Cell-Specific Alkaline Phosphatase Expression by Phytoplankton from Winyah Bay,South Carolina,USA

Alkaline phosphatase expression by phytoplankton from two sites in Winyah Bay, SC, USA was investigated using nutrient-addition bioassays and cell-specific enzyme-labeled fluorescence (ELF) measurements. Our aim was to determine whether expression was group- or species-specific within the phytoplankton community. Diatoms dominated the riverine site in May, the coastal site in July, and both sites in August. Phytoplankton growth was limited by nitrogen (N) availability at the coastal site in May and the riverine site in August, but phosphate limitation was not observed. Alkaline phosphatase expression ranged from ∼30% of cells enumerated to less than 1% and was significantly reduced by inorganic phosphorus (P; 10 μM P) additions. Expression was restricted to species with low abundance, and there were no shifts in community composition consistent with alkaline phosphatase expression. Lack of phosphate limitation at higher-than-Redfield N/P ratios (up to 40:1), however, points to a potentially wider role of dissolved organic phosphorus in nutrition of Winyah Bay phytoplankton than indicated by the ELF assay.     

Experimental investigation of the scavenging of gaseous mercury by sea salt aerosol

Sea salt aerosol may be an important sink for reactive gaseous mercury (RGM) in the marine boundary layer, reducing ambient RGM concentrations and transferring the mercury (Hg) to the oceans and coastal ecosystems. The goal of this study was to determine the affinity of gaseous mercury for sea salt aerosol (SSA) by conducting adsorption experiments with sea salt-coated sampling denuders. In the first set of experiments, ambient outdoor air was passed through denuders coated with either KCl, as in the widely accepted method to sample RGM, or with NaCl, a primary component of sea salt aerosols. On the one sampling day in which RGM was above the MDL, the NaCl coated denuders removed Hg from the ambient air, equivalent to 87% of the RGM in the air (as determined by KCl denuders). For the second set of experiments HgCl₂ generated in the laboratory was passed through denuders coated with KCl and either NaCl or sea salt. The NaCl denuders collected an average of 99 ± 16% of the mercury that the KCl denuders collected. Newly coated sea salt denuders collected 88 ± 17% of the amount of mercury that the KCl denuders collected, but interestingly the sea salt denuders capacity decreased with repeated use. These experiments demonstrate that HgCl₂, a major component of RGM has a strong affinity for NaCl and sea salt and is therefore likely to be scavenged by SSA. This study adds to the growing evidence that RGM is scavenged by sea salt aerosols and therefore more quickly deposited to the ocean and coastal environment.     

Hurricane-borne African Locusts (Schistocerca gregaria) on the Windward Islands

The research applies a geographic perspective to the interface of biotic, atmospheric and socio-economic factors. Wind as a factor in biotic distributions helps explain the existence and quality of life on many isolated islands. In the late summer of 1988, there were reports of African desert Locust (Schistocerca gregaria) invasion of the Windward Islands. The event was historically unprecedented, and agricultural experts in the eastern Caribbean were alarmed. A tentative hypothesis was that Hurricane Joan provided the transport mechanism. An alternative hypothesis is suggested here. The discussion helps explain why transatlantic African Desert Locust migrations are so unusual. Analysis is based on primary and secondary data sources that include synoptic weather maps, formal and informal scientific reports, written correspondence with agricultural experts in the impact area, and newspaper coverage of the invasion.     

Extreme variations in strontium initial ratios in ore-related fluids

Magmato-hydrothermal cassiterite-topaz ore at the Carboniferous East Kemptville (EK) greisenhosted tin deposit (Nova Scotia, Canada) is cross-cut by veins containing apatite, triplite, vivianite and fluorite. Initial ⁸⁷Sr/⁸⁶Sr ratios of these minerals have an extreme range (0.7135 to 0.8284). The initial ratios of the host rocks, EK quartz-topaz rock and Davis Lake biotite monzogranite (0.729±0.001, 0.727±0.004), are also high. The adjacent Meguma Group metasedimentary rocks are more typical of crustal material (0.712–0.719 at 330 Ma). Rb and Sr contents of EK fluorite (max.: 13.0, 1420 ppm) and apatite (max.: 88.1, 6660 ppm) are unusually high and variable. Unexpectedly, high Sr contents correlate positively with the high initial ⁸⁷Sr/⁸⁶Sr ratios. Fluorite and phosphate minerals from the first set of post-greisen veins at East Kemptville reflect the unusual chemistry of a high ⁸⁷Sr/⁸⁶Sr fluid present in the deposit after ore formation. The most extreme composition of this fluid was characterized by ⁸⁷Sr/⁸⁶Sr>0.8284, high Rb/Sr, high P, Rb, Cu, Zn and Fe contents, but low abundances of Ca, Pb and Sn with respect to the Davis Lake monzogranite. Such a fluid could have been derived from the greisen fluid and modified by reaction with the overlying Meguma metawacke. A second alternative, which cannot be well constrained at present, is that an extremely radiogenic fluid entered the deposit after ore formation and mixed with the postore fluid. In either case, the modified fluid subsequently mixed with meteoric water and precipitated the minerals with much lower ⁸⁷Sr/⁸⁶Sr ratios and Rb and Sr contents.     

