Posidonia oceanica, the most abundant seagrass species in the Mediterranean, supports a highly bio-diverse habitat and is crucial in protecting against coastal erosion. In this work, experiments in a large-scale facility have been performed, for the measurement of wave attenuation, transmission and energy dissipation over artificial Posidonia oceanica. The effects of submergence ratio corresponding to the seagrass height divided by water depth, and seagrass density as the number of stems per square metre on the above characteristics are investigated. Measurements of wave height at different locations along the vegetation meadow indicate the wave attenuation along the Posidonia oceanica for three different submergence ratios and two seagrass densities. Results are also analysed with regard to the wave-induced flow within the meadow, and the effects of the submergence ratio and the seagrass density on the mean flow characteristics, based on data of mean velocities taken at three locations within the seagrass.

Amos, C.L.; Umgiesser, G.; Ghezzo, M.; Kassem, H., and Ferrarin, C., 0000. Sea surface temperature trends in Venice lagoon and the adjacent waters. Two coastal lagoons and coastal waters in the northern Adriatic region, Italy, were examined to assess the anthropogenic impact on coastal sea surface temperature (SST). The first lagoon was the highly altered Venice lagoon, and the second was the largely natural Marano-Grado lagoon. There are converging lines of evidence for air warming in the Venice region since 1910 at a long-term rate of 0.095°C/decade. Since 1980, the warming has accelerated to 0.65°C/decade in the centre of Venice. The acceleration in air warming is also evident in the MOHAT4 data set from the northern Adriatic Sea, although the rate of warming is less (0.36°C/decade). This warming trend is mimicked in the HadISST1.1 data set of SST for the northern Adriatic Sea (0.33°C/decade), whereas no trend was detected before 1980. SST and air temperature in both Venice and Marano-Grado la...

Amos, C.L.; Brylinsky, M.; Forbes, D.L.; Robertson, A.; Thompson, C.E.L., and Kassem, H., 0000. Stability of seabed sediments in the embayments of North Rustico, Prince Edward Island, Canada. This paper describes a series of 15 deployments of the annular benthic flume Sea Carousel made along the two estuaries of North Rustico, Prince Edward Island (PEI), Canada: The Hunter River estuary and the Wheatley River estuary. The study was part of a wider study on the environmental impact of coastal changes and aquaculture (Mytilus edulis) development in the region. The study site was situated on the dynamic north shore of PEI that is characterised by sandy barrier islands, inlets and beaches, and muddy lagoons. The lagoons are dominated by the seagrass Zostera marina in the muddy outer parts and by Ulva lactuca in the eutrophic inner parts. The thresholds for surface erosion of cohesive sediments (0.10 < τ_crit,o < 0.75) derived from trends of suspended sediment concentration (C) increased with distance (d) into the estuary: τ_crit,o = 0.50e^−0.26d (±0.05) Pa. Location in the estuary is the best predictor of bed stability. The next best predictor is surface sediment wet bulk density (ρ_b), which takes the form: τ_crit,o = 6.67 × 10⁻⁴(ρ_b) − 0.55 Pa. Erosion rates (E) can only be correlated (significantly) with excess bed shear stress (τ_ex) by incorporation of a time (depth)-varying erosion threshold. A power function emerged of the form: E = E_oτ_ex^m kg/m²/s (0.28 < m < 1.06). The exponent is within the range of laboratory experiments reported in the literature. The still-water settling rates of eroded material are diagnostic of a wide range of sedimentation diameters varying from fine sand to medium silt. The deposition threshold (τ_d) was evaluated in a laboratory equivalent of Sea Carousel (Lab Carousel) for sites RUS11 and RUS12 and yielded a mean value of 0.51 Pa. The exponential decay constant (k) for still-water settling is strongly dependent on initial concentration and suggests a constant settling rate that fits with data from a wide variety of settings throughout Canada.

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.

During last three decades, rapid urbanisation in Kuwait has been concentrated along the coastal zone, especially along the southern part of Kuwait Bay. The main impacts are related to the discharge of treated and untreated sewage; aquaculture; desalination of marine water; oil refinery plants near the shoreline; land filling and dredging activities; and construction of marinas. The distribution of desalination power plants around the bay affected marine ecosystems in terms of increasing water salinity and water temperature. Two Landsat images of different dates are used in this study to demonstrate the impacts on the sea surface temperature of anthropogenic activities along the coastal of Kuwait Bay. The first one is Landsat Thematic Mapper (TM) dated June, 22 1985 and the second one is Landsat Enhanced Thematic Mapper (ETM) dated April, 29 2003. The master Landsat image of 22/6/1985 was geometrically corrected using 14 ground control points (GCPs) extracted from a topographic base map (scale 1:50,000). It was projected into a UTM coordinate system with spheroid WGS 84 and datum WGS 84 (zone 39). The other image was registered using the geometrically corrected master image. The mean square error of the georeferenced image is less than 0.5 pixels. Then, an unsupervised classification (10 classes) was used to produce a water-only mask and water-only images of the study area. ERDAS Imagine software was used to produce the subsets of the study area for different water-only images. The radiometric correction was applied to the different Landsat images to convert the digital number (DN) values of image pixels into at-sensor radiance. Finally thermal infrared sensors (band 6) of each Landsat image were used to measure the sea surface temperature (SST) of Kuwait Bay. Results indicate that there is a positive relationship between anthropogenic activities, especially the desalination power plants and increases the SST in Kuwait Bay.