A Numerical Case Study of the Implications of Secondary Circulations to the Interpretation of Eddy-Covariance Measurements Over Small Lakes

The CASES-99 experimental data are used to analyze turbulence behaviour under a range of stable conditions using an adaptive method based on Hilbert spectral analysis. The characteristic scales of intrinsic mode functions vary between different stratifications. The second-order Hilbert marginal spectra display clear separation between fine-scale turbulence and large-scale motions. After removing the large-scale motions, the statistical characteristics of the reconstructed signals confirm the distinction of different stratifications in the fine-scale range. The correlation coefficient analyses reveal that the Hilbert spectral analysis method separates turbulence from large-scale motions in the stable boundary layer.     

Structure and morphology of magnetite anaerobically-produced by a marine magnetotactic bacterium and a dissimilatory iron-reducing bacterium

Intracellular crystals of magnetite synthesized by cells of the magnetotactic vibroid organism, MV-1, and extracellular crystals of magnetite produced by the non-magnetotactic dissimilatory iron-reducing bacterium strain GS-15, were examined using high-resolution transmission electron microscopy, electron diffraction and⁵⁷Fe Mo¨ssbauer spectroscopy. The magnetotactic bacterium contained a single chain of approximately 10 crystals aligned along the long axis of the cell. The crystals were essentially pure stoichiometric magnetite. When viewed along the crystal long axis the particles had a hexagonal cross-section whereas side-on they appeared as rectangules or truncated rectangles of average dimension, 53 × 35 nm. These findings are explained in terms of a three-dimensional morphology comprising a hexagonal prism of 110 faces which are capped and truncated by 111 end faces. Electron diffraction and lattice imaging studies indicated that the particles were structurally well-defined single crystals. In contrast, magnetite particles produced by the strain, GS-15 were irregular in shape and had smaller mean dimensions (14 nm). Single crystals were imaged but these were not of high structural perfection. These results highlight the influence of intracellular control on the crystallochemical specificity of bacterial magnetites. The characterization of these crystals is important in aiding the identification of biogenic magnetic materials in paleomagnetism and in studies of sediment magnetization.     

Adaptive Delta Management for flood risk and resilience in Dordrecht,The Netherlands

Many countries across the world are experiencing strict austerity measures due to the economic crisis. As a consequence, public financing for stand-alone adaptation to flooding and drought will become scarcer in the (near) future, and this hampers the pursuit of resilience (i.e. the ability to remain functioning under a range of hazard magnitudes). In such times, key challenges for adaptation are further complicated by weaker investment dynamics and an increased tendency to ‘work in silos’. These are: to minimise regret with respect to maladaptation, which results from over- or under-investment in water hazard management; to exploit the opportunities for mainstreaming adaptation to flooding and drought into other investment agendas; and to deliver multiple benefits for society and the economy, such as increased biodiversity, liveability and competitiveness. These common challenges drive the best way in which to adapt to uncertain climate and socio-economic changes. In the Netherlands, the Delta Programme has developed and applied a structured and well-defined approach (called Adaptive Delta Management) for including and acting upon uncertainty around these future changes. This approach allows for greater transparency to decision-makers and stakeholders, because it adheres to four specific steps for strategy development. This paper presents the current understanding of Adaptive Delta Management and an illustration of the approach for the management of flood risk and resilience in Dordrecht. It examines the added value and limitations of Adaptive Delta Management concerning its application in the context of the Delta Programme, with a specific emphasis on the lessons learned from Dordrecht.     

