Evidence for a change in wind regime during the Last Glacial Maximum from the Sydney region

This paper presents the results of a small number of dates from sand samples collected at building sites in the eastern suburbs of Sydney. OSL ages of well-sorted, quartz sand ranges from 31 to 24?ka from within well-developed podzol soil profiles within a metre of the surface. The source of this sand appears to be from the east off the inner continental shelf during a period just prior to the maximum of the Last Glacial Maximum (LGM, Marine Isotope Stage 2) when sea-level was approximately 70–90 m below present level. During a later phase of the LGM, there is evidence from other coastal sites in central NSW and Gippsland, Victoria, that the dominant wind was from the west consistent with evidence from arid and semiarid Australia. Dune orientations in northern NSW into Queensland and other evidence at this time appear to reflect winds from the southeast quadrant. This study highlights the existence of a potential pivot area in dominant wind direction during the LGM between sustained westerly flow in southern area including Victoria and northeast Tasmania and southeast flow of northern NSW into Queensland. In central NSW, the circulation switched from easterly in Stage 2 to westerly as the glacial stage intensified in the LGM sometime after ca 25?ka.     

The hydromagnesite playas of Atlin, British Columbia, Canada: A biogeochemical model for CO2 sequestration

Anthropogenic greenhouse gas emissions may be offset by sequestering carbon dioxide (CO₂) through the carbonation of magnesium silicate minerals to form magnesium carbonate minerals. The hydromagnesite [Mg₅(CO₃)₄(OH)₂·4H₂O] playas of Atlin, British Columbia, Canada provide a natural model to examine mineral carbonation on a watershed scale. At near surface conditions, CO₂ is biogeochemically sequestered by microorganisms that are involved in weathering of bedrock and precipitation of carbonate minerals. The purpose of this study was to characterize the weathering regime in a groundwater recharge zone and the depositional environments in the playas in the context of a biogeochemical model for CO₂ sequestration with emphasis on microbial processes that accelerate mineral carbonation.Regions with ultramafic bedrock, such as Atlin, represent the best potential sources of feedstocks for mineral carbonation. Elemental compositions of a soil profile show significant depletion of MgO and enrichment of SiO₂ in comparison to underlying ultramafic parent material. Polished serpentinite cubes were placed in the organic horizon of a coniferous forest soil in a groundwater recharge zone for three years. Upon retrieval, the cube surfaces, as seen using scanning electron microscopy, had been colonized by bacteria that were associated with surface pitting. Degradation of organic matter in the soil produced chelating agents and acids that contributed to the chemical weathering of the serpentinite and would be expected to have a similar effect on the magnesium-rich bedrock at Atlin. Stable carbon isotopes of groundwater from a well, situated near a wetland in the southeastern playa, indicate that  12% of the dissolved inorganic carbon has a modern origin from soil CO₂.The mineralogy and isotope geochemistry of the hydromagnesite playas suggest that there are three distinct depositional environments: (1) the wetland, characterized by biologically-aided precipitation of carbonate minerals from waters concentrated by evaporation, (2) isolated wetland sections that lead to the formation of consolidated aragonite sediments, and (3) the emerged grassland environment where evaporation produces mounds of hydromagnesite. Examination of sediments within the southeastern playa–wetland suggests that cyanobacteria, sulphate reducing bacteria, and diatoms aid in producing favourable geochemical conditions for precipitation of carbonate minerals.The Atlin site, as a biogeochemical model, has implications for creating carbon sinks that utilize passive microbial, geochemical and physical processes that aid in mineral carbonation of magnesium silicates. These processes could be exploited for the purposes of CO₂ sequestration by creating conditions similar to those of the Atlin site in environments, artificial or natural, where the precipitation of magnesium carbonates would be suitable. Given the vast quantities of Mg-rich bedrock that exist throughout the world, this study has significant implications for reducing atmospheric CO₂ concentrations and combating global climate change.     

