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J. Mar. Sci. Eng., Volume 3, Issue 3 (September 2015) – 31 articles , Pages 492-1148

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Open AccessArticle
Oil Characterization and Distribution in Florida Estuary Sediments Following the Deepwater Horizon Spill
J. Mar. Sci. Eng. 2015, 3(3), 1136-1148; https://doi.org/10.3390/jmse3031136 - 23 Sep 2015
Cited by 1 | Viewed by 2223
Abstract
Barrier islands of Northwest Florida were heavily oiled during the Deepwater Horizon spill, but less is known about the impacts to the shorelines of the associated estuaries. Shoreline sediment oiling was investigated at 18 sites within the Pensacola Bay, Florida system prior to [...] Read more.
Barrier islands of Northwest Florida were heavily oiled during the Deepwater Horizon spill, but less is known about the impacts to the shorelines of the associated estuaries. Shoreline sediment oiling was investigated at 18 sites within the Pensacola Bay, Florida system prior to impact, during peak oiling, and post-wellhead capping. Only two locations closest to the Gulf of Mexico had elevated levels of total petroleum hydrocarbons (TPH) and total polycyclic aromatic hydrocarbons (PAHs). These samples showed a clear weathered crude oil signature, pattern of depletion of C9 to C19 alkanes and C0 to C4 naphthalenes, and geochemical biomarker ratios in concordance with weathered Macondo crude oil. All other locations and sample times showed only trace petroleum contamination. The results of this study are consistent with available satellite imagery and visual shoreline survey data showing heavy shoreline oiling limited to sandy beaches near the entrance to Pensacola Bay and shorelines of Santa Rosa Island. Full article
(This article belongs to the Special Issue Marine Oil Spills) Printed Edition available
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Open AccessArticle
Wind and Wave Setup Contributions to Extreme Sea Levels at a Tropical High Island: A Stochastic Cyclone Simulation Study for Apia, Samoa
J. Mar. Sci. Eng. 2015, 3(3), 1117-1135; https://doi.org/10.3390/jmse3031117 - 22 Sep 2015
Cited by 19 | Viewed by 2840
Abstract
Wind-wave contributions to tropical cyclone (TC)-induced extreme sea levels are known to be significant in areas with narrow littoral zones, particularly at oceanic islands. Despite this, little information exists in many of these locations to assess the likelihood of inundation, the relative contribution [...] Read more.
Wind-wave contributions to tropical cyclone (TC)-induced extreme sea levels are known to be significant in areas with narrow littoral zones, particularly at oceanic islands. Despite this, little information exists in many of these locations to assess the likelihood of inundation, the relative contribution of wind and wave setup to this inundation, and how it may change with sea level rise (SLR), particularly at scales relevant to coastal infrastructure. In this study, we explore TC-induced extreme sea levels at spatial scales on the order of tens of meters at Apia, the capitol of Samoa, a nation in the tropical South Pacific with typical high-island fringing reef morphology. Ensembles of stochastically generated TCs (based on historical information) are combined with numerical simulations of wind waves, storm-surge, and wave setup to develop high-resolution statistical information on extreme sea levels and local contributions of wind setup and wave setup. The results indicate that storm track and local morphological details lead to local differences in extreme sea levels on the order of 1 m at spatial scales of less than 1 km. Wave setup is the overall largest contributor at most locations; however, wind setup may exceed wave setup in some sheltered bays. When an arbitrary SLR scenario (+1 m) is introduced, overall extreme sea levels are found to modestly decrease relative to SLR, but wave energy near the shoreline greatly increases, consistent with a number of other recent studies. These differences have implications for coastal adaptation strategies. Full article
(This article belongs to the Special Issue Coastal Hazards Related to Storm Surge) Printed Edition available
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Open AccessArticle
A Flood Risk Assessment of the LaHave River Watershed, Canada Using GIS Techniques and an Unstructured Grid Combined River-Coastal Hydrodynamic Model
J. Mar. Sci. Eng. 2015, 3(3), 1093-1116; https://doi.org/10.3390/jmse3031093 - 22 Sep 2015
Cited by 3 | Viewed by 4102
Abstract
A flexible mesh hydrodynamic model was developed to simulate flooding of the LaHave River watershed in Nova Scotia, Canada, from the combined effects of fluvial discharge and ocean tide and surge conditions. The analysis incorporated high-resolution lidar elevation data, bathymetric river and coastal [...] Read more.
A flexible mesh hydrodynamic model was developed to simulate flooding of the LaHave River watershed in Nova Scotia, Canada, from the combined effects of fluvial discharge and ocean tide and surge conditions. The analysis incorporated high-resolution lidar elevation data, bathymetric river and coastal chart data, and river cross-section information. These data were merged to generate a seamless digital elevation model which was used, along with river discharge and tidal elevation data, to run a two-dimensional hydrodynamic model to produce flood risk predictions for the watershed. Fine resolution topography data were integrated seamlessly with coarse resolution bathymetry using a series of GIS tools. Model simulations were carried out using DHI Mike 21 Flexible Mesh under a variety of combinations of discharge events and storm surge levels. Discharge events were simulated for events that represent a typical annual maximum runoff and extreme events, while tide and storm surge events were simulated by using the predicted tidal time series and adding 2 and 3 m storm surge events to the ocean level seaward of the mouth of the river. Model output was examined and the maximum water level for the duration of each simulation was extracted and merged into one file that was used in a GIS to map the maximum flood extent and water depth. Upstream areas were most vulnerable to fluvial discharge events, the lower estuary was most vulnerable to the effect of storm surge and sea-level rise, and the Town of Bridgewater was influenced by the combined effects of discharge and storm surge. To facilitate the use of the results for planning officials, GIS flood risk layers were intersected with critical infrastructure, identifying the roads, buildings, and municipal sewage infrastructure at risk under each flood scenario. Roads were converted to points at 10 m spacing for inundated areas and appended with the flood depth calculated from the maximum water level subtracted from the lidar digital elevation model. Full article
(This article belongs to the Special Issue Coastal Hazards Related to Storm Surge) Printed Edition available
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Open AccessArticle
Multi-Fraction Bayesian Sediment Transport Model
J. Mar. Sci. Eng. 2015, 3(3), 1066-1092; https://doi.org/10.3390/jmse3031066 - 22 Sep 2015
Cited by 4 | Viewed by 2344
Abstract
A Bayesian approach to sediment transport modeling can provide a strong basis for evaluating and propagating model uncertainty, which can be useful in transport applications. Previous work in developing and applying Bayesian sediment transport models used a single grain size fraction or characterized [...] Read more.
