Thermal implications for the evolution of the spitsbergen transform fault

Heat flow taken between Svalbard and Greenland reveal three thermal provinces:

1. (1) the Molloy Ridge within the Spitsbergen Transform,

2. (2) the Yermak Plateau

3. (3) the northeastern margin of Svalbard (Nordaustlandet).

The Molloy Ridge is a short spreading segment and the average heat flow is much above the Sclater et al. (1971), cooling curve but agrees with values from the Norwegian-Greenland Sea. An additional zone of intrusion identified by heat flow lies to the northwest of the Molloy Ridge. It straddles both the visible fracture zone and part of the Yermak Plateau. A thermal boundary lies between the warm western segment of the Yermak Plateau and the shelf off Nordaustlandet. If the thermal subsidence of the western Yermak Plateau can be traced to the latest heating episode then it is likely that the crust is similar to oceanic in composition and not older than 13 m.y. (approximately 20 m.y. younger than the northeastern segment of the plateau). Plate rotation shows that there was no room for the western segment of the plateau prior to anomaly 7. We postulate that the original transform is associated with the Hornsund Fault zone. In response to deviatoric stress across the oblique ridge-transform system, the Nansen Ridge propagated southwestward aborting the old transform trace, and shifted to its present position.It is suggested that this propagation and migration of the ridge-transform system across a zone of extensional deviatoric stress allowed the massive intrusion of basalt forming the Western Yermak Plateau. The propagation phenomenon coincides with large-scale Tertiary volcanic activity on Svalbard.Readjustment and migration of the oblique transform is still taking place. As the transform-ridge system is liberated from continental constraints, the migration rate will diminish as orthogonality is approached.     

Survival,duration of larval stages,and size of postlarvae of grass shrimp,Palaemonetes pugio,reared from kepone® contaminated and uncontaminated populations in Chesapeake Bay

Replicate groups of larvae from each of three female grass shrimp,Palaemonetes pugio, collected at each of six sites within Chesapeake Bay were reared in the laboratory to metamorphosis at 25°C, 25 ppt salinity. They were provided with approximately 300Artemia nauplii/larva/day. Sites were selected to provide both suspected Kepone^® contaminated and non-contamined shrimp populations. A sample of eggs, adult females with and without eggs, and newly hatched larvae from each site were analyzed by Virginia Institute of Marine Science for Kepone as were postlarvae obtained through laboratory rearings. Females and eggs from the James River had highest concentrations of Kepone (0.63 and 0.47 ppm, respectively) with samples from the Lafayette River at the mouth of the James River having the second highest levels (0.04 and 0.4 ppm). Concentrations in ovigerous females and eggs in the populations most distant from the James (mouth of Potomac and upper Potomac River) were at or below the limits of detectability (0.001 to 0.015 ppm). In laboratory reared postlarvae from each site, concentrations of Kepone were undetectable. Despite these apparent differences in Kepone concentrations in the various populations we found no significant differences in larval survival, larval duration, or length of post-larvae attributable to site of origin. Highly significant differences in larval duration and size of post-larvae were attributable to parental variation.     

Fate of individual sewage disposal system wastewater within regolith in mountainous terrain

In order to improve understanding of the fate of septic tank or individual sewage disposal system (ISDS) effluent in regolith overlying fractured-rock aquifers, effluent from an ISDS in such a setting was tracked via geophysical, hydrological, and geochemical methods. Under typical precipitation conditions, the effluent entered the fractured bedrock within 5 m of the boundary of the constructed infiltration area. During a period of unusually high spring recharge, the plume migrated between 50 and 100 m within the regolith before infiltrating the fractured bedrock. The chemical signature of the effluent is similar to that required to account for the decline in water quality, suggesting a causative relationship (as estimated from mass-balance models of the surface-water chemistry near the mouth of the basin). The elevated salt content of the effluent during periods of high natural recharge to the infiltration area correlates with elevated salt concentrations in surface and groundwater at the basin scale, suggesting that some of the effluent salt load may be stored in the unsaturated zone during dry periods and flushed during periods of elevated natural recharge.     

