Genetic impact of the Prestige oil spill in wild populations of a poor dispersal marine snail from intertidal rocky shores

In November 2002, the sinking of the Prestige cargo ship produced an oil spill of 60,000 tons that affected many areas along the Galician coast (in the northwest of Spain). In a number of rocky shore sites, most organisms (particularly marine mollusks) were nearly extinct at a local scale. We tested whether the local bottleneck/extinction that occurred in affected localities caused any detectable reduction of the genetic diversity in the marine snail Littorina saxatilis, an ovoviviparous rocky shore model species characterized by a low dispersal ability, high population density, and wide distribution range. We compared the level of genetic variation and population differentiation between affected (polluted) and control sites located in seven geographical areas (three sites per area, one impacted and two controls, and two replicates per site) one and a half years after the spill. The analysis included molecular marker variation (microsatellite and AFLP loci) and quantitative trait genetic variation for shell variables in embryos extracted from pregnant females. Our results indicate that the affected populations did not show a significant overall reduction in genetic diversity when compared to the controls, suggesting that the species is highly resistant to losing genetic variability as a consequence of a local short-term pollution process in spite of its low dispersal ability and direct development. However, some genetic effects were detected in the polluted populations, particularly for quantitative shell traits and AFLPs, consistent with local adaptations resulting from the fuel contamination.     

Colony growth in the harvested octocoral Pseudopterogorgia acerosa in a Caribbean coral reef

Pseudopterogorgia acerosa is the tallest gorgonian octocoral found in the Caribbean. In the Cartagena area, Colombia, P. acerosa is commonly harvested as raw material for handicrafts, rendering important the study of its growth and population dynamics. Growth measurements of branches from multiple colonies at two different reefs during 1 year revealed that the main growth was due to rapid elongation of the main (‘mother’) branch and production of daughter branches from the same (or just a few) mother branch(es). Some small colonies doubled their original size in a year. The branches’ absolute growth rate was weakly correlated with size, with no significant relationships between branch size and percent growth. While the pinnate branching pattern in P. acerosa is similar to its congeners Pseudopterogorgia elisabethae and Pseudopterogorgia bipinnata, it produces taller colonies due to the faster growth rate in the primordial mother branch. This growth mode seems advantageous as it augments exposure to light and higher fluxes of suspended food in the benthic boundary layer. Post‐harvesting, clipped colonies exhibited clear signs of regeneration, even in cases where only the holdfast remained. Pseudopterogorgia acerosa seems to have similar regeneration capabilities respect to other Pseudopterogorgia species, where regenerating colonies may grow faster than intact ones.     

The influence of shrimp farms organic waste management on chemical water quality

We evaluated the physical–chemical properties and nutrient concentrations in two shrimp ponds under conventional management, intensive (I-P) and semi-intensive (SI-P), and one under organic management (O-P), three days after loading and before stoking. The mean’s total alkalinity concentrations were 2.26 ± 0.04 mM, 2.28 ± 0.01 mM and 2.59 ± 0.01 mM, respectively for I-P, SI-P and O-P. Bicarbonate and carbonate accounted for 62% and 37% in I-P, 64% and 36% in SI-P and 83–17% in O-P, respectively. Aragonite and calcite were oversaturated around Ω = 5. Mean total phosphate (TP) concentrations were 441.37 ± 92.06 μg/L, 449 ± 48 μg/L and 473.64 ± 84.17 μg/L, under I-P SI-P and O-P management respectively. Following this sequence, NO₃⁻ concentration was 2.98 ± 0.7 μg/L, 1.16 ± 0.16 μg/L and 0.32 ± 0.12 μg/L, under I-P, SI-P and O-P management respectively. Thus, the data suggest that different management of farm organic waste leads to different chemical water quality.     

Frequency of tidal storm surge at New York harbor (New York) and Newark bay (New Jersey)

A joint probability analysis of storm tides is made for the Battery, New York (U.S.A.), and Newark Bay, New Jersey (U.S.A.). Storm tides are caused by either low-pressure coastal storms (northeasters) or hurricanes. The analysis uses existing gage data at the Battery to construct frequency/probability curves of peak surge elevations and tidal amplitudes. These are used in a computer program to combine standard storm surge stages and tidal stage curves to produce an artificial storm tide with given peak elevation and incremental frequency. These peak elevations and incremental frequencies are ranked to produce cumulative frequency curves for northeasters and hurricanes. A frequency curve is obtained for Newark Bay via correlation.     

Geochemical trends in the alkali basaltic suite of the Assab range (Ethiopia)

Two groups of rocks are distinguished in the Assab volcanic range (Afar) on the basis of their petrology. The first one is a typical alkaline suite with high Li, Ba, Rb, Sr, Th and U concentrations. A second subalkaline group may be related to a parental basalt characterized by low trace-element concentrations and intermediate in character between alkali and tholeiitic basalt.U and Th concentrations of the analyzed Assab basalts, as well the reported values for the alkali and transitional basalts of the East African Rift and the Afar depression, are higher than values reported for similar basalts from oceanic and continental environments.     

