Salinity tolerance in Schinopsis quebracho colorado: Seed germination, growth, ion relations and metabolic responses

Soil salinity is a major abiotic stress influencing plant productivity worldwide. Schinopsis quebracho colorado is one of the most important woody species in the Gran Chaco, an arid and salt-prone subtropical biome of South America. To gain a better understanding of the physiological mechanisms that allow plant establishment under salt conditions, germination and seedling growth of S. quebracho colorado were examined under treatment with a range of NaCl solutions (germination: 0–300 mmol l⁻¹ NaCl; seedling growth: 0–200 mmol l⁻¹ NaCl). The aim was to test the hypothesis that S. quebracho colorado is a glycophite that shows different salt tolerance responses with development stage. Proline content, total soluble carbohydrates and Na⁺, K⁺ and Cl⁻ concentrations in leaves and roots of seedlings, and the chlorophyll concentration and relative water content of leaves were measured. Germination was not affected by 100 mmol l⁻¹ NaCl, but decreased at a concentration of 200 mmol l⁻¹. At 300 mmol l⁻¹ NaCl, germination did not occur. Seedling growth decreased drastically with increasing salinity. An increase in NaCl from 0 to 100 mmol l⁻¹ also significantly reduced the leaf relative water content by 22% and increased the proline concentration by 60% in roots. In contrast, total soluble carbohydrates were not significantly affected by salinity. Seedlings showed a sodium exclusion capacity, and there was an inverse correlation between Cl⁻ concentration and the total chlorophyll concentration. S. quebracho colorado was more tolerant to salinity during germination than in the seedling phase. The results suggest that this increased tolerance during germination might, in part, be the result of lower sensitivity to high tissue Na⁺ concentrations. The significant increment of proline in the roots suggests the positive role of this amino acid as a compatible solute in balancing the accumulation of Na⁺ and Cl⁻ as a result of salinity. These results help clarify the physiological mechanisms that allow establishment of S. quebracho colorado on salt-affected soils in arid and semi-arid Gran Chaco.     

Effects of conspecifics on settling juveniles of the invasive golden mussel, Limnoperna fortunei

We conducted a field experiment to assess the influence of conspecific adults on recruitment success of the golden mussel Limnoperna fortunei. Tiles, 225 cm² surface area, were used as artificial substrates in four treatments: control (blank tiles), low (800 mussels m⁻²), medium (4,000 mussels m⁻²) and high (12,000 mussels m⁻²) density treatments. Results indicated that recruitment was strongly affected by the presence and density of conspecifics. After one and 3 months of exposure, numbers of recruits were significantly higher on tiles with conspecific adults than on blank tiles, and there was a positive and significant relationship between the number of recruits and the number of adults in the three treatments assayed. Also, after 3 months of exposure, recruits in all treatments with adults present were larger than recruits in the control treatment. Our results suggest that conspecific adults have a positive effect on recruitment success and growth of newly settled juveniles through factors that enhance larval settling or that contribute to the survival of settlers in areas colonized by adult conspecifics.     

Note on Salter's energy absorber in random waves

Salter's wave theory energy device has been the object of extensive theoretical and experimental studies during recent years. This paper describes the performance of the device in random waves by means of a numerical study. Different situations are considered.First, the cam is allowed to have one degree of freedom (the cam rolls about a rigid and fixed shaft) and is in a shallow sea where the waves are modeled by the JONSWAP spectrum. Power extraction, efficiency and dynamic response are presented in terms of wind characteristics for a cam radius of 3 m. In the open sea where typical waves are longer and higher, waves are represented by the P-M spectrum and the cam radius is taken to be 7 m. Finally, it is shown for a particular set of design parameters how the efficiency decays and the power extraction decreases with lack of rigidity in the support system.     

The impact of commercial and recreational harvesting for Paracentrotus lividus on shallow rocky reef sea urchin communities in North-western Sardinia, Italy

The fishery for the edible sea urchin Paracentrotus lividus is of great importance to many European regions, although in some of them this species has shown a wide scale decline in recent years. This paper reports on direct (on P. lividus) and indirect (on the co-occurring but not fished echinoid, Arbacia lixula) effects of sea urchin harvesting in shallow rocky reefs in North-western Sardinia (Italy, central-western Mediterranean Sea), where this activity is intensively practised. Density, size (test diameter), and biomass of both species were assessed in autumn 2004 at two locations impacted by P. lividus fishery, and at two controls within an adjacent Marine Protected Area. Density of P. lividus and A. lixula was significantly greater at the controls than at the exploited locations. The average test diameter of P. lividus was also significantly larger at the controls, where large-sized specimens (i.e. >5 cm) were notably more abundant. The average size of A. lixula did not significantly differ between the impacted locations and the controls. The average biomass of P. lividus was significantly greater at the controls than at the exploited locations, whereas no differences were detected for A. lixula. These results reveal the existence of a heavy fishing impact on P. lividus in North-western Sardinia and the need for regulation of its harvesting to prevent severe direct effects on its populations. Since no indirect effects on A. lixula have been detected, it could be hypothesized that this species did not benefit from P. lividus fishery due to an only moderate competition for habitat and resources between these two echinoids. Implications for management of edible sea urchin fishery are also discussed.     

