Intersexuality in crustaceans: genetic, individual and population level effects   总被引：1，自引：0，他引：1  

Ford AT  Sambles C  Kille P 《Marine environmental research》2008,66(1):146-148

Scientists investigating toxicants such as endocrine disrupting chemicals (EDCs) at the cellular at the sub-cellular level are often faced with criticisms as to how these effects can be extrapolated to the level of individuals and their populations. This report aims to provide an overview of the studies undertaken on crustacean model, Echinogammarus marinus LEACH (AMPHIPODA), and intersex phenotypes, at the individual and population levels, and provide additional emergent data at the genomic level. These, normal and intersex, males and females have been investigated by cross-hybridisation microarray analysis and specific sexually dimorphic genes and corresponding properties identified between each sexual phenotype. The morphology, physiology and histology of these intersexes have been investigated in detail and a number of reproductive costs have been identified including reduced fecundity and fertility. These costs have been incorporated into a population model and simulated over a ten-year period to ascertain how different levels of intersexuality affect the stability of populations. Based on the information gained through study of intersex models (with known endocrine dysfunction) together with the substantial quantity of historical data relating to effects of chemicals on amphipod fecundity, growth and mortality, the development of appropriate biomarkers is nearer to being assessed from the level of genes to that of the population.  相似文献   

Circular plumes in Lake Pontchartrain estuary under wind straining     

Chunyan Li  Nan Walker  Aixin Hou  Ioannis Georgiou  Harry Roberts  Ed Laws  J. Alex McCorquodale  Eddie Weeks  Xiaofeng Li  Jessica Crochet 《Estuarine, Coastal and Shelf Science》2008

Circular shaped density plumes of low turbidity, low fecal indicator (Escherichia coli and enterococci) concentrations, and high salinity have been observed near the Industrial Canal in Lake Pontchartrain, north of the City of New Orleans. A conceptual model in polar coordinates and a numerical model are developed, together with data analysis, to illustrate the dense plume. It is demonstrated that the northward expansion of the plume occurs under northerly winds. The northward expansion of the plume occurs under northerly winds that drive downwind flow at the surface and upwind radial flow at the bottom. Northerly wind-induced straining, similar to tidal straining, promotes vertical stratification. As a result, the water becomes stratified near a thin bottom layer (<1 m), within which density currents are facilitated. The stability of the stratified plume suppresses wind-induced turbulent mixing inside the plume. The bottom water outside of the plume is more effectively stirred by the wind, the result being that the suspended sediment concentration outside of the plume area is much higher than inside. This contrast in mixing makes the plume visible from the surface by satellites even though the stratification is at the bottom. Laterally, wind stress produces a torque (vorticity) in areas of non-uniform depth such that upwind flow is developed in deep water and downwind flow in shallow water. The continuity requirement produces an upwind flow along the axis of the Industrial Canal (IC). The upwind flow is balanced by the downwind flow over the shallower peripheral areas along the coast.  相似文献   

Silent ships do not always encounter more fish: comparison of acoustic backscatter recorded by a noise-reduced and a conventional research vessel     

De Robertis  Alex; Hjellvik  Vidar; Williamson  Neal J.; Wilson  Christopher D. 《ICES Journal of Marine Science》2008,65(4):623-635

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Petrogenesis of Miller Range 07273, a new type of anomalous melt breccia: Implications for impact effects on the H chondrite asteroid          下载免费PDF全文

Alex M. Ruzicka  Melinda Hutson  Jon M. Friedrich  Mark L. Rivers  Michael K. Weisberg  Denton S. Ebel  Karen Ziegler  Douglas Rumble III  Alyssa A. Dolan 《Meteoritics & planetary science》2017,52(9):1963-1990

Miller Range 07273 is a chondritic melt breccia that contains clasts of equilibrated ordinary chondrite set in a fine‐grained (<5 μm), largely crystalline, igneous matrix. Data indicate that MIL was derived from the H chondrite parent asteroid, although it has an oxygen isotope composition that approaches but falls outside of the established H group. MIL also is distinctive in having low porosity, cone‐like shapes for coarse metal grains, unusual internal textures and compositions for coarse metal, a matrix composed chiefly of clinoenstatite and omphacitic pigeonite, and troilite veining most common in coarse olivine and orthopyroxene. These features can be explained by a model involving impact into a porous target that produced brief but intense heating at high pressure, a sudden pressure drop, and a slower drop in temperature. Olivine and orthopyroxene in chondrule clasts were the least melted and the most deformed, whereas matrix and troilite melted completely and crystallized to nearly strain‐free minerals. Coarse metal was largely but incompletely liquefied, and matrix silicates formed by the breakdown during melting of albitic feldspar and some olivine to form pyroxene at high pressure (>3 GPa, possibly to ~15–19 GPa) and temperature (>1350 °C, possibly to ≥2000 °C). The higher pressures and temperatures would have involved back‐reaction of high‐pressure polymorphs to pyroxene and olivine upon cooling. Silicates outside of melt matrix have compositions that were relatively unchanged owing to brief heating duration.  相似文献   

