J. Mar. Sci. Eng.2016, 4(2), 38; doi:10.3390/jmse4020038 - published 25 May 2016 Show/Hide Abstract
Abstract: Grain size on the surface of natural beaches has been observed to vary spatially and temporally with morphology and wave energy. The stratigraphy of the beach at Duck, North Carolina, USA was examined using 36 vibracores (~1–1.5 m long) collected along a cross-shore beach profile. Cores show that beach sediments are finer (~0.3 mm) and more uniform high up on the beach. Lower on the beach, with more swash and wave action, the sand is reworked, segregated by size, and deposited in layers and patches. At the deepest measurement sites in the swash (~−1.4 to −1.6 m NAVD88), which are constantly being reworked by the energetic shore break, there is a thick layer (60–80 cm) of very coarse sediment (~2 mm). Examination of two large trenches showed that continuous layers of coarse and fine sands comprise beach stratigraphy. Thicker coarse layers in the trenches (above mean sea level) are likely owing to storm erosion and storm surge elevating the shore break and swash, which act to sort the sediment. Those layers are buried as water level retreats, accretion occurs and the beach recovers from the storm. Thinner coarse layers likely represent similar processes acting on smaller temporal scales.
J. Mar. Sci. Eng.2016, 4(2), 36; doi:10.3390/jmse4020036 - published 20 May 2016 Show/Hide Abstract
Abstract: Many countries are very active in marine research and operate their own research fleets. In this decade, a number of research vessels have been renewed and equipped with the most modern navigation systems and tools. However, much of the research gear used for biological sampling, especially in the deep-sea, is outdated and dependent on wired operations. The deployment of gear can be very time consuming and, thus, expensive. The present paper reviews wire-dependent, as well as autonomous research gear for biological sampling at the deep seafloor. We describe the requirements that new gear could fulfil, including the improvement of spatial and temporal sampling resolution, increased autonomy, more efficient sample conservation methodologies for morphological and molecular studies and the potential for extensive in situ real-time studies. We present applicable technologies from robotics research, which could be used to develop novel autonomous marine research gear, which may be deployed independently and/or simultaneously with traditional wired equipment. A variety of technological advancements make such ventures feasible and timely. In proportion to the running costs of modern research vessels, the development of such autonomous devices might be already paid off after a discrete number of pioneer expeditions.
J. Mar. Sci. Eng.2016, 4(2), 34; doi:10.3390/jmse4020034 - published 13 May 2016 Show/Hide Abstract
Abstract: The present review will explore the most relevant findings on marine microbial biofilm, with particular attention towards its polysaccharide fraction, namely exopolysaccharide (EPS). EPSs of microbial origin are ubiquitous in nature, possess unique properties and can be isolated from the bacteria living in a variety of habitats, including fresh water or marine environments, extreme environments or different soil ecosystems. These biopolymers have many application in the field of biotechnology. Several studies showed that the biofilm formation is closely related to quorum sensing (QS) systems, which is a mechanism relying on the production of small molecules defined as “autoinducers” that bacteria release in the surrounding environment where they accumulate. In this review, the involvement of microbial chemical communication, by QS mechanism, in the formation of marine biofilm will also be discussed.
J. Mar. Sci. Eng.2016, 4(2), 35; doi:10.3390/jmse4020035 - published 10 May 2016 Show/Hide Abstract
Abstract: Wave and current energy can be harnessed in the East China Sea and South China Sea; however, both areas are subject to high frequencies of typhoon events. To improve the safety of the ocean energy conversion device, a Floating Ocean Energy Conversion Device (FOECD) with a single mooring system is proposed, which can be towed to avoid severe ocean conditions or for regular maintenance. In this paper, the structure of the FOECD is introduced, and it includes a catamaran platform, an oscillating buoy part, a current turbine blade, hydraulic energy storage and an electrical generation part. The numerical study models the large catamaran platform as a single, large buoy, while the four floating buoys were modeled simply as small buoys. Theoretical models on wave energy power capture and efficiency were established. To improve the suitability of the buoy for use in the FOECD and its power harvesting capability, a numerical simulation of the four buoy geometries was undertaken. The shape profiles examined in this paper are cylindrical, turbinate (V-shaped and U-shaped cone with cylinder), and combined cylinder-hemisphere buoys. Simulation results reveal that the suitability of a turbinate buoy is the best of the four types. Further simulation models were carried out by adjusting the tip radius of the turbinate buoy. Three performance criteria including suitability, power harvesting capability and energy capture efficiency were analyzed. It reveals that the turbinate buoy has almost the same power harvesting capabilities and energy capture efficiency, while its suitability is far better than that of a cylindrical buoy.
J. Mar. Sci. Eng.2016, 4(2), 32; doi:10.3390/jmse4020032 - published 4 May 2016 Show/Hide Abstract
Abstract: Morphological changes during a flood event in July 2010 were observed with X-band marine radar at the mouth of Tenryu River, Shizuoka, Japan. Radar images were collected hourly for more than 72 h from the beginning of the flood and processed into time-averaged images. Changes in the morphology of the area were interpreted from the time-averaged images, revealing that the isolated river dune was washed away by the flood, the width of the river mouth increased gradually, and the river mouth terrace expanded radially. Furthermore, image analysis of the radar images was applied to estimate the migration speed of the brightness pattern, which is assumed to be a proxy of bottom undulation of the river bed. The migration was observed to be faster when the water level gradient between the river channel and sea increased.
J. Mar. Sci. Eng.2016, 4(2), 33; doi:10.3390/jmse4020033 - published 3 May 2016 Show/Hide Abstract
Abstract: April 20, 2010 marked the start of the British Petroleum Deepwater Horizon oil spill, the largest marine oil spill in US history, which contaminated coastal wetland ecosystems across the northern Gulf of Mexico. We used hyperspectral data from 2010 and 2011 to compare the impact of oil contamination and recovery of coastal wetland vegetation across three ecologically diverse sites: Barataria Bay (saltmarsh), East Bird’s Foot (intermediate/freshwater marsh), and Chandeleur Islands (mangrove-cordgrass barrier islands). Oil impact was measured by comparing wetland pixels along oiled and oil-free shorelines using various spectral indices. We show that the Chandeleur Islands were the most vulnerable to oiling, Barataria Bay had a small but widespread and significant impact, and East Bird’s Foot had negligible impact. A year later, the Chandeleur Islands showed the strongest signs of recovery, Barataria Bay had a moderate recovery, and East Bird’s Foot had only a slight increase in vegetation. Our results indicate that the recovery was at least partially related to the magnitude of the impact such that greater recovery occurred at sites that had greater impact.