Untersuchungen zum ökotoxikologischen Schädigungspotenzial und Erosionsrisiko von kontaminierten Sedimenten in staugeregelten Flüssen

Particle-bound pollutants accumulate in river-bottom sediments, a process which results in a significant decrease in the ecotoxicological availability of toxicants for the majority of aquatic organisms. Under normal hydrologic conditions, the release of contaminants from bottom sediments is usually of minor importance. In contrast, flood events may remobilize highly contaminated sediments via in-stream erosion. The objective of this study was to develop a combined ecotoxicological and hydraulic approach to elucidate the ecotoxicological implications associated with the risk of erosion of contaminated sediments. This integrated strategy was applied to the lock-regulated Neckar river in Southern Germany. Both the bottom-sediment cores and suspended matter from two intensive flood events were investigated. Sediment samples below an erosional unconformity showed a sharp increase in the ecotoxicological load. Moreover, it was found that major flood events (HQ₅ and higher) could possibly erode even very old, well-consolidated and highlycontaminated sediments. The suspended matter of the high discharge events investigated (return periods of 15 to 20 years) exerted significantly higher cytotoxicity and mutagenicity than a moderate flood with a 1-year return period. These findings support the conclusion that the observed ecotoxicological effects during major floods may at least in part be due to the in-stream erosion of highly contaminated bottom sediments.     

Female aggression and male peace-keeping in a cichlid fish harem: conflict between and within the sexes in Lamprologus ocellatus

Summary Conflicts of interest within and between the sexes are important processes leading to variability in mating systems. The behavioral interactions mediating conflict are little documented. We studied pairs and harems of the snail-shell inhabiting cichlid fish Lamprologus ocellatus in the laboratory. Due to their larger size, males controlled the resource that limited breeding: snail shells. Males were able to choose among females ready to spawn. Females were only accepted if they produced a clutch within a few days of settling. When several females attempted to settle simultaneously the larger female settled first. Females were least aggressive when guarding eggs. Secondary females were more likely to settle when the primary female was guarding eggs. In established harems females continued to be aggressive against each other. The male intervened in about 80% of female aggressive interactions. Male intervention activity correlated with the frequency of aggression among the females in his harem. The male usually attacked the aggressor and chased her back to her own snail shell. When a male was removed from his harem, aggression between females increased immediately and usually the secondary female was expelled by the primary female within a few days. Time to harem break-up was shorter the more mobile the primary females' young were and did not correlate with the size difference between harem females. Male L. ocellatus interfere actively in female conflict and keep the harem together against female interests. Female conflict presumably relates to the cost of sharing male parental investment and to the potential of predation by another female's large juveniles on a female's own small juveniles.Correspondence to: F. Trillmich     

Food (miles) for Thought - Energy Balance for Locally-grown versus Imported Apple Fruit (3 pp)

- This commentary compares the primary energy requirement for apples (cultivar ‘Braeburn’), which were either imported or locally-grown in Meckenheim, Germany. Imported apples of the same cultivar were grown in a Southern hemisphere winter in Nelson, Southland, New Zealand, and were picked at the end of March with subsequent 28 d transport by sea for sale in April in Germany. Locally-grown apples (cultivar ‘Braeburn’) were picked in mid-October and required a primary energy of nearly 6 MJ/kg of fruit including 0.8 MJoule/kg for five months CA storage at 1°C during a Northern hemisphere winter until mid-March. This compared favourably with 7.5 MJoule/kg for overseas shipment from New Zealand, i.e. a ca. 27% greater energy requirement for these imported fruits. Overall, the primary energy requirement of regional produce, stored several months on-site, partially compensated for the larger energy required to import fresh fruit from overseas. This result is in marked contrast to reported overestimates of a reported up to 8-fold energy requirement for domestic versus imported apple juice concentrate [7]. Our own findings of less primary energy required for domestic apple fruit is discussed with respect to providing local employment, fruit orchards preserving the countryside, quality assurance systems for local fruit such as QS and EUREP-GAP, networking and other factors favouring regional production.     

Cumulative impact of 40 years of industrial sulfur emissions on a forest soil in west-central Alberta (Canada)

The impact of 40 years of sulfur (S) emissions from a sour gas processing plant in Alberta (Canada) on soil development, soil S pools, soil acidification, and stand nutrition at a pine (Pinus contorta x Pinus banksiana) ecosystem was assessed by comparing ecologically analogous areas subjected to different S deposition levels. Sulfur isotope ratios showed that most deposited S was derived from the sour gas processing plant. The soil subjected to the highest S deposition contained 25.9 kmol S ha(-1) (uppermost 60 cm) compared to 12.5 kmol S ha(-1) or less at the analogues receiving low S deposition. The increase in soil S pools was caused by accumulation of organic S in the forest floor and accumulation of inorganic sulfate in the mineral soil. High S inputs resulted in topsoil acidification, depletion of exchangeable soil Ca2+ and Mg2+ pools by 50%, podzolization, and deterioration of N nutrition of the pine trees.     

Humanökologie: Der sozialwissenschaftliche Ansatz

Schlagen wir den Bogen zurück zu den ideengeschichtlichen Eingangsüberlegungen, so fällt auf, daß der theoretisch differenzierteste and politisch folgenreichste sozialwissenschaftliche Ansatz zur Ortsbestimmung der Relation zwischen Mensch and Natur, das Marxsche Paradigma, in der deutschen sozialwissenschaftlich-humanökologischen Forschung nicht mehr existiert.Marx hat die Austauschbeziehungen zwischen Gesellschaft und natürlicher Umwelt mit dem der Physiologie entlehnten Terminus Stoffwechsel" bezeichnet. Der naturwissenschaftliche Anklang darf nicht darüber hinwegtäuschen, daß der Stoffwechselprozeß sehr wohl auch eine gesellschaftlich-historische Sinnkomponente hat. Stoffwechsel wird vollzogen durch den Arbeitsprozeß zwischen Mensch and Natur, Arbeit ist die Bedingung dieses Prozesses. Zweck der Arbeit schließlich ist ihr Produkt, die Verdnderung eines Gegenstandes zum Gebrauchswert.