A Bayesian approach to sediment transport modeling can provide a strong basis for evaluating and propagating model uncertainty, which can be useful in transport applications. Previous work in developing and applying Bayesian sediment transport models used a single grain size fraction or characterized the transport of mixed-size sediment with a single characteristic grain size. Although this approach is common in sediment transport modeling, it precludes the possibility of capturing processes that cause mixed-size sediments to sort and, thereby, alter the grain size available for transport and the transport rates themselves. This paper extends development of a Bayesian transport model from one to k fractional dimensions. The model uses an existing transport function as its deterministic core and is applied to the dataset used to originally develop the function. The Bayesian multi-fraction model is able to infer the posterior distributions for essential model parameters and replicates predictive distributions of both bulk and fractional transport. Further, the inferred posterior distributions are used to evaluate parametric and other sources of variability in relations representing mixed-size interactions in the original model. Successful OPEN ACCESS J. Mar. Sci. Eng. 2015, 3 1067 development of the model demonstrates that Bayesian methods can be used to provide a robust and rigorous basis for quantifying uncertainty in mixed-size sediment transport. Such a method has heretofore been unavailable and allows for the propagation of uncertainty in sediment transport applications. Full article
(This article belongs to the Special Issue Sediment Transport Modeling)
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Open AccessArticle
Coupled Wave Energy and Erosion Dynamics along a Salt Marsh Boundary, Hog Island Bay, Virginia, USA
J. Mar. Sci. Eng. 2015, 3(3), 1041-1065; https://doi.org/10.3390/jmse3031041 - 15 Sep 2015
Cited by 21 | Viewed by 3231
Abstract
The relationship between lateral erosion of salt marshes and wind waves is studied in Hog Island Bay, Virginia USA, with high-resolution field measurements and aerial photographs. Marsh retreat is compared to wave climate calculated in the bay using the spectral wave-model Simulating Waves [...] Read more.
The relationship between lateral erosion of salt marshes and wind waves is studied in Hog Island Bay, Virginia USA, with high-resolution field measurements and aerial photographs. Marsh retreat is compared to wave climate calculated in the bay using the spectral wave-model Simulating Waves Nearshore (SWAN). We confirm the existence of a linear relationship between long-term salt marsh erosion and wave energy, and show that wave power can serve as a good proxy for average salt-marsh erosion rates. At each site, erosion rates are consistent across several temporal scales, ranging from months to decades, and are strongly related to wave power. On the contrary, erosion rates vary in space and weakly depend on the spatial distribution of wave energy. We ascribe this variability to spatial variations in geotechnical, biological, and morphological marsh attributes. Our detailed field measurements indicate that at a small spatial scale (tens of meters), a positive feedback between salt marsh geometry and wave action causes erosion rates to increase with boundary sinuosity. However, at the scale of the entire marsh boundary (hundreds of meters), this relationship is reversed: those sites that are more rapidly eroding have a marsh boundary which is significantly smoother than the marsh boundary of sheltered and slowly eroding marshes. Full article
(This article belongs to the Special Issue Sediment Transport Modeling)
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Open AccessArticle
Wind Turbine Blade Life-Time Assessment Model for Preventive Planning of Operation and Maintenance
J. Mar. Sci. Eng. 2015, 3(3), 1027-1040; https://doi.org/10.3390/jmse3031027 - 07 Sep 2015
Cited by 17 | Viewed by 2890
Abstract
Out of the total wind turbine failure events, blade damage accounts for a substantial part, with some studies estimating it at around 23%. Current operation and maintenance (O&M) practices typically make use of corrective type maintenance as the basic approach, implying high costs [...] Read more.
Out of the total wind turbine failure events, blade damage accounts for a substantial part, with some studies estimating it at around 23%. Current operation and maintenance (O&M) practices typically make use of corrective type maintenance as the basic approach, implying high costs for repair and replacement activities as well as large revenue losses, mainly in the case of offshore wind farms. The recent development and evolution of condition monitoring techniques, as well as the fact that an increasing number of installed turbines are equipped with online monitoring systems, offers a large amount of information on the blades structural health to the decision maker. Further, inspections of the blades are often performed in connection with service. In light of the obtained information, a preventive type of maintenance becomes feasible, with the potential of predicting the blades remaining life to support O&M decisions for avoiding major failure events. The present paper presents a fracture mechanics based model for estimating the remaining life of a wind turbine blade, focusing on the crack propagation in the blades adhesive joints. A generic crack propagation model is built in Matlab based on a Paris law approach. The model is used within a risk-based maintenance decision framework to optimize maintenance planning for the blades lifetime. Full article
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Open AccessArticle
Mesoscale Morphological Change, Beach Rotation and Storm Climate Influences along a Macrotidal Embayed Beach
J. Mar. Sci. Eng. 2015, 3(3), 1006-1026; https://doi.org/10.3390/jmse3031006 - 02 Sep 2015
Cited by 6 | Viewed by 2872
Abstract
Cross-shore profiles and environmental forcing were used to analyse morphological change of a headland bay beach: Tenby, West Wales (51.66 N; −4.71 W) over a mesoscale timeframe (1996–2013). Beach profile variations were attuned with longer term shoreline change identified by previous research showing [...] Read more.
Cross-shore profiles and environmental forcing were used to analyse morphological change of a headland bay beach: Tenby, West Wales (51.66 N; −4.71 W) over a mesoscale timeframe (1996–2013). Beach profile variations were attuned with longer term shoreline change identified by previous research showing southern erosion and northern accretion within the subaerial zone and were statistically significant in both sectors although centrally there was little or no significance. Conversely a statistically significant volume loss was shown at all profile locations within the intertidal zone. There were negative phase relationships between volume changes at the beach extremities, indicative of beach rotation and results were statistically significant (p < 0.01) within both subaerial (R2 = 0.59) and intertidal (R2 = 0.70) zones. This was confirmed qualitatively by time-series analysis and further cross correlation analysis showed trend reversal time-lagged associations between sediment exchanges at either end of the beach. Wave height and storm events displayed summer/winter trends which explained longer term one directional rotation at this location. In line with previous regional research, environmental forcing suggests that imposed changes are influenced by variations in southwesterly wind regimes. Winter storms are generated by Atlantic southwesterly winds and cause a south toward north sediment exchange, while southeasterly conditions that cause a trend reversal are generally limited to the summer period when waves are less energetic. Natural and man-made embayed beaches are a common coastal feature and many experience shoreline changes, jeopardising protective and recreational beach functions. In order to facilitate effective and sustainable coastal zone management strategies, an understanding of the morphological variability of these systems is needed. Therefore, this macrotidal research dealing with rotational processes across the entire intertidal has significance for other macrotidal coastlines, especially with predicted climate change and sea level rise scenarios, to inform local, regional and national shoreline risk management strategies. Full article
(This article belongs to the Special Issue Coastal Morphodynamics) Printed Edition available
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Open AccessArticle
The Tsunami Vulnerability Assessment of Urban Environments through Freely Available Datasets: The Case Study of Napoli City (Southern Italy)
J. Mar. Sci. Eng. 2015, 3(3), 981-1005; https://doi.org/10.3390/jmse3030981 - 01 Sep 2015
Cited by 10 | Viewed by 2763
Abstract
The analysis of tsunami catalogues and of data published on the NOAA web site pointed out that in the Mediterranean basin, from 2000 B.C. to present, about 480 tsunamis occurred, of which at least a third involved the Italian peninsula. Within this framework, [...] Read more.