Sea-level history of past interglacial periods from uranium-series dating of corals,Curaçao,Leeward Antilles islands

Curaçao has reef terraces with the potential to provide sea-level histories of interglacial periods. Ages of the Hato (upper) unit of the “Lower Terrace” indicate that this reef dates to the last interglacial period, Marine Isotope Stage (MIS) 5.5. On Curaçao, this high sea stand lasted at least 8000 yr (~ 126 to ~ 118 ka). Elevations and age of this reef show that late Quaternary uplift rates on Curaçao are low, 0.026–0.054 m/ka, consistent with its tectonic setting. Ages of ~ 200 ka for corals from the older Cortalein unit of the Lower Terrace correlate this reef to MIS 7, with paleo-sea level estimates ranging from ? 3.3 m to + 2.3 m. The estimates are in agreement with those for MIS 7 made from other localities and indicate that the penultimate interglacial period was a time of significant warmth, on a par with the present interglacial period. The ~ 400 ka (MIS 11) Middle Terrace I on Curaçao, dated by others, may have formed from a paleo-sea level of + 8.3 to + 10.0 m, or (less likely) + 17 m to + 20 m. The lower estimates are conservative compared to previous studies, but still require major ice sheet loss from Greenland and Antarctica.     

Effects of the pharmaceuticals gemfibrozil and diclofenac on the marine mussel (Mytilus spp.) and their comparison with standardized toxicity tests

Human pharmaceuticals, like the lipid lowering agent gemfibrozil and the non-steroidal anti-inflammatory drug diclofenac are causing environmental concern. In this study, the marine mussel (Mytilus spp.) was exposed by injection to environmentally relevant and elevated (1 μg/L and 1000 μg/L) concentrations of both compounds and biomarker expression was observed. Gemfibrozil exposure induced biomarkers of stress (glutathione S-transferase and metallothionein) at both concentrations 24 h and 96 h after exposure, respectively. Biomarkers of damage (lipid peroxidation (LPO) and DNA damage) were significantly affected, as well as the biomarker for reproduction, alkali-labile phosphate assay, indicating the potential oxidative stress and endocrine disrupting effect of gemfibrozil. Diclofenac significantly induced LPO after 96 h indicating tissue damage. Additionally standard toxicity tests using the marine species Vibrio fischeri, Skeletonema costatum and Tisbe battagliai showed differences in sensitivity to both drugs in the mg/L range. Results indicate a suite of tests should be used to give accurate information for regulation.     

Large in‐stream wood studies: a call for common metrics

During the past decade, research on large in‐stream wood has expanded beyond North America's Pacific Northwest to diverse environments and has shifted toward increasingly holistic perspectives that incorporate processes of wood recruitment, retention, and loss at scales from channel segments to entire watersheds. Syntheses of this rapidly expanding literature can be facilitated by agreement on primary variables and methods of measurement. In this paper we address these issues by listing the variables that we consider fundamental to studies of in‐stream wood, discussing the sources of variability in their measurement, and suggesting more consistency in future studies. We recommend 23 variables for all studies of in‐stream wood, as well as another 12 variables that we suggest for studies with more specific objectives. Each of these variables relates either to the size and characteristics of in‐stream wood, to the geomorphic features of the channel and valley, or to the ecological characteristics of the riparian zone adjacent to the study reach. The variables were derived from an overview of those cited in the literature and from our collective field experiences. Copyright © 2010 John Wiley & Sons, Ltd.     

Simulated water budget of a small forested watershed in the continental/maritime hydroclimatic region of the United States

Annual streamflows have decreased across mountain watersheds in the Pacific Northwest of the United States over the last ~70 years; however, in some watersheds, observed annual flows have increased. Physically based models are useful tools to reveal the combined effects of climate and vegetation on long‐term water balances by explicitly simulating the internal watershed hydrological fluxes that affect discharge. We used the physically based Simultaneous Heat and Water (SHAW) model to simulate the inter‐annual hydrological dynamics of a 4 km² watershed in northern Idaho. The model simulates seasonal and annual water balance components including evaporation, transpiration, storage changes, deep drainage, and trends in streamflow. Independent measurements were used to parameterize the model, including forest transpiration, stomatal feedback to vapour pressure, forest properties (height, leaf area index, and biomass), soil properties, soil moisture, snow depth, and snow water equivalent. No calibrations were applied to fit the simulated streamflow to observations. The model reasonably simulated the annual runoff variations during the evaluation period from water year 2004 to 2009, which verified the ability of SHAW to simulate the water budget in this small watershed. The simulations indicated that inter‐annual variations in streamflow were driven by variations in precipitation and soil water storage. One key parameterization issue was leaf area index, which strongly influenced interception across the catchment. This approach appears promising to help elucidate the mechanisms responsible for hydrological trends and variations resulting from climate and vegetation changes on small watersheds in the region. Copyright © 2015 John Wiley & Sons, Ltd.     

