The significance of vivianite in archaeological settings

Vivianite is a bluish mineral sometimes encountered in archaeological deposits. It is notable for its tendency to change color from white or grayish to blue on exposure to air. Vivianite requires specific conditions for its formation—sources of iron, phosphate, and water, as well as low levels of oxygen and sulfide. Microbial activity is also thought to play a part in vivianite formation. The majority of archaeological texts do not discuss vivianite to any great degree, preventing a more detailed interpretation of site conditions and features. Vivianite was found in 25 exhumed burials from the North Brisbane Burial Ground, Queensland, Australia. Research indicated that bone or tissue samples for DNA analysis are best taken from areas distant from vivianite encrustations and that presence of vivianite has implications for artifact conservation. Vivianite at the North Brisbane Burial Grounds helped protect some skeletal and dental elements, preserved the impressions of metal coffin lacing, and also corroborated the oral history of temporary waterlogging and acted as a measure of pollution levels across the site. © 2006 Wiley Periodicals, Inc.     

Observations of foehn onset in the Southern Alps, New Zealand

Summary Local scale windfield and air mass characteristics during the onset of two foehn wind events in an alpine hydro-catchment are presented. Grounding of the topographically modified foehn was found to be dependent on daytime surface heating and topographic channelling of flow. The foehn front was observed to advance down-valley until the valley widened significantly. The foehn wind appeared to decouple from the surface downstream of the accelerated flow associated with the valley constriction, and to be lifted above local thermally generated circulations including a lake breeze. Towards evening, the foehn front retreated up valley in response to reduced surface heating and the intrusion into the study area of a deep and cool air mass associated with a regional scale mountain-plain circulation. Differences in the local windfield observed during both case study events reflect the importance of different thermal and dynamic forcings on airflow in complex terrain. These are the result of variation in surface energy exchanges, channelling and blocking of airflow. Observations presented here have both theoretical and applied implications with regard to forecasting foehn onset, wind hazard management, recreational activities and air quality management in alpine settings. Received January 23, 2001 Revised October 17, 2001     

Using stable isotopes to estimate young water fractions in a heavily regulated,tropical lowland river basin

The young water fraction of streamflow (Fyw), an important hydrological variable, has been calculated for the first time, for a monsoon-fed coastal catchment in northern Vietnam. Oxygen stable isotopes (δ¹⁸O) from six river sites in the Day River Basin (DRB) were analysed monthly, between January 2015 and December 2018. River δ¹⁸O signatures showed sine wave variability, reflecting the amount effect and tropical (dry-rainy) seasonality of the region. The δ¹⁸O composition of precipitation ranged from −12.67 to +1.68‰, with a mean value of −5.14‰, and in-streamflow signatures ranged from −11.63 to −1.37‰ with a mean of −5.02‰. Fractions of young water (Fyw) were calculated from the unweighted and flow-weighted δ¹⁸O composition of samples. Unweighted Fyw ranged between 29 ± 8% and 82 ± 21% with a mean value of 51 ± 19%, and was not significantly different from flow-weighted Fyw (range between 33 ± 25% and 92 ± 73%, mean 52 ± 36%). Both unweighted and flow-weighted Fyw were highest in the middle of stream and lowest in downstream sites, capturing the impacts of landuse changes, hydrology and human activities in the catchment. Our calculations imply that more than a half of rainwater reaches the DRB river mainstream within the first 3 months. The Fyw is much higher than the global average (of one-third) and insensitive to discharge due to the combination of a humid catchment with high rainfall, low storage capacity, flat landscape and an intensive drainage system in the DRB. Also the low discharge sensitivity of Fyw in the DRB implies that the regional hydrology is severely altered by humans.     

Population trends in the Slavonian grebe <Emphasis Type="Italic">Podiceps auritus</Emphasis> (L.) and Chironomidae (Diptera) at a Scottish loch

Loch Ruthven holds the largest British population of the rare water-bird Podiceps auritus, the Slavonian or horned grebe. The breeding success of this bird has fluctuated annually since records began in 1970. To investigate whether these trends are linked to the abundance of chironomid midges, which are an important food-source for the grebe chicks, we analysed a sediment core from the lake, which was sliced at 2.5-mm intervals and provided near-annual sampling resolution. We also analysed diatoms and algal pigments in the lake sediments and inferred changes in total phosphorus from the diatom assemblage to determine whether changes in lake productivity have influenced the abundance of chironomids. Trends in grebe productivity, chironomid abundance and algal assemblages were compared against climate data to determine whether climate, specifically, the North Atlantic Oscillation, was the ultimate driver of the trends we recorded. Our results show that grebe breeding success is positively correlated with chironomid abundance and chironomid abundance is positively correlated with diatom-inferred total phosphorus. Lake productivity and chironomid abundance began to rise early in the twentieth century and continued to rise on a steeper trajectory from the mid-twentieth century to the present. Since the mid-1960s, chironomid abundance began to fluctuate erratically and since 1970 was in phase with grebe productivity, with the grebe trends most plausibly lagging by 1 year. These trends appear to correlate with inter-annual fluctuations in diatom-inferred total phosphorus. No correlation was found between grebe productivity or chironomid abundance and climate variables, suggesting that the size of the chironomid population and breeding success of Podiceps auritus at Loch Ruthven is resource-linked.     