Monitoring the recovery of a previously exploited surf-zone fish community in the St Lucia Marine Reserve,South Africa,using a no-take sanctuary area as a benchmark

Limiting accessibility to a fishing area can reduce fishing effort effectively and may therefore promote local recovery of depleted stocks. In January 2002, beach driving was banned in South Africa, thereby reducing angler access to large areas of the coastline, particularly in less-developed areas. In November 2001 a project had been established in the St Lucia Marine Reserve, on the east coast of South Africa, to compare surf-zone fish populations inside a no-take sanctuary zone with those in an adjacent exploited area. Subsequent to the ban, the aim of the project was adapted such that surf-zone fish populations were monitored for potential recovery in what had been the exploited area, located to the north of Cape Vidal, which anglers could no longer access easily, because of the prohibition on beach driving. Standardised research fishing was conducted at two sites in the previously exploited area and two sites in the no-take sanctuary. Conventional stock-status indicators showed evidence of recovery in the four most common species caught in the previously exploited area, in terms of both abundance and biomass. Generalised additive mixed models were used to account for the influence of targeting specific species; however, subtle differences in habitat between the sampling sites, improved angling skill over time, variability in recruitment, and differential species-specific responses complicated interpretation of results. The implications of the findings are discussed in terms of the future monitoring and management of marine protected areas both within the St Lucia Marine Reserve and farther afield.     

Late Holocene Environmental Reconstructions from Lake Solai,Kenya

Playa lake systems tend to be overlooked archives of paleoenvironmental change due to the likelihood of a short and intermittent record of deposition. Groundwater-fed wetlands associated with these climate-sensitive playas, however, preserve changes in hydrologic budget and are thus valuable archives for semiarid regions. This study examines the paleoecological record of a groundwater-fed wetland from Lake Solai, Kenya. Biological proxies are used to reconstruct paleoenvironmental change and climate impacts over the past millennium. Dry conditions persisted between CE 1115 and 1490, followed by wetter conditions during the Little Ice Age. Near surface sediments indicate increasing anthropogenic impact through pastoralism.     

Radio observations of the solar neutron flare of 3 June, 1982

In this paper the solar neutron and white-light flare is studied on the basis of radioastronomical observations. It is shown that the 3 June, 1982 flare had an impulsive character. A strong shock wave (M _A 2.9) was observed unusually soon after the impulsive phase of the flare. The radio spectrum of this event shows that the primary acceleration process probably occurred in the region with an electron density of n _e = 4.4 × 10¹⁵ m^–3. The pulsations of the type IV radio burst, observed 15 min after the mass ejection process, manifest the reconnection process in the post-flare stage.Proceedings of the Workshop on Radio Continua during Solar Flares, held at Duino (Trieste), Italy, 27–31 May, 1985.     

Effect of biodeposits from mussel culture on macroinvertebrate assemblages at sites of different hydrodynamic regime

The present study examined for differences in macroinvertebrate assemblage composition inside and outside of mussel farm sites experiencing different hydrodynamic regimes. Multivariate analysis revealed that there were significant differences in macroinvertebrate assemblage composition (averaged across seasons) between samples taken inside and outside of the two relatively low energy sites, whilst no such difference was observed for the relatively high energy site. Taxa that best discriminated between the dissimilarities observed in macroinvertebrate assemblage composition inside and outside farms were principally polychaetes (more abundant inside) and ophiuroids (more abundant outside). Sediment total organic matter and number of mussel shells were the parameters that best explained the difference in macroinvertebrate assemblage observed at the two relatively sheltered farm study sites. No taxa or environmental variables were particularly good at discriminating or explaining differences observed inside and outside the relatively high energy farm site. The present study indicates there is a relationship between the hydrodynamic regime of a farm site, organic enrichment of seabed sediments by mussel biodeposits, and a subsequent modification of the macroinverebrate assemblages. This finding has implications for the site selection of mussel farms in coastal environments.     

Are juvenile coral‐trouts (Plectropomus) mimics of poisonous pufferfishes (Canthigaster) on coral reefs?

The juveniles of three species of coral‐trout (Plectropomus) resemble two species of poisonous pufferfish (Canthigaster), one of the latter having two distinct colour morphs. Qualitative data are assembled on the diet, feeding mode, palatability, relative abundance, habitat and geographical range of each species. All observations are consistent with the hypothesis that juvenile coral‐trouts are generalized mimics of pufferfishes. Speciation within Plectropomus is discussed with respect to its mimetic relationships with Canthigaster.