The analysis of tsunami catalogues and of data published on the NOAA web site pointed out that in the Mediterranean basin, from 2000 B.C. to present, about 480 tsunamis occurred, of which at least a third involved the Italian peninsula. Within this framework, a GIS-aided procedure that takes advantage of spatial analysis to apply the Papathoma Tsunami Vulnerability Assessment model of urban environments is presented, with the main purpose of assessing the vulnerability of wide areas at spatial resolution of the census district. The method was applied to the sector of Napoli city enclosed between Posillipo Hill and the Somma-Vesuvio volcano because of the high population rates (apex value of 5000 inh/km2) and potential occurrence of hazardous events such as earthquakes, volcanic eruptions and mass failures that can trigger tsunamis. The vulnerability status of the urban environment was depicted on a map. About 21% of the possibly inundated area, corresponding with the lowlands along the shoreline, shows a very high tsunami vulnerability. High vulnerability characterizes 26% of inundable zones while medium-low vulnerability typifies a wide area of the Sebeto-Volla plain, ca 800 m away from the shoreline. This map represents a good tool to plan the actions aimed at reducing risk and promoting resilience of the territory. Full article
(This article belongs to the Special Issue Tsunami Science and Engineering) Printed Edition available
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Open AccessArticle
RNA-TGGE, a Tool for Assessing the Potential for Bioremediation in Impacted Marine Ecosystems
J. Mar. Sci. Eng. 2015, 3(3), 968-980; https://doi.org/10.3390/jmse3030968 - 31 Aug 2015
Cited by 2 | Viewed by 1966
Abstract
Cultivation-independent genomic approaches have greatly advanced our understanding of the ecology and diversity of microbial communities involved in biodegradation processes. However, much still needs to be resolved in terms of the structure, composition and dynamics of the microbial community in impacted ecosystems. Here [...] Read more.
Cultivation-independent genomic approaches have greatly advanced our understanding of the ecology and diversity of microbial communities involved in biodegradation processes. However, much still needs to be resolved in terms of the structure, composition and dynamics of the microbial community in impacted ecosystems. Here we report on the RNA activity of the microbial community during the bioremediation process using RNA Temperature Gradient Gel Electrophoresis (RNA-TGGE). Dendrograms constructed from similarity matching data produced from the TGGE profiles separated a community exhibiting high remediation potential. Overall, increased Shannon Weaver Diversity indices (1–2.4) were observed in the high potential remediation treatment samples. The functionality of the microbial community was compared, with the microbial community showing the greatest organisation also showing the highest levels of hydrocarbon degradation. Subsequent sequencing of excised bands from the microbial community identified the presence of Gammaproteobacteria together with a number of uncultured bacteria. The data shows that RNA TGGE represents a simple, reproducible and effective tool for use in the assessment of a commercial bioremediation event, in terms of monitoring either the natural or augmented hydrocarbon-degrading microbial community. Full article
(This article belongs to the Special Issue Marine Oil Spills) Printed Edition available
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Open AccessArticle
Comparison of the Performance of Two Advanced Spectral Methods for the Analysis of Times Series in Paleoceanography
J. Mar. Sci. Eng. 2015, 3(3), 957-967; https://doi.org/10.3390/jmse3030957 - 19 Aug 2015
Cited by 2 | Viewed by 1988
Abstract
Many studies have revealed the cyclicity of past ocean/atmosphere dynamics at a wide range of time scales (from decadal to millennial time scales), based on the spectral analysis of time series of climate proxies obtained from deep sea sediment cores. Among the many [...] Read more.
Many studies have revealed the cyclicity of past ocean/atmosphere dynamics at a wide range of time scales (from decadal to millennial time scales), based on the spectral analysis of time series of climate proxies obtained from deep sea sediment cores. Among the many techniques available for spectral analysis, the maximum entropy method and the Thomson multitaper approach have frequently been used because of their good statistical properties and high resolution with short time series. The novelty of the present study is that we compared the two methods by according to the performance of their statistical tests to assess the statistical significance of their power spectrum estimates. The statistical significance of maximum entropy estimates was assessed by a random permutation test (Pardo-Igúzquiza and Rodríguez-Tovar, 2000), while the statistical significance of the Thomson multitaper method was assessed by an F-test (Thomson, 1982). We compared the results obtained in a case study using simulated data where the spectral content of the time series was known and in a case study with real data. In both cases the results are similar: while the cycles identified as significant by maximum entropy and the permutation test have a clear physical interpretation, the F-test with the Thomson multitaper estimator tends to find as no significant the peaks in the low frequencies and tends to give as significant more spurious peaks in the middle and high frequencies. Nevertheless, the best strategy is to use both techniques and to use the advantages of each of them. Full article
(This article belongs to the Special Issue Paleoceanography)
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Open AccessArticle
The Influence of Bed Roughness on Turbulence: Cabras Lagoon, Sardinia, Italy
J. Mar. Sci. Eng. 2015, 3(3), 935-956; https://doi.org/10.3390/jmse3030935 - 19 Aug 2015
Cited by 1 | Viewed by 2542
Abstract
Estimates of bed roughness used for predictions of sediment transport are usually derived either from simple scalars of the physical roughness (i.e., ripple height or grain size) or from the hydrodynamic roughness length (Zo) based upon velocity gradient estimates in the [...] Read more.
Estimates of bed roughness used for predictions of sediment transport are usually derived either from simple scalars of the physical roughness (i.e., ripple height or grain size) or from the hydrodynamic roughness length (Zo) based upon velocity gradient estimates in the benthic boundary layer. Neither parameter accounts for irregular bed features. This study re-evaluates the relation between hydrodynamic roughness and physical bed roughness using high-resolution seabed scanning in the inlet of a shallow lagoon. The statistically-robust relationship, based on a 1D statistical analysis of the seabed elevation at different locations of the Cabras lagoon. Sardinia, has been obtained between Zo and the topographical bed roughness Ks by defining Ks = 2*STD + skin friction, with STD the standard deviation of the seabed elevation variations. This correlation between Ks and Zo demonstrates that the roughness length is directly influenced by irregular bed features, and that the Reynolds number accounts for the total drag of the bed: the data points collapse on the Law of the Wall curves with a fitting factor x = 0.5. Further testing must be done in other locations and in the fully-rough domain in order to test how widely those new parameters can be applied. Full article
(This article belongs to the Special Issue Sediment Transport Modeling)
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Open AccessArticle
Formulating Fine to Medium Sand Erosion for Suspended Sediment Transport Models
J. Mar. Sci. Eng. 2015, 3(3), 906-934; https://doi.org/10.3390/jmse3030906 - 19 Aug 2015
Cited by 7 | Viewed by 2552
Abstract
The capacity of an advection/diffusion model to predict sand transport under varying wave and current conditions is evaluated. The horizontal sand transport rate is computed by vertical integration of the suspended sediment flux. A correction procedure for the near-bed concentration is proposed so [...] Read more.
