Different cardiac response to copper in limpets from metal polluted and clean shores of Hong Kong

The gastropod limpet, Cellana grata, is common on moderately exposed to exposed Hong Kong rocky shores. On the basis of the existing literature on trace metal contamination in Hong Kong, four sites were identified, representative of highly polluted (Aberdeen and Lei Yue Mun) and clean (Cape d'Aguilar and Clear Water Bay) conditions. Limpets from the two polluted sites showed similar, but significantly higher body concentrations of copper than limpets from the two clean sites, which were also similar. Non-invasive measurements of cardiac activity of limpets from the four sites showed between site differences in baseline heart rates under standard seawater, irrespective of pollution level. When acutely exposed to water borne copper (2 h, 0.5+/-0.06 SD ppm), however, limpets from clean sites showed a significantly higher increase in inter-beating time (bradycardia) than those from polluted sites. These results highlight the potential use of cardiac activity to assess the exposure of natural populations of limpets to trace metal pollution.     

Spatial variation patterns of subtidal seaweed assemblages along a subtropical oceanic archipelago: Thermal gradient vs herbivore pressure

The structure and composition of subtidal rocky seaweed assemblages were studied at 69 sites on the Canary Islands (northeastern Atlantic). This group of islands are situated at the southern boundary of the warm temperate region and adjacent to the cold waters from the northwest African coastal upwelling, which creates a difference of almost 2 °C in surface seawater temperature from the eastern to the western islands. This thermal variation allows an examination of the transition between the warm temperate and the tropical regions along this longitudinal gradient together with the hypothesised Fucales-dominated assemblages towards the eastern islands in contrast to the Dictyotales-dominated assemblages towards the western ones. Environmental and biological parameters were considered in order to investigate which were the main factors explaining spatial variation along the gradient in a multi-scaled approach. Although seventy-nine macroalgae were identified, 87.63% of the total mean cover was due to six taxa (Lobophora variegata, nongeniculate corallines, Canistrocarpus cervicornis, Jania adhaerens, Cystoseira abies-marina and Pseudolithoderma adriaticum). At a large scale, sea urchin density explained the highest variation in seaweed assemblages (26.94%), and its pattern of distribution across the islands. The expected pattern of distribution according to the upwelling distance only occurred in restricted areas of the Canarian Archipelago in absence of herbivore pressure and habitat degradation. Spatial variations within islands (medium scale) were mainly related to wave exposure, while at a small scale these were mostly due to the degree of sedimentation.     

Application of wavelet transform analysis to landslide generated waves

The aim of this paper is to illustrate the results of a preliminary study on aerial landslide-generated waves, which has been mainly intended to establish a method for analyzing water surface records. Some simple physical experiments, reproducing the Scott Russell's wave generator, were carried out in a small two-dimensional wave flume; the Wavelet Transform (WT) is applied to analyze wave measurements and it is shown that useful information can be obtained by means of this technique. The celerity of impulsively generated waves, reflection by an overflow structure and seiching phenomena of the flume are studied. A discussion of the results along with some remarks about ongoing research is also given.     

Seabed Morphology and Pollution Along the Bagnoli Coast (Naples, Italy): a Hypothesis for Environmental Restoration

Abstract. The interaction of coastal and submarine morphology with the hydrodynamic regimes exerts a control on coastal dynamic processes, conditioning the dispersion of sediments and potential pollutants existing in the area. Thus, the study of such parameters is useful in order to define environmental threats. Within the submerged sector of the Bagnoli coast and particularly in the southern part of the investigated area, there are sediment groups composed of very fine sands located in low-energy zones due to wave refraction and diffraction; they can also be found on the sea bottom and on the man-made structures typical of this zone. These areas show high pollutant levels of N, P, Cu, Fe, Mn, Ni, Pb, Zn, Cd, polyaromatic hydrocarbons (PAHs) and polychlorinated bi-phenyls (PCBs). The northern area, a place of high-energy hydrodynamic processes, also shows high concentration levels of pollutants due to the presence of secondary cell circulation.
Morphological research and analysis of textural characteristics of bottom sediments along the Bagnoli coast allowed the actual processes and their evolution in space and time to be defined. It has also been possible to correlate such processes to the seabed morphology system, the wave formations which affect the coast, the complex system of sediment transport, as well as to the man-made interventions in the area. The results of recent chemical analyses of beach sediments and bottom sediments off the Bagnoli coast were also incorporated. They prove the presence of heavy metals, PAHs and PCBs in high and sometimes very high concentrations. Finally, based on the results of research and analyses, a hypothesis for an intervention for environmental restoration has been formulated in order to renaturalise the coast through dredging and treatment of the sand, both on the seabed and on the emerged beach.     

