Recovery of meiofauna communities following mudflat disturbance by trampling associated with crab-tiling     

Johnson GE  Attrill MJ  Sheehan EV  Somerfield PJ 《Marine environmental research》2007,64(4):409-416

The provision of artificial shelters for the collection of crabs, known as crab-tiling, and the subsequent harvesting of the soft "peeler" crabs for angling bait, are associated with trampling disturbance of intertidal mudflats in the United Kingdom. Recovery of meiofauna communities following crab-tiling activity was investigated on an intertidal mudflat in SW England. Harvesting of experimental plots was reproduced six times over a 2-week period. Meiofauna was collected at low tides 12h, 36 h and 144 h after treatment. Meiofaunal and nematode abundance, and nematode species number, was significantly greater in controls compared to crab-tile stations at 12h. At 36 h and 144 h there were no significant differences between treatments, indicating recovery had occurred in 12-36 h. Multivariate analysis showed nematode assemblage composition from control plots to be significantly different from crab-tile plots at 12h. No significant differences were observed between sediment physical parameters with treatment. Results suggest that the predominant effect of disturbance may be vibration-induced burial, which causes nematodes to bury deeper into the sediment, beyond the depth sampled, and explains the rapid recovery.  相似文献   

Hepatic biomarkers of sediment-associated pollution in juvenile turbot, Scophthalmus maximus L     

Hartl MG  Kilemade M  Sheehan D  Mothersill C  O'Halloran J  O'Brien NM  van Pelt FN 《Marine environmental research》2007,64(2):191-208

Hatchery-reared turbot (Scophthalmus maximus L.) were exposed for 3 weeks, under laboratory conditions, to sediment collected from polluted sites in Cork Harbour and a reference site at Ballymacoda, Co. Cork, Ireland. The potential of surficial sediment for inducing hepatic biomarkers was assessed at two levels of biological organisation: expression of cytochrome P450 [Western blotting analysis and 7-ethoxy-resorufin O-dealkylase (EROD), 7-benzoxy resorufin O-dealkylase (BROD), 7-methoxy resorufin O-dealkylase (MROD), 7-pentoxy-resorufin O-dealkylase (PROD) activities] and DNA integrity (Comet assay). Positive controls were generated, either by exposing turbot to cadmium chloride-spiked seawater (Comet assay) or to beta-naphthaflavone by intraperitoneal injection (cytochrome P450 induction). The induction of cytochrome P450 activity (EROD, MROD and PROD) in animals following a 7-day exposure to contaminated sediments was significantly higher than those exposed to reference site sediment and remained elevated thereafter; BROD was not induced. DNA single-strand breaks were also significantly higher following exposure to contaminated sediments throughout the experiment. Although no direct correlation between induction of alkoxyresorufin O-dealkylase activities and a particular chemical class was established, the induction of MROD and PROD activities in fish exposed to sediments containing complex contaminant mixtures, appeared to be more sensitive than conventional EROD activity assays. We conclude from the present laboratory study that S. maximus is a suitable sentinel species for the assessment of moderately contaminated sediments and therefore allows for the further development of this model for future, ecologically relevant, field studies.  相似文献   

Ubiquitination and carbonylation as markers of oxidative-stress in Ruditapes decussatus.     

Suze Chora  Brian McDonagh  David Sheehan  Mireille Starita-Geribaldi  Michèle Roméo  Maria J Bebianno 《Marine environmental research》2008,66(1):95-97

Environmental pollutants, such as metals, are widespread in aquatic environments and can lead to the formation of reactive oxygen species (ROS). ROS are highly toxic in marine species since they can cause serious reversible and irreversible changes in proteins including ubiquitination and modifications such as carbonylation. This study aimed to confirm the potential of ubiquitination and carbonylation as markers of oxidative stress in the clam Ruditapes decussatus (Veneroida, Veneridae) exposed to cadmium (40 microg/L). After 21 days of exposure clams were dissected into gills and digestive gland. Cytosolic proteins of both tissues were separated by two-dimensional electrophoresis (2-D SDS-PAGE) and analysed by immunobloting. Higher ubiquitination and carbonylation levels were in digestive gland of contaminated organisms. These results confirm the potential of ubiquitination and carbonylation as a sensitive and specific marker of oxidative stress in marine bivalves. In this approach, changes in protein structure provide options for affinity selection of sub-proteomes for 2D SDS-PAGE, simplifying the detection of protein biomarkers using proteomic approach.  相似文献   