The capacity of an advection/diffusion model to predict sand transport under varying wave and current conditions is evaluated. The horizontal sand transport rate is computed by vertical integration of the suspended sediment flux. A correction procedure for the near-bed concentration is proposed so that model results are independent of the vertical resolution. The method can thus be implemented in regional models with operational applications. Simulating equilibrium sand transport rates, when erosion and deposition are balanced, requires a new empirical erosion law that involves the non-dimensional excess shear stress and a parameter that depends on the size of the sand grain. Comparison with several datasets and sediment transport formulae demonstrated the model’s capacity to simulate sand transport rates for a large range of current and wave conditions and sand diameters in the range 100–500 μm. Measured transport rates were predicted within a factor two in 67% of cases with current only and in 35% of cases with both waves and current. In comparison with the results obtained by Camenen and Larroudé (2003), who provided the same indicators for several practical transport rate formulations (whose means are respectively 72% and 37%), the proposed approach gives reasonable results. Before fitting a new erosion law to our model, classical erosion rate formulations were tested but led to poor comparisons with expected sediment transport rates. We suggest that classical erosion laws should be used with care in advection/diffusion models similar to ours, and that at least a full validation procedure for transport rates involving a range of sand diameters and hydrodynamic conditions should be carried out. Full article
(This article belongs to the Special Issue Sediment Transport Modeling)
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Open AccessArticle
Ocean-Atmosphere CO2 Fluxes in the North Atlantic Subtropical Gyre: Association with Biochemical and Physical Factors during Spring
J. Mar. Sci. Eng. 2015, 3(3), 891-905; https://doi.org/10.3390/jmse3030891 - 13 Aug 2015
Viewed by 2371
Abstract
Sea surface partial pressure of CO2 (pCO2) was measured continuously in a transect of the North Atlantic subtropical gyre between Santo Domingo, Dominican Republic (18.1° N, 68.5° W) and Vigo, Spain (41.9° N, 11.8° W) during spring 2011. Additional biogeochemical [...] Read more.
Sea surface partial pressure of CO2 (pCO2) was measured continuously in a transect of the North Atlantic subtropical gyre between Santo Domingo, Dominican Republic (18.1° N, 68.5° W) and Vigo, Spain (41.9° N, 11.8° W) during spring 2011. Additional biogeochemical and physical variables measured to identify factors controlling the surface pCO2 were analyzed in discrete samples collected at 16 sites along the transect at the surface and to a depth of 200 m. Sea surface pCO2 varied between 309 and 662 μatm, and showed differences between the western and eastern subtropical gyre. The subtropical gyre acted as a net CO2 sink, with a mean flux of −5.5 ± 2.2 mmol m−2 day−1. The eastern part of the transect, close to the North Atlantic Iberian upwelling off the Galician coast, was a CO2 source with an average flux of 33.5 ± 9.0 mmol m−2 day−1. Our results highlight the importance of making more surface pCO2 observations in the area located east of the Azores Islands since air-sea CO2 fluxes there are poorly studied. Full article
(This article belongs to the Special Issue Air–Sea Gas Exchange Process and Impact Factors)
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Open AccessArticle
Bubble Clouds in Coastal Waters and Their Role in Air-Water Gas Exchange of CO2
J. Mar. Sci. Eng. 2015, 3(3), 866-890; https://doi.org/10.3390/jmse3030866 - 12 Aug 2015
Cited by 4 | Viewed by 2540
Abstract
Bubbles generated by breaking waves can drive significant gas exchange between the ocean and atmosphere, but the role of bubble-mediated gas transfer in estuaries is unknown. Here, backscatter data from 41 acoustic Doppler current profiler stations was analyzed to assess subsurface bubble distributions [...] Read more.
Bubbles generated by breaking waves can drive significant gas exchange between the ocean and atmosphere, but the role of bubble-mediated gas transfer in estuaries is unknown. Here, backscatter data from 41 acoustic Doppler current profiler stations was analyzed to assess subsurface bubble distributions in nine estuaries along the U.S. East and Gulf Coast. Wind speed, wind direction, and current velocity were the dominant controls on bubble entrainment, but the relative importance of these physical drivers depended on local geomorphology. Bubble entrainment in high-current or shallow, long-fetch estuaries began at wind speeds <5 m s1. In deep or fetch-limited estuaries, bubble entrainment was less frequent and generally began at higher wind speeds. Data observed during several storms suggests that episodic bubble-driven gas exchange may be an important component of annual CO2 fluxes in large, shallow estuaries but would be less significant in other coastal systems. Full article
(This article belongs to the Special Issue Air–Sea Gas Exchange Process and Impact Factors)
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Open AccessArticle
Variations in Microbial Community Structure through the Stratified Water Column in the Tyrrhenian Sea (Central Mediterranean)
J. Mar. Sci. Eng. 2015, 3(3), 845-865; https://doi.org/10.3390/jmse3030845 - 06 Aug 2015
Cited by 4 | Viewed by 2268
Abstract
The central Mediterranean Sea is among the most oligotrophic habitats in the marine environment. In this study, we investigated the abundance, diversity and activity of prokaryoplankton in the water column (25–3000-m depth) at Station Vector (Tyrrhenian Sea, 39°32.050′ N; 13°22.280′ E). This specific [...] Read more.
The central Mediterranean Sea is among the most oligotrophic habitats in the marine environment. In this study, we investigated the abundance, diversity and activity of prokaryoplankton in the water column (25–3000-m depth) at Station Vector (Tyrrhenian Sea, 39°32.050′ N; 13°22.280′ E). This specific water column consists of three different water masses (Modified Atlantic Water (MAW), Levantine Intermediate Water (LIW) and Tyrrhenian Deep Water (TDW), possessing a typical stratification of the Central Mediterranean basin. CARD-FISH showed that the metabolically-active fraction of bacterial populations exceeded the archaeal fraction along the whole water column, except at the deepest water masses. 16S rDNA and 16S rRNA clone libraries obtained from each type of water mass were used to analyse the prokaryoplankton community structure and to distinguish between active and “less active” microbial fractions. Our results showed that the rRNA-derived bacterial libraries seemed to be more depth specific compared to 16S rDNA-derived counterparts. Major differences were detected between the active fractions of bacterioplankton thriving in photic (25 m, MAW) and aphotic layers (500–3000 m, LIW and TDW respectively), whereas no statistically-significant differences were detected within the deep, aphotic layers (500–3000 m, LIW and TDW). Archaeal communities possessed more depth-specific distribution patterns with both total and active fractions showing depth stratification. Cyanobacteria and Marine Group II MAGII of Euryarchaea dominated the MAW prokaryoplankton. A notable fraction of Geitlerinema-related cyanobacteria was detected among the metabolically-active bacterial population recovered from the mesopelagic (500 m, LIW) aphotic layer, which is indicative of their mixotrophic behaviour. Heterotrophic Gammaproteobacteria and members of Marine Group 1.1a and the PSL12-related ALOHA group of Thaumarchaeota were both abundant in the aphotic layers (both LIW and TDW). Discrepancies observed between 16S rDNA- and 16S rRNA-based libraries are most likely linked to different physiological states of the prokaryoplankton community members recovered from different layers. Taking into account the relative homogeneity of the main physicochemical parameters throughout the whole water column, light and energy source are likely the most relevant environmental variables shaping microbial biodiversity through the Station Vector water column. Full article
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Open AccessArticle
Long Wave Flow Interaction with a Single Square Structure on a Sloping Beach
J. Mar. Sci. Eng. 2015, 3(3), 821-844; https://doi.org/10.3390/jmse3030821 - 05 Aug 2015
Cited by 21 | Viewed by 2900
Abstract
In the context of dam breaks, tsunami, and flash floods, it is paramount to quantify the time-history of forces by the rapidly transient flow to vertical structures and the characteristics of the induced flow patterns. To resemble on-land tsunami-induced flow, a free-surface-piercing structure [...] Read more.
