Tolerance of ciliated protozoan Paramecium bursaria （Protozoa,Ciliophora） to ammonia and nitrites

The tolerance to ammonia and nitrites in freshwater ciliate Paramecium bursaria was measured in a conventional open system. The ciliate was exposed to different concentrations of ammonia and nitrites for 2h and 12h in order to determine the lethal concentrations. Linear regression analysis revealed that the 2h-LC50 value for ammonia was 95.94 mg/L and for nitrite 27.35 mg/L using probit scale method (with 95% confidence intervals). There was a linear correlation between the mortality probit scale and logarithmic concentration of ammonia which fit by a regression equation y=7.32x-9.51 (R^2=0.98; y, mortality probit scale; x, logarithmic concentration of ammonia), by which 2 h-LC50 value for ammonia was found to be 95.50 mg/L. A linear correlation between mortality probit scales and logarithmic concentration of nitrite is also followed the regression equation y=2.86x 0.89 (R^2=0.95; y, mortality probit scale; x, logarithmic concentration of nitrite). The regression analysis of toxicity curves showed that the linear correlation between exposed time of ammonia-N LC50 valueand ammonia-N LC50 value followed the regression equation y=2 862.85e-0.08x (R^2=0.95; y, duration of exposure to LC50 value; x, LC50 value), and that between exposed time of nitrite-N LC50 value and nitrite-N LC50 value followed the regression equation y = 127.15e-0.13x (R^2=0.91; y, exposed time of LC50 value; x, LC50 value). The results demonstrate that the tolerance to ammonia in P. bursaria is considerably higher than that of the larvae or juveniles of some metozoa, e.g. cultured prawns and oysters. In addition, ciliates, as bacterial predators, are likely to play a positive role in maintaining and improving water quality in aquatic environments with high-level ammonium, such as sewage treatment systems.     

Primary species recognitionand phylogeny of Chondrus （Gigartinales, Rhodophyta） using 18S rDNA sequence data

The nuclear-encoded small subunit ribosomal RNA gene (18S rDNA) of 16 isolates of Chondrus from 8 countries were sequenced. A total of 1796 nucleotides were obtained and aligned with the phylogenetic analysis conducted. The results suggest that the entity from Dalian, China, regarded as C. sp1 is C. pinnulatus. The C. sp2 previously depicted as C. yendoi or Mazzaella japonica may belong to genus Chondrus. So, 4 Chondrus species, i.e. C. ocellatus, C. nipponicus, C. armatus, and C. pinnulatus are distributed in China. However, the entity from Connemara, Ireland, named C. crispus, is not a Chondrus species but that of Mastocarpus stellatus, although it is morphologically similar to C. crispus. Phylogenetic analysis based on complete 18S rDNA sequence data shows that genus Chondrus includes 3 main lineages: the Northern Pacific lineage, containing C. ocellatus, C. yendoi, and C. nipponicus; C. armatus, and C. pinnulatus form the sub-North Pacific lineage; and the Northern Atlantic Ocean lineage, comprising samples of C. crispus from Canada, Portugal, Ireland, Germany and France. The phylogenetic relationships indicate that genus Chondrus might have a North Pacific ancestral origin, radiated to North Atlantic area, and then formed the species C. crispus.     

The Hadley Rille enstatite chondrite and its agglutinate-like rim: Impact melting during accretion to the Moon

Abstract— Hadley Rille is a millimeter-size EH chondrite containing euhedral and acicular enstatite grains, kamacite globules and preferentially aligned silicate aggregates separated by elongated kamacite-rich patches. The Hadley Rille chondrite was significantly impact melted when it accreted to the lunar regolith at relative velocities of ～>3 km s^?1; ～65–75% of the chondrules present initially were melted. During the impact, portions of the local regolith were melted and an agglutinate-like rim formed around the chondritic projectile; the rim consists of flow-banded vesicular glass, blebs of troilite and low-Ni metallic Fe, rock fragments, glass(?) shards, and mineral grains. The mineral grains include enstatite (which is otherwise absent from the Moon and must have been derived from the projectile) and poorly characterized, micrometer-size phases enriched in light rare-earth-elements (LREE), which probably formed during the impact. Several of the rock fragments contain <33 mg/g Cl, which was probably derived through impact-induced volatilization of Cl from chondrule mesostases in the EH projectile.     

