Fish-Habitat Relationships Along the Estuarine Gradient of the Sacramento-San Joaquin Delta,California: Implications for Habitat Restoration

Estuaries are highly variable environments where fish are subjected to a diverse suite of habitat features (e.g., water quality gradients, physical structure) that filter local assemblages from a broader, regional species pool. Tidal, climatological, and oceanographic phenomena drive water quality gradients and, ultimately, expose individuals to other habitat features (e.g., stationary physical or biological elements, such as bathymetry or vegetation). Relationships between fish abundances, water quality gradients, and other habitat features in the Sacramento-San Joaquin Delta were examined as a case example to learn how habitat features serve as filters to structure local assemblages in large river-dominated estuaries. Fish communities were sampled in four tidal lakes along the estuarine gradient during summer-fall 2010 and 2011 and relationships with habitat features explored using ordination and generalized linear mixed models (GLMMs). Based on ordination results, landscape-level gradients in salinity, turbidity, and elevation were associated with distinct fish assemblages among tidal lakes. Native fishes were associated with increased salinity and turbidity, and decreased elevation. Within tidal lakes, GLMM results demonstrated that submersed aquatic vegetation density was the dominant driver of individual fish species densities. Both native and non-native species were associated with submersed aquatic vegetation, although native and non-native fish populations only minimally overlapped. These results help to provide a framework for predicting fish species assemblages in novel or changing habitats as they indicate that species assemblages are driven by a combination of location within the estuarine gradient and site-specific habitat features.     

Holocene alluvial environments at Barking,Lower Thames Valley (London,UK)

Deposit modelling based on archived borehole logs supplemented by a small number of dedicated boreholes is used to reconstruct the main boundary surfaces and the thickness of the main sediment units within the succession of Holocene alluvial deposits underlying the floodplain in the Barking Reach of the Lower Thames Valley. The basis of the modelling exercise is discussed and the models are used to assess the significance of floodplain relief in determining patterns of sedimentation. This evidence is combined with the results of biostratigraphical and geochronological investigations to reconstruct the environmental conditions associated with each successive stage of floodplain aggradation. The two main factors affecting the history and spatial pattern of Holocene sedimentation are shown to be the regional behaviour of relative sea level and the pattern of relief on the surface of the sub-alluvial, Late Devensian Shepperton Gravel. As is generally the case in the Lower Thames Valley, three main stratigraphic units are recognised, the Lower Alluvium, a peat bed broadly equivalent to the Tilbury III peat of Devoy (1979) and an Upper Alluvium. There is no evidence to suggest that the floodplain was substantially re-shaped by erosion during the Holocene. Instead, the relief inherited from the Shepperton Gravel surface was gradually buried either by the accumulation of peat or by deposition of fine-grained sediment from suspension in standing or slow-moving water. The palaeoenvironmental record from Barking confirms important details of the Holocene record observed elsewhere in the Lower Thames Valley, including the presence of Taxus in the valley-floor fen carr woodland between about 5000 and 4000 cal BP, and the subsequent growth of Ulmus on the peat surface.     

Testing of Sydney dimension sandstone for use in the conservation of heritage buildings

This paper deals with the scientific assessment of the physical properties of sandstone used in the conservation of Sydney's historic heritage sandstone buildings. The local Hawkesbury Sandstone has been widely used for all manner of constructions since the early days of the first settlement. In the nineteenth century, dimension sandstone quarries existed all over the Sydney region, and the demand for the stone was great. During this time, a true ‘freestone’ known as ‘yellow block’ sandstone, in which bedding planes were absent, was quarried extensively. This sandstone is also known as a ‘self-colouring’ sandstone, where the rock, although grey when quarried, turns a yellow–brown after a few months exposure to the atmosphere. It can be easily carved and was eminently suitable for the ornate Victorian architecture of the time. There are very few quarries within the Sydney region today capable of producing ‘yellow block’ sandstone. Whenever possible, sandstone from suitable building excavations, particularly on the Pyrmont Peninsula, is used for this work. Conservation work is extremely expensive and the building elements that most need replacement, the overhanging and decorative elements, are usually those that cost the most. It is essential that the most durable replacement stone be selected. Thus, a strict regime of scientific testing is used for any major conservation project, in order to determine the physical properties of possible replacement stone. This is the province of the geologist and involves visual observation in the quarry or excavation, which is a simple, cost-effective means of weeding out poor quality stones, followed by laboratory engineering tests to establish the physical parameters of a sandstone and finally, petrographic analysis. The results of such tests, combined with careful sampling, ensure the best possible quality of replacement material.     

