Tidal marsh vegetation is increasingly valued for its role in ecosystem‐based coastal protection due to its wave dissipating capacity. As the efficiency of wave dissipation is known to depend on specific vegetation properties, we quantified how these morphological, biochemical, and biomechanical properties of tidal marsh vegetation are, in turn, affected by wave exposure. This was achieved by field measurements at two locations, with contrasting wave exposure, in the brackish part of the Scheldt Estuary (SW Netherlands), where Scirpus maritimus is the dominant pioneer species. Our results show that shoots from more wave‐exposed conditions developed significantly shorter and thicker stems than the ones growing in more sheltered conditions. Furthermore, we show that the more exposed shoots are more flexible whereas the shoots growing in more sheltered conditions are stiffer. This may indicate plasticity in response to wave exposure following a stress‐avoidance strategy. Increasing stiffness was shown to be related to enhanced biogenic silica and lignin contents of the shoot tissue. These properties might affect the wave‐attenuating capacity of the marsh as stiff plants are known to mitigate waves more effectively than flexible ones. However, we also found higher shoot densities on the exposed site, which may partly explain why higher relative wave attenuation rates were found on the exposed site, despite the presence of more flexible individual shoots. This study highlights that the efficiency of wave attenuation by tidal marsh vegetation ultimately depends on mutual interactions between waves and plasticity in morphological, biochemical, and biomechanical plant properties.
Some three hundred mainly steel shipwrecks from both World Wars lie buried at shallow depths along the Belgian North Sea coast. They were examined recently to estimate corrosion rates over periods in excess of 100 years. The rate was estimated by comparing the measured in-situ steel plate thicknesses with archived ship information. The estimates show distinctly lower long-term corrosion rate compared to that predicted by the Melchers (Modeling of marine immersion corrosion for mild and low alloy steelspart 1: phenomenological model. Corrosion. 2003;59(4):319-334) corrosion model, when parameterised for local North Sea conditions. Concretion after 50 years has a multi-layer structure for which SEM-EDS and XRD measurements show the innermost layer, close to the metal surface, consisting of akaganeite, and the outer layer mostly of calcium carbonates, silicates, and some siderite. In between there is a considerable layer of hard magnetite. The latter is proposed as the reason for the low long-term corrosion rate (0.016 mm y-1) in an environment with calcium carbonate available in abundance.
Baker et al. [2] show, via algebraic methods, that a regular hyperbolic fibration of PG(3, q) with constant back half gives rise to a flock of a quadratic cone in PG(3, q), and conversely. In this paper a geometric construction for q even of the flock from the hyperbolic fibration, and conversely, will be described. A proof will be given that this geometric construction indeed corresponds to the known algebraic one.
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