Variability in plankton community structure, metabolism, and vertical carbon fluxes along an upwelling filament (Cape Juby, NW Africa)

The variability in dissolved and particulate organic matter, plankton biomass, community structure and metabolism, and vertical carbon fluxes were studied at four stations (D₁–D₄), placed along a coastal-offshore gradient of an upwelling filament developed near Cape Juby (NW Africa). The filament was revealed as a complex and variable system in terms of its hydrological structure and distribution of biological properties. An offshore shift from large to small phytoplankton cells, as well as from higher to lower autotrophic biomass, was not paralleled by a similar gradient in particulate (POC) or dissolved (DOC) organic carbon. Rather, stations in the central part of the filament (D₂ and D₃) presented the highest organic matter concentrations. Autotrophic carbon (POC_Chl) accounted for 53% (onshore station, D₁) to 27% (offshore station, D₄) of total POC (assuming a carbon to chlorophyll ratio of 50), from which nano- and pico-phytoplankton biomasses (POC_{A < 10 μm}) represented 14% (D₁) to 79% (D₄) of POC_Chl. The biomass of small hetrotrophs (POC_{H < 10 μm}) was equivalent to POC_{A < 10 μm}, except at D₁, where small autotrophs were less abundant. Dark community respiration (R_d) in the euphotic zone was in general high, almost equivalent to gross production (P_g), but decreasing offshore (D₁–D₄, from 108 to 41 mmol C m⁻² d⁻¹). POC sedimentation rates (POC_sed) below the euphotic zone ranged from 17 to 6 mmol C m⁻² d⁻¹. Only at D₄ was a positive carbon balance observed: P_g−(R_d + POC_sed) = 42 mmol C m⁻² d⁻¹. Compared to other filament studies from the NE Atlantic coast, the Cape Juby filament presented lower sedimentation rates and higher respiration rates with respect to gross production. We suggest that this is caused by the recirculation of the filament water, induced by the presence of an associated cyclonic eddy, acting as a trapping mechanism for organic matter. The export capacity of the Cape Juby filament therefore would be constrained to the frequency of the interactions of the filament with island-induced eddies.     

GOCE level 1b data processing

In this article, the processing steps applied to the raw GOCE science payload instrument data (level 0) in order to obtain input data for the gravity field determination (level 1b) are described. The raw gradiometer measurements, which are given at the level of control voltages, have to be transformed into accelerations and gradients. For the latter step, knowledge about the GOCE attitude is required, which is provided by the star trackers. In addition, the data of the satellite to satellite tracking instrument are used to date the measurements, after its clock error has been corrected. All intermediate steps of the processing flow are described. Together with the explanation of the processing flow, an overview of the main level 1b products is given. The final part of the article discusses the means of quality control of the L1b data currently used and gives an outlook on potential processor evolutions.     

Differential damage in the semi-confined Munazio Ireneo cubicle in Cagliari (Sardinia): a correlation between damage and microclimate

The Early Christian Munazio Ireneo cubicle in Cagliari (Sardinia) is carved into the rock and is one of the rare monuments of Sardinia belonging to Early Christian Age. It is 166 cm under the planking level and is a semi-confined chamber in which a gate allows exchange with the outside. In 1888, when it was discovered, it was completely painted, but over the years, it suffered a serious damage and all the paintings are nearly disappeared. Now the site shows a high moisture and a differential damage characterised by delamination, powdering, salt crystallisation and biological colonisation. The research offers a multidisciplinary approach to study the salt crystallisation damage, which is a phenomenon still not completely understood today. Studies and analyses highlight that different kinds of damage can be recognised. The cement mortar and the air pollution cause crystallisation of the sulphates. Constant capillary rising and the presence of water infiltration due to the rains, which travelled into the site from the vault, were detected during qualitative inspection. Although the microclimate did not change much in the site and the humidity was almost constant during the monitoring period, the variations in temperature allowed the phase transitions of sodium sulphate, especially in summer. The greatest damage of the porous stone is associated with the phase transitions and crystallisation inside the stone of sodium sulphate, one of the most harmful salts for porous materials because of its high crystallisation pressure.     

Electrical conductivity investigation of the Corso-Sardinian microplate area

The analysis of magnetovariational data from an array quasi- simultaneously covering Sardinia (Italy) and Corsica (France), from summer 1988 to spring 1991, indicates the existence of two major conducting bodies, one north of Corsica, the other south of Sardinia. Fourier maps also show local conductivity anomalies along the Campidano Graben (Sardinia), across the Bonifacio Straits and in the northernmost part of Corsica. Two-dimensional (2D) modelling and inversion procedures have been carried out in order to find the optimum conductivity and geometrical characteristics of the conductive bodies deduced from Fourier maps, induction arrows and pseudosections studies. As a result of the 2D inversion, two zones with enhanced electrical conductivity are found, respectively, in the Sardinia Channel and in the Bonifacio Straits. The former can be related to the thermal characteristics of the area; the latter, shallower, can be ascribed to an accumulation of sediments. Some short-period magnetovariational anomalies in northern Corsica can be related to recent reheating processes that occurred there, as well as to the crustal thinning in the Ligurian sea.     

Comparison of geomagnetic planetary reference fields over Italy

Geomagnetic field measurements on a network at 106 repeat stations (1/3000 km²), and a second order network at 2550 stations (1/100 km²), were completed in 1981. Total intensity and the horizontal and vertical component of the field were measured at all stations, and in addition declination was measured at the first order stations. Normal fields for each element were computed from the first order network measurements (using a second degree polynomial in latitude and longitude), and comparisons were made for total intensity with 3 planetary reference fields. The use of the polynomial normal normal field is suggested to draw anomaly maps.