SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Coast

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It is predicted that the coastal zone will be among the environments worst affected by projected climate change. Projected losses in beach area will negatively impact on coastal infrastructure and continued recreational use of beaches. Beach nourishment practices such as artificial nourishment, replenishment and scraping are increasingly used to combat beach erosion but the extent and scale of projects is poorly documented in large areas of the world. Through a survey of beach managers of Local Government Areas and a comprehensive search of peer reviewed and grey literature, we assessed the extent of nourishment practices in Australia. The study identified 130 beaches in Australia that were subject to nourishment practices between 2001 and 2011. Compared to projects elsewhere, most Australian projects were small in scale but frequent. Exceptions were nine bypass projects which utilised large volumes of sediment. Most artificial nourishment, replenishment and beach scraping occurred in highly urbanised areas and were most frequently initiated in spring during periods favourable to accretion and outside of the summer season of peak beach use. Projects were generally a response to extreme weather events, and utilised sand from the same coastal compartment as the site of erosion. Management was planned on a regional scale by Local Government Authorities, with little monitoring of efficacy or biological impact. As rising sea levels and growing coastal populations continue to put pressure on beaches a more integrated approach to management is required, that documents the extent of projects in a central repository, and mandates physical and biological monitoring to help ensure the engineering is sustainable and effective at meeting goals.

Concepts: Sediment, Weather, Coast, Beach, Sand, Coastal geography, Extreme weather, Beach nourishment

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Distribution and levels of C. botulinum type E was determined on field sites used by Inuit hunters for butchering seals along the coast of Nunavik. The incidence of C. botulinum type E in shoreline soil along the coast was 0, 50, and 87.5% of samples tested for the Hudson Strait, Hudson Bay, and Ungava Bay regions, respectively. Spores were detected in seawater or coastal rock surfaces from 17.6% of butchering sites, almost all located in southern Ungava Bay. Concentrations of C. botulinum type E along the Ungava Bay coast were significantly higher than the coasts of Hudson Strait and Hudson Bay, with the highest concentrations (270 to 1,800/kg) found near butchering sites located along the mouths of large rivers. The Koksoak River contained high levels of C. botulinum type E, with the highest median concentration (270/kg) found in sediments of the marine portion of the river. C. botulinum type E was found in the intestinal contents (4.4%) and skins (1.4%) of seals. A high genetic biodiversity of C. botulinum type E isolates was observed among the 21 butchering sites and their surroundings along the Nunavik coastline, with 83% of isolates (44/53) yielding distinct PFGE genotypes. Multiple sources of C. botulinum type E may be involved in the contamination of seal meat during butchering, but the risk of contamination appears to be much higher from environmental sources along the shoreline of southern Ungava Bay and the sediments of the Koksoak River.

Concepts: Coast, Inuit, Beach, Quebec, Clostridium botulinum, Nunavut, Nunavik, Hudson Bay

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In coastal environments, evaporation is an important driver of subsurface salinity gradients in marsh systems. However, it has not been addressed in the intertidal zone of sandy beaches. Here, we used field data on an estuarine beach foreshore with numerical simulations to show that evaporation causes upper intertidal zone pore-water salinity to be double that of seawater. We found the increase in pore-water salinity mainly depends on air temperature and relative humidity, and tide and wave actions dilute a fraction of the high salinity plume, resulting in a complex process. This is in contrast to previous studies that consider seawater as the most saline source to a coastal aquifer system, thereby concluding that seawater infiltration always increases pore-water salinity by seawater-groundwater mixing dynamics. Our results demonstrate the combined effects of evaporation and tide and waves on subsurface salinity distribution on a beach face. We anticipate our quantitative investigation will shed light on the studies of salt-affected biological activities in the intertidal zone. It also impacts our understanding of the impact of global warming; in particular, the increase in temperature does not only shift the saltwater landward, but creates a different salinity distribution that would have implications on intertidal biological zonation.

