Investigation of the mud crab (Scylla serrata) as a potential bio-monitoring species for tropical coastal marine environments of Australia

Mud crabs, Scylla serrata, were sampled from four estuaries (the Normanby, Herbert, Burdekin and Fitzroy Rivers) along the coast of northern Queensland, Australia, representing a pollution gradient from low to high contamination based upon previous chemical monitoring. Four biomarkers; glutathione-S-transferase (GST) activity, cholinesterase (ChE) inhibition and the urinary metabolite concentrations of naphthalene (NPH) and benzo-a-pyrene (BaP) were evaluated in S. serrata hepatopancreas, haemolymph and urine. Site-specific evidence of elevated GST activity and BaP metabolite concentrations and significant ChE inhibition was detected. Biomarker responses from this field study provide evidence of contaminant exposure of S. serrata from river estuaries along the coast of northern Queensland and indicate that further investigation is warranted. Based on the current results, and with further work on characterising the dose-response and seasonal variation in this species, mud crabs have great potential as indicator species for water quality and ecosystem monitoring programs across tropical coastal regions of Australia.     

Investigations on cosmic-ray-produced nuclides in iron meteorites, 3. Exposure ages,meteoroid sizes and sample depths determined by mass spectrometric analyses of potassium and rare gases

Three physical quantities define the essentials of the cosmic ray exposure history of a sample of an iron meteorite: (1) the cosmic ray exposure age T, (2) the pre-atmospheric “size” S of the irradiated body, and (3) the location, i.e. the “depth” D, of the samples within the body. To establish these quantities for a given sample three independent quantities must be determined experimentally. In the present work T is ascertained by the ⁴¹K/⁴⁰K method and the ⁴He and ²¹Ne concentrations (C₄ and C₂₁) are measured by the isotope dilution method. Signer and Nier's evaluation of the rare gas distribution in the meteorite Grant and the measured exposure age for this meteorite provide the relationships allowing to ascertain for any meteorite the quantities S and D from the ²¹Ne production rate (P₂₁ = C₂₁/T) and the ⁴He/²¹Ne ratio.Earlier measurements have provided data on the isotopic composition of potassium in 74 different iron meteorites. New rare gas measurements are reported for some 40 samples. Results on the age, size and depth are obtained for almost 60 samples. These data suggest that Signer and Nier's model is well suited for describing not only the rare gas distribution in a single selected meteorite (Grant) but also the exposure histories of the great majority of all irons. For a few samples, however, secondary breakups of the meteoroid and a two- or multiple-stage irradiation must be invoked. Further measurements are proposed for testing and, possibly, refining the still somewhat uncertain relationships between the abundances of cosmogenic nuclides and the quantities T, S, and D in very large meteorites.Histograms are presented showing the age distributions for irons of different chemical groups and of different size ranges.The feasibility and the relative merits of other methods for the determination of T, S, and D are discussed.     

Cosmogenic21Ne and22Ne depth profiles in chondrites

The production rate profiles of²¹Ne and²²Ne as a function of depth in meteoroids due to spallation by solar flare cosmic rays (SCR) and galactic cosmic rays (GCR) are calculated and their dependence on size and composition of meteoroids has been evaluated. The GCR production rate at a given depth increases with size for radii<25cm and then decreases whereas the²²Ne²¹Ne ratio (NeR) generally decreases with size and depth. The calculated GCR production rates and NeR are consistent with the measurements in several Chondrites. A plot of track production rate vs. NeR shows that some chondrites have NeR values smaller than those expected for their sizes. Thes obeervation suggestsat least a two-stage irradiation for such meteorites; the meteoroid exposure as a small body in the interplanetary space must have been preceded by exposure under deep shielding, possibly in its parent body.     

Foraging Inhibition in Two Cladocerans Feeding on Microcystis aeruginosa

Bloom‐forming cyanobacteria are known to negatively affect their herbivores, but the possible reasons leading to the foraging inhibition of different cladoceran species are uncertain and controversial so far. Hence, in order to understand how cyanobacteria affect the feeding behavior of cladocerans with different body sizes, feeding rates (FR) of zooplankton cladocerans Daphnia carinata and Moina macrocopa on the mixture of toxic or non‐toxic Microcystis aeruginosa with Scenedesmus quadricauda during a 24‐h period was investigated. FR of M. macrocopa was found generally low in the mixed toxic Microcystis diets, except for the sudden increase after 8 h of exposure, while FR of D. carinata decreased continuously in the mixed toxic diets. The dynamics of FR of both cladocerans on specific algae was similar to that of the total FR. There is no apparent selectivity displayed for either of the two cladoceran species on the mixed diets. There is no significant difference between the strains of Microcystis, suggesting that the feeding pattern of M. macrocopa maybe more of avoiding Microcystis rather than feeding inhibition resulted from the toxicity of algae. Unlike M. macrocopa, there was a significant difference in D. carinata between the strains of Microcystis over time. The reason for feeding inhibition of D. carinata might be toxicity after continuous exposure to the toxic cyanobacteria.     

