Indications of a climate effect on Mediterranean fisheries     

Evangelos Tzanatos  Dionysios E. Raitsos  George Triantafyllou  Stylianos Somarakis  Anastasios A. Tsonis 《Climatic change》2014,122(1-2):41-54

Using the Food and Agriculture Organization’s (FAO) Mediterranean capture fisheries production dataset in conjunction with global and Mediterranean sea surface temperatures, we investigated trends in fisheries landings and landings per unit of effort of commercially important marine organisms, in relation to temperature oscillations. In addition to the overall warming trend, a temperature shift was detected in the Mediterranean Sea in the late 1990s. Fisheries landings fluctuations were examined for the most abundant commercial species (59 species) and showed significant year-to-year correlations with temperature for nearly 60 % of the cases. From these, the majority (~70 %) were negatively related and showed a reduction of 44 % on average. Increasing trends were found, mainly in the landings of species with short life spans, which seem to have benefited from the increase in water temperature. Τhe effect of oceanic warming is apparent in most species or groups of species sharing ecological (e.g. small and medium pelagic, demersal fish) or taxonomic (e.g. cephalopods, crustaceans) traits. A landings-per-unit-of-effort (LPUE) proxy, using data from the seven Mediterranean European Union member states, also showed significant correlation with temperature fluctuations for six out of the eight species examined, indicating the persistence of temperature influence on landings when the fishing effect is accounted for. The speed of response of marine landings to the warming of the Mediterranean Sea possibly shows both the sensitivity and the vulnerable state of the fish stocks and indicates that climate should be examined together with fisheries as a factor shaping stock fluctuations.  相似文献   

Complex Site Effects in Thessaloniki (Greece): I. Soil Structure and Comparison of Observations with 1D Analysis   总被引：1，自引：0，他引：1  

Dimitrios?RaptakisEmail author  Konstantia?Makra  Anastasios?Anastasiadis  Kyriazis?Pitilakis 《Bulletin of Earthquake Engineering》2004,2(3):271-290

This paper presents a 2D model of the geological structure of Thessaloniki city and results of empirical and theoretical approaches for the evaluation of site response due to complex site effects. The construction of the 2D model is based on the available geophysical and geotechnical data in terms of the most important parameters needed to model site response. The well-known subsoil structure, despite the existence of some local uncertainties, gave the possibility to correlate the geometry and the dynamic properties of the 2D model with the results of site response determined from the analysis of one event in frequency and time domains and 1D numerical modelling. The study of site response shows the effect of the lateral variations on ground motion and suggests that the contribution of locally generated surface waves to the resonant peak may be important. In this case history, the limitations of the 1D approximation to simulate ground motion under complex soil conditions in both frequency and time domains are also shown. This paper lays the ground for a companion article dealing with 2D site effects.  相似文献   

Long-Term RST Analysis of Anomalous TIR Sequences in Relation with Earthquakes Occurred in Greece in the Period 2004–2013     

Alexander Eleftheriou  Carolina Filizzola  Nicola Genzano  Teodosio Lacava  Mariano Lisi  Rossana Paciello  Nicola Pergola  Filippos Vallianatos  Valerio Tramutoli 《Pure and Applied Geophysics》2016,173(1):285-303

