Exergy,ecosystem functioning and efficiency in a coastal lagoon: The role of auxiliary energy     

Antonio Pusceddu  Roberto Danovaro 《Estuarine, Coastal and Shelf Science》2009

Exergy, as the sum of energy and information contained in a given system due to living organisms, can act as a quality indicator of ecosystems. Here, we investigated the exergy of Marsala Lagoon (Mediterranean Sea), along with microbial (prokaryotic and heterotrophic nanobenthos) biomass, prokaryotic heterotrophic production and extracellular enzymatic activities, and the biochemical composition of sediment organic matter. The aim of the study was to assess the role of auxiliary energy (e.g. hydrodynamic stress) in the ecosystem functioning and efficiency of a ‘detritus sink’ lagoon. Samples were collected at sites characterized by contrasting hydrodynamic and trophic conditions. Exergy transfer through the benthic microbial loop was influenced by two main factors: (1) organic matter bioavailability; and (2) hydrodynamic forcing. At both sites, the values of total exergy were higher in summer than in winter, and the specific exergy decreased from winter to autumn, along with increasing auxiliary energy. Our data indicate that in coastal ‘detritus sink’ systems, auxiliary energy sources can have a crucial role in exergy transfer and ecosystem functioning through modifying the efficiency of transfer to higher trophic levels of the refractory organic detritus, which is otherwise lost by burial in the sediment. As coastal lagoons are often intensively modified by human activities, we conclude that maintenance of the natural hydrodynamic regimes is a key factor in the preservation of the functioning of lagoon ecosystems and of their provision of goods and services to humans.  相似文献   

A multidisciplinary study of the Cape Peloro brackish area (Messina, Italy): characterisation of trophic conditions, microbial abundances and activities     

Marcella Leonardi  Filippo Azzaro  Maurizio Azzaro  Gabriella Caruso  Monique Mancuso  Luis Salvador Monticelli  Giovana Maimone  Rosabruna La Ferla  Francesco Raffa  & Renata Zaccone 《Marine Ecology》2009,30(S1):33-42

In the framework of the VECTOR DIVCOST Project, a 2-year investigation was started in 2006, with the aim of testing the sensibility of microbial parameters to environmental changes and of assessing whether they can provide information about functional changes in the carbon cycle. The investigation was performed in the surface waters of two small brackish ponds (Ganzirri and Faro), located in the Cape Peloro transitional area (Sicily, Italy). The seasonal changes in both the microbial compartment [bacterioplankton, vibrios, exoenzymatic hydrolysis of proteins and polysaccharides, bacterial secondary production (HBP) and community respiration] and the trophic state of suspended matter [total suspended matter (TSM), particulate organic carbon (POC), particulate organic nitrogen (PON), C/N] were analysed in relation to the hydrological characteristics [temperature, salinity, oxygen, fluorescence, NH₄, NO₂, NO₃, PO₄]. Despite marked differences in the nutritional input and the diversification in both carbon budget and trophic level, the two ponds show similar trends in many of the investigated factors, hardly influenced by seasonal variations. Temporally coupled trends were observed for some parameters (enzyme activities, vibrios abundances, respiratory activity), whereas others (POC, PON, heterotrophic bacterial production, bacterioplankton) showed a seasonal shift between the two lakes. The different behaviour found for the some biotic parameters suggests that their response to environmental conditions may be modulated differently between the two lakes, which, despite their spatial proximity and reciprocal connection, do not always show contemporaneous functional processes.  相似文献   

Optical observations of transient luminous events associated with winter thunderstorms near the coast of Israel   总被引：1，自引：0，他引：1  

Yoav Yair  Colin Price  Michal Ganot  Eran Greenberg  Roy Yaniv  Baruch Ziv  Yosef Sherez  Adam Devir  Jo'zsef Br  Gabriella Stori 《Atmospheric Research》2009,91(2-4):529-537

