Coastal vulnerability in barrier islands: The high risk areas of the Ria Formosa (Portugal) system

Coastal vulnerability in barrier island systems is extremely high. The barrier island shoreline is exposed to many threats, such as storm erosion, reductions in sediment longshore drift and sea level rise. Many of these threats to coastal areas, such as Ria Formosa, are likely to increase in the near future. The main objectives of the present study are to identify the areas in the system that are at most risk by assessing the evolution of the Ria Formosa barrier island system since the 1940s, and determine which interventions would be necessary to protect these areas.The coastal vulnerability of the system was assessed based on current literature, data available from official institutions, and aerial and terrestrial in situ examination. The results obtained for the evolution of the Ria Formosa coastal system reveal that there are several vulnerable areas that have very dynamic processes, such as extremely high evolution rates of islands and inlets. Human actions that affect the whole system, namely the construction of many physical structures, are the main cause of the instability. Moreover, as several stakeholders are involved, efficient management of the coastal system is imperative. Extensive and careful interventions are urgently needed to avoid irreversible negative impacts on the barrier island system. Three types of techniques could be adopted to deal with the threats to barrier islands: hard stabilization, soft techniques, and non-structural alternatives. However, using hard techniques has many negative effects compared to soft techniques, and as a result it is necessary to remove existing structures from the areas at most risk.     

Application of a Biological Tool for Estimating Current Annual Rates of Erosion and Deposition in Modern Coastal Environments: A Case Study in the Bay of Bengal Coast

The marine polychaete Diopatra cuprea (Bosc) produces tubes that protrude above the sediment surface. To the part above the sediment surface the worm attaches foreign particles. A sharp boundary separates the parts above and below the sediment surface. With subsequent erosion, part of the tube without attached particles becomes exposed and this exposed part indicates the amount of erosion. With subsequent sedimentation, the tubes are enlarged upward and the sharp boundary is found below the sediment surface indicating the amount of subsequent sedimentation. This mode of construction of tubes during an average life span of two years renders tubes as simple but excellent natural tools for precise and easy measurement of the latest annual rates of erosion and deposition in coastal areas, data that are essential for the solving of coastal engineering and geoenvironmental problems. Comparison of this tool with expensive long-term coastal profiling data in four areas in the Bay of Bengal coast indicates its correctness and high applicational value. This revised model can be applied to modern coastal environments only for calculating latest annual rates of both erosion and deposition as correctly as latest physical techniques. Being based on the similar organosedimentary principle, it distinctively contrasts with the earlier model of Myers which provides information on the amount of sediment accumulation only without any time connotation and, it may generate erroneous results if applied to the geologic past unless some limitations evolved in the processes of dewatering, compaction, lithification and diagenesis are removed.     

Provenance of deep-water reservoir sandstones from the Jubarte oil field,Campos Basin,Eastern Brazilian Margin

The provenance of the Maastrichtian deep-water reservoir sandstones from the Jubarte oil field (Campos Basin, eastern Brazil), was studied using an integrated approach that included quantitative petrography, conventional heavy mineral analysis, garnet mineral chemistry and zircon geochronology. The reservoirs are predominantly coarse, poorly-sorted sandstones with feldspathic composition derived from uplifted basement terrains. The fourth- and fifth-order depositional sequences analyzed show no major variations in composition or in provenance through time. However, variations in apatite:tourmaline presents potential to be used as a parameter for sandstone correlation within the field. The composition of heavy minerals indicates derivation from high temperature and low-to-medium pressure aluminous metapelitic rocks, from granites and subordinate mafic rocks, derived from the Cabo Frio Tectonic Domain and the Oriental terrain of Ribeira orogen, characterizing a supply route from SW to NE. The low ZTR index, as well as the absence of low-grade stable heavy minerals and of metasedimentary rock fragments, suggest that by the end of Cretaceous all supracrustal, low-grade terrains had already been totally eroded, and that plutonic, infracrustal rocks were exposed, similarly to the present situation.     

