Autonomous video camera system for monitoring impacts to benthic habitats from demersal fishing gear, including longlines

Studies of the interactions of demersal fishing gear with the benthic environment are needed in order to manage conservation of benthic habitats. There has been limited direct assessment of these interactions through deployment of cameras on commercial fishing gear especially on demersal longlines. A compact, autonomous deep-sea video system was designed and constructed by the Australian Antarctic Division (AAD) for deployment on commercial fishing gear to observe interactions with benthos in the Southern Ocean finfish fisheries (targeting toothfish, Dissostichus spp). The Benthic Impacts Camera System (BICS) is capable of withstanding depths to 2500 m, has been successfully fitted to both longline and demersal trawl fishing gear, and is suitable for routine deployment by non-experts such as fisheries observers or crew. The system is entirely autonomous, robust, compact, easy to operate, and has minimal effect on the performance of the fishing gear it is attached to. To date, the system has successfully captured footage that demonstrates the interactions between demersal fishing gear and the benthos during routine commercial operations. It provides the first footage demonstrating the nature of the interaction between demersal longlines and benthic habitats in the Southern Ocean, as well as showing potential as a tool for rapidly assessing habitat types and presence of mobile biota such as krill (Euphausia superba).     

The network K‐function in context: examining the effects of network structure on the network K‐function

The flaws of using traditional planar point‐pattern analysis techniques with network constrained points have been thoroughly explored in the literature. Because of this, new network‐based measures have been introduced for their planar analogues, including the network based K‐function. These new measures involve the calculation of network distances between point events rather than traditional Euclidean distances. Some have suggested that the underlying structure of a network, such as whether it includes directional constraints or speed limits, may be considered when applying these methods. How different network structures might affect the results of the network spatial statistics is not well understood. This article examines the results of network K‐functions when taking into consideration network distances for three different types of networks: the original road network, topologically correct networks, and directionally constrained networks. For this aim, four scenarios using road networks from Tampa, Florida and New York City, New York were used to test how network constraints affected the network K‐function. Depending on which network is under consideration, the underlying network structure could impact the interpretation. In particular, directional constraints showed reduced clustering across the different scenarios. Caution should be used when selecting the road network, and constraints, for a network K‐function analysis.     

Lithodiversity and Its Spatial Association with Metallic Mineral Sites,Great Basin of Nevada

Geographical information system (GIS) techniques were used to investigate the spatial association between metallic mineral sites and lithodiversity in Nevada. Mineral site data sets include various size and type subsets of about 5,500 metal-bearing occurrences and deposits. Lithodiversity was calculated by counting the number of unique geological map units within four sizes of square-shaped sample neighborhoods (2.5-by-2.5, 5-by-5, 10-by-10, and 20-by-20 km) on three different scales of geological maps (national, 1:2,500,000; state, 1:500,000; county, 1:250,000). The spatial association between mineral sites and lithodiversity was observed to increase with increasing lithodiversity. This relationship is consistent for (1) both basin-range and range-only regions, (2) four sizes of sample neighborhoods, (3) various mineral site subsets, (4) the three scales of geological maps, and (5) areas not covered by large-scale maps. A map scale of 1:500,000 and lithodiversity sampling neighborhood of 5-by-5 km was determined to best describe the association. Positive associations occurred for areas having >3 geological map units per neighborhood, with the strongest observed at approximately >7 units. Areas in Nevada with more than three geological map units per 5-by-5 km neighborhood contain more mineral sites than would be expected resulting from chance. High lithodiversity likely reflects the occurrence of complex structural, stratigraphic, and intrusive relationships that are thought to control, focus, localize, or expose mineralization. The application of lithodiversity measurements to areas that are not well explored may help delineate regional-scale exploration targets and provide GIS-supported mineral resource assessment and exploration activity another method that makes use of widely available geological map data.     