Chronology of Lateglacial ice flow reorganization and deglaciation in the Gotthard Pass area,Central Swiss Alps,based on cosmogenic 10Be and in situ 14C

We reconstruct the timing of ice flow reconfiguration and deglaciation of the Central Alpine Gotthard Pass, Switzerland, using cosmogenic ¹⁰Be and in situ ¹⁴C surface exposure dating. Combined with mapping of glacial erosional markers, exposure ages of bedrock surfaces reveal progressive glacier downwasting from the maximum LGM ice volume and a gradual reorganization of the paleoflow pattern with a southward migration of the ice divide. Exposure ages of ∼16–14 ka (snow corrected) give evidence for continuous early Lateglacial ice cover and indicate that the first deglaciation was contemporaneous with the decay of the large Gschnitz glacier system. In agreement with published ages from other Alpine passes, these data support the concept of large transection glaciers that persisted in the high Alps after the breakdown of the LGM ice masses in the foreland and possibly decayed as late as the onset of the Bølling warming. A younger group of ages around ∼12–13 ka records the timing of deglaciation following local glacier readvance during the Egesen stadial. Glacial erosional features and the distribution of exposure ages consistently imply that Egesen glaciers were of comparatively small volume and were following a topographically controlled paleoflow pattern. Dating of a boulder close to the pass elevation gives a minimum age of 11.1 ± 0.4 ka for final deglaciation by the end of the Younger Dryas. In situ ¹⁴C data are overall in good agreement with the ¹⁰Be ages and confirm continuous exposure throughout the Holocene. However, in situ ¹⁴C demonstrates that partial surface shielding, e.g. by snow, has to be incorporated in the exposure age calculations and the model of deglaciation.     

Can in-situ cosmogenic 14C be used to assess the influence of clast recycling on exposure dating of ice retreat in Antarctica?

Cosmogenic nuclide exposure dating of glacial clasts is becoming a common and robust method for reconstructing the history of glaciers and ice sheets. In Antarctica, however, many samples exhibit cosmogenic nuclide ‘inheritance’ as a result of sediment recycling and exposure to cosmic radiation during previous ice free periods. In-situ cosmogenic ¹⁴C, in combination with longer lived nuclides such as ¹⁰Be, can be used to detect inheritance because the relatively short half-life of ¹⁴C means that in-situ ¹⁴C acquired in exposure during previous interglacials decays away while the sample locality is covered by ice during the subsequent glacial. Measurements of in-situ ¹⁴C in clasts from the last deglaciation of the Framnes Mountains in East Antarctica provide deglaciation ages that are concordant with existing ²⁶Al and ¹⁰Be ages, suggesting that in this area, the younger population of erratics contain limited inheritance.     

Impaired osmoregulation in the shrimp Palaemon adspersus exposed to crude oil extract

Palaemon adspersus is a hyper- and hypo-osmoregulating shallow-water shrimp. For a maximum period of 34 days P. adspersus were exposed to 20, 70, 100 and 200 ppb WSF of North Sea crude oil. The osmotic concentration of the haemolymph was measured by freezing point depression once a week. The ability to maintain hyper-osmolality was significantly decreased (p<0.05) after one, two and three weeks exposure to 200, 70 and 100 ppb, respectively. No effect was observed in 20 ppb. After an accidental exposure of shrimps to 24 h acute oil pollution, they were placed in pure sea water. The ability to maintain hyper-osmolality was reduced one week after the accidental oil exposure, but was regained within three weeks.     

26Al in iron meteorites and the constancy of cosmic ray intensity in the past

Cosmic-ray-produced²⁶Al in iron meteorites has been measured by low-level γγ-coincidence counting. The²⁶Al activities, in dpm/kg, are: Aroos3.0 ± 1.0, Braunau2.6 ± 0.5. Kayakent4.6 ± 1.5, N'Goureyma4.4 ± 1.1, Okahandja3.6 ± 0.9, Treysa4.0 ± 0.5. Exposure ages based on²⁶Al/²¹Ne are in agreement, within experimental error(±20%), with those based on³⁶Cl/³⁶Ar and³⁹Ar/³⁸Ar but the ages based on⁴⁰K/⁴¹K are higher by about 50%. The difference in exposure ages is probably caused by a real change of the cosmic ray intensity in the inner solar system.     

