Search

Coastal dune ecosystems have been severely degraded as a result of excessive natural resource exploitation, urbanisation, industrial growth, and worldwide tourism. Coastal management often requires the use of vulnerability indices to facilitate the decision-making process. The main objective of this study was to develop a Mediterranean dune vulnerability index (MDVI) for sandy coasts, starting from the existing dune vulnerability index (DVI) proposed by Garcia-Mora et al. (2001) related to the oceanic coasts. Given that the Mediterranean sandy coasts are quite different from the Atlantic coasts, several adjustments and integrations were introduced. Our proposed index is based on the following five main group of factors: geomorphological conditions of the dune systems (GCD), marine influence (MI), aeolian effect (AE), vegetation condition (VC), and human effect (HE), for a total of 51 variables derived (and adapted) from the bibliography or proposed for the first time in this study. For each coastal site, a total vulnerability index, ranging from 0 (very low vulnerability) to 1 (very high vulnerability), was calculated as the unweighted average of the five partial vulnerability indices. Index computation was applied to 23 coastal dune systems of two different contexts in Italy, i.e. peninsular and continental island territories representative of the W-Mediterranean Basin, in order to compare the dune systems with different geomorphology, shoreline dynamics, and human pressure. In particular, our research addressed the following two questions: (1) Which variables are the most critical for the Italian coastal systems? (2) How can the coastal dune vulnerability index be used to develop appropriate strategies of conservation and management for these ecosystems? Cluster analysis and non-metric multidimensional scaling separated the peninsular from the insular sites, both of which were characterised by low to moderate values of vulnerability (0.32 < MDVI < 0.49). The most critical factors for the coastal systems examined in this study were marine negative influence, low stabilising ability of vegetation, and human disturbance. Hence, coastal managers are encouraged to plan specific management actions such as protection of foredunes from marine factors (particularly erosion), to promote dune formation with the reintroduction of native dune builder species and to minimise human pressure where vulnerability depends on these variables. [ABSTRACT FROM AUTHOR]

Acoustic anomalies in seismic records have revealed that gas-charged sediments are very common features in the coastal environments around the world. The ubiquitous gassy sediments challenge the effective acoustic mapping of shallow stratigraphy by seismic means, as well as having an important influence on environmental issues related to the coastal zone occupation and management. This paper documents examples of gassy sediments from coastal lagoons, estuaries, rivers, bays and the inner shelf and nearshore environments of Brazil, Argentina and South Africa. Seismic echograms from selected areas show several gas-related anomalies, which present distinctive morphologies for sediment-trapped gas, leaking or free gas discharge into the water column. In several places the gas-charged sediments occur in areas of palaeo-topographic lows related to fluvial channels and valleys that developed in the coastal zone due to sea level oscillations during the Quaternary period. This forcing by palaeo-topographic features results in the occurrence of shallow gas being controlled in most coastal sites by the previous environmental scenario, the stratigraphic arrangement of the transgressive infilling elements, and the local hydrodynamic conditions. [ABSTRACT FROM AUTHOR]

Abstract: Sediment age profiles reconstructed from a sequence of historical bathymetry changes are used to investigate the subsurface distribution of historical sediments in a subembayment of the San Francisco Estuary. Profiles are created in a grid-based GIS modeling program that stratifies historical deposition into temporal horizons. The model''s reconstructions are supported by comparisons to profiles of 137Cs and excess 210Pb at 12 core sites. The predicted depth of the 1951 sediment horizon is positively correlated to the depth of the first occurrence of 137Cs at sites that have been depositional between recent surveys. Reconstructions at sites that have been erosional since the 1951 survey are supported by a lack of detectable 137Cs and excess 210Pb below the upper 6–16cm of the core. A new data set of predicted near-surface sediment ages was created to illustrate an application of this approach. Results demonstrate other potential applications such as guiding the spatial positioning of future core sites for contaminant measurements. [Copyright &y& Elsevier]