Sedimentology,palaeoecology and geochronology of Marine Isotope Stage 5 deposits on the Shetland Islands,Scotland

New stratigraphical, palynological and dating evidence is presented for pre‐Late Devensian/Weichselian sediments at Fugla Ness and Sel Ayre, Shetland. The Fugla Ness Peat rests on till and formed during an interglacial that saw the development of maritime heaths, with scattered trees and shrubs, including Pinus and possibly Ilex. A decline into stadial conditions is marked by overlying periglacial breccia and till. The Sel Ayre Organic Sands and Gravels lie between periglacial breccias and beneath till and appear to record a changing interstadial environment in which trees were absent and the vegetation comprised largely heaths, with Bruckenthalia, and grasslands. The Fugla Ness Peat is dated to 110+40/?35 ka by uranium series disequilibrium, suggesting that it formed during the Ipswichian/Eemian Interglacial (Marine Isotope Substage 5e). Luminescence ages of ca. 98–105 ka on intercalated sands within the Sel Ayre Organic Sands and Gravels place these deposits in Marine Isotope Substage 5c (Brørup Interstadial). The two sites provide the first detailed record of Marine Isotope Stage 5 environments on Shetland. Copyright © 2002 John Wiley & Sons, Ltd.     

Repeating of gamma-ray bursts in light of the BATSE 2B catalog

We examine the evidence for repeating of -ray bursts in light of the BATSE 2B catalog. The temporal coverage of the 2B-1B (non-MAXBC) data set is 1/3 smaller than that of the 1B catalog. We find evidence that the distributions of the burst statistical positional errors and of the burst fluences also differ. Assuming that the bursts in the 1B catalog form a fair sample and taking these observational selection effects into account, we simulate the 2B-1B (less MAXBC) data set. We find that a repeating signal like that seen in the nearest neighbor distribution of the bursts in the 1B catalog would not be detectable in the 2B-1B (non-MAXBC) and 2B (non-MAXBC) data sets, because of the differences in the temporal coverage and in the distribution of positional errors.     

Sensitivity of the Parameterizations of Vertical Mixing and Radiative Heat Fluxes on the Seasonal Evolution of the Thermal Structure of Lake Erie

A sensitivity analysis of the parameterizations of vertical mixing and radiative fluxes on the seasonal evolution of Lake Erie's thermal structure is performed using the Massachusetts Institute of Technology general circulation model (MITgcm) and the General Estuarine Transport Model (GETM). The models have the same horizontal resolution and are forced with observed meteorological data from April to October of 2002 and 2008. For turbid waters like Lake Erie, the three-band model for the parameterization of downward shortwave radiation produces more accurate temperatures in the thermocline and less error in simulating the mixed-layer depths than the widely used two-band model. Although the two models differ in vertical and horizontal mixing, numerical methods, and vertical discretization, they produced qualitatively comparable results. Comparison with observations shows that the models can reproduce the time evolution of the lake temperature reasonably well. The MITgcm and the GETM with the Mellor-Yamada level 2.5 (MY2.5) closure produce a deeper mixed layer than observed at a station located in the eastern basin, causing large errors in simulating the temperature in the thermocline while the GETM, using a turbulence scheme called “gen,” reproduces a mixed layer in better agreement with observations. The mixed-layer obtained with the k-ε closure is between those obtained with gen and MY2.5. The error in simulating the mixed-layer depths and the thermocline temperature at a station located in the central basin using the gen closure and the GETM was about 2°C lower than that obtained by the K-Profile Parameterization mixing scheme of the MITgcm. The models simulated a lake-wide anticyclonic circulation occupying the southwest part of the central basin but showed distinct differences in simulating gyres in the northwestern part of the central basin and in the eastern basin of the lake. The signature of a basin-scale Poincaré wave observed in the current data is also well represented by the two models.     

Climatic and non-climatic effects on the δO and δC compositions of Lake Awassa, Ethiopia, during the last 6.5 ka

A comparison of a 6450 ¹⁴C yr δ¹⁸O and δ¹³C record of authigenic calcite from Lake Awassa, Ethiopia, with other proxy climate records in the area suggests that the lake records long-term regional climate changes. Co-varying and increasing δ¹⁸O and δ¹³C values from 4800 BP suggest an aridification of climate after the early Holocene insolation maximum. After 4000 BP, humid conditions return until after 2800 BP when δ¹⁸O increases again, reflecting more arid conditions recorded elsewhere in Ethiopia. In addition to these long-term changes, there are abrupt decreases in both δ¹⁸O_calcite and δ¹³C_calcite immediately after tephra layers. The likeliest explanation for these abrupt decreases in isotopes is the effect of tephra on the lake's catchment vegetation. δ¹⁸O, δ¹³C and lake-level measurements from Lake Awassa since the 1970s suggest that the lake is currently isotopically sensitive to short-term (annual–decadal) climate change. However, during this period, the catchment has undergone progressive deforestation that may have caused an increase in runoff. Caution is therefore required when reconstructing palaeoclimates as a contemporary lake may not always be a good analogue for lake hydrology in the past.     

