Arsenic levels in the soils and macrophytes of the 'Entremuros' after the Aznalcóllar mine spill

In April 1998, a holding lagoon containing pyrite ore processing waste rich in arsenic, failed and released 5-6 million m(3) of highly polluting sludge and acidic water. Over 2700 ha of the internationally important Do?ana National and Natural Parks were contaminated. The area of Natural Park to sustain the greatest impact was known as the Entremuros. This paper presents 0-5 cm soil monitoring data from the Entremuros, from sampling campaigns 6 and 18 months after the disaster; as well as macrophyte root, rhizome and stem data from samples taken 18 months after the spill. Results show a clear, decreasing, north-south arsenic soil pollution trend, both 6 and 18 months after the spill, and suggest a small reduction in total soil arsenic levels occurred over time; although a significant increase in extractable arsenic is also noted. The two macrophytes (Typha dominguensis and Scirpus maritimus) studied herein are not accumulating arsenic in stem parts, however, accumulation of arsenic on iron plaque on the roots of these plants may be occurring. Further work is recommended in order to determine the ecotoxicological significance of this process in relation to the avian food-chains of Do?ana, and elsewhere.     

Changes in enantiomeric fraction as evidence of natural attenuation of mecoprop in a limestone aquifer

Natural attenuation of the chiral pesticide mecoprop [2-(2-methyl-4-chlorophenoxy)propionic acid] has been studied by determining changes in its enantiomeric fraction in different redox environments down gradient of a landfill in the Lincolnshire Limestone. Previous studies have shown that mecoprop degrades predominantly aerobically and that differences in the biological behaviour of the two enantiomers will change their relative proportions during biodegradation. Originally deposited as a racemic mixture, there has been no change in the enantiomeric fraction in the most polluted part of the landfill plume where conditions are sulphate reducing/methanogenic. In the nitrate-reducing zone, the proportion of (S)-mecoprop increases, suggesting preferential degradation of (R)-mecoprop; while in the aerobic zone, the proportion of (R)-mecoprop increases, suggesting faster degradation of (S)-mecoprop. Mecoprop persistence in the confined Lincolnshire Limestone further downdip is explained by inhibition of degradation in sulphate-reducing conditions, which develop naturally. Laboratory microcosm experiments using up to 10 mg l(-1) of mecoprop confirm these inferences and show that under aerobic conditions, (S)-mecoprop and (R)-mecoprop degrade with zero-order kinetics at rates of 1.90 and 1.32 mg l(-1) day(-1), respectively. Under nitrate-reducing conditions (S)-mecoprop does not degrade, but (R)-mecoprop degrades with zero-order kinetics at 0.65 mg l(-1) day(-1) to produce a stoichiometric equivalent amount of 4-chloro-2-methylphenol. This metabolite only degrades when the (R)-mecoprop has disappeared. The addition of nitrate to a dormant iron-reducing microcosm devoid of nitrate stimulated anaerobic degradation of (R)-mecoprop after a lag period of 21 days. There was no evidence for enantiomeric inversion. The study demonstrates the sensitivity of changes in enantiomeric fraction for detecting natural attenuation, and reveals subtle differences in mecoprop degradation in different redox environments within the Lincolnshire Limestone aquifer.     

Laboratory study on leachability of five herbicides in South Australian soils

Norflurazon, oxadiazon, oxyfluorfen, trifluralin and simazine are herbicides widely used in the vineyards of the Barossa Valley, South Australia. The leaching behaviour of norflurazon, oxadiazon, oxyfluorfen and trifluralin was investigated on four key soils in the Barossa Valley. Leaching potential on packed soil columns and actual mobility using intact soil columns were investigated. On the packed soil columns, norflurazon was the most leachable herbicide. More of the herbicides were detected in the leachates from the sandy soils (Mountadam and Nuriootpa) than from the clayey soils (Lyndoch and Tanunda). Organic matter is generally low in soils in the Barossa region. Porosity and saturated conductivity significantly affect herbicide movement and in the sandy Mountadam and Nuriootpa soils, the water flux is greater than for the higher clay content Lyndoch and Tanunda soils. Increasing the time interval between herbicide application and the incidence of "rainfall" reduced the amounts of herbicides found in the leachates. The use of intact soil columns and including simazine for comparison showed that both norflurazon and simazine were present in the leachates. Simazine was the first herbicide to appear in leachates. Sectioning of the intact soil columns after leaching clearly demonstrated that norflurazon and simazine reached the bottom of the soil columns for all soils studied. Greater amounts of norflurazon were retained in the soil columns compared with simazine. The other herbicides were mostly retained in the initial sections of the soil columns.     