A time probabilistic approach to seismic landslide hazard estimates in Iran

Understanding where seismically induced landslides are most likely to occur is crucial in land use planning and civil protection actions aimed at reducing property damage and loss of life in future earthquakes. For this purpose an approach proposed by Del Gaudio et al. [1] has been applied to the whole Iranian territory to provide the basis to assess location and temporal recurrence of conditions of seismic activation of slope failures, according to the Newmark's model [2]. Following this approach, occurrence probabilities for different levels of seismic shaking in a time interval of interest (50 years) were first obtained through a standard hazard estimate procedure. Then, empirical formulae in the form proposed by Jibson et al. [3] and calibrated for the main seismogenic Iranian regions were used to evaluate the slope critical acceleration (Ac)_x for which a prefixed probability exists that, under seismic shakings, Newmark's displacement D_N exceeds a threshold×corresponding to landslide triggering conditions. The obtained (Ac)_x values represent the minimum slope resistance required to limit the probability of landslide seismic triggering within the prefixed value. A map reporting the spatial distribution of these values gives comparative indications on regional different exposure of slopes to shaking capable of inducing failures and provides a reference for hazard estimate at local scale. The obtained results show that the exposure to landslide seismic induction is maximum in the Alborz Mountains region, where critical accelerations up to ∼0.1 g are required to limit the probability of seismic triggering of coherent type landslides within 10% in 50 years.     

Antioxidant responses to polycyclic aromatic hydrocarbons and organochlorine pesticides in green-lipped mussels (Perna viridis): Do mussels “integrate” biomarker responses?

Polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides (OCs) are generally present in the marine environment in complex mixtures. The ecotoxicological nature of contaminant interactions, however, is poorly understood, with most scientific observations derived from single contaminant exposure experiments. The objective of this experiment was to examine dose-response relationships between antioxidant parameters and body contaminant levels in mussels exposed to different exposure regimes under laboratory conditions. Accordingly, the green-lipped mussel, Perna viridis, was challenged with a mixture of PAHs (anthracene, fluoranthene, pyrene, benzo[a]pyrene) and OC pesticides (α-HCH, aldrin, dieldrin, p,p′-DDT) over a 4 week period. Contaminants were delivered under four different dosing regimes, with all treatments receiving the same total contaminant load by the end of the exposure period. Antioxidant biomarkers were measured after 1, 2, 3 and 4 weeks, including glutathione (GSH), gluathione-S-transferase (GST), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR) and lipid peroxidase (LPO). GST and CAT were induced in hepatic tissues in most of the exposure regimes, with the majority of significant induction occurring in a constant exposure regime and a two-step alternate exposure regime. Significant differences among exposure regimes were detected in the body burden of contaminants after 28 days. Hepatic CAT and GSH are proposed as potentially useful biomarkers as they showed good correlation with target contaminants and were not readily affected by different dosing patterns.     

Responses of B-esterase enzymes in oysters (Crassostrea gigas) transplanted to pesticide contaminated bays form the Ebro Delta (NE,Spain)

Marine bivalves such as oysters are widely used as bioindicators to monitor marine coastal pollution. This study aimed to use B-esterase activity responses in oysters (Crassostrea gigas) cultured in Ebro Delta bays to monitor environmental effects of pesticides. The B esterases investigated were acetylcholinesterase, propionylcholinesterase, and carboxylesterase and their activities were measured in adductor muscle and gills from oysters transplanted in Ebro Delta bays where the are traditionally grown. Enzyme activities were related with physico-chemical parameters and pesticide levels measured in water. Cholinesterase activities measured in gills were unaffected across sites and periods. Conversely, carboxylesterase activities in oyster gills varied across periods and sites and were negatively correlated with residue levels of organophoshporous and carbamate pesticides in water. Therefore, inhibition of carboxylesterase activities can be considered a good indicator of exposure to anti-cholinergic pesticides in oysters.     

