Emerging fisheries,emerging fishery interactions with sea turtles: A case study of the large-mesh gillnet fishery for flounder in Pamlico Sound,North Carolina,USA

Emerging fisheries and changes in fishery practices are not always readily apparent, nor are their impacts on non-target species such as seabirds, sea turtles, and marine mammals. Data from several different sources led managers to discover high rates of sea turtle bycatch in an inshore large-mesh gillnet fishery in North Carolina, USA, particularly the emerging deep-water gillnet fishery. This paper reviews the history of how increased numbers of observed stranded sea turtles in 1999 led to the discovery that turtles were becoming entangled in the large-mesh gillnet fishery in Pamlico Sound, North Carolina. It also demonstrates how a variety of data sets from fisheries observers, aerial surveys, and fisheries statistics programs contributed to shaping management of the large-mesh gillnet fishery in Pamlico Sound to decrease turtle bycatch and now point towards the need of additional assessment of gillnet bycatch in other parts of North Carolina. Finally, potential approaches are discussed for a more timely detection of future fishery conflicts and development of a plan to reduce otherwise inevitable bycatch and disruptions to fishing effort.     

Comparative study of broadband damage localization methods applied to test data

This application-oriented paper presents comparison of various broadband frequency based structural damage localization indices using experimental data from a full-scale structure known as the I-40 Bridge. First, three ‘damage-sensitive’ response parameters determined in the time and/or spectral domain, modal domain and wavelet domain are presented for damage localization in the context of a ‘non-model-based’ damage identification approach. Secondly, experimental modal data (namely natural frequencies, mode shapes and modal damping) obtained from this full-scale bridge subjected to various damage conditions is employed for assessment of the robustness of these methods on ‘real-world’ applications. Consequently, the results obtained are compared with those obtained from existing resonance frequency based damage identification methods. The results obtained demonstrate the improved capability of the broadband methods to localize damage in a full-scale structure despite sparse modal information and limited measurement grid points.     

Long-term (1998–2007) trends on the spatial distribution of heterotrophic ciliates in the East China Sea in summer: effect of the Three Gorges Dam construction

The spatial distribution of heterotrophic ciliates, environmental factors and potential food items (bacteria, Synechococcus spp. and nanoflagellates) were measured in the East China Sea to examine which variables contributed importantly to the long-term distribution of ciliates between 1998 and 2007. In July 1998 and June 2003, heterotrophic ciliates were found to be abundant (1,000–2,000 × 10³ cells m⁻³) in regions where surface salinity <32 but extremely low (<500 × 10³ cells m⁻³) in shelf waters of surface salinity >32. After August 2003, shortly after the completion of the Three Gorges Dam, we found no significant areal differences in the abundance of heterotrophic ciliates (HC). However, we found a significantly negative correlation between temperature and HC abundance of surface water after the completion of the dam, suggesting that temperature had a greater influence on HC abundance, once the original saline state had changed. For the long-term trends on the vertical distribution of HC, their abundance was significantly higher in the upper 50 m of the water column than at either 75 or 100 m. Abundance of Synechococcus spp. at these levels varied significantly in regions of surface salinity <32, suggesting that ciliates and picophytoplankton contribute greatly to mediating the transfer of organic matter to higher trophic levels in this marine ecosystem.     

Distribution of some ions and minor gaseous components by concentrations in the atmospheric surface layer of some regions in Eastern Siberia and the Far East

We consider the resemblance between the ion composition of the fraction of soluble aerosols and gaseous admixtures in the atmospheric surface layer at the high-level Mondy station (East Sayan), those in the Listvyanka settlement south of Lake Baikal, in the city of Irkutsk, and at the Primorskaya station near the city of Ussuriysk (Primorskii krai). We use measurement data on the concentrations of the following ions: HCO ₃ ^? , SO ₄ ^2? , NO ₃ ^? , Cl^?, H⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺ in the soluble fraction of aerosols and gases HNO₃, HCl, NH₃, and SO₂ in air samples over a 10-year period conducted in the mode of online monitoring. We found the lognormal form of distributions of concentrations of each of the abovementioned components according to the number of samples. A versatile scheme of the distribution of mean geometric concentrations of atmospheric components was proposed for all four groups.     

Numerical simulation of groundwater flowing to horizontal seepage wells under a river

A horizontal seepage well, consisting of an interconnected vertical well, galleries, chambers and small-diameter radiating bores, is used to acquire relatively clean water that has been filtered through natural alluvial deposits in a riverbed. It has wide application, especially in arid and semi-arid areas. The lack of calculation formulae or models for horizontal seepage wells, up until now, has resulted in several false applications. Based on the analysis of groundwater flow characteristics, it has been concluded that several flow regimes coexist and hydraulic head loss exists in the horizontal seepage well. To avoid the difficulty of confirming the flux or head distribution in such a complex system, the model boundary of the whole horizontal seepage well has been moved to that of just the vertical well, and the well-aquifer system was treated as a heterogeneous medium, where the horizontal seepage well itself is a highly permeability medium. A mathematical model has been developed, based on the coupled seepage-pipe flow, by the introduction of equivalent hydraulic conductivity according to different flow regimes. Then a three-dimensional finite difference numerical model, based on the mathematical model, was developed and applied to a horizontal seepage well in China. The numerical model verified the groundwater flow characteristics of the horizontal seepage well. An erratum to this article can be found at     