Multi-proxy Stratigraphy and Paleoceanographic Variations in Sediment from the Korea Plateau,East Sea (Japan Sea), Over the Last 500 kyr

Ocean Science Journal - High-resolution geochemical measurements were performed on core E09-08, which was taken from the top flat area of the Korea Plateau in the East Sea (Japan Sea). Based on...     

Using the social cost of carbon to value earth observing systems

The goal of this study is to show how to quantify the benefits of accelerated learning about key parameters of the climatic system and use this knowledge to improve decision-making on climate policy. The US social cost of carbon (SCC) methodology is used in innovative ways to value new Earth observing systems (EOSs). The study departs from the strict US SCC methodology, and from previous work, in that net benefits are used instead of only damages to calculate the value of information of the enhanced systems. In other respects the US SCC methodology is followed closely. We compute the surfeit expected net benefits of learning the actionable information earlier, with the enhanced system, versus learning later with existing systems. The enhanced systems are designed to give reliable information about climate sensitivity on accelerated timescales relative to existing systems; therefore, the decision context stipulates that a global reduced emissions path would be deployed upon receiving suitable information on the rate of temperature rise with a suitable level of confidence. By placing the enhanced observing system in a decision context, the SCC enables valuing this system as a real option.

Policy relevance

Uncertainty in key parameters of the climatic system is often cited as a barrier for near-term reductions of carbon emissions. It is a truism among risk managers that uncertainty costs money, and its reduction has economic value. Advancing policy making under uncertainty requires valuing the reduction in uncertainty. Using CLARREO, a new proposed EOS,as an example, this article applies value of information/real option theory to value the reduction of uncertainty in the decadal rate of temperature rise. The US interagency social cost of carbon directive provides the decision context for the valuations. It is shown that the real option value of the uncertainty reduction, relative to existing observing systems, is a very large multiple of the new system's cost.     

A Bayesian Analysis of the Correlations Among Sunspot Cycles

Sunspot numbers form a comprehensive, long-duration proxy of solar activity and have been used numerous times to empirically investigate the properties of the solar cycle. A number of correlations have been discovered over the 24 cycles for which observational records are available. Here we carry out a sophisticated statistical analysis of the sunspot record that reaffirms these correlations, and sets up an empirical predictive framework for future cycles. An advantage of our approach is that it allows for rigorous assessment of both the statistical significance of various cycle features and the uncertainty associated with predictions. We summarize the data into three sequential relations that estimate the amplitude, duration, and time of rise to maximum for any cycle, given the values from the previous cycle. We find that there is no indication of a persistence in predictive power beyond one cycle, and we conclude that the dynamo does not retain memory beyond one cycle. Based on sunspot records up to October 2011, we obtain, for Cycle 24, an estimated maximum smoothed monthly sunspot number of 97±15, to occur in January??C?February 2014 ± six months.     