Abstract: Major accidental oil spills still affect sensitive marine areas and shorelines around the world, constituting a challenge for operational as well as strategic contingency management. As a rationale basis for addressing both issues we here propose a Decision Support System (DSS) consisting of a combination of modelling and evaluation methods which in particular assesses various impacts on habitats and local economies. By integrating the state-of-the-art oil spill contingency simulation system OSCAR with wind and current forecasts, environmental GIS data and multi-criteria analysis techniques, the DSS is able to rank different response actions to a chemical or oil spill. In this study, the usefulness of the approach is tested by hindcasting the Prestige accident off the coast of Spain in 2002. In particular, the short- to mid-term economic and ecological consequences of different mitigation measures are estimated. We identified clearly one worst option matching the actual decision taken by the responsible parties and one or two almost equally well performing routes. Two procedures of including uncertainty at various stages of the DSS are tested. The first method averages ensembles of outcomes between each modelling/evaluation stage, while the second one preserves the entire degree of freedom till the final ranking procedure. Results in the Prestige case turned out to be rather insensitive against both ways to account for uncertainties. The robustness as well as clarity of the DSS has the potential to enhance the efficiency of decision making even in politically sensitive situations. Limitations as well as ongoing improvements of the system are highlighted, in particular emphasizing linkages to environmental economics. [Copyright &y& Elsevier]

Abstract: Competitive interactions among marsh plant species are mediated by the influence of the vegetation on sediment accretion and modifications of the relative elevation of the marsh surface. A model described here demonstrates some of the feedbacks between physical processes like sediment accretion and biological processes such as those that determine species zonation patterns. Changes in geomorphology, primary productivity and the spatial distribution of plant species are explained by competitive interactions and by interactions among the tides, biomass density, and sediment accretion that regulate the elevation of intertidal wetlands toward an equilibrium with mean sea level (MSL). This equilibrium is affected positively (relative elevation of the marsh surface increases) by the biomass density of emergent, salt marsh macrophytes and negatively by the rate of sea-level rise (SLR). It was demonstrated that a dominant, invading species is able to modify its environment, raising the elevation of the habitat, to exclude competitively inferior species, a process I refer to as geomorphological displacement. However, the outcome depends on a number of variables including the rate of sea-level rise and the distributions of the species across the intertidal gradient. The model predicts that a marsh will evolve toward alternative stable states, depending on the rate of sea-level rise and the species'' fundamental and realized distributions within the intertidal zone. [Copyright &y& Elsevier]

Abstract: The evolution of the cross section of a salt-marsh channel is explored using a numerical model. Deposition on the marsh platform and erosion and deposition in the channel affect the tidal prism flowing through the cross section, such that the model captures the evolution of the stage–discharge relationship as the channel and marsh platform evolve. The model also captures the growth of salt-marsh vegetation on the marsh platform, and how this vegetation affects flow resistance and the rate of sedimentation. The model is utilized to study the influence of hydroperiod and vegetation encroachment on channel cross section. Numerical results show that a reduction in hydroperiod due to the emergence of the marsh platform causes an infilling of the channel. Vegetation encroachment on the marsh surface produces an increase in flow resistance and accretion due to organic and mineral sedimentation, with important consequences for the shape of the channel cross section. Finally, modeling results indicate that in microtidal marshes with vegetation dominated by Spartina alterniflora, the width-to-depth ratio of the channels decreases when the tidal flats evolve in salt marshes, whereas the cross-sectional area remains proportional to the tidal peak discharge throughout channel evolution. [Copyright &y& Elsevier]