Real-time integration of multi-parametric observations is expected to accelerate the process toward improved, and operationally more effective, systems for time-Dependent Assessment of Seismic Hazard (t-DASH) and earthquake short-term (from days to weeks) forecast. However, a very preliminary step in this direction is the identification of those parameters (chemical, physical, biological, etc.) whose anomalous variations can be, to some extent, associated with the complex process of preparation for major earthquakes. In this paper one of these parameters (the Earth’s emitted radiation in the Thermal InfraRed spectral region) is considered for its possible correlation with M ≥ 4 earthquakes occurred in Greece in between 2004 and 2013. The Robust Satellite Technique (RST) data analysis approach and Robust Estimator of TIR Anomalies (RETIRA) index were used to preliminarily define, and then to identify, significant sequences of TIR anomalies (SSTAs) in 10 years (2004–2013) of daily TIR images acquired by the Spinning Enhanced Visible and Infrared Imager on board the Meteosat Second Generation satellite. Taking into account the physical models proposed for justifying the existence of a correlation among TIR anomalies and earthquake occurrences, specific validation rules (in line with the ones used by the Collaboratory for the Study of Earthquake Predictability—CSEP—Project) have been defined to drive a retrospective correlation analysis process. The analysis shows that more than 93 % of all identified SSTAs occur in the prefixed space–time window around (M ≥ 4) earthquake's time and location of occurrence with a false positive rate smaller than 7 %. Molchan error diagram analysis shows that such a correlation is far to be achievable by chance notwithstanding the huge amount of missed events due to frequent space/time data gaps produced by the presence of clouds over the scene. Achieved results, and particularly the very low rate of false positives registered on a so long testing period, seems already sufficient (at least) to qualify TIR anomalies (identified by RST approach and RETIRA index) among the parameters to be considered in the framework of a multi-parametric approach to t-DASH.  相似文献   

A knowledge-based software for the preliminary design of seismically isolated bridges     

George C. Manos  Stergios A. Mitoulis  Anastasios G. Sextos 《Bulletin of Earthquake Engineering》2012,10(3):1029-1047

Seismic design of isolated bridges involves conceptual, preliminary and detailed structural design. However, despite the variety of commercial software currently available for the analysis and design of such systems, conceptual and preliminary design can prove to be a non-straightforward procedure because of the sensitivity of bridge response on the initial decisions made by the designer of the location, number and characteristics of the bearings placed, as well as on a series of broader criteria such as serviceability, target performance level and cost-effectiveness of the various design alternatives. Given the lack of detailed design guidelines to ensure, at this preliminary stage, compliance with the above requirements, a “trial and error” procedure is typically followed in the design office to decide on the most appropriate design scheme in the number and location of the bearing systems; the latter typically based on engineering judgment to balance performance with cost. To this end, the particular research effort aims to develop a decision-making system for the optimal preliminary design of seismically isolated bridges, assumed to respond as single degree of freedom (SDOF) systems. The proposed decision-making process is based on the current design provisions of Eurocode 8, but is complemented by additional criteria set according to expert judgment, laboratory testing and recent research findings, while using a combined cost/performance criterion to select from a database of bearings available on the international market. Software is also developed for the implementation of the system. The paper concludes with the application, and essentially the validation of the methodology and software developed through more rigorous MDOF numerical analysis for the case of a real bridge.  相似文献   

Numerical Modeling of the Long-Term Transport, Dispersion, and Accumulation of Black Sea Pollutants into the North Aegean Coastal Waters     

Kyriakos I. Kopasakis  Anastasios N. Georgoulas  Panagiotis B. Angelidis  Nikolaos E. Kotsovinos 《Estuaries and Coasts》2012,35(6):1530-1550

This study investigates the long-term capacity of the North Aegean coastal systems to transport and store conservative pollutants that originate from the Black Sea. Emphasis is placed on modeling the dispersion and accumulation of a passive tracer that represents a Black Sea pollutant (BSP) substance that continuously discharges from the Dardanelles exit into the North Aegean, for a long period of time (16?years). The effects of the Black Sea water (BSW) inflows, meteorological forcing, and seasonal stratification are assessed with a 3D hydrodynamic model (Estuary, Lake and Coastal Ocean Model), after validation with available field data. The salinity, water temperature, and discharge from the Dardanelles Strait are taken to be seasonally varied. According to the authors' best knowledge, the present paper constitutes the first numerical modeling attempt in the literature that apart from the long-term hydrodynamic characteristics that have also been studied in previous works, a suitable tracer is introduced in order to predict the long-term fate, distribution, and accumulation of pollutants that originate from the Black Sea into the North Aegean coastal regions. The overall results of the present investigation indicate that the BSP concentration is very high at the coastal waters of Thassos, Samothraki, and Limnos islands, as well as along the mainland coastal waters between Alexandroupolis and Strymonikos Gulf, during summer and autumn when strong water column stratification occurs. In general, the BSP concentration in the North Aegean surface waters reaches considerable high values (47?C58?% of the initial pollutant concentration at Dardanelles inflow) within 16?years. Even for depths more than 500?m the BSP concentration is still remarkable, slightly increasing with time. The increase of the BSP concentration with respect to time at various depths (from free surface up to 750?m) is also investigated.  相似文献   

