Megabenthic diversity patterns and community structure of the Blanes submarine canyon and adjacent slope in the Northwestern Mediterranean: a human overprint?     

Eva Ramirez-Llodra  Joan Baptista Company  Francisco Sardà  & Guiomar Rotllant 《Marine Ecology》2010,31(1):167-182

The composition and structure of megabenthic communities in the Blanes canyon and adjacent open margin (Northwestern Mediterranean) were studied. The aim was to assess the effect of the canyon and commercial fishing intensity on the community composition and structure of benthic megafauna by (i) describing the megabenthic community composition, (ii) quantifying faunal abundance and biomass and (iii) describing community structure with MDS analyses and biodiversity indices. The results are compared between three sites (canyon head, canyon wall and open margin) located between 435 m and 700 m. Samples were collected using a commercial bottom trawl between April 2003 and March 2004. These sites are exploited by the local fishing fleet that targets the rose shrimp Aristeus antennatus . A total of 131 megabenthic species were identified from the three sites, with fishes and decapod crustaceans being the most speciose, most abundant and of higher biomass. The species richness, abundance and biomass of non-crustacean invertebrates were low. There were no significant differences in total abundance and biomass between the three sites. However, community structure analysis suggests that the open margin community is significantly different from the canyon head and canyon wall, with a lower species richness, lower diversity and lower evenness. The open margin community also reflects a higher degree of disturbance compared to the two canyon habitats. The results indicate that there is a canyon effect on the community structure of benthic megafauna, but this may be modulated by differing fishing pressure, which adds an additional factor to margin heterogeneity.  相似文献   

Propagation anomalies in Northwestern Italy by inversion of teleseismic residuals     

M. Cattaneo  C. Eva 《地学学报》1990,2(6):577-584

Travel-time residuals of teleseismic P waves were analysed in order to elucidate the crust–upper mantle structure in Northwestern Italy, and the Western Alpine Arc. Using digital data obtained from both fixed seismograph networks operating in NW Italy (notably Liguria–Piedmont) and temporary arrays with the aid of cross-correlation techniques reliable travel-time residuals were calculated which were then inverted to obtain models of propagation anomalies. The reliability of the inversion procedure was tested using synthetic data. The model thus obtained appears to be stable and shows strong lateral heterogeneities at a litho–asthenospheric level; in particular, it confirms the high velocity contrast caused by the ‘Ivrea Body’ in the shallower layers and the presence of Alpine ‘roots’ reaching down to at least 200 km. A statistical analysis performed on the propagation times of rays crossing the resulting four-layered model reveals rms below 0.1 s.  相似文献   

A siliceous chrysophycean cyst-based pH transfer function for Central European lakes   总被引：2，自引：0，他引：2  

Eva Facher  Roland Schmidt 《Journal of Paleolimnology》1996,16(3):275-321

The surface sediments of 50 Central European low to high mountain, acid-sensitive lakes were examined for chrysophycean stomatocysts. One hundred and twenty sic siliceous stomatocyst morphotypes were differentiated by using scanning electron microscope (SEM), counted and illustrated (light microscopy and SEM). Canonical Correspondence Analysis (CCA) showed that pH is the most important measured variable in explaining the cyst distributions, with a strong correlation to the first axis (r²=-0.78). Simple Weighted Averaging (WA) regression and calibration was performed to generate a transfer function for lake water pH. Finally, the transfer function was evaluated by reconstructing pH for a short annually laminated and ¹³⁷Cs dated core from Lake Plené, a strongly acid lake, in the Bohemian Forest. A comparison of the measured and inferred pH values indicates that the model has good predictive power. The cyst-inferred pH and the diatom-inferred pH both indicate that pH was low during the 1970s and that the lake has experienced recovery in recent years.  相似文献   

A statistical-mechanics model of ordering in aluminosilicate solid solutions     

Eva R. Myers 《Physics and Chemistry of Minerals》1998,25(6):465-468

A statistical-thermodynamic approximation for order-disorder phase transitions in aluminosilicate solid solutions is presented. The approximation involves estimating the number of configurations with long range order parameter Q and short range order parameter σ, using an approximation to the probability that a configuration with the correct amount of long range order will also have the correct amount of short range order. This estimate is then used to give a free energy F(Q, σ, x, T), where x is the concentration of Al in the structure, and hence quantities such as T _c (x) are estimated. The predictions of the model for T _c (x) and the critical concentration x _c at which T _c falls to zero are shown to be in good agreement with the results of Monte Carlo simulations. Received: 14 May 1997 / Revised, accepted: 2 June 1997  相似文献   

Spatio-temporal variations in reproductive patterns and population structure of Pasiphaea multidentata (Decapoda: Caridea) in the Blanes canyon and adjacent margin, North-western Mediterranean Sea     

