Trophic structure of zooplankton in the Fram Strait in spring and autumn 2003

The trophic structure of zooplankton was investigated in Fram Strait (north western Svalbard) in spring and autumn of 2003. Depth-stratified zooplankton samples were collected at 12 stations on the shelf (200 m), across the shelf-slope (500 m) and over deep water (>750 m), using a Multiple Plankton Sampler equipped with 0.180-mm mesh size nets.Higher zooplankton abundance and estimated biomass were found in the shelf area. Abundance and biomass were two times higher in August, when sea-surface temperature was higher than in May. Herbivores dominated numerically in May, and omnivores in August, suggesting a seasonal sequence of domination by different trophic groups. Cirripedia nauplii and Fritillaria borealis prevailed in spring, whereas copepod nauplii and Calanus finmarchicus were numerically the most important herbivores in autumn. Small copepods, Oithona similis and Triconia borealis, were the most numerous omnivorous species in both seasons, but their abundances increased in autumn. Chaetognatha (mainly Eukrohnia hamata) accounted for the highest abundance and biomass among predatory taxa at all deep-water stations and during both seasons. Regarding vertical distribution, herbivores dominated numerically in the surface layer (0–20 m), and omnivores were concentrated somewhat deeper (20–50 m) during both seasons. Maximum abundance of predators was found in the surface layer (0–20 m) in spring, and generally in the 20–50 m layer in autumn. This paper presents the first comprehensive summary of the zooplankton trophic structure in the Fram Strait area. Our goals are to improve understanding of energy transfer through this ecosystem, and of potential climate-induced changes in Arctic marine food webs.     

Fire on the horizon: contemporary Aboriginal burning issues in the Tanami Desert,central Australia

As part of a collaborative research project created to promote the coexistence of fire, people and biodiversity in central Australia, a case study was conducted on Aboriginal perceptions of fire and its management in the southern Tanami Desert of Central Australia. The Tanami was chosen due to consecutive wildfire events and reported fire conflicts between Aboriginal and pastoral (cattle station) landholders on fire issues. This paper addresses fire issues from the perspective of Warlpiri Aboriginal people in this region. It shows that many Warlpiri hold strong views concerning the use of fire and its management. Elders, in particular, have retained tradition-based knowledge about fire and its effects on the environment. The complex cultural protocols that structure decisions about who burns, when and where are discussed. It is shown that, although there have been dramatic changes to their subsistence economy, Warlpiri still burn for cultural and economic reasons. At the same time, social change has given rise to new fire-related issues, including lack of access to remote areas in order to undertake burning and a decrease in fire knowledge among younger generations. The paper argues that Warlpiri perceptions of fire management, needs and skills must be incorporated in a regional fire management strategy if the cycle of wildfire that follows above average rainfall periods in the Tanami is to be broken. Proper resourcing of Aboriginal people to fire their land in customary ways will enhance Aboriginal livelihoods as well as benefit other stakeholders in the region.     

Toward an experimental synthesis of the chondritic insoluble organic matter

Based on the statistical model proposed for the molecular structure of the insoluble organic matter (IOM) isolated from the Murchison meteorite, it was recently proposed that, in the solar T‐Tauri disk regions where (photo)dissociation of gaseous molecules takes place, aromatics result from the cyclization/aromatization of short aliphatics. This hypothesis is tested in this study, with n‐alkanes being submitted to high‐frequency discharge at low pressure. The contamination issue was eliminated using deuterated precursor. IOM was formed and studied using solid‐state nuclear magnetic resonance, pyrolysis coupled to gas chromatography and mass spectrometry, RuO₄ oxidation, and high‐resolution transmission electron microscopy. It exhibits numerous similarities at the molecular level with the hydrocarbon backbone of the natural IOM, reinforcing the idea that the initial precursors of the IOM were originally chains in the gas. Moreover, a fine comparison between the chemical structure of several meteorite IOM suggests either that (i) the meteorite IOMs share a common precursor standing for the synthetic IOM or that (ii) the slight differences between the meteorite IOMs reflect differences in their environment at the time of their formation i.e., related to plasma temperature that, in turn, dictates the dissociation–recombination rates of organic fragments.     