Low-O18 Igneous Rocks from the Intrusive Complexes of Skye, Mull, and Ardnamurchan, Western Scotland     

TAYLOR  HUGH P.  JR.; FORESTER  RICHARD W. 《Journal of Petrology》1971,12(3):465-497

Oxygen isotope analyses have been obtained on rocks and coexistingminerals from the Tertiary stocks, ring-dikes, and cone-sheetsin Ardnamurchan (18 samples), Skye (41 samples), and Mull (18samples); these include a few samples of the plateau basaltcountry rocks. Almost all of the rocks in the vicinity of thecentral ring complexes (within 2 mi. of an intrusive contact)are strongly depleted in O¹⁸ relative to ‘normal’igneous rocks from other areas. The rocks in Skye ( 150 sq.mi.) and Mull ( 150 sq. mi.) have suffered an overall O¹⁸ depletionof about 6 to 7 per mil, and those in Ardnamurchan ( 30 sq.mi.) about 3 to 6 per mil. These data indicate that very large hydrothermal convectionsystems involving heated low. O¹⁸ meteoric ground waters wereestablished in these areas at the time of igneous intrusion.The heated ground waters exchanged with the gabbros, granities,and basaltic lavas, locaclly lowering their O¹⁸/ O¹⁶ rationsby at least 12 per mil. Much, if not all, of this exchange occurredafter crystallization of a given igneous rock was essentiallycomplete, inasmuch as feldspars invariably have undergone muchmore depletion in O¹⁸ than has coexisting quartz or pyroxen.The meteoric-hydrothermal process and the presence of an aqueousgas phase may possibly be responsible for the widespread epidote-chloritealteration, the turbid or cloudy feldspars, the abundant feldspathicveins, the felsitic and granophyric textures, the miaroliticcavities, and much of the explosive volcanic activity and brecciationthat are found in these areas.  相似文献   

New chemical stratigraphy over the last millennium for Byrd Station, Antarctica   总被引：4，自引：0，他引：4  

C. C. LANGWAY  JR.    K. OSADA  H. B. CLAUSEN  C. U. HAMMER  H. SHOJI  A. MITANI 《Tellus. Series B, Chemical and physical meteorology》1994,46(1):40-51

  相似文献   

Available Clay and Feldspar Reference Samples As Standards for Archaeological Pottery Studies     

F. J. FLANAGAN  L. J. SCHWARZ  J. J. ROWE  A. F. DORRZAPF  JR 《Geostandards and Geoanalytical Research》1977,1(1):61-66

The available clay and feldspar reference samples, rather than the frequently used rock reference samples, are suggested as standards for archaeological pottery studies because their trace-element contents are more like those of the artefacts. Such samples may provide a basis for correlating archaeological studies throughout the world. The assumption that bottles of such reference samples should have homogeneous trace-element contents because of the nature of the materials has been confirmed by the analysis of variance of trace -element data by instrumental neutron activation analysis.  相似文献   

Reactions in Amphibolite, Greenschist and Blueschist   总被引：2，自引：0，他引：2  

THOMPSON  JAMES B.  JR.; LAIRD  JO; THOMPSON  ALAN B. 《Journal of Petrology》1982,23(1):1-27

Mineral assemblages in which chlorite [CHL], epidote [EPI],clinoamphibole [AMP], plagioclase [PLG] and quartz [QTZ] aremajor phases are characteristic of many low-grade mafic schists.The possible heterogeneous reactions in such an assemblage maybe separated into two types, exchange reactions and net-transferreactions. Only the latter alter significantly the modal proportionsof the minerals. A set of linearly independent reactions defines a reaction spaceof as many dimensions as there are independent reactions. Thespace defined by the net-transfer reactions alone is a sub-spacethat can be portrayed in three dimensions for the above assemblage.A procedure is presented herein that gives a set of independentreactions that may be taken as basis reactions for definingsuch a reaction space. All other reactions that can be writtenfor this assemblage, as well as observed whole-rock reactions,can be portrayed as vectors in these reaction spaces. Thesevectors connect the region (mineral facies) accessible to theabove assemblage. The whole-rock reactions of Laird (1980) relatinggreenschist, blueschist and various low-grade amphibolites fromVermont, provide informative examples, as do the whole-rockexperiments of Liou et al. (1974). Although reaction spaces apply to both equilibrium and disequilibriumassemblages the reactions selected as basis vectors correspondone-for-one to the chemical conditions for equilibrium thatmust obtain in any fully equilibrated assemblage. The set selectedis one that provides maximum sensitivity for geothermometric,geobarometric and geohygrometric purposes.  相似文献   