Study of air-ventilated cavity under model hull on water surface     

Konstantin I. Matveev  Tyrel J. Burnett  Alex E. Ockfen 《Ocean Engineering》2009,36(12-13):930-940

The use of air cavities beneath ship hulls can lead to significant drag reduction. A study of air-ventilated cavities under a simplified hull has been undertaken. Experiments with a 56-cm-long stepped-hull model were carried in an open-surface water channel at flow velocities 28–86 cm/s. The air-cavity parameters were measured at different model positions. Different cavity forms, a strong growth of the cavity length with the flow velocity, and an optimal trim angle for the largest air-cavity area were identified. Numerical studies were conducted using a linear potential-flow method and the finite-volume viscous code Fluent. The computationally inexpensive three-dimensional potential-flow modeling predicted air-cavity shapes and provided qualitative agreement with the measured average length of the air cavity. Two-dimensional viscous modeling reasonably predicted macroscopic features and viscous effects in the air-cavity flow, while exaggerated the mixed-phase flow regions.  相似文献   

Ecological assessment to detect imminent change in coral reefs of Admiral Cockburn Land and Sea National Park,Turks and Caicos Islands     

Angela Dikou  Colin Ackerman  Carly Banks  Alex Dempsey  Michael Fox  Meagan Gins  Patricia Hester  Adam Parnes  Stephanie Roach  Jessica Rohde  Cliff Spital  Mackai Tapleshay  Luke Thomas 《Marine Ecology》2009,30(4):425-436

Coral reefs of the Turks and Caicos Islands (TCIs) (Caribbean Sea) constitute some of the few pristine coral reef systems in the world and play a crucial role in the islands’ economy because they support rich fisheries catches and tourism development. Ambitious development plans involving increase in fishing and tourism pressures are about to bring changes in coastal zone resources of the TCIs associated with increased sediments and nutrients and reduced predation by herbivorous fish on coral reefs. Understanding change is critical when attempting to protect the resources that these coral reefs support and to adopt proper management strategies. Yet, an environmental assessment program to detect imminent human‐induced changes on the surrounding reefs of the TCIs is lacking. Thus, (i) we obtained baseline data on benthic composition and coral community structure at seven reef sites of representative reefs of the TCIs within the Admiral Cockburn Land and Sea National Park (ACLSNP) of South Caicos Island and (ii) performed a priori statistical power analysis to calculate replication requirements for safely and confidently detecting small (δ = 0.1), medium (δ = 0.3), and large (δ = 0.5) effect sizes for a number of relevant to anticipated changes, univariate, benthic indices and for power β = 0.95. The platforms of the margin reefs studied (9–12 m depth) appeared rather variable regarding benthic composition but quite homogeneous regarding hard coral community structure. Mean percent cover of algal functional groups was 0.1 ± 0.3 (mean ± sd) percent for coralline algae and Halimeda, 0.1 ± 0.6 (mean ± sd) percent for macroalgae, 21.7 ± 33 (mean ± sd) percent for turf algae and 4.8 ± 4.0 (mean ± sd) percent for hard coral cover. The dominant benthic component, however, was carbonate substrate (mean ± sd = 30.4 ± 34.3), thus indicating an accreting reef framework. Mean hard coral density, colony size and recruit density were 5.5 ± 1.8 (mean ± sd) corals per 20‐m line transect, 13.0 ± 2.3 (mean ± sd) cm maximum colony diameter, and 1.3 ± 1.4 (mean ± sd) recruits per square foot, respectively. Due to high natural variance, hard coral colony size and density were practically the most sensitive indices in detecting even small size changes on benthos. Also, the geometric mean of log‐transformed colony size‐frequency distributions of the most abundant hard coral taxa, i.e. Montastrea annularis, Agaricia spp., Siderastrea spp. and Porites asteroides were practically sensitive for the same purpose. We hope that the study will optimize the spatial component of a necessary environmental impact assessment program on coral reefs of the TCIs once the natural spatial variability of the system has been assessed and sensitive, benthic, univariate indices have been identified for representative reference coral reef sites of the TCIs.  相似文献   

