J. Mar. Sci. Eng.2015, 3(1), 23-51; doi:10.3390/jmse3010023 - published 15 January 2015 Show/Hide Abstract
Abstract: We propose a methodological approach for a comprehensive and total probabilistic tsunami hazard assessment (TotPTHA), in which many different possible source types concur to the definition of the total tsunami hazard at given target sites. In a multi-hazard and multi-risk perspective, the approach allows us to consider all possible tsunamigenic sources (seismic events, slides, volcanic eruptions, asteroids, etc.). In this respect, we also formally introduce and discuss the treatment of interaction/cascade effects in the TotPTHA analysis and we demonstrate how the triggering events may induce significant temporary variations in short-term analysis of the tsunami hazard. In two target sites (the city of Naples and the island of Ischia in Italy) we prove the feasibility of the TotPTHA methodology in the multi—source case considering near submarine seismic sources and submarine mass failures in the study area. The TotPTHA indicated that the tsunami hazard increases significantly by considering both the potential submarine mass failures and the submarine seismic events. Finally, the importance of the source interactions is evaluated by applying a triggering seismic event that causes relevant changes in the short-term TotPTHA.
J. Mar. Sci. Eng.2015, 3(1), 1-20; doi:10.3390/jmse3010001 - published 26 December 2014 Show/Hide Abstract
Abstract: Remote sensing shows potential for assessing biodiversity of coral reefs. Important steps in achieving this objective are better understanding the spectral variability of various reef components and correlating these spectral characteristics with field-based ecological assessments. Here we analyze >9400 coral reef field spectra from southwestern Puerto Rico to evaluate how spectral variability and, more specifically, spectral similarity between species influences estimates of biodiversity. Traditional field methods for estimating reef biodiversity using photoquadrats are also included to add ecological context to the spectral analysis. Results show that while many species can be distinguishedusing in situ field spectra, the addition of the overlying water column significantly reduces the ability to differentiate species, and even groups of species. This indicates that the ability to evaluate biodiversity with remote sensing decreases with increasing water depth. Due to the inherent spectral similarity amongst many species, including taxonomically dissimilar species, remote sensing underestimates biodiversity and represents the lower limit of actual species diversity. The overall implication is that coral reef ecologists using remote sensing need to consider the spatial and spectral context of the imagery, and remote sensing scientists analyzing biodiversity need to define confidence limits as a function of both water depth and the scale of information derived, e.g., species, groups of species, or community level.
J. Mar. Sci. Eng.2014, 2(4), 616-632; doi:10.3390/jmse2040616 - published 18 November 2014 Show/Hide Abstract
Abstract: A stormwater runoff model based on the Soil Conservation Service (SCS) method and a finite-volume based water quality model have been developed to investigate the use of Simulink for use in teaching and research. Simulink, a MATLAB extension, is a graphically based model development environment for system modeling and simulation. Widely used for mechanical and electrical systems, Simulink has had less use for modeling of hydrologic systems. The watershed model is being considered for use in teaching graduate-level courses in hydrology and/or stormwater modeling. Simulink’s block (data process) and arrow (data transfer) object model, the copy and paste user interface, the large number of existing blocks, and the absence of computer code allows students to become model developers almost immediately. The visual depiction of systems, their component subsystems, and the flow of data through the systems are ideal attributes for hands-on teaching of hydrologic and mass balance processes to today’s computer-savvy visual learners. Model development with Simulink for research purposes is also investigated. A finite volume, multi-layer pond model using the water quality kinetics present in CE-QUAL-W2 has been developed using Simulink. The model is one of the first uses of Simulink for modeling eutrophication dynamics in stratified natural systems. The model structure and a test case are presented. One use of the model for teaching a graduate-level water quality modeling class is also described.
J. Mar. Sci. Eng.2014, 2(4), 593-615; doi:10.3390/jmse2040593 - published 14 October 2014 Show/Hide Abstract
Abstract: Limfjorden is a major Danish water system that connects the North Sea via Thyborøn Kanal in the west and to the Kattegat in the east. Limfjorden is heavily eutrophicated and certain areas suffer from oxygen depletion each summer. Bottom-dwelling fish have disappeared as the number of jellyfish and ctenophores has increased. The abundance and predation impact of jellyfish and ctenophores in Limfjorden have been described in a number of studies conducted during the last decade, and a mini-review of this literature is given here in Section 2. The common jellyfish Aurelia aurita may, in a few years, be very abundant and exert a considerable predatory impact on zooplankton and fish larvae. Abundance, species composition, and population dynamics of A. aurita may, at irregular time intervals, be strongly influenced not only by the water brought into Limfjorden from the North Sea, but also by competition with the invasive ctenophore Mnemiopsis leidyi that occurred for the first time in extremely high numbers in 2007, brought into the fjord system with North Sea water. It has been suggested that Limfjorden may function as an incubator for M. leidyi with the potential to further seed M. leidyi into the Kattegat and adjacent Danish waters, and recent observations seem to support this hypothesis. In Section 3, we report on two bloom events of ctenophores, Pleurobrachia pileus and M. leidyi, along with their predators (Beroe spp.) in Limfjorden in the autumns of 2012 and 2013, when the usually dominating A. aurita was absent. However, the present observation of B. ovata being M. leidyi’s native predator and a new species in Limfjorden may in the future reduce the abundance of M. leidyi.
J. Mar. Sci. Eng.2014, 2(3), 568-592; doi:10.3390/jmse2030568 - published 19 August 2014 Show/Hide Abstract
Abstract: Results from a series of field experiments, conducted to investigate the influence of infragravity waves (from wave groups), ripple type and location relative to the breaker line on cross-shore suspended sediment flux close to the sea bed in nearshore environments, are presented. The field data were collected from Cable Beach (Broome) and Mullaloo Beach in Western Australia and Chilaw in Sri Lanka. These beaches experience different incident wave, tidal and morphological conditions, with Cable Beach having a 10-m spring tidal range, whilst the other two beaches have tidal ranges <1.0 m. Measurements included simultaneous records of surface elevation, two-dimensional horizontal current velocities and suspended sediment concentrations, together with half-hourly observations of the seabed topography. Although most of the data sets were obtained just outside of the surf zone, a few results from inside of the surf zone were also included. A significant correlation between wave groups and suspended sediment concentration was found at all of the measurement sites, either with or without bed ripples. The direction and magnitude of cross-shore suspended sediment flux varied with location with respect to the breaker line; however, other parameters, such as bed ripples and velocity skewness, could have influenced this result. In Broome, where the measurement location with respect to the breaker line varied with the tidal cycle, the cross-shore sediment flux due to swell waves was shoreward inside and just outside of the surf zone and seaward farther offshore of the breaker line. Further, sediment flux due to swell waves was onshore when the seabed was flat and offshore over post-vortex ripples. Sediment flux due to swell waves was onshore when the normalised velocity skewness towards the shore was high (positive); the flux was offshore when the skewness was lower, but positive, suggesting the influence of other parameters, such as ripples and grain size. The net cross-shore sediment flux was onshore when the Dean number was less than 1.67 and offshore when the Dean number was greater than 1.67. Nevertheless, the Dean number did not account for the influence of ripples or velocity skewness. The cross-shore sediment flux at the infragravity frequency was mainly offshore outside of the surf zone, whereas it varied between onshore and offshore inside of the surf zone.