In the context of dam breaks, tsunami, and flash floods, it is paramount to quantify the time-history of forces by the rapidly transient flow to vertical structures and the characteristics of the induced flow patterns. To resemble on-land tsunami-induced flow, a free-surface-piercing structure is exposed to long leading depression waves in a tsunami flume where long waves run up and down a 1:40 smooth and impermeable sloping beach after its generation by a volume-driven wave maker. The structure and its surrounding were monitored with force transducers, pressure gauges and cameras. Preparatory steady-state experiments were accomplished to determine the drag force coefficient of the square cylinder at various water depths. The flow during wave run-up and draw-down acting on the structure resulted in distinct flow pattern which were characteristic for the type of flow-structure interaction. Besides bow wave propagating upstream, a standing or partially-standing wave was observed in front of the structure together with a wake formation downstream, while a von Kármán vortex street developed during the deceleration phase of the flow motion and during draw-down. Force measurements indicated a sudden increase in the stream-wise total force starting with the arrival of the flow front during initial run-up. Lateral velocities showed significant oscillations in correlation with the von Kármán vortex street development. A comparison of the total measured base force with the analytically-calculated share of the drag force revealed that forces were prevailingly drag-dominated. Full article
(This article belongs to the Special Issue Tsunami Science and Engineering) Printed Edition available
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Open AccessArticle
The Dynamics, Ecological Variability and Estimated Carbon Stocks of Mangroves in Mahajamba Bay, Madagascar
J. Mar. Sci. Eng. 2015, 3(3), 793-820; https://doi.org/10.3390/jmse3030793 - 04 Aug 2015
Cited by 8 | Viewed by 3829
Abstract
Mangroves are found throughout the tropics, providing critical ecosystem goods and services to coastal communities and supporting rich biodiversity. Globally, mangroves are being rapidly degraded and deforested at rates exceeding loss in many tropical inland forests. Madagascar contains around 2% of the global [...] Read more.
Mangroves are found throughout the tropics, providing critical ecosystem goods and services to coastal communities and supporting rich biodiversity. Globally, mangroves are being rapidly degraded and deforested at rates exceeding loss in many tropical inland forests. Madagascar contains around 2% of the global distribution, >20% of which has been deforested since 1990, primarily from over-harvest for forest products and conversion for agriculture and aquaculture. While historically not prominent, mangrove loss in Madagascar’s Mahajamba Bay is increasing. Here, we focus on Mahajamba Bay, presenting long-term dynamics calculated using United States Geological Survey (USGS) national-level mangrove maps contextualized with socio-economic research and ground observations, and the results of contemporary (circa 2011) mapping of dominant mangrove types. The analysis of the USGS data indicated 1050 hectares (3.8%) lost from 2000 to 2010, which socio-economic research suggests is increasingly driven by commercial timber extraction. Contemporary mapping results permitted stratified sampling based on spectrally distinct and ecologically meaningful mangrove types, allowing for the first-ever vegetation carbon stock estimates for Mahajamba Bay. The overall mean carbon stock across all mangrove classes was estimated to be 100.97 ± 10.49 Mg C ha−1. High stature closed-canopy mangroves had the highest average carbon stock estimate (i.e., 166.82 ± 15.28 Mg C ha−1). These estimates are comparable to other published values in Madagascar and elsewhere in the Western Indian Ocean and demonstrate the ecological variability of Mahajamba Bay’s mangroves and their value towards climate change mitigation. Full article
(This article belongs to the Special Issue Biogeochemical Cycles in Mangrove Forests)
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Open AccessArticle
Development of a Site-Specific Kinetic Model for Chlorine Decay and the Formation of Chlorination By-Products in Seawater
J. Mar. Sci. Eng. 2015, 3(3), 772-792; https://doi.org/10.3390/jmse3030772 - 31 Jul 2015
Cited by 2 | Viewed by 2820
Abstract
Chlorine is used commonly to prevent biofouling in cooling water systems. The addition of chlorine poses environmental risks in natural systems due to its tendency to form chlorination by-products (CBPs) when exposed to naturally-occurring organic matter (NOM). Some of these CBPs can pose [...] Read more.
Chlorine is used commonly to prevent biofouling in cooling water systems. The addition of chlorine poses environmental risks in natural systems due to its tendency to form chlorination by-products (CBPs) when exposed to naturally-occurring organic matter (NOM). Some of these CBPs can pose toxic risks to aquatic and benthic species in the receiving waters. It is, therefore, important to study the fate of residual chlorine and CBPs to fully understand the potential impacts of chlorination to the environment. The goal of this study was to develop improved predictions of how chlorine and CBP concentrations in seawater vary with time, chlorine dose and temperature. In the present study, chlorination of once-through cooling water at Ras Laffan Industrial City (RLIC), Qatar, was studied by collecting unchlorinated seawater from the RLIC cooling water system intake, treating it with chlorine and measuring time series of chlorine and CBP concentrations. Multiple-rate exponential curves were used to represent fast and slow chlorine decay and CBP formation, and site-specific chlorine kinetic relationships were developed. Through extensive analysis of laboratory measurements, it was found that only some of the control parameters identified in the literature were important for predicting residual chlorine and CBP concentrations for this specific location. The new kinetic relationships were able to significantly improve the predictability and validity of Generalized Environmental Modeling System for Surfacewaters (GEMSS)-chlorine kinetics module (CKM), a three-dimensional hydrodynamic and chlorine kinetics and transport model when applied for RLIC outfall studies using actual field measurements. Full article
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Open AccessArticle
A Numerical Modelling Study on the Potential Role of Tsunamis in the Biblical Exodus
J. Mar. Sci. Eng. 2015, 3(3), 745-771; https://doi.org/10.3390/jmse3030745 - 28 Jul 2015
Cited by 2 | Viewed by 3027
Abstract
The reliability of the narrative of the Biblical Exodus has been subject of heated debate for decades. Recent archaeological studies seem to provide new insight of the exodus path, and although with a still controversial chronology, the effects of the Minoan Santorini eruption [...] Read more.
