Assessing the additive risks of PSII herbicide exposure to the Great Barrier Reef

Herbicide residues have been measured in the Great Barrier Reef lagoon at concentrations which have the potential to harm marine plant communities. Monitoring on the Great Barrier Reef lagoon following wet season discharge show that 80% of the time when herbicides are detected, more than one are present. These herbicides have been shown to act in an additive manner with regards to photosystem-II inhibition. In this study, the area of the Great Barrier Reef considered to be at risk from herbicides is compared when exposures are considered for each herbicide individually and also for herbicide mixtures. Two normalisation indices for herbicide mixtures were calculated based on current guidelines and PSII inhibition thresholds. The results show that the area of risk for most regions is greatly increased under the proposed additive PSII inhibition threshold and that the resilience of this important ecosystem could be reduced by exposure to these herbicides.     

Using genetic techniques to investigate the sources of the invasive alga Caulerpa taxifolia in three new locations in Australia

The invasive green alga Caulerpa taxifolia has gained a high profile due to 'outbreaks' in the Mediterranean and California. During the year 2000 three new discrete locations colonised by abundant C. taxifolia were discovered in New South Wales (NSW), Australia. Sequencing of the internal transcribed spacer (ITS) region of the ribosomal DNA was used to explore the source(s) of these new records, which is an important prerequisite for subsequent environmental management responses. Our results indicate that the NSW C. taxifolia originated from several sources and, hence, through different invasion events. For two of the new records (Port Hacking, Careel Bay) it can be excluded that they are derived from the so-called "aquarium strain" of C. taxifolia, closely related to the invasive Mediterranean populations. Port Hacking is likely to have originated from tropical native populations. However, samples from Lake Conjola cannot be sufficiently distinguished with the applied technique from native C. taxifolia in Moreton Bay and the Mediterranean/"aquarium strain".     

Cretaceous–Tertiary Rhenodanubian flysch wedge (Eastern Alps): clues to sediment supply and basin configuration from zircon fission-track data

The provenance of Cenomanian to Eocene flysch deposits accreted along the northern margin of the Eastern Alps has been investigated by means of zircon fission-track (FT) geochronology and zircon morphology. The Rhenodanubian flysch and Ybbsitz klippen zone comprise several nappes representing the Main flysch and Laab basins. The Laab basin received sediments of stable European provenance, indicated by pre-Variscan, Variscan, and Permian–Triassic zircon FT ages, and was thus located in the immediate south of the European margin. The Main flysch basin was supplied mainly from the evolving Eastern Alps and was therefore situated south of the Laab basin. Zircon populations with Permian to Jurassic cooling ages in the Main flysch basin are related to increased heat fluxes during the break-up of Pangaea and are probably derived from the northwestern part of the Eastern Alps. The dominant Cretaceous zircon FT cooling ages reflect Eoalpine metamorphism in the Austroalpine realm.     

Obtaining stable redox potential readings in gneiss groundwater and mine water: difficulties,meaningfulness, and potential improvement

Natural samples were run in three parallel flow-through cells in the laboratory in order to study the difficulties of obtaining stable redox potential readings, especially in gneiss groundwater and mine water with little redox buffer capacity. Redox potentials were recorded every 2 min for up to 5 days. Measured redox potentials were compared to means of partial potentials, modeled based on species-selective determinations of the most predominant redox-sensitive elements iron and nitrogen. Redox potentials stabilized reproducibly within minutes for a synthetic redox buffer solution and two well-buffered acid mine water samples at pH 2.3 and 3.5. For waters in redox disequilibrium, species-selective analytics might still be the better alternative compared to measuring the redox potential as summary parameter for modeling species distribution. In cases where the redox potential is the only readily available parameter, filtration and possibly acidification is recommended for quicker stabilization of redox potential readings and less deviations between measured and modeled values. A minimum of 2% was achieved in the samples investigated, however, often after measuring significantly longer than the previously suggested 30 min. Final stabilization could take up to several hours in waters with low buffer capacity.

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Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.

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Résumé Afin d’étudier les difficultés à obtenir des lectures stables des potentiels redox, notamment sur les eaux souterraines présentes dans des gneiss et dans les mines, qui présentent un faible pouvoir tampon, des échantillons ont été prélevés régulièrement en laboratoire, dans trois cellules d’écoulement parallèles. Les potentiels redox ont été enregistrés toutes les deux minutes durant cinq jours. Ces potentiels redox mesurés ont été comparés aux moyennes des potentiels partiels, modélisés à partir des déterminations sélectives des espèces chimiques des éléments sensibles aux conditions redox les plus prédominants, le fer et l’azote. Les potentiels redox se sont systématiquement stabilisés en quelques minutes pour une solution tampon synthétique et pour deux échantillons d’eaux de mines acides bien tamponnées à pH 2.3 à 3.5. Pour les eaux en déséquilibre redox, des analyses sélectives des espèces chimiques seraient toujours la meilleure alternative aux mesures sommaires du potentiel redox, pour modéliser la distribution des espèces. Dans les cas où le potentiel redox est le seul paramètre directement disponible, une filtration et éventuellement une acidification sont recommandées pour obtenir une stabilisation plus rapide des lectures des potentiels redox, et pour réduire les écarts entre les valeurs mesurées et modélisées. Un minimum de 2% a été atteint parmi les échantillons étudiés, mais en prolongeant souvent les mesures au-delà des 30 minutes suggérées initialement. La stabilisation finale pourrait prendre jusqu’à plusieurs heures dans des eaux à faible pouvoir tampon.

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Resumen Se han llevado a cabo experimentos en laboratorio sobre tres muestras naturales en tres células de flujo paralelas, para estudiar las dificultades en la obtención de medidas de potencial redox estables, especialmente en aguas subterráneas procedentes de gneisses y en agua de minas con capacidades tampón redox bajas. Los potenciales redox fueron medidos cada dos minutos durante más de cinco días. Los potenciales redox medidos fueron comparados con medias de potenciales parciales, modelizados en base a determinaciones selectivas de especies de hierro y nitrógeno, los elementos predominantes redox-sensitivos. Los potenciales redox se estabilizaron de forma reproducible en minutos en una solución redox tampón y dos muestras de agua ácida de pozos de mina a pH 2.3 y 3.5. Para aguas en desequilibrio redox los análisis selectivos por especies deberían ser todavía la mejor alternativa comparados con la medida del potencial redox como una suma de parámetros para modelizar la distribución de especies. En casos en los que el potencial redox sea el único parámetro fácilmente obtenible, se recomienda una filtración y una posible acidificación para una estabilización más rápida de las medidas de potencial redox y que haya menos desviaciones entre los valores medidos y los del modelo. En las muestras investigadas se consiguió un mínimo de un 2%, sin embargo, a menudo incluso después de medidas significativamente más largas que las previamente sugeridas de 30 minutos. La estabilización final tuvo lugar después de más de varias horas en aguas con capacidad tampón baja.

     

A Degenerate Bifurcation In The Hénon-Heiles Family

The normalised Hénon–Heiles family exhibits a degenerate bifurcation when passing through the separable case =0. We clarify the relation between this degeneracy and the integrability at =0. Furthermore we show that the degenerate bifurcation carries over to the Hénon–Heiles family itself.