Evaluation of policy options for the live reef food fish trade in the province of Palawan,Western Philippines

The live reef food fish (LRFF) trade has an estimated annual retail value of US$1 billion in the Asia-Pacific region and at least US$30 million in the Philippines. Palawan Province is the trade's center accounting for as much as 55% of the commodity's total export. Concern about the LRFF trade has caused the Palawan Provincial government to take action to regulate the trade. Four key policy options to address the short-term policy objective of developing a sustainable LRFF industry through the reduction of threats associated with destructive fishing and overfishing were proposed. These four policy options and associated analyses were presented to stakeholders at three separate policy consultations. The stakeholders reached a consensus that a regulated LRFF trade was the most sensible option. As a result, the Provincial Government of Palawan took action to enact “The Palawan Live Reef Fish Ordinance of 2006”, which provides for the sustainable and integrated regulation of the LRFF industry. This provincial ordinance will assist in crafting a national policy for the LRFF trade and may also be useful in revising the 1998 Philippine Fisheries Code. The key challenge is how to translate the ordinance provisions into effective on-the-ground actions.     

Sampling the vertical particle flux in the upper water column using a large diameter free-drifting NetTrap adapted to an Indented Rotating Sphere sediment trap

Further development of the large, surface-tethered sediment trap (NetTrap) employed as part of the MedFlux program is described whereby the large collection capacity of the NetTrap is combined with an Indented Rotating Sphere/Sample Carousel (IRSC) sediment trap (IRSC–NT). This trap is capable of collecting particle flux either in a time series or settling velocity mode; settling velocity mode allows the collection of particles that fall within discrete settling velocity intervals. During short field deployments in the Mediterranean Sea the IRSC–NT configured in the settling velocity mode successfully collected unpoisoned samples for chemical and microbiological experiments. In addition to the development of the IRSC–NT, particle-settling behavior above and below the swimmer-excluding IRS valve was tested during on-deck experiments using a specially constructed water-tight trap. Chemical analyses of settling materials (published elsewhere) suggested that separation of particles by settling velocity was achieved. However, due to the motion of the ship, it was not possible to directly measure particle-settling velocities within the trap. Particle release from the IRS did not bias the apparent settling velocity spectrum. Rotation of the IRS did not engender turbulence at the surface of the sphere or within the skewed funnel below. Tests of different ball designs over the course of the MedFlux program showed that a “ridge and saddle” pattern was optimal for efficiently transferring particles under the IRS seal while still reducing swimmer entrance to the collection funnel. The large size of the IRSC–NT did not prevent it from drifting effectively with the current. Several modifications of the present design are proposed that should improve the accuracy of the settling velocity measurements.     

Experimental investigation of water impact on axisymmetric bodies

The results of an elaborate experimental investigation on bottom slamming of axisymmetric objects are presented. Drop tests have been performed on a hemisphere and two conical shapes with different deadrise angles. The test setup is designed so as to prevent small rotations of the test objects which cause scatter in the measurement data. The pressure distribution and evolution as well as the body motion parameters are measured during impact. By means of a high speed camera the water uprise is visualized and the wetting factor is determined for the cones. The results are compared with a three-dimensional asymptotic theory for axisymmetric rigid bodies with constant entry velocity. The ratio between the registered peak pressures and the asymptotic theory are in accordance with comparable experiments in the literature. The asymptotic theory, however, is found to be quite conservative, since the measured peak pressure levels appear to be approximately 50% to 75% of the theoretical levels.     

Does sediment grain size affect diatom grazing by harpacticoid copepods?