The reliability of the narrative of the Biblical Exodus has been subject of heated debate for decades. Recent archaeological studies seem to provide new insight of the exodus path, and although with a still controversial chronology, the effects of the Minoan Santorini eruption have been proposed as a likely explanation of the biblical plagues. Particularly, it has been suggested that flooding by the associated tsunamis could explain the first plague and the sea parting. Recent modelling studies have shown that Santorini’s tsunami effects were negligible in the eastern Nile Delta, but the released tectonic stress could have triggered local tsunamigenic sources in sequence. This paper is aimed to a quantitative assessment of the potential role of tsunamis in the biblical parting of the sea. Several “best case” scenarios are tested through the application of a numerical model for tsunami propagation that has been previously validated. The former paleogeographic conditions of the eastern Nile Delta have been implemented based upon recent geological studies; and several feasible local sources for tsunamis are proposed. Tsunamis triggered by submarine landslides of 10–30 km3 could have severely impacted the northern Sinai and southern Levantine coasts but with weak effects in the eastern Nile Delta coastline. The lack of noticeable flooding in this area under the most favorable conditions for tsunamis, along with the time sequence of water elevations, make difficult to accept them as a plausible and literally explanation of the first plague and of the drowning of the Egyptian army in the surroundings of the former Shi-Hor Lagoon. Full article
(This article belongs to the Special Issue Tsunami Science and Engineering) Printed Edition available
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Open AccessArticle
Hydrodynamic and Sediment Modelling within a Macro Tidal Estuary: Port Curtis Estuary, Australia
J. Mar. Sci. Eng. 2015, 3(3), 720-744; https://doi.org/10.3390/jmse3030720 - 24 Jul 2015
Cited by 7 | Viewed by 2266
Abstract
An understanding of sediment transport processes and resultant concentration dynamics in estuaries is of great importance to engineering design awareness and the management of these environments. Predictive modelling approaches provide an opportunity to investigate and address potential system responses to nominated events, changes, [...] Read more.
An understanding of sediment transport processes and resultant concentration dynamics in estuaries is of great importance to engineering design awareness and the management of these environments. Predictive modelling approaches provide an opportunity to investigate and address potential system responses to nominated events, changes, or conditions of interest, often on high temporal and spatial resolution scales. In this study, a three-dimensional hydrodynamic model and wave model were validated and applied to generate forcing conditions for input into a sediment transport model for the period 7 May 2010–30 October 2010 within a macro tidal estuary, Port Curtis estuary (Australia). The hydrodynamic model was verified against surface and near-bottom current measurements. The model accurately reproduced the variations of surface and near-bottom currents at both a mid-estuary and upper-estuary location. Sediment transport model predictions were performed under varying meteorological conditions and tidal forcing over a 180-day period and were validated against turbidity data collected at six stations within Port Curtis estuary. The sediment transport model was able to predict both the magnitudes of the turbidity levels and the modulation induced by the neap and spring tides and wind-wave variations. The model-predicted (converted) turbidity levels compared favourably with the measured surface water turbidity levels at all six stations. The study results have useful practical application for Port Curtis estuary, including providing predictive capabilities to support the selection of locations for monitoring/compliance sites. Full article
(This article belongs to the Special Issue Sediment Transport Modeling)
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Open AccessArticle
Phylogenetic Diversity of Diazotrophs along an Experimental Nutrient Gradient in Mangrove Sediments
J. Mar. Sci. Eng. 2015, 3(3), 699-719; https://doi.org/10.3390/jmse3030699 - 24 Jul 2015
Cited by 6 | Viewed by 2368
Abstract
The diversity of diazotrophs was studied in the sediment of mangrove forests (Twin Cays, Belize) subjected to a long-term fertilization with nitrogen and phosphorus. Terminal Restriction Fragment Length Polymorphism (TRFLP) and cloning of PCR-amplified nifH genes were combined via in silico analysis to [...] Read more.
The diversity of diazotrophs was studied in the sediment of mangrove forests (Twin Cays, Belize) subjected to a long-term fertilization with nitrogen and phosphorus. Terminal Restriction Fragment Length Polymorphism (TRFLP) and cloning of PCR-amplified nifH genes were combined via in silico analysis to assign clones to TRFLP-nifH phylotypes, as well as to characterize the occurrence of phylotypes in response to environmental conditions. Results indicated that mangrove sediments from Belize harbor a unique diazotrophic community with a low metabolic diversity dominated by sulfate reducers. The variability of potential nitrogen-fixing sulfate reducers was explained by several environmental parameters, primarily by the abundance of dead roots in the sediments, and the concentration of H2S in the pore-waters. This study describes the complexity of microbial communities within the mangrove sediments with specific functional groups varying along environmental gradients. Full article
(This article belongs to the Special Issue Biogeochemical Cycles in Mangrove Forests)
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Open AccessArticle
Observations and Predictions of Wave Runup, Extreme Water Levels, and Medium-Term Dune Erosion during Storm Conditions
J. Mar. Sci. Eng. 2015, 3(3), 674-698; https://doi.org/10.3390/jmse3030674 - 24 Jul 2015
Cited by 31 | Viewed by 3214
Abstract
Monitoring of dune erosion and accretion on the high-energy macrotidal Vougot beach in North Brittany (France) over the past decade (2004–2014) has revealed significant morphological changes. Dune toe erosion/accretion records have been compared with extreme water level measurements, defined as the sum of [...] Read more.
Monitoring of dune erosion and accretion on the high-energy macrotidal Vougot beach in North Brittany (France) over the past decade (2004–2014) has revealed significant morphological changes. Dune toe erosion/accretion records have been compared with extreme water level measurements, defined as the sum of (i) astronomic tide; (ii) storm surge; and (iii) vertical wave runup. Runup parameterization was conducted using swash limits, beach profiles, and hydrodynamic (Hm0, Tm0,–1, and high tide water level—HTWL) data sets obtained from high frequency field surveys. The aim was to quantify in-situ environmental conditions and dimensional swash parameters for the best calibration of Battjes [1] runup formula. In addition, an empirical equation based on observed tidal water level and offshore wave height was produced to estimate extreme water levels over the whole period of dune morphological change monitoring. A good correlation between this empirical equation (1.01Hmoξo) and field runup measurements (Rmax) was obtained (R2 85%). The goodness of fit given by the RMSE was about 0.29 m. A good relationship was noticed between dune erosion and high water levels when the water levels exceeded the dune foot elevation. In contrast, when extreme water levels were below the height of the toe of the dune sediment budget increased, inducing foredune recovery. These erosion and accretion phases may be related to the North Atlantic Oscillation Index. Full article
(This article belongs to the Special Issue Coastal Hazards Related to Storm Surge) Printed Edition available
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Open AccessArticle
Channel Shallowing as Mitigation of Coastal Flooding
J. Mar. Sci. Eng. 2015, 3(3), 654-673; https://doi.org/10.3390/jmse3030654 - 21 Jul 2015
Cited by 26 | Viewed by 9586
Abstract
Here, we demonstrate that reductions in the depth of inlets or estuary channels can be used to reduce or prevent coastal flooding. A validated hydrodynamic model of Jamaica Bay, New York City (NYC), is used to test nature-based adaptation measures in ameliorating flooding [...] Read more.