We report the results of two observation campaigns conducted during the Northern Hemisphere winters of 2005–6 and 2006–7 aiming to detect transient luminous events (TLEs) above winter thunderstorms in the vicinity of Israel and the eastern coastline of the Mediterranean Sea. In 10 out of 31 different observation nights we detected 66 events: 56 sprites and 10 Elves. The detection ranges varied from 250 to 450 km. Sprites were found to be produced by active cells with a vertical dimension of 5–9 km and cloud top temperature ~ − 40 °C, embedded in a much larger matrix of stratiform precipitating cloudiness. This configuration closely resembles the conditions for winter sprites in the Hokuriku region of Japan. Synchronized with the optical observations, ELF data were recorded at two observation stations in Israel and Hungary in order to qualify and quantify parameters of the parent lightning discharge associated with the TLEs. These stations are located 500 km and 2100 km respectively from the Eastern Mediterranean Sea, where most TLEs occur. Among the optically observed TLE events, we found that all the ELF signals were produced solely by positive cloud-to-ground flashes (+ CGs), most of which were recorded in Israel (88%) and Hungary (77%). Calculation of the Charge Moment Change showed average values of 1400 ± 600 C km, with some extreme events exceeding 3500 C km. The average time delay between the ELF transient of the parent + CG and the observed sprites was 55 ms, with shorter delays for column sprites (42 ± 34 ms) compared to carrot sprites (68 ± 34). Furthermore, based on the ELF data, there were no early identifiable precursors to TLE occurrence in the regional lightning activity. From the spatial formation of the observed columniform sprites, we propose that columniform sprites are sometimes arranged in a 3-dimensional circular pattern, thus mapping the instantaneous electric field in the mesosphere.  相似文献   

The many manifestations of downsizing: hierarchical galaxy formation models confront observations     

Fabio Fontanot  Gabriella De Lucia  Pierluigi Monaco  Rachel S. Somerville  Paola Santini 《Monthly notices of the Royal Astronomical Society》2009,397(4):1776-1790

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Improving digital tools for Quaternary field survey: a case study of the Rodoretto Valley (NW Italy)     

Maria Gabriella Forno  Andrea Lingua  Stefano Lo Russo  Glenda Taddia 《Environmental Earth Sciences》2011,64(5):1487-1495

In the modern geological mapping activities geomatics technologies can facilitate data collection during field survey and avoid practical problems related to the transposition of that data onto topographic maps. This paper describes an innovative tool (the Solid True OrthoPhoto; STOP) for the structured acquisition and recording of geological field survey data that is immediately available in a GIS framework. An experimental software graphical interface has been developed to manage the STOP application during the survey. The benefits of the STOP system were tested by producing a digital map of the Quaternary formations and landforms in a 3-km² sector of the Rodoretto Valley, a minor tributary of the Germanasca Valley, northwestern Italy.  相似文献   

Effects of temperature on cellular and biochemical parameters in the crab Carcinus aestuarii (Crustacea, Decapoda)     

Matozzo V  Gallo C  Marin MG 《Marine environmental research》2011,71(5):351-356

The effects of temperature on cellular and biochemical parameters of the crab Carcinus aestuarii were evaluated. Crabs were kept for 7 days at 4, 17 (reference value) and 30 °C (salinity of 35 psu), and total haemocyte count (THC), haemocyte volume, haemocyte proliferation, phenoloxidase (PO) activity in both haemocyte lysate (HL) and cell-free haemolymph (CFH), CFH total protein and glucose levels, superoxide dismutase (SOD) and catalase (CAT) activities in both gills and digestive gland were evaluated. The lowest and the highest temperature significantly decreased THC, whereas haemocyte volume and haemolymph glucose concentration did not differ significantly among experimental conditions. Haemolymph protein concentration significantly reduced in crabs maintained at 30 °C, when compared with that of animals kept at 4 and 17 °C. Haemocyte proliferation increased significantly in crabs kept at 4 and 30 °C, when compared with that of crabs held at 17 °C. Likewise, a significantly higher PO activity was recorded in CFH from crabs kept at 4 and 30 °C, than in control crabs. Conversely, PO activity did not vary significantly in HL. With regard to antioxidant enzyme activities, a significant decrease in CAT activity was observed in gills from crabs kept at 4 °C, when compared to that of crabs kept at 17 °C and 30 °C. Results obtained demonstrated that the highest and lowest temperature tested influenced crab biological responses, and indicated that C. aestuarii modulated its cellular and biochemical parameters (mainly haemocyte proliferation, CFH protein concentrations and CFH PO activity) in order to cope with temperature.  相似文献   