Strontium isotopic geochemistry of Pan-African/Brasiliano rocks,Chapada copper deposit,Goiás,Brazil

Whole rock and mineral Rb-Sr isochrons from the upper amphibolite grade metamorphic host rocks of the Chapada copper deposit in Goiás, Brazil, yield an age of 561±9 Ma, with a⁸⁷Sr/⁸⁶Sr initial (I) of 0.70414±0.00005, for the crystallization of pre-metamorphic volcanic and igneous rocks and 532 ±1 Ma for their metamorphism during the Pan-African/Brasiliano orogeny (700-450 Ma). A porphyritic diorite stock which intruded the host schists yields a mineral isochron age of 534±16 Ma (I=0.70415±0.00004). The low I values determined from these isochrons suggest that the host schists at Chapada were derived from upper mantle or lower crust material and are characteristic of magmatic products associated with island arcs. The Early Cambrian age of the host rocks at Chapada contradicts the previously assigned mid-Proterozoic age and suggests that Pan-African/Brasiliano magmatic activity may have been more extensive in central Brazil than previously thought.

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Zusammenfassung Das Trägergestein der Chapada Kupferlagerstätte in Goiás ist in metamorpher Hoch-Amphibolitfazies ausgebildet. Gesamtgesteins- und individuelle Mineral Rb-Sr-Isochronen mit einem⁸⁷Sr/⁸⁶Sr-Initialwert (I) von 0,70414±0.00005 ergeben für die Kristallisation der Vulkanite und Magmatite, die die Metamorphose vordatieren, ein Alter von 561±9 Mio Jahre. Die Datierung der Metamorphose während der panafrikanisch/brasilianischen Orogenese (700 bis 450 Mio Jahre) ergibt 532±1 Mio Jahre. Das Mineral-Isochronenalter eines Dioritkörpers porphyrischen Gefüges, der in die Schiefer intrudierte, beträgt 534±16 Mio Jahre (I=0,70415 ±0,00004). Das Ergebnis niedriger Initial-Werte dieser Isochronen ergibt für die Schiefer bei Chapada ein Ausgangs-Material im Bereich des oberen Mantels oder der tieferen Kruste; diese Ausgangswerte sind charakteristisch für magmatische Tätigkeit in Verbindung mit Inselbögen. Das unterkambrische Alter des Trägergesteins bei Chapada steht im Widerspruch zu dem bisher angenommenen mittelproterozoischen Alter und ist ein Hinweis auf eine mögliche Phase intensiverer pan-afrikanisch/brasilianischer magmatischer Aktivität in Zentral-Brasilien als ursprünglich angenommen wurde.

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Résumé Les roches qui contiennent le gisement de cuivre de Chapada (Goias, Brésil) sont des schistes cristallins appartenent au facies dupérieur des amphibolites. Dans des volcanites et des roches orthomagmatiques appartenant à cet ensemble, des isochrones Rb-Sr sur roches totales et sur minéraux donnent un âge de 561±9 Ma avec un rapport initial de 0,70414±0,00005 pour la cristallisation pré-métamorphique et un âge de 532±1 Ma pour le métamorphisme, lié à l'orogenèse pan-africaine / brésilienne. Un pluton de diorite porphyrique, qui intrude les schistes cristallins donne, par isochrone sur minéraux, un âge de 534±16 Ma (rapport initial de 0,70415±0,00004). Les valeurs basses des rapports initiaux de ces diverses roches suggèrent que les schistes de Chapada sont dérivés de matériaux mantelliques ou crustaux profonds et présentent les caractères des produits magmatiques associés aux arcs insulaires. Leur âge éo-cambrien, en contradiction avec l'âge mésoprotérozoïque admis jusqu'ici, permet de penser que l'activité magmatique pan-africaine/brésilienne dans le centre du Brésil a été plus intense que ce qu'on croyait jusqu'ici.

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Chapada Gois . 0,70414±0,00005, 561± 9 , 532±1 , . . - / 700 450 /. , , 534±16 / 1 = 0,70415 = 0,00004 /. , Chapada , . . - ; , . , - - , , , .