A wind-tunnel study of turbulent flow close to regularly arrayed rough surfaces

Recent observations of flux-gradient anomalies in atmospheric flow close to forests, and similar rough surfaces, prompted a wind-tunnel investigation in which cross-wire anemometry was used to study the vertical development and horizontal variability of adiabatic flow over five regularly arrayed rough surfaces, encompassing a 32-fold range of roughness concentration . The roughness elements were cylinders, 6 mm in both height and diameter.Below a layer in which the velocity profile is semi-logarithmic, two surface influences upon the mean velocity field can be distinguished: wake diffusion and horizontal inhomogeneity. The wake diffusion effect causes non-dimensional vertical velocity gradients to be smaller than in the semi-logarithmic region; at least for elements with aspect ratios l/h 1, it is governed by the transverse dimension l of the roughness elements, and is observed when z > h + 1.5l (where z is height above the underlying surface, and h is the height of the roughness elements). A simple diffusivity model successfully describes the horizontally averaged velocity profiles in the region of wake influence, despite conceptual disadvantages. The horizontal inhomogeneity of the flow is negligible when z > h + D (D being the inter-element spacing), and does not entirely mask the wake diffusion effect except over very sparsely roughened surfaces ( 0.02). A criterion for negligibility of both effects, and hence for applicability of conventional turbulent diffusivity theory for momentum, is z > h + 1.5D. These results are compared with atmospheric data, and indicate that wake diffusion may well cause some underestimation of the zero-plane displacement d over typical vegetated surfaces.     

Deep-sea macrourid fishes scavenge on plant material: Evidence from in situ observations

Deep-sea benthic communities primarily rely on an allochthonous food source. This may be in the form of phytodetritus or as food falls e.g. sinking carcasses of nekton or debris of marine macrophyte algae. Deep-sea macrourids are the most abundant demersal fish in the deep ocean. Macrourids are generally considered to be the apex predators/scavengers in deep-sea communities. Baited camera experiments and stable isotope analyses have demonstrated that animal carrion derived from the surface waters is an important component in the diets of macrourids; some macrourid stomachs also contained vegetable/plant material e.g. onion peels, oranges, algae. The latter observations led us to the question: is plant material an attractive food source for deep-sea scavenging fish? We simulated a plant food fall using in situ benthic lander systems equipped with a baited time-lapse camera. Abyssal macrourids and cusk-eels were attracted to the bait, both feeding vigorously on the bait, and the majority of the bait was consumed in <30 h. These observations indicate (1) plant material can produce an odour plume similar to that of animal carrion and attracts deep-sea fish, and (2) deep-sea fish readily eat plant material. This represents to our knowledge the first in situ documentation of deep-sea fish ingesting plant material and highlights the variability in the scavenging nature of deep-sea fishes. This may have implications for food webs in areas where macrophyte/seagrass detritus is abundant at the seafloor e.g. canyon systems and continental shelves close to seagrass meadows (Bahamas and Mediterranean).     

A shallow subsurface controlled release facility in Bozeman, Montana, USA, for testing near surface CO2 detection techniques and transport models

A controlled field pilot has been developed in Bozeman, Montana, USA, to study near surface CO₂ transport and detection technologies. A slotted horizontal well divided into six zones was installed in the shallow subsurface. The scale and CO₂ release rates were chosen to be relevant to developing monitoring strategies for geological carbon storage. The field site was characterized before injection, and CO₂ transport and concentrations in saturated soil and the vadose zone were modeled. Controlled releases of CO₂ from the horizontal well were performed in the summers of 2007 and 2008, and collaborators from six national labs, three universities, and the U.S. Geological Survey investigated movement of CO₂ through the soil, water, plants, and air with a wide range of near surface detection techniques. An overview of these results will be presented.     

Factors influencing spatial and annual variability in eelgrass (Zostera marina L.) meadows in Willapa Bay, Washington, and Coos Bay, Oregon, estuaries

Environmental factors that influence annual variability and spatial differences (within and between estuaries) in eelgrass meadows (Zostera marine L.) were examined within Willapa Bay, Washington, and Coos Bay, Oregon, over a period of 4 years (1998–2001). A suite of eelgrass metrics were recorded annually at field sites that spanned the estuarine gradient from the marine-dominated to mesohaline region of each estuary. Plant density (shoots m^?2) of eelgrass was positively correlated with summer estuarine salinity and inversely correlated with water temperature gradients in the estuaries. Eelgrass density, biomass, and the incidence of flowering plants all increased substantially in Willapa Bay, and less so in Coos Bay, over the duration of the study. Warmer winters and cooler summers associated with the transition from El Niño to La Niña ocean conditions during the study period corresponded with this increase in eelgrass abundance and flowering. Large-scale changes in climate and nearshore ocean conditions may exert a strong regional influence on eelgrass abundance that can vary annually by as much as 700% in Willapa Bay. Lower levels of annual variability observed in Coos Bay may be due to the stronger and more direct influence of the nearshore Pacific Ocean on the Coos Bay study sites. The results suggest profound effects of climate variation on the abundance and flowering of eelgrass in Pacific Northwest coastal estuaries.     

