J. Mar. Sci. Eng.2016, 4(3), 45; doi:10.3390/jmse4030045 (registering DOI) - published 30 July 2016 Show/Hide Abstract
Abstract: Large estuaries are especially vulnerable to coastal flooding due to the potential of combined storm surges and riverine flows. Numerical models can support flood prevention and planning for coastal communities. However, while recent advancements in the development of numerical models for storm surge prediction have led to robust and accurate models; an increasing number of parameters and physical processes’ representations are available to modelers and engineers. This study investigates uncertainties associated with the selection of physical parameters or processes involved in storm surge modeling in large estuaries. Specifically, we explored the sensitivity of a hydrodynamic model (ADCIRC) and a coupled wind-wave and circulation model system (ADCIRC + SWAN) to Manning’s n coefficient, wind waves and circulation interaction (wave setup), minimum depth (H0) in the wetting and drying algorithm, and spatially constant horizontal eddy viscosity (ESLM) forced by tides and hurricane winds. Furthermore, sensitivity analysis to Manning’s n coefficient and the interaction of waves and circulation were analyzed by using three different numerical meshes. Manning’s coefficient analysis was divided into waterway (rivers, bay and shore, and open ocean) and overland. Overall, the rivers exhibited a larger sensitivity, and M2 amplitude and maximum water elevations were reduced by 0.20 m and 0.56 m, respectively, by using a high friction value; similarly, high friction reduced maximum water levels up to 0.30 m in overland areas; the wave setup depended on the offshore wave height, angle of breaking, the profile morphology, and the mesh resolution, accounting for up to 0.19 m setup inside the bay; minimum depth analysis showed that H0 = 0.01 added an artificial mass of water in marshes and channels, meanwhile H = 0.1 partially solved this problem; and the eddy viscosity study demonstrated that the ESLM = 40 values reduced up to 0.40 m the peak of the maximum water levels in the upper side of narrow rivers.
J. Mar. Sci. Eng.2016, 4(3), 43; doi:10.3390/jmse4030043 - published 9 July 2016 Show/Hide Abstract
Abstract: Acoustic methods used in fish abundance estimation constitute a key part of the analytic assessment that makes the basis for abundance estimation of marine resources. The methods rely on power-budget equations and calibrated systems. Different formulations of power-budget equations and calibration factors have been proposed for use in scientific echo sounder and sonar systems. There are unresolved questions and apparent inconsistencies in prior literature related to this field. A generic (instrument independent) and unifying theory is presented that attempts to explain the different power-budget and calibration factor formulations proposed and used in prior literature, and how these are mutually related. Deviations and apparent inconsistencies in this literature appear to be explained and corrected. This also includes different (instrument specific) formulations employed in important modern scientific echo sounder systems, and their relationship to the generic theory of abundance estimation. Prior literature is extended to provide more complete power-budget equations for fish abundance estimation and species identification, by accounting for echo integration, electrical termination, and the full range of electrical and acoustical echo sounder parameters. The expressions provide a consistent theoretical basis for improved understanding of conventional methods and instruments used today, also enabling improved sensitivity and error analyses, and correction possibilities.
J. Mar. Sci. Eng.2016, 4(3), 42; doi:10.3390/jmse4030042 - published 8 July 2016 Show/Hide Abstract
Abstract: A recently developed BioEnergetic Growth (BEG) model for blue mussels (Mytilus edulis), valid for juvenile mussels, has been further developed to an ‘extended model’ and an alternative ‘ad hoc BEG model’ valid for post-metamorphic mussels, where the latter accounts for changing ambient chl a concentration. It was used to predict the growth of M. edulis on optimally thinned farm-ropes in Great Belt (Denmark), from newly settled post-metamorphic mussels of an initial shell size of 0.8 mm to marketable juvenile 30–35 mm ‘mini-mussels’. Such mussels will presumably in the near future be introduced as a new Danish, smaller-sized consumer product. Field data for actual growth (from Day 0 = 14 June 2011) showed that size of ‘mini-mussel’ was reached on Day 109 (Oct 1) and length 38 mm on Day 178 (Dec 9) while the corresponding predictions using the extended model were Day 121 (Oct 13) and Day 159 (Nov 20). Similar results were obtained by use of the ad hoc BEG model which also demonstrated the sensitivity of growth prediction to levels of chl a concentration, but less to temperature. The results suggest that it is possible (when the conditions are optimal, i.e., no intraspecific competition ensured by sufficient thinning) to produce ‘mini-mussels’ in Great Belt during one season, but not the usual marketable 45-mm mussels. We suggest that the prediction model may be used as a practical instrument to evaluate to what degree the actual growth of mussels on farm ropes due to intraspecific competition may deviate from the potential (optimal) growth under specified chl a and temperature conditions, and this implies that the effect of thinning to optimize the individual growth by eliminating intraspecific competition can be rationally evaluated.