Estuarine soft sediments support a diverse group of eukaryotic and prokaryotic organisms though the role of the sediment per se for the functioning of these organisms remains largely unknown. The present study aimed to test the effect of sediment grain size on the grazing activities of harpacticoid copepods. In controlled experiments, two common intertidal harpacticoid species (Paramphiascella fulvofasciata and Nitokra spinipes) were each offered a mix of two benthic diatom species (Navicula phyllepta and Seminavis robusta) in different sedimentary conditions. Several microcosms were created using a variety of sediment types, including fine silt (<63 microm), coarser grained sands (125-250, 250-450, 100-300 microm), artificial 'sediments' of glass beads (250-500, 2000 microm) and even the absence of sediment was tested. The diatoms were enriched in the stable carbon (13)C to facilitate tracing in the harpacticoids. Both copepod species were able to graze on the diatoms with highest uptake when sediment was absent. In contrast, both harpacticoid species showed no uptake in silty conditions. In general, grazing was favoured when mean sediment grain size increased. The strong negative effect of fine grains on the grazer's efficiency can be explained by the resulting differences in the structure (and accessibility) of the diatom biofilm on the one hand and the mobility of the grazer on the other hand. In view of the subtle equilibrium between primary producers and grazers, these results might have important implications for the effect of siltation of tidal flats due to, e.g., human activities.     

A mass mortality of subtropical intertidal populations of the sea urchin Paracentrotus lividus: analysis of potential links with environmental conditions

An outbreak of bald sea urchin disease was detected affecting intertidal populations of the edible temperate species Paracentrotus lividus at its southernmost geographical limit. The mortality event was detected in three sites (Güímar, Palmar and Alcalá) off Tenerife, Canary Islands (Northeastern Atlantic), in October 2003, coinciding with the highest sea surface temperatures (SST) and the lowest wave heights of the year. The prevalence of infection reached 100% but did not affect equally all studied sites or the different size classes. The disease was more prevalent in large sea urchins (>40 mm). The prevalence appeared to be positively correlated with the environmental variable SST and negatively correlated with wave height. In October 2004, only two infected urchins were found (prevalence 1%) at one of the studied sites. However, during 2004 no such extreme values of temperature and wave height were observed. We conclude that high SSTs and low wave heights such as those observed during 2003 are conditions that may trigger outbreaks of urchin disease.     

Formation and stability of mixed Mg/Ca/phytate species in synthetic seawater media: Consequences on ligand speciation

The results of a potentiometric investigation (by ISE-H⁺, glass electrode) on the speciation of phytate ion (Phy¹²⁻) in an ionic medium simulating the major components (Na⁺, K⁺, Ca²⁺, Mg²⁺, Cl⁻ and SO₄²⁻) of natural seawater, at different salinities and t = 25 °C, are reported. The work was particularly aimed at determining the possible formation of mixed Ca²⁺–Mg²⁺–phytate ion pairs, and to establish how including the formation of these mixed species would affect the speciation modeling in seawater media. After testing various speciation models, that considering the formation of the MgCaH₃Phy⁵⁻, MgCaH₄Phy⁴⁻, Mg₂CaH₃Phy³⁻ and Mg₂CaH₄Phy²⁻ species was accepted, and corresponding stability constants were determined at two salinities (S = 5, 10). A discussion is reported both on the choice of the experimental conditions and on the possibility to extend these results to those typical of real seawater. A detailed procedure is also described to demonstrate that the stability of these species is higher than that statistically predicted. As reported in literature, a parameter, namely log X, has been determined in order to quantify this extra stability for the formation of each mixed species at various salinities. For example, at S = 10, log X₁₁₃ = 2.67 and log X₁₁₄ = 1.37 for MgCaH₃Phy⁵⁻ and MgCaH₄Phy⁴⁻ (statistical value is log X_stat = 0.60), and log X₂₁₃ = 6.11 and log X₂₁₄ = 2.15 for Mg₂CaH₃Phy³⁻ and Mg₂CaH₄Phy²⁻ (log X_stat = 1.43), respectively. Results obtained also showed that the formation of these species may occur even in conditions of low salinity (i.e. low concentration of alkaline earth cations) and low pH (i.e., more protonated ligand).