Tectonics of an extinct ridge-transform intersection,Drake Passage (Antarctica)

New swath bathymetric, multichannel seismic and magnetic data reveal the complexity of the intersection between the extinct West Scotia Ridge (WSR) and the Shackleton Fracture Zone (SFZ), a first-order NW-SE trending high-relief ridge cutting across the Drake Passage. The SFZ is composed of shallow, ridge segments and depressions, largely parallel to the fracture zone with an `en echelon' pattern in plan view. These features are bounded by tectonic lineaments, interpreted as faults. The axial valley of the spreading center intersects the fracture zone in a complex area of deformation, where N120° E lineaments and E–W faults anastomose on both sides of the intersection. The fracture zone developed within an extensional regime, which facilitated the formation of oceanic transverse ridges parallel to the fracture zone and depressions attributed to pull-apart basins, bounded by normal and strike-slip faults.On the multichannel seismic (MCS) profiles, the igneous crust is well stratified, with numerous discontinuous high-amplitude reflectors and many irregular diffractions at the top, and a thicker layer below. The latter has sparse and weak reflectors, although it locally contains strong, dipping reflections. A bright, slightly undulating reflector observed below the spreading center axial valley at about 0.75 s (twt) depth in the igneous crust is interpreted as an indication of the relict axial magma chamber. Deep, high-amplitude subhorizontal and slightly dipping reflections are observed between 1.8 and 3.2 s (twt) below sea floor, but are preferentially located at about 2.8–3.0 s (twt) depth. Where these reflections are more continuous they may represent the Mohorovicic seismic discontinuity. More locally, short (2–3 km long), very high-amplitude reflections observed at 3.6 and 4.3 s (twt) depth below sea floor are attributed to an interlayered upper mantle transition zone. The MCS profiles also show a pattern of regularly spaced, steep-inclined reflectors, which cut across layers 2 and 3 of the oceanic crust. These reflectors are attributed to deformation under a transpressional regime that developed along the SFZ, shortly after spreading ceased at the WSR. Magnetic anomalies 5 to 5 E may be confidently identified on the flanks of the WSR. Our spreading model assumes slow rates (ca. 10–20 mm/yr), with slight asymmetries favoring the southeastern flank between 5C and 5, and the northwestern flank between 5 and extinction. The spreading rate asymmetry means that accretion was slower during formation of the steeper, shallower, southeastern flank than of the northwestern flank.     

Metal binding by humic acids in recent sediments from the SW Iberian coastal area

The concentrations of Cu, Zn, Cr, Ni, Pb, As, Mn and Co were determined by Inductively Coupled Plasma–Mass Spectrometry both in recent sediments from different locations of the Huelva littoral (SW Iberian Peninsula) and in their humic acid (HA) fractions in order to evaluate distribution and binding capacity of those trace elements to HAs. In addition, elemental composition (C, N, S) and δ¹³C values were determined to appraise the sources of organic matter in the area. This study involved the comparison of selected samples taken from different environments including the estuary of the Guadiana River, the main fluvial system of the region, the Tinto and Odiel estuary system and the proximal shelf. Significant positive correlations were found among Cu, Zn, As and Pb in bulk sediments, suggesting a common origin of all of those elements: the mining activities and pyrite deposits located hinterland. On the other hand, results for Cr, Co and Ni pointed to the basic rocks from the low basin of the Guadiana River as their main source. Elemental (C, N) and isotopic (δ¹³C) composition of sediments indicated a significant contribution of autochthonous plankton in coastal shelf sediments, whereas estuarine and riverine sediments showed a major contribution of terrestrial biomass. Geochemical values for their corresponding HAs suggested a greater terrestrial contribution in the sedimentary OM of the coastal shelf sediments than in bulk sediments, which evidenced the influence of coastal currents and sediment fluxes. Humic acids sequester considerable amounts of Cu and Zn contributing to reduce the bioavailability of these contaminants.     

Parabolic Wave Propagation Modelling in Orthogonal Coordinate Systems

This paper presents a numerical model study of the propagation of water waves using the parabolic approximation of the mild-slope equation in the orthogonal coordinate system. Two types of coordinate systems are studied: (a) a general form of orthogonal coordinate system and (b) the conformal system, a special form of orthogonal coordinate system. Two typical examples, namely, expanded breakwaters and a circular channel, are studied to validate the model. First, the examples are studied by use of the general orthogonal coordinates. Then the same examples are computed by use of the confonnal system. The computational results show that the confonnal coordinate system generally gives better predictions than the general orthogonal system. A numerical technique for generating the conformal grid is combined with the numerical model to improve the practicability of the model. The comparison between the result from the numerical grid system and that from the analytical grid system shows that reliable computational results can be obtained by use of the numerical confonnal grid system.     