Eva Ramirez-Llodra  Joan B. Company  Mercedes Camps  & Guiomar Rotllant 《Marine Ecology》2007,28(4):470-479

Pasiphaea multidentata is a deep‐water caridean shrimp fished in the Mediterranean in association with the commercially exploited red‐shrimp Aristeus antennatus. A previous study describes seasonality in the reproductive pattern of P. multidentata using external morphological parametres. This study assesses the spatio‐temporal variations in the population structure, sex ratio, ovary cycle and gametogenesis of P. multidentata from three different fishing grounds in the Blanes canyon and adjacent margin (North‐western Mediterranean) over an annual cycle. The oogenetic pattern of this species is typical of a caridean shrimp. There is a pool of previtellogenic oocytes at all times that develop from the periphery of the gonad towards the centre during maturation. Previtellogenic oocytes grow to approximately 200 μm before undergoing vitellogenesis. The vitellogenic oocytes are surrounded by a monolayer of accessory cells. The maximum size observed for a mature oocyte was 1420 μm. The oocyte‐size distribution confirmed the seasonal reproductive pattern of this species; in winter, the ovaries contained mainly previtellogenic oocytes, some of which start maturing in spring, resulting in a slightly bimodal distribution. In summer, the vitellogenic oocytes reach approximately 1000 μm and in late autumn the ovaries are fully mature and ready to spawn. There were no significant differences in the reproductive and population structure patterns of P. multidentata among the three sites, suggesting that the population’s distribution is not affected by the geomorphology of the area, in particular the presence of the canyon. The populations are dominated by females at all sites and all seasons, with the arrival of juveniles in spring. The seasonal variations in the reproduction and recruitment of P. multidentata and the lack of spatial segregation within the population are discussed in terms of the species’ known biology, the effects of canyons in energy supply to the deep‐sea floor and the relationships of this species with the red‐shrimp A. antennatus.  相似文献   

Horse mackerel egg identification using DNA methodology     

Nikoletta Karaiskou  Alexander Triantafyllidis  Paula Alvarez  Placida Lopes  Eva Garcia-Vazquez  & Costas Triantaphyllidis 《Marine Ecology》2007,28(4):429-434

Egg identification in plankton samples is usually needed for purposes of stock assessment. Until recently, only morphological characters were used for identifying the eggs of different fish species. Late developmental stages are easily distinguishable due to pigmentation as well as egg and oil globule size range. However, for early stages, these characteristics are difficult to be discriminated and may overlap with other species. European horse mackerel species (Trachurus trachurus, T. mediterraneus, T. picturatus) overlap significantly in their spawning areas in some European waters. Because of the fact that their eggs are morphologically similar, genetic methodologies are needed to identify eggs and larvae to species correctly. In the present study, formalin‐ and ethanol‐preserved eggs were tested to estimate the efficacy of genetic methodologies for species identification of eggs when different preservatives are used. A 370‐bp fragment of cytochrome b was successfully amplified followed by restriction fragment analysis with two restriction enzymes aiming to identify the eggs to species. Horse mackerel egg identification was accomplished with the maximum success in ethanol‐preserved eggs. However, it seems that various preservatives had different effects on the DNA quality of eggs as genetic identification was less successful in formalin‐preserved eggs. Preserving in ethanol a part of the eggs obtained in plankton surveys is suggested for purposes of accurate genetic identification, even if their morphological features are distorted in time.  相似文献   

Mechanisms of imposex induction in the mud snail, Ilyanassa obsoleta: TBT as a neurotoxin and aromatase inhibitor     

Eva Oberdrster  Patricia McClellan-Green 《Marine environmental research》2002,54(3-5)

The occurrence of imposex, imposition of male sex characteristics on female snails, has been extensively documented throughout the world. Tributyltin (TBT) and other organotins have been causally linked to imposex induction at levels as low as 2 ng/l. There are several proposed mechanisms of action. First, TBT has been shown to be neurotoxic and to accumulate in snail ganglia. Peptide hormones control sexual differentiation in gastropods, and one hypothesis is that TBT acts as a neurotoxin to abnormally release the peptide hormone Penis Morphogenic Factor (PMF). However, PMF has not been characterized to date. The neuropeptide APGWamide significantly induces imposex in the mud snail, Ilyanassa obsoleta, at 10⁻¹⁶ moles sub-cutaneous (SQ) injection over 2 weeks, and could be the PMF in this species. A second hypothesis is that TBT inhibits aromatase activity leading to increased testosterone levels and decreased estradiol. In vitro studies with snail digestive gland microsomes showed that TBT-dosed snails not exhibiting imposex had a 52% reduction in aromatase activity. Although the role of vertebrate sex steroids is not known in gastropods, it is possible that the combination of changes in peptide and steroid hormones may lead to imposex induction at extremely low doses of TBT.  相似文献   

