Tolerance of calluna vulgaris and peatland plant communities to sulphuric acid deposition

Critical loads offer a unique way of evaluating impacts of acid deposition by quantifying environmental sensitivity. The critical loads of acidity for UK peat soils have been based upon an arbitrary reduction in pH of 0.2 units. This chemical shift needs to be better related to adverse effects on sensitive biological receptors. It is known that effective precipitation pH equates closely to soil solution pH, and the latter is directly linkable to biotic effects of pH change. On continuation of a long-term experiment assessing impacts of simulated acid rain on peat microcosms in a realistic outdoor environment, Calluna vulgaris continued to flourish at acid deposition loads well above the existing critical load. Calluna plants were harvested and analysed, and acid deposition treatments to the microcosms continued to allow natural vegetation to regenerate. A diverse mixture of moorland plants and bryophytes established at acidity treatments well above the existing critical load, and only a very high acid load resulted in no natural regeneration. A critical effective rain pH value of 3.6 is suggested as a basis for setting critical loads. At this pH, Calluna grows well, and a healthy diverse vegetation community re-establishes when harvested. It is suggested that the peat critical load should be set at the acid load that, at any specific site, would result in a mean effective precipitation pH of 3.6.     

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     

Prenatal prediction of childhood-onset spinal muscular atrophy (SMA) in Turkish families

Childhood-onset spinal muscular atrophy (SMA) is one of the most common neurodegenerative genetic disorders. SMN1 is the SMA-determining gene deleted or mutated in the majority of SMA cases. There is no effective cure or treatment for this disease yet. Thus, the availability of prenatal testing is important. Here we report prenatal prediction for 68 fetuses in 63 Turkish SMA families using direct deletion analysis of the SMN1 gene by restriction digestion. The genotype of the index case was known in 40 families (Group A) but unknown in the remaining 23 families (Group B). A total of ten fetuses were predicted to be affected. Eight of these fetuses were derived from Group A and two of these fetuses were from Group B families. Two fetuses from the same family in Group A had the SMNhyb1 gene in addition to homozygous deletion of the NAIP gene. One fetus from Group A was homozygously deleted for only exon 8 of the SMN2 gene, and further analysis showed the presence of both the SMN1 and SMNhyb1 genes but not the SMN2 gene. In addition, one carrier with a homozygous deletion of only exon 8 of the SMN1 gene was detected to have a SMNhyb2 gene, which was also found in the fetus. To our knowledge, these are the first prenatal cases with SMNhyb genes. Follow-up studies demonstrated that the prenatal predictions and the phenotype of the fetuses correlated well in 33 type I pregnancies demonstrating that a careful molecular analysis of the SMN genes is very useful in predicting the phenotype of the fetus in families at risk for SMA. Copyright © 2002 John Wiley & Sons, Ltd.     

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.     

A closed-chamber CO2-flux method for estimating intertidal primary production and respiration under emersed conditions

This paper describes a closed-chamber method for measuring CO₂ fluxes in intertidal soft sediments during periods of emersion. The method relies on closed-circuit incubations of undisturbed sediment and measurement of CO₂ exchanges using an infrared gas analyser. The method was assessed during field experiments, both in light and dark conditions, on an exposed sandy beach and in an estuary. The rates of gross community production measured under moderate irradiance (4.2 mg C m^-2 h^-1 on the exposed sandy beach and 35 mg C m^-2 h^-1 in the estuary) are in good agreement with rates reported in the literature. In conjunction with appropriate sampling strategies, this method can be useful for estimating and comparing production of intertidal areas or for assessing factors that influence production.     

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.