J. Mar. Sci. Eng.2016, 4(2), 41; doi:10.3390/jmse4020041 - published 3 June 2016 Show/Hide Abstract
Abstract: Evaluating the degree of metal exposure and bioaccumulation in estuarine organisms is important for understanding the fate of metals in estuarine food webs. We investigated the bioaccumulation of Hg, methylmercury (MeHg), Cd, Se, Pb, and As in common intertidal organisms across a watershed urbanization gradient of coastal marsh sites in New England to relate metal exposure and bioaccumulation in fauna to both chemical and ecological factors. In sediments, we measured metal and metalloid concentrations, total organic carbon (TOC) and SEM-AVS (Simultaneously extracted metal-acid volatile sulfides). In five different functional feeding groups of biota, we measured metal concentrations and delta 15N and delta 13C signatures. Concentrations of Hg and Se in biota for all sites were always greater than sediment concentrations whereas Pb in biota was always lower. There were positive relationships between biota Hg concentrations and sediment concentrations, and between biota MeHg concentrations and both pelagic feeding mode and trophic level. Bioavailability of all metals measured as SEM-AVS or Benthic-Sediment Accumulation Factor was lower in more contaminated sites, likely due to biogeochemical factors related to higher levels of sulfides and organic carbon in the sediments. Our study demonstrates that for most metals and metalloids, bioaccumulation is metal specific and not directly related to sediment concentrations or measures of bioavailability such as AVS-SEM.
J. Mar. Sci. Eng.2016, 4(2), 40; doi:10.3390/jmse4020040 - published 3 June 2016 Show/Hide Abstract
Abstract: Sandy beaches play a key role in regional tourism. It is important to understand the principal morphological processes behind preserving attractive beaches. In this study, morphological variation on the Chirihama Coast, Japan, an important local tourism resource, was investigated using two sets of field surveys. The objective was to analyze and document the multi-scale behaviors of the beach. First, long-term shoreline changes were examined based on shoreline surveys over the last two decades. Then, the middle-term behavior of multiple bar systems was analyzed based on the cross-shore profile surveys from 1998 to 2010. An empirical orthogonal function (EOF) analysis was conducted to capture the principal modes of the systematic bar migration. The shoreline analysis indicated a long-term eroding trend and showed that the seasonal variation has recently tended to increase. The profile analysis demonstrated that net offshore migrations of bars have been repeated with a return period of approximately four years. This general behavior of the bar system is similar to the net offshore migration phenomena observed at other sites in the world. EOF analysis revealed a relationship between bar configuration and middle-term variations in shoreline location; when a new bar is generated near the shoreline and a triple bar configuration is established, the shoreline tends to temporarily retreat, whereas the shoreline experiences an advance when the outer bar has most evolved.
J. Mar. Sci. Eng.2016, 4(2), 39; doi:10.3390/jmse4020039 - published 1 June 2016 Show/Hide Abstract
Abstract: Using a panel of genes stimulated by oil exposure in a laboratory study, we evaluated gene transcription in blood leukocytes sampled from sea otters captured from 2006–2012 in western Prince William Sound (WPWS), Alaska, 17–23 years after the 1989 Exxon Valdez oil spill (EVOS). We compared WPWS sea otters to reference populations (not affected by the EVOS) from the Alaska Peninsula (2009), Katmai National Park and Preserve (2009), Clam Lagoon at Adak Island (2012), Kodiak Island (2005) and captive sea otters in aquaria. Statistically, sea otter gene transcript profiles separated into three distinct clusters: Cluster 1, Kodiak and WPWS 2006–2008 (higher relative transcription); Cluster 2, Clam Lagoon and WPWS 2010–2012 (lower relative transcription); and Cluster 3, Alaska Peninsula, Katmai and captive sea otters (intermediate relative transcription). The lower transcription of the aryl hydrocarbon receptor (AHR), an established biomarker for hydrocarbon exposure, in WPWS 2010–2012 compared to earlier samples from WPWS is consistent with declining hydrocarbon exposure, but the pattern of overall low levels of transcription seen in WPWS 2010–2012 could be related to other factors, such as food limitation, pathogens or injury, and may indicate an inability to mount effective responses to stressors. Decreased transcriptional response across the entire gene panel precludes the evaluation of whether or not individual sea otters show signs of exposure to lingering oil. However, related studies on sea otter demographics indicate that by 2012, the sea otter population in WPWS had recovered, which indicates diminishing oil exposure.