Concepts: Water, Coast, Beach, Intertidal zone, Coastal geography, Tide, Shore, Tide pool

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Sea level changes are typically caused by several natural phenomena, including ocean thermal expansion, glacial melt from Greenland and Antarctica. Global average sea level is expected to rise, through the twenty-first century, according to the IPCC projections by between 0.18 and 0.59 cm. Such a rise in sea level will significantly impact coastal area of the Nile Delta, consisting generally of lowland and is densely populated areas and accommodates significant proportion of Egypt’s economic activities and built-up areas. The Nile Delta has been examined in several previous studies, which worked under various hypothetical sea level rise (SLR) scenarios and provided different estimates of areas susceptible to inundation due to SLR. The paper intends, in this respect, to identify areas, as well as land use/land cover, susceptible to inundation by SLR based upon most recent scenarios of SLR, by the year 2100 using GIS. The results indicate that about 22.49, 42.18, and 49.22 % of the total area of coastal governorates of the Nile Delta would be susceptible to inundation under different scenarios of SLR. Also, it was found that 15.56 % of the total areas of the Nile Delta that would be vulnerable to inundation due to land subsidence only, even in the absence of any rise in sea level. Moreover, it was found that a considerable proportion of these areas (ranging between 32.32 and 53.66 %) are currently either wetland or undeveloped areas. Furthermore, natural and/or man-made structures, such as the banks of the International Coastal Highway, were found to provide unintended protection to some of these areas. This suggests that the inundation impact of SLR on the Nile Delta is less than previously reported.

Concepts: Coast, Population density, Egypt, Nile, Cairo, Nile Delta, Aswan Dam, Suez Canal

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Colonial breeding is an evolutionary puzzle, as the benefits of breeding in high densities are still not fully explained. Although the dynamics of existing colonies are increasingly understood, few studies have addressed the initial formation of colonies, and empirical tests are rare. Using a high-resolution larval drift model, we here document that the distribution of seabird colonies along the Norwegian coast can be explained by variations in the availability and predictability of fish larvae. The modelled variability in concentration of fish larvae is, in turn, predicted by the topography of the continental shelf and coastline. The advection of fish larvae along the coast translates small-scale topographic characteristics into a macroecological pattern, viz. the spatial distribution of top-predator breeding sites. Our findings provide empirical corroboration of the hypothesis that seabird colonies are founded in locations that minimize travel distances between breeding and foraging locations, thereby enabling optimal foraging by central-place foragers.

Concepts: Scientific method, Larva, Bird, Coast, Optimal foraging theory, Foraging, Marine debris, Behavioral ecology

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In this paper we analyse the spatial footprint and temporal clustering of extreme sea level and skew surge events around the UK coast over the last 100 years (1915-2014). The vast majority of the extreme sea level events are generated by moderate, rather than extreme skew surges, combined with spring astronomical high tides. We distinguish four broad categories of spatial footprints of events and the distinct storm tracks that generated them. There have been rare events when extreme levels have occurred along two unconnected coastal regions during the same storm. The events that occur in closest succession (<4 days) typically impact different stretches of coastline. The spring/neap tidal cycle prevents successive extreme sea level events from happening within 4-8 days. Finally, the 2013/14 season was highly unusual in the context of the last 100 years from an extreme sea level perspective.

Concepts: Oceanography, Coast, Moon, United Kingdom, Marine debris, Tide, Storm surge, Nautical chart

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Plastic, as a form of marine litter, is found in varying quantities and sizes around the globe from surface waters to deep-sea sediments. Identifying patterns of microplastic distribution will benefit an understanding of the scale of their potential effect on the environment and organisms. As sea ice extent is reducing in the Arctic, heightened shipping and fishing activity may increase marine pollution in the area. Microplastics may enter the region following ocean transport and local input, although baseline contamination measurements are still required. Here we present the first study of microplastics in Arctic waters, south and southwest of Svalbard, Norway. Microplastics were found in surface (top 16 cm) and sub-surface (6 m depth) samples using two independent techniques. Origins and pathways bringing microplastic to the Arctic remain unclear. Particle composition (95% fibres) suggests they may either result from the breakdown of larger items (transported over large distances by prevailing currents, or derived from local vessel activity), or input in sewage and wastewater from coastal areas. Concurrent observations of high zooplankton abundance suggest a high probability for marine biota to encounter microplastics and a potential for trophic interactions. Further research is required to understand the effects of microplastic-biota interaction within this productive environment.