How many and from where? Assessing the sensitivity of exposure durations calculated from paired bedrock 14C/10Be measurements in glacial troughs

We present a sensitivity analysis of the isochron approach of Goehring et al. (2013) for paired measurements of in situ ¹⁴C/¹⁰Be from glacially sculpted bedrock surfaces. This analysis tests how sensitive the resulting exposure durations from this technique are to both the number of samples analyzed and their locations along a glacial trough transect, using a dataset from Goehring et al. (2011) as a test case. A simple equally weighted combinatorial approach was employed to (1) generate non-repetitive combinations of n subsets of samples arranged from the ten possible samples (where n < 10), and (2) estimate the exposure duration and uncertainty for each set of simulations. Results from the Goehring et al. (2011) data indicate that five samples evenly distributed along a transect parallel to the ice margin are the minimum number of samples required for this method, while eight or more samples provide an optimal combination of accuracy and precision at the 1σ level. These findings should be applicable to paired in situ ¹⁴C/¹⁰Be measurements from other polished bedrock troughs at glacial margins, but need further experimental confirmation.     

The effects of copper on the heart rate and filtration rate of Mytilus edulis

Exposure of Mytilus edulis to dissolved copper led to a decrease in heart rate and filtration rate. After 4 days exposure to copper, the concentration of copper causing a 50% reduction in heart rate (EC₅₀) was 0.17 ppm. After 5 days exposure to copper, the EC₅₀ for filtration rate was only 0.002 ppm copper. Reductions in heart rate and filtration rate are not caused by valve or siphon closure.     

Cosmogenic and radiogenic noble gases in the Dhajala chondrite

Whole rock and chondrules of the Dhajala chondrite were analyzed for Ne, Ar, Kr and Xe by total melting as well as by stepwise heating techniques. The cosmic ray exposure ages for the whole rock and the chondrules are6.2 ± 0.8 and6.3 ± 1.0m.y. as determined by the²¹Ne method and4.8 ± 1.5 and4.2 ± 2.0m.y. by the³⁸Ar method, respectively. The K-Ar age of the whole rock is4.2 ± 0.4b.y. The elemental composition of the trapped gas in this chondrite is of “planetary” type. The radiogenic¹²⁹Xe contents in the whole rock and chondrules are similar and this component is very retentively sited in the chondrules.     

Empirical model of Skeletonema costatum photosynthetic rate,with applications in the San Francisco Bay estuary

An empirical model of Skeletonema costatum photosynthetic rate is developed and fit to measurements of photosynthesis selected from the literature. Because the model acknowledges existence of: 1) a light-temperature interaction (by allowing optimum irradiance to vary with temperature), 2) light inhibition, 3) temperature inhibition, and 4) a salinity effect, it accurately estimates photosynthetic rates measured over a wide range of temperature, light intensity, and salinity. Integration of predicted instantaneous rate of photosynthesis with time and depth yields daily net carbon assimilation (pg C cell^?1 day^?1) in a mixed layer of specified depth, when salinity, temperature, daily irradiance and extinction coefficient are known. The assumption of constant carbon quota (pg C cell^?1) allows for prediction of mean specific growth rate (day^?1), which can be used in numerical models of Skeletonema costatum population dynamics.Application of the model to northern San Francisco Bay clearly demonstrates the limitation of growth by low light availability, and suggests that large population densities of S. costatum observed during summer months are not the result of active growth in the central deep channels (where growth rates are consistently predicted to be negative). But predicted growth rates in the lateral shallows are positive during summer and fall, thus offering a testable hypothesis that shoals are the only sites of active population growth by S. costatum (and perhaps other neritic diatoms) in the northern reach of San Francisco Bay.     

Cosmogenic surface exposure dating the last deglaciation in Denmark: Discrepancies with independent age constraints suggest delayed periglacial landform stabilisation

Cosmogenic nuclide surface exposure ages are determined from in situ ¹⁰Be and ³⁶Cl analysis of 38 rock surfaces found in different glacial landforms in Denmark. Dating of erratic boulders and adjacent ice-sculpted bedrock on the island of Bornholm in the western Baltic Sea reveals almost identical values. This suggests that little if any inherited nuclides are present in the sampled boulders. West of the Last Glacial Maximum (LGM) ice margin in Denmark ages reflect exposure from the Middle Weichselian. East of the LGM margin exposure ages from 35 samples show Late Weichselian ages in a range between 20.6–11.9 ka. To test to what extent these dates reflect the onset of deglaciation immediately after cessation of active glacier flow, surface exposure ages are evaluated against independent chronologies of Late Weichselian ice-sheet fluctuations in southwestern Scandinavia. The Bornholm dates agree with the independent age model, however, in the data set for eastern Denmark only less than half the surface exposure ages lie within the expected age envelope. This apparent mismatch is most likely due to post-glaciation shielding and delayed surface stabilisation compared to the timing of ice-margin retreat. Thus ages from boulders resting in dead-ice moraines and mass wasting landscapes underestimate deglaciation by 3–6 thousand years. The results quantify the impact of exhumation and landform stabilisation on cosmogenic surface exposure ages on millennial scales. We conclude, that interpretation of cosmogenic exposure ages should include careful evaluation of possible post-depositional landform transformation in attempts to fine tune ages of e.g. end moraine features. With reference to independent age models we critically evaluate glacier advance – retreat scenarios from regions around the southern Baltic that alone are based on weighted average ages of cosmogenic exposure dating.     

