排序方式： 共有22条查询结果，搜索用时 843 毫秒
1.
Alkylphenolic compounds are present in estuarine and marine environments. They are moderately bioaccumulative, and oestrogenic to fish following three week, in vivo, exposures. The effects of prolonged exposure are, as yet, unclear. Sand goby (Pomatoschistus minutus) were exposed to measured concentrations of 4-tert-octylphenol (OP) in a 28-day, dose-ranging study, and a six month temporal response study. Following 28-days exposure to measured 31+/-6 or 101+/-47 microg l(-1) OP (mean+/-SD), immature male sand goby showed elevated vitellogenin (VTG) mRNA expression. Plasma alkali-labile phosphate concentrations were elevated in both sexes and were higher in females than males. Although measured OP concentrations were variable, they were significantly different for each treatment and a range of concentration-dependent effects were observed. The LC(50) for chronic OP exposure (8 weeks) was 29+/-6 microg l(-1), and both sexes demonstrated concentration and duration dependent increases in VTG mRNA expression. Exposure to 28+/-20 microg l(-1) OP (median+/-95% CI) for 6 months inhibited development of male nuptial colouration and sperm duct glands. These findings are discussed in relation to environmental concentrations of alkylphenols and ecological concerns. 相似文献
2.
Ross A. Brittain Arndt Schimmelmann David F. Parkhurst Christopher B. Craft 《Estuaries and Coasts》2012,35(2):633-645
Conservationists need to know the degree of habitat fidelity for species of conservation concern. Stable Isotope Analysis in R quantified the contribution of terrestrial vs. saltmarsh primary production sources to terrestrial passerine food webs from
four habitats of Sapelo Island, Georgia (USA), saltmarsh, maritime scrub–shrub, maritime broadleaf (oak), and maritime narrowleaf
(pine) forests, using δ
13C and δ
15N. Models suggested Northern Parula (Parula americana) in oak forests, White-eyed Vireos (Vireo griseus) in shrub, and Brown-headed Nuthatches (Sitta pusilla) in pine forests derived most of their food from habitats they occupied (53–100%). Saltmarsh provided 47–94% of Painted Bunting
(Passerina ciris) food sources, supporting previous findings by Springborn and Meyers (2005). Thus, Painted Bunting conservation in the Southeastern USA should focus on Springborn and Meyers’ suggestion of maritime
scrub–shrub habitat and forests with <75% canopy, >50% ground cover, and patches of shrubs that are within 700 m of saltmarsh. 相似文献
3.
Soils (n=250) were collected from ten salt and brackish-water marshes of North Carolina and analyzed for organic matter content by loss on ignition (LOI) and Kjeldahl nitrogen (KN). Total organic carbon and total nitrogen were determined on the same samples using an elemental CHN analyzer. Regression analyses indicated that LOI and KN were excellent estimators of organic C (R2=0.990) and total N(R2=0.986), respectively, in low clay content (0–11%) marsh soils containing a wide range of soil organic C (0.1–28%) and total N (0–1.6%). A quadratic equation best described the relationship between organic C and organic matter (Organic C=0.40 [LOI] +0.0025 [LOI]2) while a linear model accurately described the relationship between total N and Kjeldahl N (Total N=1.048 [KN]?0.010). The proportion of organic C in organic matter (C/OM) increased with increasing soil organic matter content, probably as a result of aging. Young marshes, which are characterized by low soil organic content contain C/OM ratios similar to emergent vegetation (40–45%). In old organic soils (70–80% organic matter), C/OM increased to 57–60% due to accumulation of reduced organic materials. 相似文献
4.
Matthiessen P Allen Y Bamber S Craft J Hurst M Hutchinson T Feist S Katsiadaki I Kirby M Robinson C Scott S Thain J Thomas K 《Marine environmental research》2002,54(3-5):645-649
This paper summarises results of the EDMAR programme which is investigating oestrogenic and androgenic endocrine disruption in UK coastal waters. Most of the data concern fish. Four species (flounder, viviparous blenny and two sand gobies) are experiencing feminisation in industrialised estuaries. In males this includes vitellogenin (VTG) synthesis, ovotestis induction and/or feminised sexual characteristics. Although reproductive success may be impaired in some cases, implications for fish populations are still unclear. Suspected causative contaminants include natural oestrogenic substances and synthetic oestrogen mimics. The majority of the oestrogenic activity is adsorbed to sediments, and routes of exposure may include benthic food chain transfer. Some natural androgenic substances are also being discharged to estuaries, but their activity appears low. 相似文献
5.
The paper summarizes a new type of second-moment closure, more elaborate in form than earlier versions but designed to satisfy the two-component limit to which turbulence reduces at a wall or at a sharp density interface. Because they are intrinsically realizable, closures of this type are believed to offer the prospects of a wider range of applicability than earlier schemes. They may also be expected to display better numerical stability. Several illustrative applications are provided including the downward directed warm jet, the stratified mixing layer and buoyancy affected grid-turbulence decay. Extension of the scheme to near wall flows appears possible without introducing empirical ‘wall-reflection’ terms, at least in flows parallel to walls. 相似文献
6.
