of Alfvén wave turbulence.  相似文献   

Temperature–composition–time (T–X–t) data from authigenic K-feldspar: An integrated methodology for dating fluid flow events     

Darren F. Mark  John Parnell  Simon P. Kelley  Sarah C. Sherlock 《Journal of Geochemical Exploration》2006,89(1-3):259

Integration of fluid inclusion analysis with high spatial resolution Ar–Ar dating of K-feldspar cements has been used to resolve and reconstruct palaeo-fluid flow. Fluid inclusion analysis allows discrimination of distinct cement phases, thereby identifying discrete episodes of fluid flow. Ar–Ar dating of the same cements via high spatial resolution laserprobe establishes absolute age constraints on the framework previously constructed. Integration of these two datasets yields temperature–composition–time data.  相似文献   

Paleoenvironmental records of water level and climatic changes from the middle to late Holocene at a Lake Erie coastal wetland, Ontario, Canada   总被引：2，自引：0，他引：2  

Sarah A. Finkelstein  Anthony M. Davis 《Quaternary Research》2006,65(1):33-43

Pollen and diatom assemblages, and peat stratigraphies, from a coastal wetland on the northern shore of Lake Erie were used to analyze water level and climatic changes since the middle Holocene and their effects on wetland plant communities. Peat deposition began 4700 cal yr B.P. during the Nipissing II transgression, which was driven by isostatic rebound. At that time, a diatom-rich wild rice marsh existed at the site. Water level dropped at the end of the Nipissing rise at least 2 m within 200 yr, leading to the development of shallower-water plant communities and an environment too dry for most diatoms to persist. The sharp decline in water level was probably driven primarily by outlet incision, but climate likely played some role. The paleoecological records provide evidence for post-Nipissing century-scale transgressions occurring around 2300, 1160, 700 and 450 cal yr B.P. The chronology for these transgressions correlates with other studies from the region and implies climatic forcing. Peat inception in shallow sloughs across part of the study area around 700 cal yr B.P. coincides with the Little Ice Age. These records, considered alongside others from the region, suggest that the Little Ice Age may have resulted in a wetter climate across the eastern Great Lakes region.  相似文献   

Late Holocene sea-level changes and isostasy in western Denmark     

W. Roland Gehrels  Katie Szkornik  Jason R. Kirby  William A. Marshall  Jørn B.T. Pedersen 《Quaternary Research》2006,66(2):288-302

Cores and exposed cliff sections in salt marshes around Ho Bugt, a tidal embayment in the northernmost part of the Danish Wadden Sea, were subjected to ¹⁴C dating and litho- and biostratigraphical analyses to reconstruct paleoenvironmental changes and to establish a late Holocene relative sea-level history. Four stages in the late Holocene development of Ho Bugt can be identified: (1) groundwater-table rise and growth of basal peat (from at least 2300 BC to AD 0); (2) salt-marsh formation (0 to AD 250); (3) a freshening phase (AD 250 to AD 1600?), culminating in the drying out of the marshes and producing a distinct black horizon followed by an aeolian phase with sand deposition; and (4) renewed salt-marsh deposition (AD 1600? to present). From 16 calibrated AMS radiocarbon ages on fossil plant fragments and 4 calibrated conventional radiocarbon ages on peat, we reconstructed a local relative sea-level history that shows a steady sea-level rise of 4 m since 4000 cal yr BP. Contrary to suggestions made in the literature, the relative sea-level record of Ho Bugt does not contain a late Holocene highstand. Relative sea-level changes at Ho Bugt are controlled by glacio-isostatic subsidence and can be duplicated by a glacial isostatic adjustment model in which no water is added to the world's oceans after ca. 5000 cal yr BP.  相似文献   

The Record of an Extreme Flood in the Sediments of Montane Lillooet Lake, British Columbia: Implications for Paleoenvironmental Assessment     

Robert Gilbert  Sarah Crookshanks  Kyle R. Hodder  John Spagnol  Roland B. Stull 《Journal of Paleolimnology》2006,35(4):737-745

Severe rainfall in mid October, 2003 produced the largest floods in almost a century of record on rivers in the Cordillera of southwestern British Columbia. Sediment deposited in Lillooet Lake as a result of this event is clearly distinguished by stratigraphy, colour, texture, magnetic properties, and organic content. Each of these physical properties is related to the lacustrine processes, especially turbid underflow, that distributed the sediment through the lake. The flood, which lasted less than a week, delivered 8–12 times the amount of sediment that accumulates in most entire years in the deepest, central parts of the lake. Recognition of events of this type in the stratigraphic record offers a means of assessing the changing nature of extreme hydroclimatic events, and their relation to more ubiquitous, lower-energy processes.  相似文献   

Seismological identification of the 1998 May 28 Pakistan nuclear test     

D. Bowers  A. Douglas  N. D. Selby  P. D. Marshall  D. Porter  N. J. Wallis 《Geophysical Journal International》2002,150(1):153-161

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