Movement patterns of the limpet Cellana grata (Gould) observed over a continuous period through a changing tidal regime

Time-lapse videography of limpets mounted with light-emitting diodes was used to monitor the movements of a population of the non-homing Cellana grata on a vertical gully wall in Hong Kong. Animals were monitored for >7 days to examine spatial and temporal variation in their behaviour as the tides transited from a semi-diurnal to an almost diurnal pattern. Movement was synchronised with the tides, irrespective of the day–night cycles. Limpets rested low on the shore and were stimulated to move by the rising tide. Individuals moved up shore with the flooding tide, maintaining themselves in the awash zone, and then down shore on the ebbing tide, until they reached a resting height when the tide then fell beneath them, exhibiting ‘zonal shuttling’. A tight coupling of limpet position to tide height persisted through the changing tidal pattern, and almost all animals displayed the same organisation of activity over all tides. Initiation of activity and maximum height reached were probably controlled by the tides, but the cessation of activity may have been controlled by an internal clock. The pattern observed is consistent with the threat of attack from aquatic predators coupled with the need to minimise physical stresses while exposed. It is also consistent with the avoidance of grazing lower on the shore where interspecific competition may be more intense. Limpets showed two peaks of activity per tide, corresponding to when the rate of change of tide height was the greatest, except when tides became much reduced during the transit to a diurnal pattern. Movement was triphasic: an initial rapid phase, followed by a slower phase in the high shore and then a rapid phase before the limpets stopped moving. This structure is common in limpets and in this case is likely to be a consequence of animals maintaining themselves within the awash zone. Tide height appears to determine foraging activity, but with modifications in the behaviour in response to factors operating at more local temporal and spatial scales.     

The influence of temperature and salinity on<Emphasis Type="Italic"> Acartia</Emphasis> (Copepoda: Calanoida) nauplii survival

Adult Acartia congeners, A. bifilosa, A. clausi, A. discaudata and A. tonsa, have distinct seasonal and spatial distribution patterns in Southampton Water (UK), reflecting patterns of temperature and salinity, respectively. The effect of these factors on other life stages, hatch success and naupliar survival was investigated by exposing the congeners to a range of salinity (15.5–33.3) and of temperature (5–20°C). A. clausi is known to prefer more saline waters, and showed highest hatch success at 33.3 salinity. A. tonsa is most tolerant to dilution, and at 15.5 salinity it had the highest hatch success of all the congeners. Hatch success in both A. bifilosa and A. discaudata was similar over the range of salinities investigated, confirming that they are intermediate species in terms of spatial distribution. The nauplii of all species survived well at the higher salinities and best at 33.3, which allows for differential transport of the poorly swimming nauplii to the mouth of the estuary until size and swimming ability increase, after which they can then return to regions of preferred salinity. The summer species, A. clausi and A. tonsa showed higher hatch success at 20°C, whereas A. discaudata, which is present in the water column all year round, showed no significant temperature-related differences in hatch success. A. bifilosa, which diapauses over summer, showed significantly higher hatch success at 10°C than at 20°C. The physiological relationship between temperature and development time was clear; naupliar survival of all species was highest at 20°C and all congeners reached the first copepodite stage (CI) significantly faster at 20°C. However, no consistent pattern was seen for salinity. It would appear that the adult Acartidae in Southampton Water remain in regions of their preferred salinity and lay eggs there which hatch well. However, because the nauplii are not good swimmers, they are swept towards the mouth of the estuary and into areas of higher salinity, where they remain and develop into more advanced stages before moving back up the estuary to take up their adult distribution pattern.Communicated by J.P. Thorpe, Port Erin     

No genetic differentiation of giant clam (Tridacna gigas) populations in the Great Barrier Reef,Australia

Six Tridacna gigas populations were sampled in 1990 from locations throughout the central and northern Great Barrier Reef (GBR). Despite separations in excess of 1000 km, mean Nei's unbiased genetic distances among the populations was 0.0007. The complete lack of spatial variation observed among populations did not results from lack of genetic variability. Genetic variation within populations was high, with mean heterozygosities from 0.221 to 0.250. Gene frequencies were consistent with expectations under conditions of Hardy-Weinberg equilibrium. These data suggest panmixis, or random mating, throughout the highly connected reef system of the central and northern GBR. The large gene exchange among the giant clam populations has important implications for conservation management of one of the few large populations of T. gigas in the world. Small local effects are likely to be overcome in time by inputs from other sources. However, large genetic perturbations, particularly from up-current sources, may spread rapidly through the population.Contribution No. 561 from the Australian Institute of Marine Science     