     

A comparison of geographic datasets and field measurements to model soil carbon using random forests and stepwise regressions (British Columbia,Canada)

We used geographic datasets and field measurements to examine the mechanisms that affect soil carbon (SC) storage for 65 grazed and non-grazed pastures in southern interior grasslands of British Columbia, Canada. Stepwise linear regression (SR) modeling was compared with random forest (RF) modeling. Models produced with SR performed better than those produced using RF models (r² = 0.56–0.77 AIC = 0.16–0.30 for SR models; r² = 0.38–0.53 and AIC = 0.18–0.30 for RF models). The factors most significant when predicting SC were elevation, precipitation, and the normalized difference vegetation index (NDVI). NDVI was evaluated at two scales using: (1) the MOD 13Q1 (250 m/16-day resolution) NDVI data product from the moderate resolution imaging spectro-radiometer (MODIS) (NDVI_MODIS), and (2) a handheld multispectral radiometer (MSR, 1 m resolution) (NDVI_MSR) in order to understand the potential for increasing model accuracy by increasing the spatial resolution of the gridded geographic datasets. When NDVI_MSR data were used to predict SC, the percentage of the variance explained by the model was greater than for models that relied on NDVI_MODIS data (r² = 0.68 for SC for non-grazed systems, modeled with SR based on NDVI_MODIS data; r² = 0.77 for SC for non-grazed systems, modeled with SR based on NDVI_MSR data). The outcomes of this study provide the groundwork for effective monitoring of SC using geographic datasets to enable a carbon offset program for the ranching industry.     

A Regional Measure of Neighborhood Multiple Environmental Deprivation: Relationships with Health and Health Inequalities

The health impacts of simultaneous exposure to multiple adverse environmental factors are of concern in the United Kingdom. UK-wide indicators exist, but context-specific finer resolution measures are lacking. An environmental deprivation index was developed for 398 neighborhoods (average population = 760) in a Scottish council area, including measures of air pollution, noise pollution, traffic environment, undesirable land uses, and crime. Adverse environmental conditions were related to ill health in the region and implicated in wider socioeconomic health inequalities. The results suggest an independent role for environmental deprivation in explaining poor health and health inequalities.     

Decomposition of litter in a dry sclerophyll eucalypt forest and a Pinus radiata plantation in southeastern Australia

This study of litter decomposition was part of an extensive project examining the partitioning of rainfall, the associated chemistry, and litterfall in a dry sclerophyll eucalypt forest and a Pinus radiata plantation in southeastern Australia. The eucalypt species studied were Eucalyptus rossii, E. mannifera and E. dives. The components tested were Pinus radiata needles, leaves of the three eucalypt species, and the bark of E. rossii and E. mannifera. During the first 16 weeks of the decomposition experiment there was a rapid decrease in the concentrations of potassium, magnesium, sodium and phosphorus; this was attributed to leaching. During this period, concentrations of nitrogen and calcium increased for most components. After this period, decomposition became the dominant process, during which the concentrations of most elements increased. By the end of the experiment there was, compared with the initial values, a marked reduction in concentrations of sodium, magnesium and potassium for all eucalypt and pine litter. Calcium concentrations increased through time, with eucalypt bark showing a mid‐period decline. Phosphorus concentrations decreased for the eucalypt leaves but increased substantially for the pine needles and the eucalypt bark. For all components of both the eucalypts and pines, total nitrogen concentrations rose consistently throughout the decomposition period. This was attributed to the formation of nitrogen‐substituted lignin, which was more resistant to decomposition than the other nitrogen‐containing compounds, as well as some nitrogen being stored in the micro‐organisms responsible for decomposition. Because of loss of fragmented litter from the litter bags after 16 weeks, the weight changes could not be confidently measured after this period. Copyright © 2002 John Wiley & Sons, Ltd.     

Crater clusters on Mars: Shedding light on martian ejecta launch conditions

We have identified two classes of crater clusters on Mars. One class is “small clusters” (crater diameter D∼ tens m, spread over few hundred m), fitting our earlier calculations for the breakup of weak stone meteoroids in the martian atmosphere [Popova, O.P., Nemtchinov, I.V., Hartmann, W.K., 2003. Meteorit. Planet. Sci. 38, 905-925]. The second class is “large clusters” (D∼ few hundred m, spread over 2 to 30 km), which do not fit any predictions for breakup of known meteoroid types. We consider a range of possible explanations. The best explanation relates to known, high-speed ejection of large, semi-coherent, fractured rock masses from the surface, as secondary debris from primary impacts. The clusters are probably due to breakup of partly fracture, few-hundred-meter scale weak blocks, especially during ascent (producing moderate lateral spreading velocities among the fragments during sub-orbital flight), and also during descent of the resulting swarm. These conclusions illuminate the launch conditions of martian meteorites, including fragmentation processes, although more work is needed on the lateral separation of fragments (during either atmosphere descent or ascent) due to the effects of volatiles in the projectiles. Martian meteorites probably come from smaller martian craters than the clusters' source craters. The latter probably have D?85 km, although we have not ruled out diameters as small as 15 km.