Christopher Sanchez Evelyn E. Gaiser Colin J. Saunders Anna H. Wachnicka Nicholas Oehm Christopher Craft 《Journal of Paleolimnology》2013,49(1):45-66
Successfully rehabilitating drained wetlands through hydrologic restoration is dependent on defining restoration targets, a process that is informed by pre-drainage conditions, as well as understanding linkages between hydrology and ecosystem structure. Paleoecological records can inform restoration goals by revealing long-term patterns of change, but are dependent on preservation of biomarkers that provide meaningful interpretations of environmental change. In the Florida Everglades, paleohydrological hind-casting could improve restoration forecasting, but frequent drying of marsh soils leads to poor preservation of many biomarkers. To determine the effectiveness of employing siliceous subfossils in paleohydrological reconstructions, we examined diatoms, plant and sponge silico-sclerids from three soil cores in the central Everglades marshes. Subfossil quality varied among cores, but the abundance of recognizable specimens was sufficient to infer 1,000–3,000 years of hydrologic change at decadal to centennial resolution. Phytolith morphotypes were linked to key marsh plant species to indirectly measure fluctuations in water depth. A modern dataset was used to derive diatom-based inferences of water depth and hydroperiod (R2 = 0.63, 0.47; RMSE = 14 cm, 120 days, respectively). Changes in subfossil quality and abundances at centennial time-scales were associated with mid-Holocene climate events including the Little Ice Age and Medieval Warm Period, while decadal-scale fluctuations in assemblage structure during the twentieth century suggested co-regulation of hydrology by cyclical climate drivers (particularly the Atlantic Multidecadal Oscillation) and water management changes. The successful reconstructions based on siliceous subfossils shown here at a coarse temporal scale (i.e., decadal to centennial) advocate for their application in more highly resolved (i.e., subdecadal) records, which should improve the ability of water managers to target the quantity and variability of water flows appropriate for hydrologic restoration. 相似文献
7.
James M.L. Newhard Norman S. Levine Angelina D. Phebus Sarah Craft John D. Littlefield 《制图学和地理信息科学》2013,40(1):3-17
This article explores the integration of GIS technology with archaeological survey, focusing primarily on two case studies from central Anatolia, the Göksu Archaeological Project and the Avkat Archaeological Project. The methodology employed allows for expediency and accuracy in data recording, which enables refined analyses of anthropogenic and environmental phenomena. The approaches outlined in this article allowed the investigators to move from field observation to publication quality results within a single field day, usually within a four-hour window from initial field observation. The techniques described in the article are some of the geoinformatic applications that classical archaeology is implementing increasingly to develop a robust archaeoinformatic tool kit. 相似文献
8.
New evidence for widespread mass transport on the Northeast Newfoundland Shelf revealed by Olex single-beam echo sounding 总被引：5，自引：5，他引：0
John Shaw David J. W. Piper Thomas Skulski Michael J. Lamplugh Andrew Craft André Roy 《Geo-Marine Letters》2012,32(1):5-15
Based on Olex single-beam sounder data, multibeam sonar surveys, and sparse seismic reflection profiles, we recognize a large
area of anomalous bathymetry on the Northeast Newfoundland Shelf as having formed as a result of mass-transport processes.
Transported masses include (1) an arcuate ridge of deformed material with an area of 430 km2, which has moved distances of ~20 km; (2) a 70-km2 mass of deformed material displaced 50 km along a nearly horizontal track flanked by 90-m-high berms. The movement of these
and other sediment bodies has created a 150-m-high headwall escarpment extending 110 km along the north flank of the Notre
Dame glacial trough. In addition, a 35-km2 block of undeformed material has moved 5 km to the southeast, away from the headwall, creating a gap of the same dimensions,
while a smaller block of material originating in this vicinity has been displaced 24 km in the opposite direction, creating
a 20-m-deep groove on the seafloor. There is evidence for mass transport and headwall formation elsewhere on the Northeast
Newfoundland Shelf. Analysis of seismic reflection data indicates that the transported material most likely consists of stacked
Quaternary till sheets that overlie Cenozoic, Mesozoic and older sedimentary rocks. Given the very low gradients involved,
glaciotectonism is the most likely process to account for transport and deformation of the large sediment masses. However,
some mass transport may have resulted from submarine sliding away from the headwalls that were created by the glacial transport. 相似文献
9.
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
10.
Total nitrogen, phosphorus and organic carbon were compared in natural and transplanted estuarine marsh soils (top 30 cm) to assess nutrient storage in transplanted marshes. Soils were sampled in five transplanted marshes ranging in age from 1 to 15 yr and in five nearby natural marshes along the North Carolina coast. Dry weight of macroorganic matter (MOM), soil bulk density, pH, humic matter, and extractable P also were measured. Nutrient pools increased with increasing marsh age and hydroperiod. Nitrogen, phosphorus and organic carbon pools were largest in soils of irregularly flooded natural marshes. The contribution of MOM to marsh nutrient reservoirs was 6–45%, 2–22%, and 1–7% of the carbon, nitrogen and phosphorus, respectively. Rates of nutrient accumulation in transplanted marshes ranged from 2.6–10.0, 0.03–1.10, and 84–218 kmol ha?1yr?1 of nitrogen, phosphorus and organic carbon, respectively. Accumulation rates were greater in the irregularly flooded marshes compared to the regularly flooded marshes. Approximately 11 to 12% and 20% of the net primary production of emergent vegetation was buried in sediments of the regularly flooded and irregularly flooded transplanted marshes, respectively. Macroorganic matter nutrient pools develop rapidly in transplanted marshes and may approximate natural marshes within 15 to 30 yr. However, development of soil carbon, nitrogen and phosphorus reservoirs takes considerably longer. 相似文献