Retention of arsenic and phosphorus in iron-rich concretions of Tagus salt marshes

Iron-rich concretions are frequently found around plant roots in Tagus estuary (Portugal) where radial delivery of O₂ takes place. Salt marsh sediments exhibit cracks that are an additional feature to introduce O₂ and other solutes in the upper sediments. Metal concentrations in salt marsh sediments are clearly above the background levels reflecting the anthropogenic sources from a large city with 2.5 million inhabitants, and several industrial centres. In order to evaluate how both oxidised structures influences the redistribution of redox sensitive elements in salt marsh sediments, concretions were collected from roots of Halimione portucaloides below the oxygenated zone. These tubular cylindrical structures were analysed for Fe, Al, Mn, As, and P along 1-cm radial transect in a millimetre scale from the inner part to the adjacent anoxic sediment. In addition, oxidised cracks were analysed for the same spatial resolution, from the sediment–water interface to anoxic layers (2-cm transept). The parallelism between Fe, As, and P concentrations at this microscale is the most noticeable aspect. Iron and As presented very high concentrations in the 4-mm concretions (3.4 mmol g⁻¹ and 3.1 μmol g⁻¹, respectively) and decreased sharply to the host sediment. Oxygen released from roots oxidise the solid sulphides, and the reduced Fe and As are transported towards the root by both diffusion and pore water flow associated with the root water uptake. Subsequently, Fe(III) precipitates and As is retained by sorption and/or coprecipitation. These elements are also enriched in the first 2-mm of oxidised cracks, but in lower concentrations (50% and 30%, respectively). Manganese concentrations in concretions were low (11.8 μmol g⁻¹), indicating that Fe dominates the sediment chemistry. Phosphorus and iron concentrations in the ascorbate fraction were higher in the oxidising surfaces of concretions (10.7 μmol g⁻¹ and 1.6 mmol g⁻¹, respectively) and of cracks (5.1 μmol g⁻¹ and 0.47 mmol g⁻¹). The parallelism of Fe and As distributions includes not only their similar redox chemistries, but also that to phosphate, including control by coprecipitation of the host iron phases. The mechanisms involved in the mobilisation of As and P are however different, whereas As comes from the oxidation of iron sulphides; dissolved P derives from reduction of ferri-hydroxide phases.     

Factors to consider in evaluating the management and conservation effectiveness of a whale sanctuary to protect and conserve the North Atlantic right whale (Eubalaena glacialis)

This paper examines key factors used in protecting the migratory North Atlantic right whale within the context of a marine protected area (MPA) system, using the Grand Manan Whale Conservation Area, in New Brunswick Canada, as a case study example. Designated as a conservation area in 1993, before the Oceans Act came into effect, the Grand Manan conservation area currently does not form part of the Canadian network of MPAs. Given the possibility that MPA designation may occur, the paper examines factors that should be considered in meeting International Union for Conservation of Nature (IUCN) MPA design criteria and IUCN evaluation model requirements. An MPA evaluation framework based on an IUCN evaluation model (Hockings et al., 2000 [1]) is designed to assess the effectiveness of an MPA in protecting a migratory right whale. Case study results indicate that current management and research activities for the Grand Manan conservation area address most governance, biophysical and socio-economic issues under an IUCN evaluation framework. On a site basis, it is recommended that the Grand Manan conservation area be designated as a component of the Canadian network of MPAs and that regulations be developed and implemented under the Species at Risk Act to clearly define activities considered damaging or destructive to right whale critical habitat. Recommendations also suggest the preparation of a combined site management-action plan for the Grand Manan conservation area indicating how activities specified in North Atlantic Right Whale Recovery Strategy will be implemented locally. On a regional and international basis, recommendations call for an internationally coordinated and integrated approach to right whale protection within the context of a network of designated critical habitat areas. Recommended activities include: continued Canadian participation in cross-border research and actions to mitigate threats to the right whales over their migratory range; development of a regional right whale management and monitoring strategy; and designation of additional critical habitats in national/international waters. It is further recommended that the evaluation framework developed by this paper be used as a model in assessing the conservation and management effectiveness of MPAs protecting other migratory marine species.     

Hydraulics of runoff and loess loam deposition

On many more or less loamy soils, rill erosion is reported to start on slopes that are equal to or steeper than 2–3°; critical Froude numbers for the start of rill wash on these slopes vary between 2·0 and 3·0. This explains why colluvial deposition often occurs on slopes below 2–3°, when water spreads out at the downslope extremities of the rills. The critical hydraulic conditions for loess loam deposition were tested in the laboratory for slopes of 0·5° and 2°, applying unit-discharges (q) up to 10 cm²/s. It appeared from these experiments that for afterflow, without raindrop impact, deposition starts for critical load concentrations (c_cr) varying between several g/1 and about 60 g/l. Under rain c_cr amounts to a minimum value of 100–125 g/l and it increases when the runoff film becomes thinner. Nevertheless, deposition in pluvial runoff is also possible, as was the case during the Weichselian, according to data from quarries in Belgium and in The Netherlands. A modified Kalinske equation is proposed for c_cr prediction, with the introduction of a typical empirical coefficient C_r and considering such factors as shear stress and mean particle size. Massive sedimentation may occur when it stops raining and afterflow starts, since c_cr values are then much lower. It is shown from the Shields' diagram that loamy suspensions are more sensitive to sedimentation than sands in clear water.