Distribution and transport of organic matter along a filament-eddy system in the Canaries – NW Africa coastal transition zone region

The distribution and transport of chlorophyll a (Chla), particulate (POC) and dissolved (DOC) organic carbon, and the respiratory ETS activity of the microplankton community were studied along a filament-eddy system located in the transition zone between the NW Africa upwelling and Canary Islands waters. Two independent filaments (F1 and F2) stemming from the coastal jet, between Cape Juby and Cape Bojador, merged about 100 km offshore, turning southward and onshore forced by the circulation of a recurrent oceanic cyclonic eddy. In general, the coastal upwelling waters presented higher Chla, but lower POC, DOC and ETS activity than filament waters. However, differences in organic carbon distribution and respiratory activity were observed among stations from the two filaments. The bio-chemical fields were strongly influenced by a complex sub-mesoscale hydrography resulting from the interaction of cyclonic and anticyclonic island eddies with the filaments. The combined F1 + F2 filament system transported 97.1 kg s⁻¹ of excess (non-refractory) total organic carbon (e-TOC), a value comparable to other published estimates from upwelling filaments in the NE Atlantic. About 90% of e-TOC was exported as DOC, since eddy re-circulation precluded the offshore transport of POC. Assuming that the calculated transport of e-TOC is representative of the annual average, the yearly offshore transport (3.1 x 10⁹ kg C) would represent about 25% of the upwelling primary production of the region of study.     

On the vertical distribution of

The aim of this paper is to present an analytical expression for the vertical distribution of the correlation between the horizontal ( ) and vertical ( ) wave velocity components. This quantity, , which appears explicitly in the time-averaged momentum balance equations, has been shown to play an important role in the vertical distribution of wave-induced currents.The proposed formulation for is based on an identity that relates the effective (wave) shear stress to the effective (wave) normal stresses ( ² and ²) and to the vorticity of the oscillatory flow gw. This general expression has been applied to simplified situations and has been shown to degenerate into other existing formulations with comparable simplifying assumptions, viz. irrotational waves in shallow water over an arbitrary bottom topography and breaking waves over a horizontal bottom.The model has also been applied to the case of waves interacting with a depth-varying current over a horizontal bottom, in which preliminary results have been obtained for a simplified situation invoking linear (small-amplitude) wave theory.     

Sea,freshwater or saltpans? Foraging ecology of terns to assess mercury inputs in a wetland landscape: The Ebro Delta

The Ebro catchment, the largest river basin in Spain, includes various heavily industrialized areas. Among these is the Flix site, where a chemical plant has been operating since the beginning of the 20th century. This extended operational period, together with the construction of a dam next to the factory around 1960, resulted in the accumulation of large amounts of heavily polluted sediments in the adjacent riverbed, many of which are contaminated by mercury. Pollutants from Flix are carried downstream by the Ebro River to its delta. In order to assess the transfer of mercury to the complex river estuary ecosystem, we studied the ecology of the tern community living there as these birds segregate into a range of habitats. For this purpose, first we used stable isotope analysis (SIA) (δ³⁴S, δ¹³C, δ¹⁵N) of eggs to determine the trophic ecology and habitat partitioning of several tern species (Common, Sandwich, Little, Gull-Billed and Whiskered Tern) breeding sympatrically, in order to link their foraging ecology with habitat types. Next we measured mercury concentrations in eggs to monitor the input of this metal into the diverse habitats. With the exception of the Little Tern, the other terns used a restricted habitat range in the Ebro Delta, as shown by C and S isotopes; the Gull-Billed and Whiskered Tern foraged in freshwater habitats, while the Common and Sandwich Tern used marine habitats. This restricted feeding behavior of the Gull-Billed and Common Tern contrasts with previous reports in other breeding sites. The Little Tern, which showed a wide range of isotopic values, was found to be an opportunistic forager but fed mainly in saltpans, a feeding habitat not reported previously for this species in this area. We found that mercury concentrations are related to foraging habitat and diet, and are unexpectedly higher in species feeding on demersal prey in marine habitats and also higher in birds feeding in saltpans than in those feeding in freshwater habitats. The mercury concentrations found in the Little and Common Tern eggs sampled in “Punta de la Banya” may be sufficiently high to endanger breeding success.     

Chemosynthetic trophic support for the benthic community at an intertidal cold seep site at Mocha Island off central Chile

We analyzed C and N stable isotope ratios of benthic fauna and their potential food sources at an intertidal methane seep site and a control site without emanation at Mocha Island (central Chile). The objective was to trace the origin of the main food sources used by the local heterotrophic fauna, based on the hypothesis that chemosynthetic production could be partially fueling the local food web at the seep site. Food sources sampled at both sites included macroalgae, particulate organic matter and bacteria-like filaments found growing over the red algae Gelidium lingulatum within the areas of active methane release.     

Hierarchical classification of marine rocky landscape as management tool at southeast Mediterranean coast

The existence and distribution of European marine reef habitat (1170), defined as rocky substrates and biogenic concretions in the UE habitats Directive, remain incomplete especially for the Mediterranean region. It is necessary to cartography the habitats but also it is important to classify and develop tools to asses at adequate management scales. Rocky habitats occur in a variety of spatial configurations and pattering landscape. It is necessary to define a typology of landscape to permit a realistic comparison of similar units recognizing, for example, its favourable conservation status. The aim of this study is to identify the rocky landscape units and to propose a hierarchical classification, for identifying the units with a favourable conservation status, based on the presence of listed species. Non-parametric multivariate techniques were used to classify the 88 landscape units based on presence of different biocoenoses and environmental factors. A hierarchical typology was recognised according to the increase of complexity. The study comprises six sorts of landscape typologies included in two major groups. High correlations of selected environmental variables with biocenosis composition were obtained depending on the scale of analysis. We observed that both geomorphologic structure and depth influence presence of biocenosis. The reef landscape typology proposal can be the base for the definition of reference ecological conditions or the favourable conservation state of the habitats, it is also an interesting tool for decision-making in the marine management.     