Carbon pools in stream‐riparian corridors: legacy of disturbance along mountain streams of south‐eastern Wyoming

Streams and their accompanying riparian environments are intrinsic components of terrestrial carbon cycling. However, they have been understudied in terms of the magnitude of their storage components and the role of disturbance in determining carbon storage capacity. This study presents partial carbon budgets for stream‐riparian corridors along six study reaches in mountain headwater streams of southeast Wyoming to evaluate the impact of tie‐driving, a historic disturbance legacy, on contemporary carbon storage. Detailed measurements of biomass were collected for in‐stream components of carbon including fine and coarse particulate organic matter and in‐stream large wood. Biomass was also estimated for riparian components including standing trees (live and dead), regenerating conifers, shrubs and herbaceous vegetation, downed wood, litter, and duff (partially decayed litter). Biomass was converted to carbon for all components and differences in storage were compared between tie‐driven and non‐driven reaches. Carbon content in riparian soils (to approximately 20 cm) was also measured. Twice the amount of carbon was stored in the riparian areas relative to the streams; most carbon was stored in standing trees (live and dead). While overall carbon storage within the riparian areas and streams were similar between disturbance conditions, the amount of carbon stored in large in‐stream wood and downed wood on the floodplain was significantly higher in systems that were not tie‐driven. The results of this study indicate that legacies of tie‐driving influence carbon storage within the region, while also capturing baseline estimates of carbon storage in the wake of recent bark beetle infestations. Copyright © 2015 John Wiley & Sons, Ltd.     

Decomposition of saltmeadow cordgrass (Spartina patens) in Louisiana coastal marshes

In Louisiana, plant production rates and associated decomposition rates may be important in offsetting high rates of land loss and subsidence in organic marsh soils. Decomposition ofSpartina patens shoot and leaf material was studied by using litter bags in mesohaline marshes in the Barataria and Terrebonne basins of coastal Louisiana.Spartina patens decomposed very slowly with an average decay constant of 0.0007, and approximately 50% of the material remained after 2 years in the field. Material at the Barataria site decomposed faster than did Terrebonne material with trend differences apparent during the first 150 days. This difference might be explained by the higher content of phosphorus in the Barataria material or a flooding period experienced by the Barataria bags during their first 10 days of deployment. Nitrogen and carbon content of the plant material studied did not differ between the two basins. We detected no consistent significant differences in decomposition above, at, or below sediment/water level. BecauseS. patens is the dominant plant in these marshes, and because it is so slow to decompose, we believe thatS. patens shoots are an important addition to vertical accretion and, therefore, marsh elevation.     

Mercury-binding proteins in the slipper limpet,Crepidula fornicata,exposed to increased soluble mercury

Crepidula fornicata were held in a flow-through bioassay system and exposed to sand-filtered seawater to which no soluble mercury (control) was added or to which either 5, 25, or 50 μg 1^?1 soluble Hg was added. At specific intervals during the 16-week experiment, a group of limpets was removed from each tank; one subgroup was exposed for 48 h to high concentrations of Hg, and another was analyzed for Hg-binding proteins by gelpermeation chromatography and spectrometry. Mortality from exposure to Hg in the 48-h acute toxicity tests was related to concentrations of Hg experienced both during the long-term exposure period and the 48-h exposure period. Chronic exposure to low levels of Hg resulted in increased amounts of total Hg in the whole body and in the low-molecular-weight Hg-binding proteins. No evidence was found for increased tolerance to Hg with preexposure.