Hydro-acoustic remote sensing of benthic biological communities on the shallow South East Australian continental shelf     

Alex Rattray  Daniel Ierodiaconou  Laurie Laurenson  Shoaib Burq  Marcus Reston 《Estuarine, Coastal and Shelf Science》2009

Information regarding the composition and extent of benthic habitats on the South East Australian continental shelf is limited. In this habitat mapping study, multibeam echosounder (MBES) data are integrated with precisely geo-referenced video ground-truth data to quantify benthic biotic communities at Cape Nelson, Victoria, Australia. Using an automated decision tree classification approach, 5 representative biotic groups defined from video analysis were related to hydro-acoustically derived variables in the Cape Nelson survey area. Using a combination of multibeam bathymetry, backscatter and derivative products produced highest overall accuracy (87%) and kappa statistic (0.83). This study demonstrates that decision tree classifiers are capable of integrating variable data types for mapping distributions of benthic biological assemblages, which are important in maintaining biodiversity and other system services in the marine environment.  相似文献   

Shallow-water imaging multibeam sonars: A new tool for investigating seafloor processes in the coastal zone and on the continental shelf   总被引：8，自引：1，他引：8  

John E. Hughes Clarke  Larry A. Mayer  David E. Wells 《Marine Geophysical Researches》1996,18(6):607-629

Hydrographic quality bathymetry and quantitative acoustic backscatter data are now being acquired in shallow water on a routine basis using high frequency multibeam sonars. The data provided by these systems produce hitherto unobtainable information about geomorphology and seafloor geologic processes in the coastal zone and on the continental shelf.Before one can use the multibeam data for hydrography or quantitative acoustic backscatter studies, however, it is essential to be able to correct for systematic errors in the data. For bathymetric data, artifacts common to deep-water systems (roll, refraction, positioning) need to be corrected. In addition, the potentially far greater effects of tides, heave, vessel lift/squat, antenna motion and internal time delays become of increasing importance in shallower water. Such artifacts now cause greater errors in hydrographic data quality than bottom detection. Many of these artifacts are a result of imperfect motion sensing, however, new methods such as differential GPS hold great potential for resolving such limitations. For backscatter data, while the system response is well characterised, significant post processing is required to remove residual effects of imaging geometry, gain adjustments and water column effects. With the removal of these system artifacts and the establishment of a calibrated test site in intertidal regions (where the seabed may be intimately examined by eye) one can build up a sediment classification scheme for routine regional seafloor identification.When properly processed, high frequency multibeam sonar data can provide a view of seafloor geology and geomorphology at resolutions of as little as a few decimetres. Specific applications include quantitative estimation of sediment transport rates in large-scale sediment waves, volume effects of iceberg scouring, extent and style of seafloor mass-wasting and delineation of structural trends in bedrock. In addition, the imagery potentially provides a means of quantitative classification of seafloor lithology, allowing sedimentologists the ability to examine spatial distributions of seabed sediment type without resorting to subjective estimation or prohibitively expensive bottom-sampling programs. Using Simrad EM100 and EM1000 sonars as an example, this paper illustrates the nature and scale of possible artifacts, the necessary post-processing steps and shows specific applications of these sonars.  相似文献   

绿色撒哈拉     

Alex Stone  胡德良 《海洋地质前沿》2007,23(1):41-41

占非洲面积将近三分之一的撒哈拉沙漠一度是热带稀树大草原,野生动植物种类丰富,充满鱼类的湖泊星罗棋布,而且有许多古人类生活在那里。“在约5 550~10 500年以前,撒哈拉是理想的生存地带,”斯特凡·克洛普林这样说过。克洛普林是德国科隆大学的地质考古学家,在过去的30年里,他  相似文献   

Challenger at sea. A SHIP THAT REVOLUTIONIZED EARTH SCIENCE by Kenneth J. Hsu. Princeton University Press,Princeton, 1992. No. of pages: 417. Price: £20.00 ($35.00) (hardback). ISBN 0 691 08735 0.     

Alex Maltman 《Geological Journal》1994,29(2):191-191

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