Impacts of marine aquaculture at large spatial scales: evidences from N and P catchment loading and phytoplankton biomass   总被引：1，自引：0，他引：1  

Sarà G  Lo Martire M  Sanfilippo M  Pulicanò G  Cortese G  Mazzola A  Manganaro A  Pusceddu A 《Marine environmental research》2011,71(5):317-324

While several studies point at off-shore aquaculture as a possible source of impacts on the local marine environment, very few have analysed its effects at large scales such as at the bay, gulf or basin levels. Similar analyses are hampered by the multiple sources of disturbance that may concomitantly affect a given area. The present paper addresses these issues taking the Gulf of Castellammare (Southern Tyrrhenian Sea) as an example. Nitrogen (N) and phosphorous (P) loads were calculated for the period 1970-2007, and compared to chlorophyll-a concentration as measured inside and outside the Gulf over the same period. Results indicate that N and P catchment loading has constantly decreased because of improved environmental management. Nevertheless, nutrient concentration in the Gulf has steadily increased since the establishment of aquaculture facilities in 1999. Chlorophyll-a concentration followed this trend, showing a marked increase from 2001 onwards. In the same period, chlorophyll-a concentrations measured inside and outside the Gulf have significantly diverged. As all the other possible causes can be ruled out, aquaculture remains the sole explanation for the observed situation. This paper demonstrates for the first time ever that off-shore aquaculture may affect the marine ecosystem well beyond the local scale and provides an additional element of concern to be kept into consideration when allocating oceans' space for new fish-farming activities.  相似文献   

Trophic status of earthen ponds used for semi-intensive shrimp (Litopenaeus stylirostris, Stimpson, 1874) farming in New Caledonia (Pacific Ocean)     

Pusceddu A  Della Patrona L  Beliaeff B 《Marine environmental research》2011,72(4):160-171

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Dependence on the observational time intervals and domain of convergence of orbital determination methods     

Alessandra Celletti  Gabriella Pinzari 《Celestial Mechanics and Dynamical Astronomy》2006,95(1-4):327-344

In the framework of the orbital determination methods, we study some properties related to the algorithms developed by Gauss, Laplace and Mossotti. In particular, we investigate the dependence of such methods upon the size of the intervals between successive observations, encompassing also the case of two nearby observations performed within the same night. Moreover we study the convergence of Gauss algorithm by computing the maximal eigenvalue of the jacobian matrix associated to the Gauss map. Applications to asteroids and Kuiper belt objects are considered.  相似文献   

Thermal effects in partially saturated soils: a constitutive model   总被引：1，自引：0，他引：1  

Gabriella Bolzon  Bernhard A. Schrefler 《国际地质力学数值与分析法杂志》2005,29(9):861-877

The present paper is centred on the assessment of an elastic–plastic model for partially saturated soils, earlier proposed by the authors, for its predictive capability with respect to temperature changes, on the light of available experimental results. The model is cast within a constitutive framework that uses Bishop's stress and suction as main variables governing the volumetric response of the material. Some enhancement to the original temperature‐independent formulation is proposed. In particular, functions describing the yield surface and the compressibility modulus are modified to account for the shrinking of the elastic domain and for the increase of irreversible volumetric strain with heating. Some examples illustrate the main features of the present proposal. Comparison with some experimental results is also included. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献