Artificial recharge through a thick, heterogeneous unsaturated zone

Thick, heterogeneous unsaturated zones away from large streams in desert areas have not previously been considered suitable for artificial recharge from ponds. To test the potential for recharge in these settings, 1.3 x 10(6) m(3) of water was infiltrated through a 0.36-ha pond along Oro Grande Wash near Victorville, California, between October 2002 and January 2006. The pond overlies a regional pumping depression 117 m below land surface and is located where thickness and permeability of unsaturated deposits allowed infiltration and saturated alluvial deposits were sufficiently permeable to allow recovery of water. Because large changes in water levels caused by nearby pumping would obscure arrival of water at the water table, downward movement of water was measured using sensors in the unsaturated zone. The downward rate of water movement was initially as high as 6 m/d and decreased with depth to 0.07 m/d; the initial time to reach the water table was 3 years. After the unsaturated zone was wetted, water reached the water table in 1 year. Soluble salts and nitrate moved readily with the infiltrated water, whereas arsenic and chromium were less mobile. Numerical simulations done using the computer program TOUGH2 duplicated the downward rate of water movement, accumulation of water on perched zones, and its arrival at the water table. Assuming 10 x 10(6) m(3) of recharge annually for 20 years, a regional ground water flow model predicted water level rises of 30 m beneath the ponds, and rises exceeding 3 m in most wells serving the nearby urban area.     

Numerical studies of flow over a sill: sensitivity of the non-hydrostatic effects to the grid size

A non-hydrostatic terrain-following model in cross sectional form is applied to study the processes in the lee of a sill in an idealized stratified fjord during super-critical tidal inflow. A sequence of numerical studies with horizontal grid sizes in the range from 100 to 1.5625 m are performed. All experiments are repeated using both hydrostatic and non-hydrostatic versions of the model, allowing a systematic study of possible non-hydrostatic pressure effects and also of the sensitivity of these effects to the horizontal grid size. The length scales and periods of the internal waves in the lee of the sill are gradually reduced and the amplitudes of these waves are increased as the grid size is reduced from 100 down to 12.5 m. With a further reduction in grid size, more short time and space scale motions become superimposed on the internal waves. Associated with the internal wave activity, there is a deeper separation point that is fairly robust to all parameters investigated. Another separation point nearer to the top of the sill appears in the numerical results from the high-resolution studies with the non-hydrostatic model. Associated with this shallower separation point, an overturning vortex appears in the same set of numerical solutions. This vortex grows in strength with reduced grid size in the non-hydrostatic experiments. The effects of the non-hydrostatic pressure on the velocity and temperature fields grow with reduced grid size. In the experiments with horizontal grid sizes equal to 100 or 50 m, the non-hydrostatic pressure effects are small. For smaller grid sizes, the time mean velocity and temperature fields are also clearly affected by the non-hydrostatic pressure adjustments.     

Re–Os geochronology of a Mesoproterozoic sedimentary succession,Taoudeni basin,Mauritania: Implications for basin-wide correlations and Re–Os organic-rich sediments systematics

The exceptionally well-preserved sedimentary rocks of the Taoudeni basin, NW Africa represent one of the world's most widespread (> 1 M km²) Proterozoic successions. Hitherto, the sedimentary rocks were considered to be Mid Tonian based on Rb–Sr illite and glauconite geochronology of the Atar Group. However, new Re–Os organic-rich sediment (ORS) geochronology from two drill cores indicates that the Proterozoic Atar Group is ～ 200 Ma older (1107 ± 12 Ma, 1109 ± 22 Ma and 1105 ± 37 Ma). The Re–Os geochronology suggests that the Rb–Sr geochronology records the age of diagenetic events possibly associated with the Pan African collision.The new Re–Os geochronology data provide absolute age constraints for recent carbon isotope chemostratigraphy which suggests that the Atar Group is Mesoproterozoic and not Neoproterozoic.The new Re–Os ORS geochronology supports previous studies that suggest that rapid hydrocarbon generation (flash pyrolysis) from contact metamorphism of a dolerite sill does not significantly disturb the Re–Os ORS systematics. Modelled contact conditions suggest that the Re–Os ORS systematics remain undisturbed at ～ 650 °C at the sill/shale contact and ≥ 280 °C 20 m from the sill/shale contact.Moreover, the Re–Os geochronology indicates that the West African craton has a depositional history that predates 1100 Ma and that ORS can be correlated on a basin-wide scale. In addition, the Re–Os depositional ages for the ORS of the Taoudeni basin are comparable to those of ORS from the São Francisco craton, suggesting that these cratons are correlatable. This postulate is further supported by identical Os_i values for the Atar Group and the Vazante Group of the São Francisco craton.     