Here, we demonstrate that reductions in the depth of inlets or estuary channels can be used to reduce or prevent coastal flooding. A validated hydrodynamic model of Jamaica Bay, New York City (NYC), is used to test nature-based adaptation measures in ameliorating flooding for NYC's two largest historical coastal flood events. In addition to control runs with modern bathymetry, three altered landscape scenarios are tested: (1) increasing the area of wetlands to their 1879 footprint and bathymetry, but leaving deep shipping channels unaltered; (2) shallowing all areas deeper than 2 m in the bay to be 2 m below Mean Low Water; (3) shallowing only the narrowest part of the inlet to the bay. These three scenarios are deliberately extreme and designed to evaluate the leverage each approach exerts on water levels. They result in peak water level reductions of 0.3%, 15%, and 6.8% for Hurricane Sandy, and 2.4%, 46% and 30% for the Category-3 hurricane of 1821, respectively (bay-wide averages). These results suggest that shallowing can provide greater flood protection than wetland restoration, and it is particularly effective at reducing "fast-pulse" storm surges that rise and fall quickly over several hours, like that of the 1821 storm. Nonetheless, the goal of flood mitigation must be weighed against economic, navigation, and ecological needs, and practical concerns such as the availability of sediment. Full article
(This article belongs to the Special Issue Coastal Hazards Related to Storm Surge) Printed Edition available
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Open AccessArticle
The Measurement of Personal Self-Efficacy in Preparing for a Hurricane and Its Role in Modeling the Likelihood of Evacuation
J. Mar. Sci. Eng. 2015, 3(3), 630-653; https://doi.org/10.3390/jmse3030630 - 21 Jul 2015
Cited by 7 | Viewed by 2228
Abstract
Storm surges require that coastal residents make necessary preparations and evacuate the coast prior to hurricane landfall. An important individual characteristic in preparing for tropical cyclones is hurricane personal self-efficacy. Coastal residents who believe that it is possible to prepare for and evacuate [...] Read more.
Storm surges require that coastal residents make necessary preparations and evacuate the coast prior to hurricane landfall. An important individual characteristic in preparing for tropical cyclones is hurricane personal self-efficacy. Coastal residents who believe that it is possible to prepare for and evacuate ahead of a hurricane (hurricane response possibilities) and, further, believe that they personally can prepare and evacuate (hurricane personal self-efficacy) will be better prepared for hurricanes. In this study the author used a sample of 334 people to evaluate an 8-item self-report measure, the Hurricane Personal Self-Efficacy Scale (HPSES). This measure can be used to assess beliefs that it is possible in general to prepare for a hurricane and that the respondent him or herself can make these preparations and evacuate ahead of a hurricane. A factor analysis confirmed that the items measured two characteristics: (1) beliefs that is it possible for people in general to prepare for a hurricane; and (2) beliefs that the respondent personally could prepare for a hurricane and evacuate. The author also examined the functionality of the measure within a framework that was informed by Protection Motivation Theory (PMT). Hurricane response possibility beliefs, prior experiences with hurricane evacuation and hurricane-related property damages, and a tendency for people to sense and observe the weather were all predictive of personal self-efficacy in preparing for hurricanes, R2adj = 0.36. In operationalizing other constructs associated with PMT using weather-related psychological measures in a path analysis model, it was found that personal self-efficacy, fear of consequences of the severe and extreme weather, and appraisal of the threats posed by behaviors that could result in injury or death during severe weather together predicted the self-reported likelihood of evacuating, R2adj = 0.26. The implications of the study for coastal engineers and planners, ways of increasing hurricane personal self-efficacy in preparing for hurricanes, and the study's limitations are discussed. Full article
(This article belongs to the Special Issue Coastal Hazards Related to Storm Surge) Printed Edition available
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Open AccessArticle
Modeling Storm Surge and Inundation in Washington, DC, during Hurricane Isabel and the 1936 Potomac River Great Flood
J. Mar. Sci. Eng. 2015, 3(3), 607-629; https://doi.org/10.3390/jmse3030607 - 21 Jul 2015
Cited by 11 | Viewed by 3310
Abstract
Washington, DC, the capital of the U.S., is located along the Upper Tidal Potomac River, where a reliable operational model is needed for making predictions of storm surge and river-induced flooding. We set up a finite volume model using a semi-implicit, Eulerian-Lagrangian scheme [...] Read more.
Washington, DC, the capital of the U.S., is located along the Upper Tidal Potomac River, where a reliable operational model is needed for making predictions of storm surge and river-induced flooding. We set up a finite volume model using a semi-implicit, Eulerian-Lagrangian scheme on a base grid (200 m) and a special feature of sub-grids (10 m), sourced with high-resolution LiDAR data and bathymetry surveys. The model domain starts at the fall line and extends 120 km downstream to Colonial Beach, VA. The model was used to simulate storm tides during the 2003 Hurricane Isabel. The water level measuring 3.1 m reached the upper tidal river in the vicinity of Washington during the peak of the storm, followed by second and third flood peaks two and four days later, resulting from river flooding coming downstream after heavy precipitation in the watershed. The modeled water level and timing were accurate in matching with the verified peak observations within 9 cm and 3 cm, and with R2 equal to 0.93 and 0.98 at the Wisconsin Avenue and Washington gauges, respectively. A simulation was also conducted for reconstructing the historical 1936 Potomac River Great Flood that inundated downtown. It was identified that the flood water, with a velocity exceeding 2.7 m/s in the downstream of Roosevelt Island, pinched through the bank northwest of East Potomac Park near DC. The modeled maximum inundation extents revealed a crescent-shaped flooding area, which was consistent with the historical surveyed flood map of the event. Full article
(This article belongs to the Special Issue Coastal Hazards Related to Storm Surge) Printed Edition available
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Open AccessArticle
Climate Change, Coastal Vulnerability and the Need for Adaptation Alternatives: Planning and Design Examples from Egypt and the USA
J. Mar. Sci. Eng. 2015, 3(3), 591-606; https://doi.org/10.3390/jmse3030591 - 15 Jul 2015
Cited by 10 | Viewed by 3508
Abstract
Planning and design of coastal protection for high-risk events with low to moderate or uncertain probabilities are a challenging balance of short- and long-term cost vs. protection of lives and infrastructure. The pervasive, complex, and accelerating impacts of climate change on coastal [...] Read more.
Planning and design of coastal protection for high-risk events with low to moderate or uncertain probabilities are a challenging balance of short- and long-term cost vs. protection of lives and infrastructure. The pervasive, complex, and accelerating impacts of climate change on coastal areas, including sea-level rise, storm surge and tidal flooding, require full integration of the latest science into strategic plans and engineering designs. While the impacts of changes occurring are global, local effects are highly variable and often greatly exacerbated by geophysical (land subsidence, faulting), oceanographic (ocean circulation, wind patterns) and anthropogenic factors. Reducing carbon emissions is needed to mitigate global warming, but adaptation can accommodate at least near future change impacts. Adaptation should include alternatives that best match region-specific risk, time frame, environmental conditions, and the desired protection. Optimal alternatives are ones that provide protection, accommodate or mimic natural coastal processes, and include landforms such as barrier islands and wetlands. Plans are often for 50 years, but longer-term planning is recommended since risk from climate change will persist for centuries. This paper presents an assessment of impacts of accelerating climate change on the adequacy of coastal protection strategies and explores design measures needed for an optimum degree of protection and risk reduction. Three coastal areas facing similar challenges are discussed: Abu-Qir Bay, Nile River delta plain, Egypt; Lake Borgne, New Orleans, Louisiana delta plain; and the New York City region. Full article
(This article belongs to the Special Issue Coastal Hazards Related to Storm Surge) Printed Edition available
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Open AccessArticle
Coastal Flood Assessment Based on Field Debris Measurements and Wave Runup Empirical Model
J. Mar. Sci. Eng. 2015, 3(3), 560-590; https://doi.org/10.3390/jmse3030560 - 15 Jul 2015
Cited by 18 | Viewed by 2881
Abstract
On 6 December 2010, an extra-tropical storm reached Atlantic Canada, causing coastal flooding due to high water levels being driven toward the north shore of Chaleur Bay. The extent of flooding was identified in the field along the coastline at Maria using DGPS. [...] Read more.