Autochthonous inheritance of zircon through Cretaceous partial melting of Carboniferous plutons: the Arthur River Complex,Fiordland, New Zealand

TIMS and SHRIMP U–Pb analyses of zircons from Milford Orthogneiss metadiorite (P = 1–1.4 GPa; T ≥ 750°C) of the Arthur River Complex of northern Fiordland reveal a bimodal age pattern. Zircons are predominantly either Paleozoic (357.0 ± 4.2 Ma) and prismatic with oscillatory zoning, or Cretaceous (133.9 ± 1.8 Ma) and ovoid with sector or patchy zoning. The younger age component is not observed overgrowing older grains. Most grains of both ages are overgrown by younger Cretaceous (~120 Ma) metamorphic zircon with very low U and Th/U (0.01). We interpret the bimodal ages as indicating initial igneous emplacement and crystallisation of a dioritic protolith pluton at ~357 Ma, followed by Early Cretaceous granulite-facies metamorphism at ~134 Ma, during which a significant fraction (~60%) of the zircon grains dissolved, and subsequently reprecipitated, effectively in situ, in partial melt pockets. The remaining ~40% of original Paleozoic grains were apparently not in contact with the partial melt, remained intact, and show only slight degrees of Pb loss. Sector zoning of the Cretaceous grains discounts their origin by solid state recrystallisation of Paleozoic grains. The alternative explanation—that the Paleozoic component represents a 40% inherited component in an Early Cretaceous transgressive dioritic magma—is considered less likely given the relatively high solubility of zircon in magma of this composition, the absence of 134 Ma overgrowths, the single discrete age of the older component, equivalent time-integrated ¹⁷⁷Hf/¹⁷⁶Hf compositions of both age groups, and the absence of the Cambrian-Proterozoic detrital zircon that dominates regional Cambro-Ordovician metasedimentary populations. Similar bimodal Carboniferous-Early Cretaceous age distributions are characteristic of the wider Arthur River Complex; 8 of 12 previously dated dioritic samples have a Paleozoic component averaging 51%. Furthermore, the age and chemical suite affinity of these and several more felsic rocks can be matched with those of the relatively unmetamorphosed Carboniferous plutonic terrane along the strike of the Mesozoic margin in southern Fiordland, also supporting the in situ derivation of the Carboniferous “inherited” component.     

Sedimentary processes and trace metal contaminants in the buccaneer oil/gas field,northwestern gulf of Mexico

Sediments are the ultimate sink for contaminants in the marine environment, and physical processes of sedimentation influence the distribution and accumulation of these contaminants. Evaluation of contaminant levels in sediments is one approach to assessing environmental impact; data interpretation depends on consideration of sediment texture and mineralogy, however, which profoundly influence chemical composition. In this study, comparison of potentially contaminated sediments from the production field with control populations was done only within the context of similar (as to texture and organic carbon and carbonate content) sample groups as determined by cluster analysis. Ba, Cd, and Sr are identified as contaminants. Supported by the identification of a well-crystallized expandable clay—possibly bentonite—drilling fluids are a potential source of Ba. Ba and Sr may be unnaturally high because of their abundance in discharged produced formation waters, but may also be naturally controlled by the unique faunal assemblage associated with the structures. Cd is probably derived from corrosion of the structures and assorted debris on the seafloor. In general, contamination is limited to an area within 100 m of the platforms. Furthermore, substantial erosion around platforms has probably effectively removed and dispersed the bulk of the contaminants introduced into the marine environment by the offshore exploration/production operations.     

Seasonal Dynamics of Microbial Processes in Bottom Sediments of the Sevastopol Coastal Area

Oceanology - A seasonal study of microbial methane oxidation (MO) and sulfate reduction (SR) processes in bottom sediments was carried out at five stations in the estuarian Sevastopol coastal area,...     

Heat and mass transfer effects during displacement of deepwater methane hydrate to the surface of Lake Baikal

The present paper focuses on heat and mass exchange processes in methane hydrate fragments during in situ displacement from the gas hydrate stability zone (GHSZ) to the water surface of Lake Baikal. After being extracted from the methane hydrate deposit at the lakebed, hydrate fragments were placed into a container with transparent walls and a bottom grid. There were no changes in the hydrate fragments during ascent within the GHSZ. The water temperature in the container remained the same as that of the ambient water (~3.5 °С). However, as soon as the container crossed the upper border of the GHSZ, first signs of hydrate decomposition and transformation into free methane gas were observed. The gas filled the container and displaced water from it. At 300 m depth, the upper and lower thermometers in the container simultaneously recorded noticeable decreases of temperature. The temperature in the upper part of the container decreased to –0.25 °С at about 200 m depth, after which the temperature remained constant until the water surface was reached. The temperature at the bottom of the container reached –0.25 °С at about 100 m depth, after which it did not vary during further ascent. These observed effects could be explained by the formation of a gas phase in the container and an ice layer on the hydrate surface caused by heat consumption during hydrate decomposition (self-preservation effect). However, steady-state simulations suggest that the forming ice layer is too thin to sustain the hydrate internal pressure required to protect the hydrate from decomposition. Thus, the mechanism of self-preservation remains unclear.