Determination of 137Cs activities in surface sediments and derived sediment accumulation rates in Thessaloniki Gulf, Greece     

C. Tsabaris  V. Kapsimalis  G. Eleftheriou  M. Laubenstein  H. Kaberi  W. Plastino 《Environmental Earth Sciences》2012,67(3):833-843

Surficial and core samples collected from the eastern Thessaloniki Gulf, located in the NW Aegean Sea, were analyzed for their sedimentation rate and inventories of ¹³⁷Cs and ²¹⁰Pb. The study of the spatial radionuclide dispersion in the specific region is essential for the assessment of marine pollution levels. The sedimentation rates were calculated from the vertical distribution of ¹³⁷Cs and excess ²¹⁰Pb in the sediment cores. The spatial distribution of ¹³⁷Cs was studied with respect to sediment characteristics such as the grain size of the sample and the organic carbon content. The activity concentrations were measured by means of gamma ray spectrometry using HPGe detector for ¹³⁷Cs and gross alpha counting using alpha counter for ²¹⁰Pb. The average sedimentation rate along the sediment cores is characterized by a consistent pattern and varies from 0.18?±?0.02 to 0.22?±?0.03?cm?year^?1. The ¹³⁷Cs inventories varied from 205?±?15 to 602?±?39?Bq?m^?2, while the ²¹⁰Pb inventories of the studied cores exhibited average value of 140?±?9?Bq?m^?2. Elevated ¹³⁷Cs activities were observed compared to certain Mediterranean marine areas; however, they were lower than the reported values in the Black Sea.  相似文献   

Improving NWP through radar rainfall-driven land surface parameters: A case study on convective precipitation forecasting     

Anastasios Papadopoulos  Efthymios Serpetzoglou  Emmanouil Anagnostou 《Advances in water resources》2008

In this study we investigate the effect of forcing the land surface scheme of an atmospheric mesoscale model with radar rainfall data instead of the model-generated rainfall fields. The goal is to provide improved surface conditions for the atmospheric model in order to achieve accurate simulations of the mesoscale circulations that can significantly affect the timing, distribution and intensity of convective precipitation. The performance of the approach is evaluated in a set of numerical experiments on the basis of a 2-day-long mesoscale convective system that occurred over the US Great Plains in July 2004. The experimental design includes multiple runs covering a variety of forcing periods. Continuous data integration was initially used to investigate the sensitivity of the model’s performance in varying soil state conditions, while shorter time windows prior to the storm event were utilized to assess the effectiveness of the procedure for improving convective precipitation forecasting. Results indicate that continuous integration of radar rainfall data brings the simulated precipitation fields closer to the observed ones, as compared to the control simulation. The precipitation forecasts (up to 48 h) appear improved also in the cases of shorter integration periods (24 and 36 h), making this technique potentially useful for operational settings of weather forecasting systems. A physical interpretation of the results is provided on the basis of surface moisture and energy exchange.  相似文献   

Bacterial response to seasonal changes in labile organic matter composition on the continental shelf and bathyal sediments of the Cretan Sea     

Roberto Danovaro  Daniela Marrale  Antonio Dell'Anno  Norberto Della Croce  Anastasios Tselepides  Mauro Fabiano 《Progress in Oceanography》2000,46(2-4)