Re-evaluating Nd/Nd in lunar mare basalts with implications for the early evolution and bulk Sm/Nd of the Moon

The Moon likely accreted from melt and vapor ejected during a cataclysmic collision between Proto-Earth and a Mars-sized impactor very early in solar system history. The identical W, O, K, and Cr isotope compositions between materials from the Earth and Moon require that the material from the two bodies were well-homogenized during the collision process. As such, the ancient isotopic signatures preserved in lunar samples provide constraints on the bulk composition of the Earth. Two recent studies to obtain high-precision ¹⁴²Nd/¹⁴⁴Nd ratios of lunar mare basalts yielded contrasting results. In one study, after correction of neutron fluence effects imparted to the Nd isotope compositions of the samples, the coupled ¹⁴²Nd-¹⁴³Nd systematics were interpreted to be consistent with a bulk Moon having a chondritic Sm/Nd ratio [Rankenburg K., Brandon A. D. and Neal C. R. (2006) Neodymium isotope evidence for a chondritic composition of the Moon. Science312, 1369-1372]. The other study found that their data on the same and similar lunar mare basalts were consistent with a bulk Moon having a superchondritic Sm/Nd ratio [Boyet M. and Carlson R. W. (2007) A highly depleted Moon or a non-magma origin for the lunar crust? Earth Planet. Sci. Lett.262, 505-516]. Delineating between these two potential scenarios has key ramifications for a comprehensive understanding of the formation and early evolution of the Moon and for constraining the types of materials available for accretion into large terrestrial planets such as Earth.To further examine this issue, the same six lunar mare basalt samples measured in Rankenburg et al. [Rankenburg K., Brandon A. D. and Neal C. R. (2006) Neodymium isotope evidence for a chondritic composition of the Moon. Science312, 1369-1372] were re-measured for high-precision Nd isotopes using a multidynamic routine with reproducible internal and external precisions to better than ±3 ppm (2σ) for ¹⁴²Nd/¹⁴⁴Nd ratios. The measurements were repeated in a distinct second analytical campaign to further test their reproducibility. Evaluation of accuracy and neutron fluence corrections indicates that the multidynamic Nd isotope measurements in this study and the 3 in Boyet and Carlson [Boyet M. and Carlson R. W. (2007) A highly depleted Moon or a non-magma origin for the lunar crust? Earth Planet. Sci. Lett.262, 505-516] are reproducible, while static measurements in the previous two studies show analytical artifacts and cannot be used at the resolution of 10 ppm to determine a bulk Moon with either chondritic or superchondritic Sm/Nd ratios. The multidynamic data are best explained by a bulk Moon with a superchondritic Sm/Nd ratio that is similar to the present-day average for depleted MORB. Hafnium isotope data were collected on the same aliquots measured for their ¹⁴²Nd/¹⁴⁴Nd isotope ratios in order to assess if the correlation line for ¹⁴²Nd-¹⁴³Nd systematics reflect mixing processes or times at which lunar mantle sources formed. Based on the combined ¹⁴²Nd-¹⁴³Nd-¹⁷⁶Hf obtained we conclude that the ¹⁴²Nd-¹⁴³Nd correlation line measured in this study is best interpreted as an isochron with an age of 229⁺²⁴₋₂₀Ma after the onset of nebular condensation. The uncertainties in the data permit the sources of these samples to have formed over a 44 Ma time interval. These new results for lunar mare basalts are thus consistent with a later Sm-Nd isotope closure time of their source regions than some recent studies have postulated, and a superchondritic bulk Sm/Nd ratio of the Moon and Earth. The superchondritic Sm/Nd signature was inherited from the materials that accreted to make up the Earth-Moon system. Although collisional erosion of crust from planetesimals is favored here to remove subchondritic Sm/Nd portions and drive the bulk of these bodies to superchondritic in composition, removal of explosive basalt material via gravitational escape from such bodies, or chondrule sorting in the inner solar system, may also explain the compositional features that deviate from average chondrites that make up the Earth-Moon system. This inferred superchondritic nature for the Earth similar to the modern convecting mantle means that there is no reason to invoke a missing, subchondritic reservoir to mass balance the Earth back to chondritic for Sm/Nd ratios. However, to account for the subchondritic Sm/Nd ratios of continental crust, a second superchondritic Sm/Nd mantle reservoir is required.     

