In situ assessment of modification of sediment properties by burrowing invertebrates

Benthic organisms can significantly alter the physical properties of marine sediments, but it has hitherto been difficult to assess and quantify the effects of bioturbation. In situ geophysical techniques offer new methods for measuring these effects: measurement of acoustic shear-wave velocity and electrical resistivity allows nondestructive assessment of the properties of the grain framework and pore-fluid matrix, respectively, of the seabed sediment. The influence of burrowing invertebrates on the structural properties of sandy sediments at intertidal locations on the coast of Wales (UK) was investigated during the periol 1986–1987 using these techniques. Three species (Arenicola marina, Corophium arenarium and Lanice conchilega) were selected on the basis of their contrasting styles of burrow construction. All three species produced measurable and significant, although different, changes in bed properties. They modified shear-wave propagation through the bed by changing bed rigidity: while A. marina and C. arenarium decreased rigidity by creating open burrows, L. conchilega increased rigidity by building shell-lined tubes. All produced a decrease in electrical resistivity by altering porosity and/or tortuosity, which implies an increase in permeability; these changes were attributable not only to the presence of the burrows but also to modification of the between-burrow sediment texture and bed properties.     

Fetal cardiac anomalies and genetic syndromes

Cardiac anomalies may occur in isolation or can be part of a genetic syndrome. In this article, we describe some of the genetic syndromes commonly associated with cardiac anomalies where there are other sonographic features that may aid accurate prenatal diagnosis. Copyright © 2004 John Wiley & Sons, Ltd.     

Biological productivity of bogs in the middle taiga subzone of Western Siberia

New experimental data on biological productivity of plant communities in oligotrophic and mesotrophic bogs of the middle taiga subzone over the past five years are presented. The relationship between net primary production and the stock of live phytomass is estimated. The stock of necromass in oligotrophic bog ecosystems increases from west to east, while the stock of live phytomass and net primary production decrease.     

Perceptions toward stewardship among residents living near U.S. Department of Energy Nuclear Facilities

Although stewardship has been widely defined and used in environmental management and planning, there is a dearth of studies that describe how the lay public perceives this concept. A national sample of residents in 14 states who live near DOE nuclear facilities were interviewed to delineate public understanding and awareness of the stewardship program of the U.S. Department of Energy (DOE). This study discusses the findings of the survey and discusses how institutional trust influences public participation and resident’s choices of potential stewards. Almost 40% of the respondents could not define stewardship; those who did, believed that ‘responsibility,’ ‘management,’ and ‘accountability’ are key elements of stewardship. In addition, about a third of the respondents identified Federal groups and the DOE as potential stewards. Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue     

Paleosols of the Solonchanka IX site and climate of the Transural steppe zone in the fourth century AD

Studies on paleosols under an archaeological landmark of a rare type (a complex of kurgans with “whiskers”) dating from the Early Iron Age (the fourth century AD) have been performed in the steppe zone of the Transural Plateau. The size and shape of third-order soil polygons under stony ridges (“whiskers”) between the kurgans have been described in detail. The results have shown that the paleosol under the kurgans erected at the turn of the Late Sarmatian and Hun times (1600 years ago) is characterized by a higher humus content and deeper location of the carbonate horizon, compared to the recent soil. This indicates that an increase in atmospheric humidity took place in the fourth century AD.     

Isotope tracing of submarine groundwater discharge offshore Ubatuba, Brazil: results of the IAEA–UNESCO SGD project