Tracing offshore low-salinity plumes in the Northeastern Gulf of Mexico during the summer season by use of multispectral remote-sensing data

To trace offshore surface low-salinity water (LSW) in the northeastern Gulf of Mexico, a proxy was developed using the surface water beam attenuation coefficient (c _p), and salinity matched with synchronous Sea-viewing Wide Field-of-view Sensor (SeaWiFS) satellite data from three annual summer cruises (July 1998–August 2000) using a two-step empirical approach. First, a relationship between in-situ salinity and c _p was obtained. Second, in-situ c _p was matched with SeaWiFS radiance ratios of all available blue-to-green wavelengths. Finally, satellite-derived surface salinity was determined directly by combining the two empirical relationships, providing a robust estimate over a range of salinities (26–36). This significantly improves the limited spatial and temporal resolution of surface salinity distribution obtained by shipboard sampling. The resulting correlation is best explained as mixing between low-salinity plume waters and normal salinity Gulf waters. The empirical relationships were used to map satellite-derived salinity using the average of SeaWiFS images during each summer cruise. As expected for summer, spatial patterns of LSW plumes with high c _p, particulate matter (PM), particulate organic carbon (POC), and chlorophyll-a (Chl-a) were connected to the mouth of the Mississippi River Delta and extended to the east-southeast. Normal salinity Gulf water with lower c _p, PM, POC, and Chl-a was confined to the shelf and upper slope in the eastern part of the study area, outside the plumes. This proxy approach can be applied throughout the region of shipboard sampling for more detailed coverage and analysis.     

Possible variation in methane flux caused by gas hydrate formation on the northeastern continental slope off Sakhalin Island, Russia

The Sakhalin Slope Gas Hydrate Project (SSGH) is an international collaborative effort by scientists from Japan, Korea, and Russia to investigate natural gas hydrates (GHs) that have accumulated on the continental slope off Sakhalin Island, Okhotsk Sea. From 2009 to 2011, field operations of the SSGH-09, -10, and -11 projects were conducted. GH-bearing and -free sediment cores were retrieved using steel hydro- and gravity corers. The concentrations of sulfate ions in sediment pore waters were measured to investigate sulfate concentration–depth profiles. Seventeen cores showed linear depth profiles of sulfate concentrations. In contrast, eight cores and two cores showed concave-up and -down profiles plausibly explained by sudden increase and decrease in methane flux from below, respectively, presumably caused by the formation of gas hydrate adjacent to the core sampling sites.     

A meltwater origin for Antarctic shelf bedforms with special attention to megalineations

The geomorphology of troughs crossing the Antarctic shelf is described and interpreted in terms of ice-stream hydrology. The scale of tunnel channels on the inner shelf and the absence of sediment at their mouths are taken to infer catastrophic drainage. Drumlins on the inner and outer shelves with pronounced crescentic and hairpin scours are also interpreted as products of catastrophic flow. Gullies and channels on the continental slope and turbidites on the rise and abyssal plain point to abundant meltwater discharge across the shelf. Attempts to explain this morphology and sedimentology in terms of release or discharge of meltwater by pressure melting, strain heating, Darcian flow, or advection in deforming till are shown to be unrealistic. We suggest that meltwater flow across the middle and outer shelves might have been in broad, turbulent floods, which raises the possibility that megascale glacial lineations (MSGL) on the shelf might originate by erosion in turbulent flow. This possibility is explored by use of analogs for MSGL from flood and eolian landscapes and marine environments. An extended discussion reflects on objections that stand in the way of the flood hypothesis.     

Massive stars exploding in a He-rich circumstellar medium – II. The transitional case of SN 2005la

We present photometric and spectroscopic data of the peculiar SN 2005la, an object which shows an optical light curve with some luminosity fluctuations and spectra with comparably strong narrow hydrogen and helium lines, probably of circumstellar nature. The increasing full width at half-maximum velocity of these lines is indicative of an acceleration of the circumstellar material. SN 2005la exhibits hybrid properties, sharing some similarities with both Type IIn supernovae and 2006jc-like (Type Ibn) events. We propose that the progenitor of SN 2005la was a very young Wolf–Rayet (WN-type) star which experienced mass ejection episodes shortly before core collapse.