Decision making in dune management: theory and practice

Effective decision making depends upon the availability of quality information. Procedures involved in assessing dune vulnerability and protection require monitoring of sporadic processes and information must be collected from many discipline sources. In particular, a significant challenge to strategic management is recognition of subtle discontinuities which could undermine the long term stability of the dune system. These changes may be irregular and/or non linear requiring managers to be aware of existing parameters, patterns and emerging discontinuities. A range of components within the system should be measured on a systematic, temporal and spatial basis. An environmentalchecklist is a useful management technique which systematises information, so that strategic objectives can be made operational and achievable. Problems can be identified and solved with this methodology particularly if it is incorporated into aW problem solving model. The checklist procedure proposed in this paper has been developed and tested in field conditions for a range of north-west and south-European dune systems. Whereas a universalchecklist applicable to all systems is utopian in aim, intra and extra-regional comparisons can be undertaken with only minor modifications of some components. Parameters covering site and dune morphology, beach condition; surface character of the seaward 200 m of the dunes; pressure of use and recent protection measures are the basis for calculating vulnerability and protection indices. The balance between these indices can be determined, analysed and form the foundation for future informed management decisions.     

Chemically mediated burrow recognition in the Mexican tarantula <Emphasis Type="Italic">Brachypelma vagans</Emphasis> female

Chemically mediated communication is common in spiders but has been poorly studied in burrowing tarantulas. This study aimed to determine whether chemical cues influence the behaviour of females of Brachypelma vagans, a Mexican species of tarantula, during encounters with previously inhabited burrows or with extracts from the silk of conspecific females. In laboratory choice tests, female tarantulas entered a burrow that had previously been inhabited by a conspecific female significantly more frequently than a burrow that had never been inhabited. The identity of the previous inhabitant also affected the number of spiders that chose to enter a burrow. Spiders were quicker to choose and enter a burrow previously inhabited by themselves than a burrow previously inhabited by a conspecific or a burrow that had not been previously inhabited. Hexane, methanol and dichloromethane extracts of conspecific silk elicited different responses from female tarantulas when extracts were placed on filter paper disks at one end of an experimental arena with a control filter paper disk, on to which the corresponding solvent alone had been pipetted, placed on the other end of the arena. Spiders showed the strongest responses to hexane extracts of silk, with a significant preference to move towards the hexane extract and a significantly greater period of time spent in proximity to the hexane extract compared to the control disk. Overall and in contrast to expectations, tarantulas were most strongly attracted to the cues left by other conspecific females. As encounters between B. vagans females usually lead to aggression and mortality of one of the participants, we conclude that chemical cues are not signals that are deliberately released by burrow-inhabiting females but may inadvertently escape and cannot be easily suppressed.     

Near-real-time determination of hydrogen peroxide generated from cigarette smoke

The ability to monitor hydrogen peroxide (H2O2) in aqueous smoke extracts will advance our understanding of the relationship between cigarette smoke-induced oxidative stress, inflammation, and disease and help elucidate the pathways by which the various smoke constituents exert their pathogenic effects. We have demonstrated, for the first time, the measurement of H2O2 production from cigarette smoke without prior separation of the sample. Cigarettes were tested on a commercial smoking machine, such that the whole smoke or gas vapor phase was bubbled through phosphate buffered saline solution at pH 7.4. Aliquots of these solutions were analyzed using an Amplex Red/horseradish peroxidase fluorimetric assay that required only a 2 minute incubation time, facilitating the rapid, facile collection of data. Catalase was used to demonstrate the selectivity and specificity of the assay for H2O2 in the complex smoke matrix. We measured approximately 7-8 microM H2O2 from two reference cigarettes (i.e., 1R4F and 2R4F). We also observed 9x more H2O2 from whole smoke bubbled samples compared to the gas vapor phase, indicating that the major constituent(s) responsible for H2O2 formation reside in the particulate phase of cigarette smoke. Aqueous solutions of hydroquinone and catechol, both of which are particulate phase constituents of cigarette smoke, generated no H2O2 even though they are free radical precursors involved in the production of reactive oxygen species in the smoke matrix.     

Fat solubility — A property of environmental relevance?

Solubilities in fats ranging from 0.88 g l^?1 to completely miscible are reported for twelve organic chemicals. Comparison of these and other literature values with bioconcentration factors and octanol: water partition coefficients indicate that fat solubility is not a reliable predictor for either parameter. The results for the solubilities of seven chemicals in eight different fats cover a restricted range, indicating that the composition of the fat is not a critical parameter in determining the solubility.