Survival of two species of amphipods in aqueous extracts of petroleum oils

Aqueous extracts of two petroleum oils, No. 2 fuel oil and Southern Louisiana crude, were tested on two amphipods, Gammarus muccronatus and Amphithoe valida, for survival. The oils were toxic at concentrations of 0.8 ppm (fuel oil) and 2.4 ppm (S. Louisiana crude). Mortalities increased with the concentration and length of exposure. Few or no young were produced at these and higher concentrations (breeding adults were decreasing rapidly in numbers). The amphipods are more sensitive to aqueous extracts of these oils than benthic polychaetes and shrimp, for which data are available.     

Uptake and tissue distribution of C4-C7 alkylphenols in Atlantic cod (Gadus morhua): relevance for biomonitoring of produced water discharges from oil production

The sensitivity of different tissues for assessment of chronic low-dose environmental exposure of fish to alkylphenols (APs) was investigated. We exposed Atlantic cod (Gadus morhua) in the laboratory to tritium labelled 4-tert-butylphenol, 4n-pentylphenol, 4n-hexylphenol, and 4n-heptylphenol via seawater (8 ng/l) and via contaminated feed (5 μg/kg fish per day). Measurements of different fish tissues during eight days of exposure and eight subsequent days of recovery revealed that APs administered via spiked seawater were readily taken up whereas the uptake was far less efficient when APs were administered in spiked feed. AP residues were mainly located in the bile fluid whereas the concentrations in liver were very low, indicating a rapid excretion and the liver-bile axis to be the major route of elimination. The biological half-life of APs in the exposed cod was short, between 10 and 20 h. Our study shows that in connection with biomonitoring of AP exposure in fish, assessment of AP metabolites in bile fluid is a more sensitive tool than detection of parent AP levels in liver or other internal tissues.     

Neutron capture effects in lunar gadolinium and the irradiation histories of some lunar rocks

The Gd isotopic composition in 19 lunar rock and soil samples from three Apollo sites is reported. The analytical techniques and the high precision mass spectrometric measurements are discussed. Enrichments in¹⁵⁸GdO/¹⁵⁷GdO due to neutron capture range up to 0.75%. Integrated ‘thermal’ neutron fluxes derived from the isotopic anomalies of Gd are compared with spallation Kr data from aliquot samples to construct a model which gives both average cosmic-ray irradiation depths and effective neutron exposure ages (T_n) for some rocks. In the case of rock 12053, this yields an average sample location of ∼300 g/cm² below the lunar surface and an effective irradiation age of ∼230 my, compared to 99 my obtained by the⁸¹Kr-Kr method. Rock 14310 is the first lunar sample where Kr anomalies due to resonance neutron capture in Br are observed. A⁸¹Kr-Kr exposure age of 262 ± 7 my is calculated for this rock.     

The erosion rates of cohesive sediments in Venice lagoon,Italy

The stability of cohesive sediments from Venice lagoon has been measured in situ using the benthic flume Sea Carousel. Twenty four stations were occupied during summertime, and a sub-set of 13 stations was re-occupied during the following winter. Erosion thresholds and first-order erosion rates were estimated and showed a distinct difference between inter-tidal and sub-tidal stations. The higher values for inter-tidal stations are the result of exposure that influences consolidation, density, and organic adhesion. The thresholds for each state of sediment motion are well established. However, the rate of erosion once the erosion threshold has been exceeded has been poorly treated. This is because normally a time-series of sediment concentration (C) and bed shear stress (τ₀(t)) is used to define threshold stress or cohesion (τ_crit,z) and erosion rate (E). Whilst solution of the onset of erosion, τ_crit,0, is often reported, the evaluation of the erosion threshold variation through the process of erosion (eroded depth) is usually omitted or not estimated. This usually leads to assumptions on the strength profile of the bed which invariably has no credibility within the topmost mm of the bed where most erosion takes place. It is possible to extract this information from a time-series through the addition of a step in data processing. This paper describes how this is done, and the impact of this on the accuracy of estimates of the excess stress (τ₀(t)–τ_crit,z) on E.