Regional variation of spectral parameters for seismic design from broadband probabilistic seismic hazard analysis

The characterisation of the seismic hazard input is a critical element of any seismic design code, not only in terms of the absolute levels of ground motion considered but also of the shape of the design spectrum. In the case of Europe, future revisions of the seismic design provisions, both at a national and a pan‐European level, may implement considerable modifications to the existing provisions in light of recent seismic hazard models, such as the 2013 European Seismic Hazard Model. Constraint of the shape of the long‐period design spectrum from seismic hazard estimates on such a scale has not been possible, however, owing to the limited spectral period range of existing ground motion models. Building upon recent developments in ground motion modelling, the 2013 European Seismic Hazard Model is adapted here with a new ground motion logic tree to provide a broadband Probabilistic Seismic Hazard Analysis for rock sites across a spectral period range from 0.05 seconds to 10.0 seconds. The resulting uniform hazard spectra (UHS) are compared against existing results for European and broadband Probabilistic Seismic Hazard Analysis and against a proposed formulation of a generalised design spectrum in which controlling parameters can be optimised to best fit the uniform hazard spectra in order to demonstrate their variability on a European scale. Significant variations in the controlling parameters of the design spectrum are seen both across and within stable and active regions. These trends can help guide recalibrations of the code spectra in future revisions to seismic design codes, particularly for the longer‐period displacement spectrum.     

Major active faults determine the location of the Tongonan geothermal field: Evidence provided by rock alteration and stable isotope geochemistry

Abstract The influence of major active faults on rock alteration and stable isotope geochemistry is described for the Tongonan geothermal field, Leyte, the Philippines. In the Pliocene, acid alteration with characteristic iron enrichment (3 g/100 g) and calcium depletion (2 g/100 g) occurred along a Riedel shear fault in the Malitbog sector, and initial minor acid alteration also occurred along a similar shear in the Mahiao sector. Later, sodium metasomatism (5 g/100 g) coincided with the highest aquifer chloride (10 000 mg/kg) as a result of dissociation of saline magmatic fluids discharging through the reservoir rocks in the Upper Mahiao. The incursion of magmatic fluids (possibly δD 35‰, δ¹⁸O +7‰) set up a vigorous convection cell of meteoric water, which focused around low‐angle (L) shears centered in the Sambaloran sector. Meteoric water (δD ?35 to ?40‰, δ¹⁸O ?6 ± 1‰) depleted the reservoir in silica (6 g/100 g) and potassium (1–2 g/100 g). It also completely exchanged oxygen isotopes rapidly (within months) at high temperatures (300–400°C), and now does so continuously with fractured isotopically fresh or incompletely altered rock at small scales (centimeters or less) exposed by a 2 cm/year creep around the L shears to form a new component called geothermal water. Geothermal water mixes with meteoric water at lower temperatures (<300°C) to create the characteristic shift in δ¹⁸O of 6‰ at near constant δD (?35 ± 5‰). The 10‰ variation in δD is due to groundwater recharge derived from rain falling on steep terrain (5‰) and to enrichment of deuterium in boiling saline solutions (5‰); it is not due to two‐component mixing of meteoric with magmatic water. The low (～1) isotopic water/rock (W/R) ratios calculated from oxygen isotopes in previously published reports are meaningless, because the water contains four components (predominantly geothermal and meteoric water; <10% magmatic and rock water). W/R ratios of up to 1500 calculated from spring and rock chemistry are more realistic and, with a flow rate of approximately 50 L/s through a 30 km³ reservoir, can account for the estimated 3 My age of the system.