A new model for the vibration isolation via pile rows consisting of infinite number of piles

In this study, on the basis of the Floquet transform method, a numerical model for the simulation of the vibration isolation via multiple periodic pile rows with infinite number of piles is established. By means of the fictitious pile method due to Muki and Sternberg, the second kind of Fredholm integral equations for the pile rows are developed by using the fundamental solutions for the half‐space and the compatibility conditions between the piles and half‐space. Employing the Floquet transform method, integral equations for the pile rows in the wavenumber domain are then derived. Solution of the integral equations yields the wavenumber domain solution for the pile rows. The space domain solution can then be retrieved by inversion of the Floquet transform. Numerical results show that the proposed model with the Floquet transform method is in a good agreement with those of the conventional direct superposition method. On the basis of the new model, influences of the spacing between neighboring piles, the Young's modulus of the piles, and the pile length on the vibration isolation effect of the pile rows are investigated. Numerical simulations conducted in this study show that compared with the direct superposition method, the efficiency of the proposed model for simulation of the vibration isolation via pile rows is very high. Copyright © 2012 John Wiley & Sons, Ltd.     

The history of water salinity in the Pearl River estuary,China, during the Late Quaternary

This research reconstructed the Late Quaternary salinity history of the Pearl River estuary, China, from diatom records of four sedimentary cores. The reconstruction was produced through the application of a diatom–salinity transfer function developed based on 77 modern surface sediment samples collected across the estuary from shallow marine environment to deltaic distributaries. The statistical analysis indicates that the majority of sediment samples from the cores has good modern analogues, thus the reconstructions are reliable. The reconstructed salinity history shows the older estuarine sequence formed during the last interglacial was deposited under similar salinity conditions to the younger estuarine sequence, which was formed during the present interglacial. Further analysis into the younger estuarine sequence reveals the interplays between sea level, monsoon‐driven freshwater discharge, and deltaic shoreline movement, key factors that have influenced water salinity in the estuary. In particular, a core from the delta plain shows the effects of sea‐level change and deltaic progradation, while cores from the mouth region of the estuary reveal changes of monsoon‐driven freshwater discharge. This study demonstrates the advantages of quantitative salinity reconstructions to improve the quality of reconstruction and allow direct comparison with other quantitative records and the instrumentally observed values of salinity. Copyright © 2010 John Wiley & Sons, Ltd.     

The Scale of VGI in Map Production: A Perspective on European National Mapping Agencies

The perspective of European National Mapping Agencies (NMA) on the role of citizen sensing in map production was explored. The NMAs varied greatly in their engagement with the community generating volunteered geographic information (VGI) and in their future plans. From an assessment of NMA standard practices, it was evident that much VGI was acquired with a positional accuracy that, while less than that typically acquired by NMAs, actually exceeded the requirements of the nominal data capture scale used by most NMAs. Opportunities for VGI use in map revision and updating were evident, especially for agencies that use a continuous rather than cyclical updating policy. Some NMAs had also developed systems to engage with citizen sensors and examples are discussed. Only rarely was VGI used to collect data on features beyond the standard set used by the NMAs. The potential role of citizen sensing and so its current scale of use by NMAs is limited by a series of concerns, notably relating to issues of data quality, the nature and motivation of the contributors, legal issues, the sustainability of data source, and employment fears of NMA staff. Possible priorities for future research and development are identified to help ensure that the potential of VGI in mapping is realized.     

Severe soil erosion during a 3‐day exceptional rainfall event: combining modelling and field data for a fallow cereal field

Exceptional rainfall events cause significant losses of soil, although few studies have addressed the validation of model predictions at field scale during severe erosive episodes. In this study, we evaluate the predictive ability of the enhanced Soil Erosion and Redistribution Tool (SERT‐2014) model for mapping and quantifying soil erosion during the exceptional rainfall event (~235 mm) that affected the Central Spanish Pyrenees in October 2012. The capacity of the simulation model is evaluated in a fallow cereal field (1.9 ha) at a high spatial scale (1 × 1 m). Validation was performed with field‐quantified rates of soil loss in the rills and ephemeral gullies and also with a detailed map of soil redistribution. The SERT‐2014 model was run for the six rainfall sub‐events that made up the exceptional event, simulating the different hydrological responses of soils with maximum runoff depths ranging between 40 and 1017 mm. Predicted average and maximum soil erosion was 11 and 117 Mg ha^?1 event^?1, respectively. Total soil loss and sediment yield to the La Reina gully amounted to 16.3 and 9.0 Mg event^?1. These rates are in agreement with field estimations of soil loss of 20.0 Mg event^?1. Most soil loss (86%) occurred during the first sub‐event. Although soil accumulation was overestimated in the first sub‐event because of the large amount of detached soil, the enhanced SERT‐2014 model successfully predicted the different spatial patterns and values of soil redistribution for each sub‐event. Further research should focus on stream transport capacity. Copyright © 2014 John Wiley & Sons, Ltd.