Concepts: Ecology, Coast, Ocean, Norway, Arctic Ocean, Arctic, Polar bear, Arctic shrinkage

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Salt marsh losses have been documented worldwide because of land use change, wave erosion, and sea-level rise. It is still unclear how resistant salt marshes are to extreme storms and whether they can survive multiple events without collapsing. Based on a large dataset of salt marsh lateral erosion rates collected around the world, here, we determine the general response of salt marsh boundaries to wave action under normal and extreme weather conditions. As wave energy increases, salt marsh response to wind waves remains linear, and there is not a critical threshold in wave energy above which salt marsh erosion drastically accelerates. We apply our general formulation for salt marsh erosion to historical wave climates at eight salt marsh locations affected by hurricanes in the United States. Based on the analysis of two decades of data, we find that violent storms and hurricanes contribute less than 1% to long-term salt marsh erosion rates. In contrast, moderate storms with a return period of 2.5 mo are those causing the most salt marsh deterioration. Therefore, salt marshes seem more susceptible to variations in mean wave energy rather than changes in the extremes. The intrinsic resistance of salt marshes to violent storms and their predictable erosion rates during moderate events should be taken into account by coastal managers in restoration projects and risk management plans.

Concepts: Marsh, Coast, Wind, Salt marsh, Extreme weather, Wind wave, Wave power, Tidal marsh

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Natal homing is a pattern of behavior in which animals migrate away from their geographic area of origin and then return to reproduce in the same location where they began life [1-3]. Although diverse long-distance migrants accomplish natal homing [1-8], little is known about how they do so. The enigma is epitomized by loggerhead sea turtles (Caretta caretta), which leave their home beaches as hatchlings and migrate across entire ocean basins before returning to nest in the same coastal area where they originated [9, 10]. One hypothesis is that turtles imprint on the unique geomagnetic signature of their natal area and use this information to return [1]. Because Earth’s field changes over time, geomagnetic imprinting should cause turtles to change their nesting locations as magnetic signatures drift slightly along coastlines. To investigate, we analyzed a 19-year database of loggerhead nesting sites in the largest sea turtle rookery in North America. Here we report a strong association between the spatial distribution of turtle nests and subtle changes in Earth’s magnetic field. Nesting density increased significantly in coastal areas where magnetic signatures of adjacent beach locations converged over time, whereas nesting density decreased in places where magnetic signatures diverged. These findings confirm central predictions of the geomagnetic imprinting hypothesis and provide strong evidence that such imprinting plays an important role in natal homing in sea turtles. The results give credence to initial reports of geomagnetic imprinting in salmon [11, 12] and suggest that similar mechanisms might underlie long-distance natal homing in diverse animals.

Concepts: Magnetic field, Earth's magnetic field, Magnet, Coast, Reptile, Marine debris, Sea turtle, Loggerhead Sea Turtle

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Coastal protection design heights typically consider the superimposed effects of tides, surges, waves, and relative sea-level rise (SLR), neglecting non-linear feedbacks between these forcing factors. Here, we use hydrodynamic modelling and multivariate statistics to show that shallow coastal areas are extremely sensitive to changing non-linear interactions between individual components caused by SLR. As sea-level increases, the depth-limitation of waves relaxes, resulting in waves with larger periods, greater amplitudes, and higher run-up; moreover, depth and frictional changes affect tide, surge, and wave characteristics, altering the relative importance of other risk factors. Consequently, sea-level driven changes in wave characteristics, and to a lesser extent, tides, amplify the resulting design heights by an average of 48-56%, relative to design changes caused by SLR alone. Since many of the world’s most vulnerable coastlines are impacted by depth-limited waves, our results suggest that the overall influence of SLR may be greatly underestimated in many regions.

Concepts: Fundamental physics concepts, Oceanography, Coast, Multivariate statistics, Wave, Tide, Storm surge, Current sea level rise