Persistent Differences in Horizontal Gradients in Phytoplankton Concentration Maintained by Surf Zone Hydrodynamics

Surf zones, regions of breaking waves, are at the interface between the shore and coastal ocean. Surf zone hydrodynamics may affect delivery of phytoplankton subsidies to the intertidal zone. Over a month of daily sampling at an intermediate surf zone with bathymetric rip currents and a reflective surf zone, we measured surf zone hydrodynamics and compared concentrations of coastal phytoplankton taxa in the surf zones to concentrations offshore. At the intermediate surf zone, ~80% of the variability in the concentration of coastal phytoplankton taxa within the surf zone was explained by their variation offshore; however, concentrations were much higher and lower than those offshore in samples from a bathymetric rip current and over the adjacent shoal, respectively. Hydrodynamics at this intermediate surf zone did not hinder the delivery of coastal phytoplankton to the surf zone, but the bathymetric rip current system appeared to redistribute phytoplankton concentrating them within eddies. At the reflective shore, we sampled surf zones at a beach and two adjacent rocky intertidal sites. Concentrations of typical coastal phytoplankton taxa were usually an order of magnitude or more lower than those offshore, even when offshore samples were collected just 20 m beyond the breakers. The phytoplankton assemblages inside and outside the surf zone often appeared to be disconnected. Surf zone hydrodynamics at the steep, reflective shore coupled with low phytoplankton concentrations in near-surface water appeared to limit delivery of phytoplankton subsidies to the surf zone. Surf zone hydrodynamics may be a key factor in the alongshore variation in phytoplankton subsidies to coastal communities.     

Trajectories of protection: Protectorates of Aborigines in early 19th century Australia and Aotearoa New Zealand

Abstract: This article tracks the passage of Aboriginal protection, as a contested imperial institution, from the Caribbean to Australia and Aotearoa New Zealand via the Cape Colony and Britain. In doing so, it reconfigures the historical geographies of colonial philanthropy, and of those individuals who sought to implement and resist it, as a set of specific, intersecting trajectories. These trajectories, of people, ideas and texts, both connected and remade multiple colonial places. The article also advocates positioning the contemporary politics of the colonial past in Britain, Australia and Aotearoa New Zealand, within a wider, trans‐imperial, set of connections.     

Coincidental Compositional and Orbital Correspondences Among Some Ordinary Chondrites: No Strong Evidence for Meteoroid Streams

Previous attempts to assign ordinary chondrites (OC) to meteoroid streams have been unsuccessful because the orbits of the proposed members had different radiants and, in some cases, the meteorites had significantly different cosmic-ray exposure (CRE) ages. Using more conservative criteria, we have identified four pairs of equilibrated OC (L6 Nejo, Salem; L6 Perpeti, Vouillé; L6 Drake Creek, Forsyth; H5 Okabe, Kerilis) wherein each member of the pair could conceivably have been derived from the same immediate precursor body (IPB). The members of each pair are of the same chondrite group and petrologic type; they have similar CRE ages and fell within 1 calendar day of each other (in different years). Because there is a moderate range in oxidation state (represented by mean olivine Fa) among equilibrated OC in each group, similarities in this intrinsic geochemical property between the members of two of the proposed pairs offer some support for the hypothesis that these rocks were derived from the same IPB. If the pairs are genuine, their precursor bodies were probably meter-size near-Earth asteroids (NEAs) with aphelia within or beyond the Main Asteroid Belt. Fragmentation of such NEAs is most likely to have occurred near aphelia; in principle, the ejecta could have spread somewhat along the NEAs’ orbits and collided with Earth on approximately the same calendar date but in different years. However, literature data show that, although ～670 meteorites with masses ≥10 kg reach the Earth’s surface each year, only five or six falls (typically in this mass range) are observed and recovered. This suggests that the chances of recovering more than one meteorite from a disrupted meter-size body in Earth-crossing orbit are small. It thus seems likely that the similar properties of the proposed OC pairs are due to coincidence.