Application of Non-Ionic Solid Sorbents (XAD Resins) for the Isolation and Fractionation of Water-Soluble Organic Compounds from Atmospheric Aerosols

A detailed procedure using non-ionic macropourous XAD-8 and XAD-4 resins is presented for the isolation and fractionation of aerosol water-soluble organic compounds (WSOC) from aerosol samples. The procedure entails adsorption of WSOC fraction onto XAD-8 and XAD-4 resins, desalting of the adsorbed organic material with ultra-pure water, elution of the retained organic matter with 40% MeOH solution and freeze-drying. Due to resin’s different properties and to certain hydrophobic/hydrophilic interactions between the resin polymers and the organic matter, two major fractions were obtained; namely the XAD-8 and the XAD-4 eluates. The XAD-8 eluate, which accounts for 55–60% of total aerosol WSOC, is represented by partially acidic compounds with significant hydrophobic moieties. The XAD-4 fraction holds few conjugated systems and a higher content of hydrophilic structures with low molecular size, and accounts for 9% of total WSOC. The isolated WSOC sub-fractions were nearly free from inorganic species, and successful recoveries of organic matter from the resins were accomplished. With this procedure the XAD-8 eluate yields a mixture representative of those WSOC that are highly conjugated compounds in atmospheric aerosols. It also allows a successful characterisation of the organic material by advanced analytical techniques without the interference of inorganic species present in the original sample of atmospheric particles.     

Pretunnel technology: applications and design methods

The Pretunnel technology allows the final or preliminary lining to be built ahead of a tunnel face. The paper shows how this technology has been used for mechanizing the full-face excavation of large tunnels in difficult ground conditions with minimum settlements. Analytical methods are presented for the analysis of the lining both in deep and shallow applications. Fields of applicability are established using results of parametric studies based on the methods proposed.     

Empirical relationships for estimating stream depletion by a well pumping near a gaining stream

Siting wells near streams requires an accurate estimate of the quantity of water derived from the river due to pumping. A number of hydrogeological and hydraulic parameters influence this value. This study estimates stream depletion under steady-state conditions for a variety of hydrogeological systems. A finite differences model was used to analyze several hydrogeological situations, and for each of these the stream depletion was estimated using an advective transport method. An empirical equation for stream depletion was obtained for the case of a stream that partially penetrates the aquifer and a pumping well that is screened over a portion of the aquifer. The derived equation, which is valid for both isotropic and anisotropic conditions, expresses stream depletion as a function of the unit inflow to the river, the discharge of the pumping well, the well screen length, the distance between the river and pumping well, the wetted perimeter, and a new parameter called "overlap," which is defined to be the distance between the riverbed and the top of well screen. The overlap parameter makes it possible to consider indirectly the vertical component of flow, which is accentuated when the well is screened below the streambed. The formula proposed here should be useful in deciding where to locate a pumping well and to decide the appropriate length of its screen.     

Detecting Randomness in Spatial Point Patterns: A “Stat-Geometrical” Alternative

There are several methods to test the hypothesis of complete spatial randomness of point patterns. This work involves a new geometrical-based strategy to detect spatial arrangements, which takes into account both Euclidean and angular distances, defining a triangle-based network. An asymptotic test based on the Kolmogorov–Smirnov statistic is proposed to accommodate this situation. To assess the usefulness of this method (Stat-Geo), simulations based on Monte Carlo procedures, conducted using SPLUS, give satisfactory results with a high degree of accuracy. As expected, the new technique proposed in this paper, performs better than traditional ones like distance-based or angle-based, since more information (combining distance and angle) is introduced in the decision-making system. This approach is a very simple way to offer high efficiency results for a low computational cost. Furthermore, this alternative method allows barycentric interpolation of the unsampled points into a two-dimensional simplex (triangular) framework.     

Radiative heating of interstellar grains falling toward the solar nebula: 1-D diffusion calculations

As the dense molecular cloud that was the precursor of our Solar System was collapsing to form a protosun and the surrounding solar-nebula accretion disk, infalling interstellar grains were heated much more effectively by radiation from the forming protosun than by radiation from the disk's accretion shock. Accordingly, we have estimated the temperatures experienced by these infalling grains using radiative diffusion calculations whose sole energy source is radiation from the protosun. Although the calculations are 1-dimensional, they make use of 2-D, cylindrically symmetric models of the density structure of a collapsing, rotating cloud. The temperature calculations also utilize recent models for the composition and radiative properties of interstellar grains (Pollack et al. 1994. Astrophys. J. 421, 615-639), thereby allowing us to estimate which grain species might have survived, intact, to the disk accretion shock and what accretion rates and molecular-cloud rotation rates aid that survival. Not surprisingly, we find that the large uncertainties in the free parameter values allow a wide range of grain-survival results: (1) For physically plausible high accretion rates or low rotation rates (which produce small accretion disks), all of the infalling grain species, even the refractory silicates and iron, will vaporize in the protosun's radiation field before reaching the disk accretion shock. (2) For equally plausible low accretion rates or high rotation rates (which produce large accretion disks), all non-ice species, even volatile organics, will survive intact to the disk accretion shock. These grain-survival conclusions are subject to several limitations which need to be addressed by future, more sophisticated radiative-transfer models. Nevertheless, our results can serve as useful inputs to models of the processing that interstellar grains undergo at the solar nebula's accretion shock, and thus help address the broader question of interstellar inheritance in the solar nebula and present Solar System. These results may also help constrain the size of the accretion disk: for example, if we require that the calculations produce partial survival of organic grains into the solar nebula, we infer that some material entered the disk intact at distances comparable to or greater than a few AU. Intriguingly, this is comparable to the heliocentric distance that separates the C-rich outer parts of the current Solar System from the C-poor inner regions.