Functional attributes of epilithic diatoms for palaeoenvironmental interpretations in South-West Greenland lakes

Benthic diatoms are commonly used for palaeoenvironmental reconstruction in Arctic regions, but interpretation of their ecology remains challenging. We studied epilithic diatom assemblages from the shallow margins of 19 lakes from three areas (coast-inland-ice sheet margin) along a climate gradient in Kangerlussuaq, West Greenland during two periods; shortly after ice-off (spring) and in the middle of the growth season (summer). We aimed to understand the distribution of Arctic epilithic diatoms in relation to water chemistry gradients during the two seasons, to investigate their incorporation into lake sediments and to assess their applicability as palaeoenvironmental indicators. Diatoms were correlated with nutrients in the spring and alkalinity/major ions in the summer, when nutrients were depleted; approximately half of the variance explained was independent of spatial factors. When categorised by functional attributes, diatom seasonal succession differed among regions with the most obvious changes in inland lakes where summer temperatures are warmer, organic nutrient processing is prevalent and silicate is limiting. These conditions led to small, motile and adnate diatoms being abundant in inland lakes during the summer (Nitzschia spp., Encyonopsis microcephala), as these functional attributes are suited to living within complex mats of non-siliceous microbial biofilms. Seasonal succession in silica-rich lakes at the coast was less pronounced and assemblages included Tabellaria flocculosa (indicating more acidic conditions) and Hannaea arcus (indicating input from inflowing rivers). The nitrogen-fixing diatom Epithemia sorex increased from the coast to the ice sheet, negatively correlating with a gradient of reactive nitrogen. The presence of this diatom in Holocene sediment records alongside cyanobacterial carotenoids during arid periods of low nitrogen delivery, suggests that it is a useful indicator of nitrogen limitation. Nitzschia species appear to be associated with high concentrations of organic carbon and heterotrophy, but their poor representation in West Greenland lake sediments due to taphonomic processes limits their palaeoenvironmental application in this region. Proportions of epilithic taxa in lake sediment records of coastal lakes increased during some wetter periods of the Holocene, suggesting that snowpack-derived nutrient delivery may offer diatom taxa living at lake margins a competitive advantage over planktonic diatoms during the “moating” ice melt period. Thus, further research investigating linkages between epilithic diatoms, snowpack and nutrient delivery in seasonally frozen lakes is recommended as these taxa live on the ‘front-line’ during the spring and may be especially sensitive to changes in snowmelt conditions.     

Correlated optical and X-ray variability in LMC X-2

We have obtained high time resolution (seconds) photometry of LMC X-2 in 1997 December, simultaneously with the Rossi X-ray Timing Explorer ( RXTE ), in order to search for correlated X-ray and optical variability on time-scales from seconds to hours. We find that the optical and X-ray data are correlated only when the source is in a high, active X-ray state. Our analysis shows evidence for the X-ray emission leading the optical with a mean delay of <20 s. The time-scale for the lag can be reconciled with disc reprocessing, driven by the higher-energy X-rays, only by considering the lower limit for the delay. The results are compared with a similar analysis of archival data of Sco X-1.     

Co-management of sea turtle fisheries: Biogeography versus geopolitics

Co-management between local communities and government agencies is promoted as a strategy to improve fisheries management. This paper considers the potential for co-management of sea turtle fisheries within four UK Overseas Territories (OTs) in the Caribbean, and for co-ordinated management among those territories. We focus on fisher incentives for engaging in co-management and on the potential to scale up co-management to a regional level. This paper presents data from Anguilla, British Virgin Islands, Montserrat, and Turks and Caicos Islands, where 110 turtle fishers participated in a socio-economic survey undertaken as part of the ‘Turtles in the UK Overseas Territories in the Caribbean’ project. Based on three established criteria for co-management (perceived crisis in stock, willingness to participate and community cohesion), results suggest that fisher support for co-management exists within each OT, but the extent of support for and views of specific management interventions varies among OTs. The implications of results for co-management in each territory, and for establishing co-ordinated management regimes in the region, are discussed in the context of current debates about the nature of resources and scalar (mis)matches between resource and management regimes.     

Coastal phytoplankton blooms in the Southern California Bight

Surface chlorophyll (CHL) measured at the Scripps Pier in the Southern California Bight (SCB) for 18 years (1983–2000) reveals that the spring bloom occurs with irregular timing and intensity each year, unlike sea-surface temperature (SST), which is dominated by a regular seasonal cycle. In the 1990s, the spring bloom occurred earlier in the year and with larger amplitudes compared to those of the 1980s. Seasonal anomalies of the Pier CHL have no significant correlation with local winds, local SST, or upwelling index, which implies that classical coastal upwelling is not directly responsible for driving chlorophyll variations in nearshore SCB.The annual mean Pier CHL exhibits an increasing trend, whereas the Pier SST has no evident concomitant trend during the CHL observation period. The interannual variation of the Pier CHL is not correlated with tropical El Niño or La Niña conditions over the entire observing period. However, the Pier CHL was significantly influenced by El Nino/Southern Oscillation during the 1997/1998 El Niño and 1998/1999 La Niña transition period. The Pier CHL is highly coherent at long periods (3–7 years) with nearby offshore in situ surface CHL at the CalCOFI (California Cooperative Fisheries Investigations) station 93.27.     

High resolution provenancing of long travelled dust deposited on the Southern Alps, New Zealand

On 7 February 2000 an atypical orange discolouration of snowfields in the central Southern Alps, New Zealand occurred following the passage of a cold front. Analysis of snow samples identified fine orangey-brown dust mixed with much coarser grey dust. Air parcel forward trajectories from dust sources in southern and central Australia, where dust storms were reported on 4 February 2000, were computed to identify the deposits source. Geochemical analyses of the dust deposit using 26 trace elements, unaffected by regional air pollution and gravitational sorting, indicate that 20% of the dust was sourced from western New South Wales, with 45% from the eastern Eyre Peninsula of South Australia and the remaining 35% was local New Zealand dust. This provenancing approach provides a spatial resolution of long travelled dust sourcing not previously achieved.