Variations of mixed layer properties in the Norwegian Sea for the period 1948-1999     

J. Even Ø. Nilsen  Eva Falck 《Progress in Oceanography》2006,70(1):58-90

The mixed layer of the ocean and the processes therein affect the ocean’s biological production, the exchanges with the atmosphere, and the water modification processes important in a climate change perspective. To provide a better understanding of the variability in this system, this paper presents time series of the mixed layer properties depth, temperature, salinity, and oxygen from Ocean Weather Station M (OWSM; 66° N,2° E) as well as spatial climatologies for the Norwegian Sea. The importance of underlying mechanisms such as atmospheric fluxes, advective signals, and dynamic control of isopycnal surfaces are addressed. In the region around OWSM in the Norwegian Atlantic Current (NwAC) the mixed layer depth varies between ∼20 m in summer and ∼300 m in winter. The depth of the wintertime mixing here is ultimately restrained by the interface between the Atlantic Water (AW) and the underlying water mass, and in general, the whole column of AW is found to be mixed during winter. In the Lofoten Basin the mean wintertime mixed layer reaches a depth of ∼600 m, while the AW fills the basin to a mean depth of ∼800 m. The temperature of the mixed layer at OWSM in general varies between 12 °C in summer and 6 °C in winter. Atmospheric heating controls the summer temperatures while the winter temperatures are governed by the advection of heat in the NwAC. Episodic lateral Ekman transports of coastal water facilitated by the shallow summer mixed layer is found important for the seasonal salinity cycle and freshening of the northward flowing AW. Atmospheric freshwater fluxes have no significant influence on the salinity of the AW in the area. Oxygen shows a clear annual cycle with highest values in May-June and lowest in August-September. Interannual variability of mixed layer oxygen does not appear to be linked to variations in any of the physical properties of the mixed layer.  相似文献   

Total hydrocarbons,polycyclic aromatic hydrocarbons and synthetic organic compounds in the Hard shell clam, Mercenaria mercenaria, purchased at commercial seafood stores     

Richard J. Pruell  Eva J. Hoffman  James G. Quinn 《Marine environmental research》1984,11(3):163-181

An analytical method for the determination of polycyclic aromatic h hydrocarbons (PAHs) and substituted benzotriazoles in clams was developed using a combination of silica gel and Sephadex chromatography to isolate these compounds from large concentrations of polyolefinic hydrocarbons. The concentrations of total hydrocarbons, PAHs and substituted benzotriazoles were measured in hard shell clams (Mercenaria mercenaria) purchased from Rhode Island seafood stores. The levels of total hydrocarbons, PAHs and substituted benzotriazoles in these clams were generally higher than the concentrations found in clams collected from a lower Narragansett Bay control location. The significance of these findings on the health of consumers is unknown at this time because human health standards or alert levels for these compounds in seafoods have not been established. However, this study illustrates that contaminants entering Narragansett Bay from a variety of sources may eventually make their way to commercial outlets.  相似文献   

Adjusted Daily Rainfall and Snowfall Data for Canada     

Xiaolan L. Wang  Hong Xu  Budong Qian  Yang Feng  Eva Mekis 《大气与海洋》2017,55(3):155-168

This article documents how Environment and Climate Change Canada’s Adjusted Daily Rainfall and Snowfall (AdjDlyRS) dataset was developed. The adjustments include (i) conversion of ruler measurements of snowfall to its water equivalent using a previously developed snow water equivalent (SWE) ratio map for Canada; (ii) corrections for gauge-related issues including undercatch and evaporation caused by wind effects and gauge-specific wetting loss, as well as for trace precipitation amounts, using previously developed procedures for Canada. Various data flags (e.g., accumulation flags) were also treated. This dataset contains all Canadian stations reporting daily rainfall and snowfall for which we have metadata to implement the adjustments. The length of the data record varies from one station to another, starting as early as 1840. The results show that the original unadjusted total precipitation data in Environment and Climate Change Canada’s digital archive underestimate the total precipitation in northeastern Canada by more than 25% and by about 10–15% in most of southern Canada. Such large underestimates make the original data unsuitable for water availability and/or balance studies or for numerical model validation, among many other applications. The use of the assumed 10:1 SWE ratio for the archived total precipitation data is the primary cause of the underestimate, which is most severe in northeastern Canada. The trace correction adds 5–20% to precipitation values in northern Canada but less than 5% in southern Canada. The gauge-related corrections do not show an organized spatial pattern but add 5–10% to the precipitation at 312 stations. Long runs (≥3 months) of miscoded missing values were also identified and corrected.

The latest version of the AdjDlyRS dataset is available from the Canadian Open Data Portal; currently it is version 2016, which contains 3346 stations and covers the period from station inception to February 2016. This dataset is suitable for producing gridded precipitation datasets, as well as other applications.  相似文献