On 6 December 2010, an extra-tropical storm reached Atlantic Canada, causing coastal flooding due to high water levels being driven toward the north shore of Chaleur Bay. The extent of flooding was identified in the field along the coastline at Maria using DGPS. Using the assumption that the maximum elevation of flooded areas represents the combination of astronomical tide, storm surge and wave runup, which is the maximum elevation reached by the breaking waves on the beach, all flood limits were identified. A flood-zone delineation was performed using GIS and LiDAR data. An empirical formula was used to estimate runup elevation during the flood event. A coastal flood map of the 6 December flood event was made using empirical data and runup calculations according to offshore wave climate simulations. Along the natural beach, results show that estimating runup based on offshore wave data and upper foreshore beach slope represents well the observed flood extent. Where a seawall occupies the beach, wave breaking occurs at the toe of the structure and wave height needs to be considered independently of runup. In both cases (artificial and natural), flood risk is underestimated if storm surge height alone is considered. There is a need to incorporate wave characteristics in order to adequately model potential flood extent. A coastal flooding projection is proposed for Pointe Verte based on total water levels estimated according to wave climate simulation return periods and relative sea-level rise for the Chaleur Bay. Full article
(This article belongs to the Special Issue Coastal Hazards Related to Storm Surge) Printed Edition available
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Open AccessArticle
Artificial Crab Burrows Facilitate Desalting of Rooted Mangrove Sediment in a Microcosm Study
J. Mar. Sci. Eng. 2015, 3(3), 539-559; https://doi.org/10.3390/jmse3030539 - 15 Jul 2015
Cited by 7 | Viewed by 2328
Abstract
Water uptake by mangrove trees can result in salt accumulation in sediment around roots, negatively influencing growth. Tidal pumping facilitates salt release and can be enhanced by crab burrows. Similarly, flushing of burrows by incoming tidal water decreases sediment salinity. In contrast to [...] Read more.
Water uptake by mangrove trees can result in salt accumulation in sediment around roots, negatively influencing growth. Tidal pumping facilitates salt release and can be enhanced by crab burrows. Similarly, flushing of burrows by incoming tidal water decreases sediment salinity. In contrast to burrows with multiple entrances, the role of burrows with one opening for salinity reduction is largely unknown. In a microcosm experiment we studied the effect of artificial, burrow-like macro-pores with one opening on the desalting of mangrove sediment and growth of Rhizophora mangle L. seedlings. Sediment salinity, seedling leaf area and seedling growth were monitored over six months. Artificial burrows facilitated salt release from the sediment after six weeks, but seedling growth was not influenced. To test whether crab burrows with one opening facilitate salt release in mangrove forests, sediment salinities were measured in areas with and without R. mangle stilt roots in North Brazil at the beginning and end of the wet season. In addition, burrows of Ucides cordatus were counted. High crab burrow densities and sediment salinities were associated with stilt root occurrence. Precipitation and salt accumulation by tree roots seem to have a larger effect on sediment salinity than desalting by U. cordatus burrows. Full article
(This article belongs to the Special Issue Biogeochemical Cycles in Mangrove Forests)
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Open AccessArticle
Novel Solution for Low-Lying Land Areas Safe from Natural Hazards—Toward Reconstruction of Lost Coastal Areas in Northeast Japan
J. Mar. Sci. Eng. 2015, 3(3), 520-538; https://doi.org/10.3390/jmse3030520 - 10 Jul 2015
Cited by 1 | Viewed by 2513
Abstract
The imminent fear of water-related hazards such as flooding hangs over low-lying areas, in particular now because climate changes have led to increased hazards, like storm surges, that could result in serious harm. This paper aims to provide a novel solution—namely “the floating [...] Read more.
The imminent fear of water-related hazards such as flooding hangs over low-lying areas, in particular now because climate changes have led to increased hazards, like storm surges, that could result in serious harm. This paper aims to provide a novel solution—namely “the floating platform”—that can transform dangerous low-lying areas into those safeguarded against potential hazards. Additionally, by utilizing this solution as a secure base for society to build atop this new artificial reservoir, we offer a better future role for such areas. Meanwhile, we propose adoption of our concept soon at two low-lying areas in northeast Japan hard-hit by the huge 11 March 2011 tsunami: Sendai’s Arahama coastal district and the still-devastated residential harbor area of Kesennuma, both cities in need of a fresh perspective. Full article
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Open AccessArticle
Temperature Dependence of Respiration in Larvae and Adult Colonies of the Corals Acropora tenuis and Pocillopora damicornis
J. Mar. Sci. Eng. 2015, 3(3), 509-519; https://doi.org/10.3390/jmse3030509 - 29 Jun 2015
Cited by 3 | Viewed by 1945
Abstract
Although algal symbionts can become a source of reactive oxygen species under stressful conditions, symbiotic planulae of the coral Pocillopora damicornis are highly tolerant to thermal stress compared with non-symbiotic planulae of Acropora tenuis. As a first step to understand how [...] Read more.
Although algal symbionts can become a source of reactive oxygen species under stressful conditions, symbiotic planulae of the coral Pocillopora damicornis are highly tolerant to thermal stress compared with non-symbiotic planulae of Acropora tenuis. As a first step to understand how P. damicornis planulae attain high stress tolerance, we compared the respiration rate and temperature dependence between symbiotic planulae of P. damicornis and non-symbiotic planulae of A. tenuis, as well as between larvae and adult branches within each species. Larvae and adult branches of both species had similar temperature dependency of respiration rate, with the temperature coefficient (Q10) values of about 2. Planula larvae of P. damicornis had a significantly lower respiration rate than that of A. tenuis larvae at 25–30 °C, but not at 32 °C, whereas adult branches of P. damicornis had a significantly higher respiration rate than that of A. tenuis branches at all temperatures. Thus, P. damicornis larvae appear to be capable of reducing their respiration rate to a greater extent than A. tenuis larvae, which could partly explain why P. damicornis larvae had high survivorship under thermal stress, although other antioxidant or photoprotective mechanisms should be investigated in the future. Full article
(This article belongs to the Special Issue Climate Change and Coral Reefs Ecosystems)
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