The genus Pseudo-nitzschia (Bacillariophyceae) in New Zealand: analysis of the last decade's monitoring data

The diatom genus Pseudo-nitzschia blooms throughout New Zealand's coastal waters. More than a decade of monitoring data were analysed in this study and seasonality was a significant factor in the appearance of Pseudo-nitzschia blooms. Austral spring and summer were the main bloom periods, although there were regional differences. Between January 2000 and August 2011, 8.4% of 29,000 seawater samples analysed for Pseudo-nitzschia exceeded the voluntary trigger level for biotoxin testing (10×10⁴ cells l^?1), and these were analysed by fluorescent in situ hybridisation (FISH) assays. Pseudo-nitzschia fraudulenta and P. pseudodelicatissima (low domoic acid [DA] producers) were the dominant bloom formers throughout New Zealand (each contributing 25%) followed by the highly toxic P. australis (10%). Shellfish flesh testing for DA was triggered on 8477 occasions between 2000 and 2011, but no samples exceeded the regulatory limit (20 mg/kg); the maximum concentration was 13 mg/kg (Marlborough Sounds, mid-winter 2010).     

The effect of burning and sheep grazing on soil water composition in a blanket bog: evidence for soil structural changes?

This study considers the impact of managed rotational burning of vegetation and sheep grazing upon the composition of soil waters within an upland peat soil. The study has considered soil water compositions from a complete factorial design of treatment plots where three different burning treatments were considered in replication with grazing and no grazing. All plots were sampled across a complete year with three dipwells in each plot. The study included aluminium (Al), iron, calcium, sodium (Na), magnesium (Mg), potassium, sulphate, chloride (Cl^?), bromide, fluoride, phosphate (PO )and nitrate; and in order to clarify the nature of the results, the pH, conductivity and dissolved organic carbon were also considered, but the major results for these are reported elsewhere. The study finds: (1) Ca, Na, Mg and PO concentrations are significantly lower on all burnt plots, with only Al concentration being significantly higher on burnt plots. (2) Only Cl^? showed any significant changes (a decrease) with the presence of sheep grazing, and then only when plots were also burnt. (3) A principal component analysis shows that the composition of most soil waters can be described by rainwater and soil water components, but in unburnt plots a base‐rich, high ionic strength water is sometimes present. The study suggests that burning, but not grazing, caused significant changes in soil water composition leading to increased interaction between incoming rainwaters and the peat soil but led to loss of interaction with deeper waters. However, no evidence was found for structural change in the soils even after long term (50 years) grazing and burning management. Copyright © 2007 John Wiley & Sons, Ltd.     

Long‐term records of dissolved organic carbon flux from peat‐covered catchments: evidence for a drought effect?

This study considers three long records of dissolved organic carbon (DOC) flux from two catchments with peat‐covered headwaters. The catchments vary in size from 11 to 818 km² and the records are at least 12 years old, with one record going back to 1965. The study compares both annual and monthly DOC flux records with a range of hydroclimatic indicators in order to test which component of droughts may contribute to increasing DOC flux. The study found that: (1) there was no significant correlation between any of the proposed drought variables and DOC flux in any of the study catchments over periods of up to 34 years; (2) the most important variable for explaining the DOC flux was the runoff from the catchments overlying a seasonal cycle and an underlying upward trend was present in some records; (3) the residual time‐series, after removal of the best‐fit models, showed no evidence of increased production after times of severe drought. The lack of any evidence for any additional biogeochemical reactions associated with drought supports evidence that DOC loss from peat is limited by its solubility and that its production is fast on the time‐scale of runoff events. Copyright © 2008 John Wiley & Sons, Ltd.     

The 10-μm profile of molecular-cloud and diffuse ISM silicate dust

High signal-to-noise ratio spectra are presented of the 10-μm silicate absorption feature in lines of sight towards Elias 16 and 18 in the Taurus dark cloud, and towards the heavily reddened supergiant Cyg OB2 no. 12. The observations are fitted with laboratory and astronomical spectra to produce intrinsic absorption profiles. These features, which represent molecular-cloud and diffuse ISM dust respectively, are better fitted with emissivity spectra of the Trapezium and μ Cephei than they are with those of laboratory, terrestrial, or other observations of circumstellar silicates. The difference in width between the silicate band in the two environments can be almost entirely ascribed to a broad excess absorption in the long-wavelength wing of the profiles, which is much stronger in the molecular-cloud lines of sight, and possibly reflects grain growth in the denser environment. Limits are placed on the strength of fine spectral structure; if there is a crystalline silicate component in these spectra, it is most likely to be serpentine. Column-density upper limits for methanol and the photolysis product hexamethylenetetramine (HMT) are less than a few per cent of those of water ice and silicates.     