Abstract: The dynamics of plumes from large rivers are relatively well known. Many estuaries are small, however, and discharge directly onto exposed, open shorelines and presumably produce smaller plumes that may have different properties. Therefore this study measured traits of a small estuary on the Australian East Coast as a model system, focusing on (a) plume size, (b) distinctness of plume edges, and (c) imprints on the seafloor. Although plumes were found to be limited in spatial extent (ca. 1km offshore×2.4km longshore) and were constrained near the shore by onshore winds, they exported high nutrient loads from an urbanised watershed. The small plumes were shallow (<2m) and strongly buoyant, with sharp vertical and horizontal clines similar to much larger plumes. The edges of the plumes were highly distinct, clearly separating disparate water masses that trapped significantly higher amounts of nutrients inside the plume. Some particulate material exported from the estuary in the plumes reached the benthos of the nearshore zone, as evidenced by increases in copper concentrations in sediments under the plume. By contrast, the amount of land-sourced carbon delivered by small plumes to the seafloor was minor in comparison to larger inputs from marine sources (e.g. onshore advection of phytoplankton blooms or algae dislodged from reefs) that swamped any contribution from plumes. Overall, small plumes can be important in land–ocean coupling, but their zone of influence may be limited. [Copyright &y& Elsevier]

Abstract: This study investigates the distribution of macrozoobenthos in relation to meso-scale bedforms in the southern North Sea. Three sites on the Dutch Continental Shelf were sampled that are representative of large areas of the North Sea and show diverse morphological settings. These sites are (i) part of a shoreface-connected ridge, (ii) the lower part of a concave shoreface and (iii) a sandwave area. Within these sites, two or three different morphological units were distinguished. Sampling was undertaken in two seasons for two consecutive years. The species composition was analysed for differences in benthic assemblage within sites, based on the meso-scale morphology, and between sites and seasons. In addition, the benthic assemblage was correlated to water depth, median grain size (D50) and sorting (D60/D10). Results show that significant differences in the benthic assemblage can be found related to meso-scale bedforms, but macro-scale morphological setting and seasonal effects are more important. [Copyright &y& Elsevier]

Abstract: Definitions of the ‘foreshore’ are described as presented in various coastal geomorphological and related textbooks. To many geomorphologists, the term foreshore is considered synonymous with the intertidal zone. These definitions are compared with the legal definitions of the foreshore as exist in Britain under the three different property law regimes: English, Scottish and Udal law. The legal definitions and many of the geomorphological definitions are based on tidal data. The differences between the observed tides at a tide gauge and on a beach at a distance from the gauge are considered. It is concluded that the term foreshore has a very specific legal meaning in each property law regime, therefore the authors propose that the term ‘foreshore’ should be used to relate to the legally defined area of the coast and, unless specifically referring to the foreshore, scientists should use the term intertidal. [Copyright &y& Elsevier]

Mangroves have long been associated with human populations, as coastal communities rely on the various ecosystem services that mangroves provide. However, human degradation and destruction of mangrove forests is common, despite and because of our reliance on them as valuable ecosystems. Mangrove research and management must elucidate and reconcile these conflicts to maintain mangrove forests and the services that humans depend on. To better understand the complex dynamics, interactions and relationships that exist between mangroves and coastal communities, the 5th Mangrove Macrobenthos and Management (MMM5) conference was held in Singapore in July 2019, with the theme " Mangroves and People: Impacts and Interactions". This theme was chosen because Southeast Asia is the epicentre of ongoing mangrove loss, and a large number of coastal communities in the region rely on the ecosystem services that mangroves provide. The 32 papers published in this Special Issue represent the breadth of mangrove research presented at MMM5, including topics in faunal biology, ecosystem ecology, genetics, physical geography, biogeochemistry, remote sensing and the social sciences. The articles are characterized under the following topics: 1) mangrove ecosystem functioning; 2) range expansion of mangroves; 3) ecosystem services of mangroves; 4) anthropogenic and natural threats to mangroves; and 5) the management and social-ecology of mangroves. This Special Issue highlights the current state of the art of mangrove research and application, and describes a number of emerging new ideas and research opportunities that will continue to advance mangrove ecosystem science into the future. [ABSTRACT FROM AUTHOR]