Impact of a combined sewer overflow on the abundance,distribution and community structure of subtidal benthos

A biological survey of the subtidal fauna near an intertidal combined sewer overflow (CSO) discharging into Puget Sound, Washington, USA, was conducted during April and May, 1977. The purpose of this study was to determine the effect of the CSO on the surrounding marine invertebrate communities.The shallowest subtidal sites studied (9 m below MLLW) appeared to be more affected by the CSO than deeper sites (13 and 24 m below MLLW). The subtidal area affected, as reflected in the levels of organic material, heavy metals and pesticides in the sediments, as well as the composition of the benthic macrofauna, appeared to be highly localised. The numerically dominant species at sites closest to the CSO was the polychaete Capitella capitata while the abundance of the bivalve Axinopsida serricata increased with distance from the CSO.Burrowing deposit feeders were the numerically dominant polychaete feeding type at sites nearest the CSO. Surface deposit feeders were more abundant at sites farther from the CSO, perhaps due to reduced sedimentation rates.Site-classification analyses indicated that sites adjacent to the CSO were more similar to one another than to sites which were farther away and apparently less affected.The positions of the sites along the first three principal component ordination axes were significantly correlated with depth and volatile organics (traceable to the CSO) in the sediments.     

Kinematics of the Galactic halo from horizontal branch stars in the Hamburg/ESO survey

Large samples of field horizontal branch (FHB) stars make excellent tracers of the Galactic halo; by studying their kinematics, one can infer important physical properties of our Galaxy. Here we present the results of a medium-resolution spectroscopic survey of 530 FHB stars selected from the Hamburg/ESO survey. The stars have a mean distance of ∼7 kpc and thus probe the inner parts of the Milky Way halo. We measure radial velocities from the spectra in order to test the model of Sommer-Larsen et al., who suggested that the velocity ellipsoid of the halo changes from radially dominated orbits to tangentially dominated orbits as one proceeds from the inner to the outer halo. We find that the present data are unable to discriminate between this model and a more simple isothermal ellipsoid; we suggest that additional observations towards the Galactic Centre might help to differentiate them.     

Foraging by juvenile salmon in a restored estuarine wetland

The functional value of a restored estuarine wetland as a foraging area for juvenile chum salmon (Oncorhynchus keta) and fall chinook salmon (O. tshawytscha) was evaluated during the spring seaward migrations of each species in 1987 and 1988. During both years, fish foraged selectively. While temporarily residing in the restored wetland, both salmon selected primarily chironomid insects (midge larvae, pupae, and adults) over all other organisms considered available prey. A detritus-based food chain (detritus-chironomids-juvenile chum salmon or chinook salmon) suggests that the restored wetland provides productive foraging habitat for migrating juvenile chum and fall chinook salmon during their early residency in the estuary. However, the equivalency of foraging in restored or created estuarine wetlands compared to foraging in altered riverine or natural habitats remains untested.     

Effects of persistent organic pollutants on the thyroid function of the European sea bass (Dicentrarchus labrax) from the Aegean sea, is it an endocrine disruption?

We evaluated the alterations of organochlorinated compounds such as polychlorobiphenyls (PCB), dichloro-diphenyl-dichloroethylene (DDE) and dichloro-diphenyl-trichloroethane (DDT) on the thyroid in wild and cultured sea bass (Dicentrarchus labrax) at environmental concentrations. These compounds influence the endocrine system of many fish species and are qualified as endocrine disruptors. The thyroid seems to be a target organ. Two alteration endpoints: the thyroid histology and the muscular thyroid hormone concentrations, were used simultaneously.High concentrations in PCBs and DDT were detected in muscles, supporting the idea that the Mediterranean fauna could be more polluted than the Atlantic fauna. The high abundance of DDE indicates a progressive degradation of remnant DDT load and the absence of new inputs in this area. Aquaculture sea bass shows a significant higher amount of pollutants on fresh weight basis (especially PCBs) in their muscles compared to the wild sea bass. Those differences may be related mainly to the contaminations of diet.Thyroid parameters vary between wild and aquaculture sea bass, wild sea bass were characterized by higher follicle diameters, epithelial cell heights and muscular T₄ concentrations. A significant relationship between persistent organic pollutants (muscular PCBs and DDT concentration) and the different thyroid parameters (diameters of follicles, epithelial cell heights and muscular T₄ levels) could be observed, which support the hypothesis that these compounds have an adverse impact on thyroid morphometry and function.