Danish seabird disasters in 1972

In recent years the Danish Game Biology Station has studied casualties to seabirds from oil pollution. 1972 was a particularly disastrous year and preliminary information on the events are given here. Very large losses of seabirds have been caused by quite small spillages of oil.     

Loss of patch-scale heterogeneity on secondary productivity in the arid shrubland of Western Australia

General models of degradation suggest soil and nutrients are lost and conversion of rainfall into primary productivity is diminished when rangeland is degraded. These models are supported by studies on non-resilient landscapes, where loss of primary productivity also translated into loss of secondary productivity, but have not been tested on resilient landscapes. Elsewhere we showed that loss of chenopod shrubs from a landscape characterized as resilient was associated with declines in plant productivity and efficiency of conversion of rainfall into plant mass. To explore whether these differences in primary productivity translated into differences in secondary productivity, we grazed sheep at five rates of stocking for 10 years on 2000 ha of this landscape. The experiment was necessarily replicated in time not space (i.e. pseudo-replicated), which limits confident extrapolation of results to other landscapes.Productivity of sheep at all except highest rates of stocking varied little between sites where shrubs were abundant or scarce. From an animal production point of view, greater rates of stocking were unsustainable through dry years on the degraded site, but animal performance was generally unaffected on the non-degraded site, where shrubs were abundant. While these results provide evidence of economic penalties associated with degrading a resilient landscape, important ecological penalties were only partially explored.     

Lipids and trophic linkages in harp seal (Phoca groenlandica) from the eastern Barents Sea

Fatty acid profiles and lipid biomarkers from 20 harp seals were used to investigate the foraging ecology of harp seals and the transfer of energy through the Franz Josef Land-Novaya Zemlya food chain. High levels of the Calanus fatty acid trophic markers (FATMs) 20:1(n-9) (mean 14.6%) and 22:1(n-11) (mean 6.5%), together with the typical dinoflagellate FATMs 22:6(n-3) (mean 6.5%) and C18PUFA (mean 5.5%), were found in blubber samples. Based on the analyses of the fatty acid profiles separated by principal component analysis, we confirmed the importance of polar cod ( Boreogadus saida ) and the pelagic amphipod Themisto libellula in the diet of harp seal. The high levels of 22:6(n-3), C18PUFA and C20 and C22 FATMs show that the harp seal lipids mainly originate from dinoflagellates consumed by Calanus copepods.     

Replenishment episodes and crustal assimilation in the development of an early Tertiary magma chamber, East Greenland: evidence from layered cumulates of the Kælvegletscher ultramafic complex, Kangerlussuaq

Summary  From the early Tertiary K?lvegletscher ultramafic cumulate complex, emplaced into the Archaean basement on the west side of the Kangerlussuaq Fjord, East Greenland, we present geochemical and isotopic data from an outcrop of finely layered dunitic adcumulates. The dunites were deposited in a trough structure, interpreted to be a fossilized feeder channel to the K?lvegletscher magma chamber. Detailed geochemical sampling of the trough reveals subtle cryptic compositional variations of olivines (Fo = 86.5–89.3; Ni = 2000–2700 ppm) and chromites (Cr# = 66–80) in a stratigraphical profile perpendicular to the layering as well as relatively large simultaneous variations of whole-rock ⁸⁷Sr/⁸⁶Sr ratios. The dunites are separable into sequences of normal and reverse cryptic zonations which are interpreted as resulting from fractional crystallisation and magma chamber recharge, respectively. Up to 20% of magma chamber replenishment by high-Mg melts is suggested. Sr-isotope compositions of the cumulates correlate with olivine compositions and suggest mixing of fractionated and unfractionated parental melts assimilating up to 8% local basement. We propose the existence of a vigorous volcanic system at the K?lvegletscher site in early Tertiary times, where plume-derived magmas incorporated minor amounts of local basement and underwent fractionation and mixing in crustal chambers. Estimates of processed magma volumes during deposition of the trough cumulates are in the range of 100–130 km³. Received January 18, 2000;/revised version accepted December 19, 2000     

A magnetotelluric investigation of the structural geology beneath Charlevoix Crater, Quebec

The results of ten tensor magnetotelluric soundings recorded within the Charlevoix crater are presented. The geological complexity of the region (the crater is located at the junction of two major geological provinces, i.e. the crystalline basement of the Canadian shield and the more conductive sediments of the Appalachian system) and the amount of cultural noise present in our data prevent a highly definitive interpretation of the shallow structure. A subhorizontal conductive fault related to Rondot's (1971) structural sketch of the original impact structure may exist within the upper 5 km, but it is not completely constrained by the data. Pseudo 3D modelling using stacked thin sheets indicates that superficial patches of high conductivity may explain the large anisotropy observed at the long periods and suggests that our deeper structures fit well with the 2D model previously proposed by Kurtz (1982) for the region.     

A general model for Mt. Ruapehu lahars

A mathematical model of the motion of lahars is presented. Lahar flows and travel speeds are calculated using a kinematic wave model which equates gravitational accelerations to frictional losses. A chezyor Manning-type law of friction is assumed, in which lahar flow rate is a simple power function of lahar depth, multiplied by another simple power of the chanel slope. Use of the model requires knowledge of essentially only one parameter which appears to be relatively insensitive for flows down a given channel. Variable channel slope effects are removed by a longitudinal scaling which applies to all flows down a given channel. For lahars generated by a single explosive event it is unnecessary to perform numerical calculations to predict lahar flow and travel time, but for lahnars produced by multiple sources in which different lahar flows are interacting, numerical calculations appear necessary. The model is applied to all recorded lahar flows from Mt. Ruapehu, and satisfactorily described all lahar flows generated by a single explosive mechanism. Such flows depend essentially only on total lahar volume. The 1968 Mt. Ruapehu lahar, generated by a series of smaller eruptive mechanisms, was modelled as the interaction of seven point sources of fluid originating from positions mathematically extrapolated up the mountain. Good agreement was obtained between the predicted times of formation of these 1968 lahars, and the times of greatest seismic amplitude.     

Mapping and measuring the ecological embeddedness of food supply chains

The status of nature in food systems is the subject of this paper, which looks into the ecological embeddedness of the Austrian food system both on the national level and in a regional case study. By a first attempt to measure and map ecological embeddedness, the author intends to contribute to the operationalisation of the embeddedness concept, which is characterised as ambivalent, fuzzy and dynamic (see e.g., [Goodman, D., 2003. The quality ‘turn’ and alternative food practices: reflections and agenda. Editorial. Journal of Rural Studies 19 (1), 1-7; Markusen, A., 1999. Fuzzy concepts, scanty evidence, policy distance: the case for rigour and policy relevance in critical regional studies. Regional Studies 33, 869-884; Hess, M., 2004. ‘Spatial’ relationships? Towards a reconceptualization of embeddedness. Progress in Human Geography 28 (2), 165-186]). The paper starts with a critical outline of the academic discourse on embeddedness in food chain studies. In the second section, general developments in the Austrian food system and their ecological implications are illustrated for the national level. Thereafter in a case study, the author tries to map and measure the ecological embeddedness of two conventional bread chains. The focus on conventional food chains provides a contrast with the growing body of embeddedness studies concentrating on alternative food chains. The author concludes that for both conventional as well as alternative food chains, the mode of ecological embeddedness or the degree of a food chain’s commitment to particular landscapes could become important factors for the maintenance, enhancement and capture of ecological value.