Results of groundwater and seawater analyses for radioactive (³H, ²²²Rn, ²²³Ra, ²²⁴Ra, ²²⁶Ra, and ²²⁸Ra) and stable (D and ¹⁸O) isotopes are presented together with in situ spatial mapping and time series ²²²Rn measurements in seawater, direct seepage measurements using manual and automated seepage meters, pore water investigations using different tracers and piezometric techniques, and geoelectric surveys probing the coast. This study represents first time that such a new complex arsenal of radioactive and non-radioactive tracer techniques and geophysical methods have been used for simultaneous submarine groundwater discharge (SGD) investigations. Large fluctuations of SGD fluxes were observed at sites situated only a few meters apart (from 0 cm d⁻¹ to 360 cm d⁻¹; the unit represents cm³/cm²/day), as well as during a few hours (from 0 cm d⁻¹ to 110 cm d⁻¹), strongly depending on the tidal fluctuations. The average SGD flux estimated from continuous ²²²Rn measurements is 17 ± 10 cm d⁻¹. Integrated coastal SGD flux estimated for the Ubatuba coast using radium isotopes is about 7 × 10³ m³ d⁻¹ per km of the coast. The isotopic composition (δD and δ¹⁸O) of submarine waters was characterised by significant variability and heavy isotope enrichment, indicating that the contribution of groundwater in submarine waters varied from a small percentage to 20%. However, this contribution with increasing offshore distance became negligible. Automated seepage meters and time series measurements of ²²²Rn activity concentration showed a negative correlation between the SGD rates and tidal stage. This is likely caused by sea level changes as tidal effects induce variations of hydraulic gradients. The geoelectric probing and piezometric measurements contributed to better understanding of the spatial distribution of different water masses present along the coast. The radium isotope data showed scattered distributions with offshore distance, which imply that seawater in a complex coast with many small bays and islands was influenced by local currents and groundwater/seawater mixing. This has also been confirmed by a relatively short residence time of 1–2 weeks for water within 25 km offshore, as obtained by short-lived radium isotopes. The irregular distribution of SGD seen at Ubatuba is a characteristic of fractured rock aquifers, fed by coastal groundwater and recirculated seawater with small admixtures of groundwater, which is of potential environmental concern and has implications on the management of freshwater resources in the region.     

Effects of ocean temperature on the southern range limits of two understory kelps, <Emphasis Type="Italic">Pterygophora californica</Emphasis> and <Emphasis Type="Italic">Eisenia arborea</Emphasis>, at multiple life-stages

Environmental factors have long been shown to influence species distributions, with range limits often resulting from environmental stressors exceeding organism tolerances. However, these abiotic factors may differentially affect species with multiple life-history stages. Between September 2004 and January 2006, the roles of temperature and nutrient availability in explaining the southern distributions of two understory kelps, Pterygophora californica and Eisenia arborea (Phaeophyceae, Laminariales), were investigated along the coast of California, USA and the Baja California Peninsula, Mexico, by limiting either: (a) tissue nitrogen uptake and storage by adult sporophytes during periods of elevated temperature, and/or (b) production of embryonic sporophytes by microscopic gametophytes. Results suggest that while adult sporophytes of both species are tolerant of high temperatures and low nutrients, reproduction by their microscopic stages is not. Specifically, while E. arborea produced embryonic sporophytes at both 12 and 18°C, temperatures commonly observed throughout the southern portion of its range, P. californica produced sporophytes at 12 but not at 18°C. As a result, it appears that the southern distribution of P. californica, which ends in northern Baja California, Mexico, may be limited by temperature acting on its microscopic stages. In contrast, the ability of E. arborea’s microscopic and adult stages to tolerate elevated temperatures allows it to persist in the warmer southern waters of Baja California, as well as to the north along the California coast where both species co-occur.     

GCM-based analysis of water availability along the Tone River and Tokyo Metropolitan Area under climatic changes

Tone River supplies most of the water requirements of the Tokyo Metropolitan Area (TMA). Lowering of Tone flow and yearly fluctuation, however, is causing water shortage along TMA nowadays. This study investigated the future water availability scenarios under climatic changes. A state-of-the-art approach to utilize the output of several GCM has been demonstrated to investigate the future water availability scenarios for TMA from the Tone River. An integrated modeling approach for water balance considering several hydrological risk indices was adopted to quantify the future changes in this case. It is observed that the future summer precipitation along the Tone basin is going to be increased considerably, while an almost constant or decreasing trend is observed for winter season. Natural flow availability for winter or spring seasons thus can be crucial under future scenarios. After reservoir routing, the hydrological risk indices estimated, however, were not found to be changed significantly due to the presence of a robust reservoir system at the upstream.     

The use of ecological scales for indication of the current state of forest communities

A method for estimating the current state of plant communities based on the ecological amplitudes of constituent species is proposed. An original program, Fitoindikatsiya, has been developed to compute the indices of disturbance and homogeneity of plant communities from species ecological scale values. The current state of pine forests in the part of Novosibirsk oblast east of the Ob River has been analyzed; slightly, moderately, and severely disturbed zones have been distinguished.