Bacterial abundance, biomass and cell size were studied in the oligotrophic sediments of the Cretan Sea (Eastern Mediterranean), in order to investigate their response to the seasonal varying organic matter (OM) inputs. Sediment samples were collected on a seasonal basis along a transect of seven stations (ranging from 40 to 1570 m depth) using a multiple-corer. Bacterial parameters were related to changes in chloroplastic pigment equivalents (CPE), the biochemical composition (proteins, lipids, carbohydrates) of the sedimentary organic matter and the OM flux measured at a fixed station over the deep basin (1570 m depth). The sediments of the Cretan Sea represent a nutrient depleted ecosystem characterised by a poor quality organic matter. All sedimentary organic compounds were found to vary seasonally, and changes were more evident on the continental shelf than in deeper sediments. Bacterial abundance and biomass in the sediments of the Cretan Sea (ranging from 1.02 to 4.59 × 10⁸ cells g⁻¹ equivalent to 8.7 and 38.7 μgC g⁻¹) were quite high and their distribution appeared to be closely related to the input of fresh organic material. Bacterial abundance and biomass were sensitive to changes in nutrient availability, which also controls the average cell size and the frequency of dividing cells. Bacterial abundance increased up to 3-fold between August '94 and February '95 in response to the increased amount of sedimentary proteins and CPE, indicating that benthic bacteria were constrained more by changes in quality rather than the quantity of the sedimentary organic material. Bacterial responses to the food inputs were clearly detectable down to 10 cm depth. The distribution of labile organic compounds in the sediments appeared to influence the vertical patterns of bacterial abundance and biomass. Cell size decreased significantly with water depth. Bacterial abundance and biomass were characterised by clear seasonal changes in response to seasonal OM pulses. The strong coupling between protein flux and bacterial biomass together with the strong bacterial dominance over the total biomass suggest that the major part of the carbon flow was channelled through the bacteria and the benthic microbial loop.  相似文献   

Meiofauna of the deep Eastern Mediterranean Sea: distribution and abundance in relation to bacterial biomass, organic matter composition and other environmental factors     

Roberto Danovaro  Norberto Della Croce  Anastasios Eleftheriou  Mauro Fabiano  Nadia Papadopoulou  Chris Smith  Anastasios Tselepides 《Progress in Oceanography》1995,36(4)

Quantitative information on the abundance and biomass of metazoan meiofauna was obtained from samples collected at 15 deep-sea stations in the Eastern Mediterranean Sea (533–2400m). Meiofaunal abundance was compared to bacterial biomass and other environmental factors such as the total sedimentary organic matter content, the concentrations of the main biochemical classes of organic compounds (i.e. proteins, carbohydrates and lipids) and to ATP. To estimate the sedimentation potential of primary organic matter, sediment bound chloroplastic pigment equivalents (CPE) were assayed. Meiofaunal density was very low ranging from 4 ind.10cm⁻² (Station A4, 1658m depth) to 290 ind.10cm⁻² (Station A12, 636m depth). Nematodes were the numerically dominant taxon (68% of total meiofauna) and were usually confined to the top 6cm of the sediments. Total meiofaunal biomass ranged from 2.78μgC 10cm⁻² (Station A4) to 598.34μgC 10cm⁻² (Station 15A). There was a significant decrease in the density of metazoan meiofauna with water depth. Bacterial biomass largely dominated the total biomass (as the sum of bacterial and meiofaunal biomass) with an average of 73.2% and accounted for 35.8% of the living biomass (as ATP carbon) whereas meiofaunal biomass accounted only for 6.56%. Bacterial biomass was significantly related to the DNA concentrations of the sediment. A significant correlation between ATP concentration and CPE content was also found. No correlations were found between meiofauna, ATP and CPE, or between meiofauna and bacterial parameters. The significant relationship between meiofaunal density and the ratio of labile organic matter/total organic matter indicates that deep-sea meiofauna inhabiting an extremely oligotrophic environment (such as the Eastern Mediterranean) may be more nutritionally dependent upon the quality than on the quantity of sedimentary organic matter.  相似文献   

Brittle-Ductile Transition and Hoek–Brown mi Constant of Low-Porosity Carbonate Rocks     

Tsikrikis  Anastasios  Papaliangas  Theodosios  Marinos  Vassilis 《Geotechnical and Geological Engineering》2022,40(4):1833-1849

Geotechnical and Geological Engineering - The mechanical behavior of low porosity carbonate rocks is investigated by a series of conventional triaxial compression tests performed at room...  相似文献