Late-glacial vegetation associated with caribou and mastodon in central Indiana     

Donald R. Whitehead  Stephen T. Jackson  Mark C. Sheehan  Barbara W. Leyden 《Quaternary Research》1982,17(2):241-257

The Christensen Mastodon Site, located in central Indiana, contains a rich assemblage of vertebrates (including mastodon, caribou, and giant beaver), invertebrates, and plant macrofossils in situ in lake and bog sediments of late-glacial age. Studies of pollen and plant macrofossils suggest the existence of open, white spruce-dominated boreal forests from >; 14,000 yr B.P. to ca. 13,000 yr B.P. The regional decline of spruce, local occurrence of black spruce, white spruce, and larch, immigration of many hardwood taxa (e.g., ash, oak, elm), and the initiation of bog development are recorded beginning about 13,000 yr B.P. Recent reconstructions of late-glacial and early postglacial vegetational changes provide a context for understanding the disappearance of mastodons. The dramatic and rapid restriction of boreal forests along the retreating ice margin from 11,000 to 9000 yr B.P. may have caused a substantial reduction of mastodon populations. A diminished population would be more susceptible to small-scale, stochastic events such as short-term extremes of weather, outbreaks of disease, or predation pressure from paleoindian hunters.  相似文献   

Deep-water fan-channel conglomerates of Late Cretaceous age, southern Chile     

R. D. WINN  JR  R. H. DOTT  JR 《Sedimentology》1979,26(2):203-228

The exceptionally well exposed Lago Sofia conglomerate and sandstone lenses in the Upper Cretaceous Cerro Toro Formation of southern Chile are interpreted as the channel and channel margin facies of a deep-sea fan. The north-to-south oriented channels formed on an elongate fan in a narrow retroarc basin between a rising cordillera to the west and the South American craton to the east. The great length of some of the channels (> 120 km) seems to reflect the long duration (> 30 m.y.) and stable nature of the basin. Enclosing the lenses is the fine-grained Cerro Toro Formation which represents overbank turbidite flows and hemipelagic sedimentation on levee and levee flank areas. Foraminiferal assemblages suggest deposition in 1000-2000 m of water. Most of the conglomerate has features developed by tractive currents (parallel- and cross-stratified conglomerate). Most is moderately well sorted, imbricated, and has parallel to inclined stratification; large-scale dunes up to 4 m high are exposed. Typical sediment, gravity flow structures and bedding styles (e.g. pebbly mudstones, graded conglomerate, giant flutes) are not as common in the channel deposits as are tractive features. Tractive features in the gravels apparently were developed by rolling, sliding, and saltation as the bed-load component of highly turbulent, moderate- to low-density turbidity currents flowing in a confined channel. Graded-to-massive conglomerates appear to have been deposited rapidly from fully turbulent flows; diamictites were deposited from debris flows in which fluid viscosity, yield strength, and buoyancy of the fluid were dominant. The three major conglomerate classes recognized do not occur in a systematic manner; vertical and lateral heterogeneity is the rule.  相似文献   

Stadial subdivisions of early Pleistocene glaciations in central United States - a developing chronology     

WAKEFIELD DORT JR. 《Boreas: An International Journal of Quaternary Research》1972,1(1):55-61

Recently recognized field evidence clearly indicates that both the Nebraskan and Kansan Glaciations are divisible into stades on the basis of a stratigraphic record of ice-margin fluctuations. Two Nebraskan stades and three Kansan stades have been identified; it is suggested that others will be found. Recognition of multiple stades requires a thorough review of all Early Pleistocene stratigraphic and paleontologic age assignments applied in the American Midwest.  相似文献