The role of shelf morphology on storm‐bed variability and stratigraphic architecture,Lower Cretaceous,Svalbard

The dominance of isotropic hummocky cross‐stratification, recording deposition solely by oscillatory flows, in many ancient storm‐dominated shoreface–shelf successions is enigmatic. Based on conventional sedimentological investigations, this study shows that storm deposits in three different and stratigraphically separated siliciclastic sediment wedges within the Lower Cretaceous succession in Svalbard record various depositional processes and principally contrasting sequence stratigraphic architectures. The lower wedge is characterized by low, but comparatively steeper, depositional dips than the middle and upper wedges, and records a change from storm‐dominated offshore transition – lower shoreface to storm‐dominated prodelta – distal delta front deposits. The occurrence of anisotropic hummocky cross‐stratification sandstone beds, scour‐and‐fill features of possible hyperpycnal‐flow origin, and wave‐modified turbidites within this part of the wedge suggests that the proximity to a fluvio‐deltaic system influenced the observed storm‐bed variability. The mudstone‐dominated part of the lower wedge records offshore shelf deposition below storm‐wave base. In the middle wedge, scours, gutter casts and anisotropic hummocky cross‐stratified storm beds occur in inferred distal settings in association with bathymetric steps situated across the platform break of retrogradationally stacked parasequences. These steps gave rise to localized, steeper‐gradient depositional dips which promoted the generation of basinward‐directed flows that occasionally scoured into the underlying seafloor. Storm‐wave and tidal current interaction promoted the development and migration of large‐scale, compound bedforms and smaller‐scale hummocky bedforms preserved as anisotropic hummocky cross‐stratification. The upper wedge consists of thick, seaward‐stepping successions of isotropic hummocky cross‐stratification‐bearing sandstone beds attributed to progradation across a shallow, gently dipping ramp‐type shelf. The associated distal facies are characterized by abundant lenticular, wave ripple cross‐laminated sandstone, suggesting that the basin floor was predominantly positioned above, but near, storm‐wave base. Consequently, shelf morphology and physiography, and the nature of the feeder system (for example, proximity to deltaic systems) are inferred to exert some control on storm‐bed variability and the resulting stratigraphic architecture.     

Changes in the composition of planktonic ostracod populations across a range of latitudes in the North-east Atlantic

A large database representing the bathymetric distribution of 117 species of halocyprid ostracods has been compiled from seven stations forming a transect from the equator to 60°N along 20°W, plus an additional station at 32°N, 65°W. This data base is analysed to examine the latitudinal and bathymetric changes in species composition and diversity of assemblages of this important, yet neglected, holoplanktonic group. At each station stratified sampling of the complete water column from the surface down mostly to 2000 m was carried out both day and night. Each sample resulted from the filtration of at least 2500 m³ of water and was analysed using a consistent protocol. The differences between the day and night profiles are attributable to diel vertical migrations, to local-scale heterogeneity, and possibly to a degree of net avoidance. There is a gradient of increasing species richness and diversity from high to low latitudes. By day, halocyprids are either infrequent or absent from the upper 50 m of the water column, but at night after diel vertical migration they become quite abundant in the epipelagic zone, particularly at low latitudes. Bathymetric profiles show ostracod abundances increase rapidly below the thermocline, reaching maxima at 200-400 m and then declining by at least an order of magnitude at 2000 m. Diversity (both species richness, H′ and evenness, J) also increases below the thermocline and thereafter is either maintained or declines only slightly to 2000 m. There are no relationships among diversity, abundance and productivity, but analysis of the whole database shows that the changes in community structure are consistent with Longhurst’s [Longhurst, A.R., 1998. Ecological Geography of the Sea. Academic Press, San Diego, pp. xiv, 398.] biogeochemical provinces.