Documentary reconstruction of monsoon rainfall variability over western India, 1781–1860

Investigations into the climatic forcings that affect the long-term variability of the Indian summer monsoon are constrained by a lack of reliable rainfall data prior to the late nineteenth century. Extensive qualitative and quantitative meteorological information for the pre-instrumental period exists within historical documents, although these materials have been largely unexplored. This paper presents the first reconstruction of monsoon variability using documentary sources, focussing on western India for the period 1781–1860. Three separate reconstructions are generated, for (1) Mumbai, (2) Pune and (3) the area of Gujarat bordering the Gulf of Khambat. A composite chronology is then produced from the three reconstructions, termed the Western India Monsoon Rainfall reconstruction (WIMR). The WIMR exhibits four periods of generally deficient monsoon rainfall (1780–1785, 1799–1806, 1830–1838 and 1845–1857) and three of above-normal rainfall (1788–1794, 1813–1828 and 1839–1844). The WIMR shows good correspondence with a dendroclimatic drought reconstruction for Kerala, although agreement with the western Indian portion of the tree-ring derived Monsoon Asia Drought Atlas is less strong. The reconstruction is used to examine the long-term relationship between the El Nino-Southern Oscillation (ENSO) and monsoon rainfall over western India. This exhibits peaks and troughs in correlation over time, suggesting a regular long-term fluctuation. This may be an internal oscillation in the ENSO-monsoon system or may be related to volcanic aerosol forcings. Further reconstructions of monsoon rainfall are necessary to validate this. The study highlights uncertainties in existing published rainfall records for 1817–1846 for western India.     

Geological note: Pyro‐intrusive veins in the northeastern Sydney Basin

Stratigraphic and sedimentological investigation of the interglacial succession within the Cryogenian-aged Umberatana Group of the Northern and Central Flinders Ranges reveals a complex array of sedimentary successions lying between the Sturtian and Marinoan glacial deposits. The Sturtian–Marinoan Series boundary was first defined from the Adelaide area at the uppermost contact of the Brighton Limestone. In the Northern Flinders Ranges the Sturtian–Marinoan Series boundary has been positioned at the uppermost contact of the Balcanoona Formation, which is thought to correlate with the Brighton Limestone. In the Northern Flinders Ranges a major unconformity separates the Sturtian and Marinoan-aged sedimentary successions (Nepouie–Upalinna Subgroups). In moderately deep marine depositional settings, this submarine unconformity is located at the base of the Yankaninna Formation where erosion has deeply incised (up to 300 m) into the underlying Tapley Hill Formation. In shallower marine settings the unconformity is found at the base of the Weetootla Dolomite. In very deep water depositional settings this unconformity is not recognised, and the Yankaninna Formation appears to conformably overlie the Tapley Hill Formation suggesting that this erosional feature is restricted to shallow and moderately deep depositional settings. This unconformity presents a regionally persistent chronostratigraphic marker horizon, which reliably marks the Sturtian–Marinoan Series boundary at the base of the Yankaninna Formation from shallow shelfal to deep-water basinal settings throughout the Northern Flinders Ranges. In the Central Flinders Ranges the post-Sturtian glacial stratigraphy records a very similar depositional record to that observed in the Northern Flinders Ranges. In the Central regions the Tapley Hill Formation is overlain by deep-marine carbonates and calcareous shales of the Wockerawirra Dolomite and Sunderland Formations, respectively. The base of the Wockerawirra Dolomite is found to be in erosional contact with the underlying Tapley Hill Formation. This stratigraphic relationship, together with lithological similarities, indicates the Wockerawirra Dolomite and Sunderland Formation of the Central Flinders Ranges are lateral correlatives of the Yankaninna Formation of the Northern Flinders Ranges. The regional nature of the Sturtian–Marinoan unconformity in the Adelaide Geosyncline suggest the possible existence of a glacio-eustatic event that may correlate with glacials/glaciation elsewhere on the Earth during the Cryogenian.