Macrophytes and phytobenthos as indicators of ecological status in German lakes — a contribution to the implementation of the water framework directive

A new assessment system for macrophytes and phytobenthos in German lakes according to the Water Framework Directive of the European Community is described. Based on biological, chemical and hydromorphological data from about 100 lake sites covering the main ecoregions, hydromorphological lake types and degradation forms, biocoenotic types could be defined. For developing a classification system the quality element macrophytes and phytobenthos was divided into two components: macrophytes and benthic diatoms. For macrophytes 4 and for benthic diatoms 4 lake types were identified. The benthic vegetation at reference conditions is described and degradation is characterised as deviation in benthic vegetation species composition and abundance from the reference biocoenosis. For classification in five ecological status classes, several metrics were developed and used in combination with existing indices. For a few of the described lake types further investigations are necessary before a classification can be developed.     

Chemical Composition of Urban Street Sediments and Its Sources

INTRODUCTIONBeijingfacesseveredustpollutionduetosuchsourcesasdustimportedfromwesterndeserts,industryandpowerplants,domesticcombustionprocessesandtraffic .Inthelastdecades ,theurbanpopulationhasgrowntomorethan10million .TheeconomicgrowthofChinahasalsoleftitsfootprintsinBeijing .Newindustrialzonesanddomesticar easweredeveloped ,inducinganincreasingtrafficcirculation(Shi,2 0 0 1) .Thedroughtclimateinalmostthewholeyear ,thestrongmonsoonsinwinterbringingdustsfromtheGobidesert,theheavytraffic…     

Managing food shortages in Central Tanzania

Famine prevention and mitigation strategies have become an established area of interest for researchers concerned with food insecurity. Studies often focus on one famine event and the coping strategies immediately preceding or accompanying it. By contrast, this case study adopts a long-term perspective and depicts the changes of indigenous and exogenous famine-coping strategies among the Gogo, an ethnic group in semi-arid central Tanzania, over a time-span of one and half centuries. By doing so, this paper tries to give insights into the continuity and adaptability of human reactions to a persistent problem under changing socio-economic circumstances.     

Measuring and monitoring persistent organic pollutants in the context of risk assessment

Due to growing concerns regarding persistent organic pollutants (POPs) in the environment, extensive studies and monitoring programs have been carried out in the last two decades to determine their concentrations in water, sediment, and more recently, in biota. An extensive review and analysis of the existing literature shows that whilst the vast majority of these efforts either attempt to compare (a) spatial changes (to identify "hot spots"), or (b) temporal changes to detect deterioration/improvement occurring in the environment, most studies could not provide sufficient statistical power to estimate concentrations of POPs in the environment and detect spatial and temporal changes. Despite various national POPs standards having been established, there has been a surprising paucity of emphasis in establishing accurate threshold concentrations that indicate potential significant threats to ecosystems and public health. Although most monitoring programs attempt to check compliance through reference to certain "environmental quality objectives", it should be pointed out that many of these established standards are typically associated with a large degree of uncertainty and rely on a large number of assumptions, some of which may be arbitrary. Non-compliance should trigger concern, so that the problem can be tracked down and rectified, but non-compliance must not be interpreted in a simplistic and mechanical way. Contaminants occurring in the physical environment may not necessarily be biologically available, and even when they are bioavailable, they may not necessarily elicit adverse biological effects at the individual or population levels. As such, we here argue that routine monitoring and reporting of abiotic and biotic POPs concentrations could be of limited use, unless such data can be related directly to the assessment of public health and ecological risks. Risk can be inferred from the ratio of predicted environmental concentration (PEC) and the predicted no effect concentration (PNEC). Currently, the paucity of data does not allow accurate estimation of PNEC, and future endeavors should therefore, be devoted to determine the threshold concentrations of POPs that can cause undesirable biological effects on sensitive receivers and important biological components in the receiving environment (e.g. keystone species, populations with high energy flow values, etc.), to enable derivation of PNECs based on solid scientific evidence and reduce uncertainty. Using the threshold body burden of POPs required to elicit damages of lysosomal integrity in the green mussel (Perna virvidis) as an example, we illustrate how measurement of POPs in body tissue could be used in predicting environmental risk in a meaningful way.     

3D Hydrodynamical Simulations of Colliding Wind Binaries: TheoryConfronts Observations

The link between gas dynamical models and observations is crucial. The general progress in numerical simulations must be accompanied by predictions for observable quantities, which not only allow to test the models or parts of them against observations but which also improve the understanding of observational data. In this paper we focus on predictions for observations, for three examples of 3Dhydrodynamical simulations of binary star systems, and the techniques required for their derivation. The examples include synthetic, optically thin Doppler broadened line profiles for colliding wind symbiotic binaries, the UV light curve of an accretion model for the symbiotic binary RW Hya, and the X-ray light curve of the WR+O binaryγ Velorum. The main purpose is to emphasize the importance of such studies and to illustrate the capabilities of the emploiedtools. The tools are all contained in the A-MAZE code package we have developed and are publicly available. Seminar for Applied Mathematics This revised version was published online in July 2006 with corrections to the Cover Date.     

Decadal variation of surface solar radiation in the Tibetan Plateau from observations, reanalysis and model simulations

In this study, the annual and seasonal variations of all-sky and clear-sky surface solar radiation (SSR) in the eastern and central Tibetan Plateau (TP) during the period 1960–2009 are investigated, based on surface observational data, reanalyses and ensemble simulations with the global climate model ECHAM5-HAM. The mean annual all-sky SSR series shows a decreasing trend with a rate of ?1.00 Wm^?2 decade^?1, which is mainly seen in autumn and secondly in summer and winter. A stronger decrease of ?2.80 Wm^?2 decade^?1 is found in the mean annual clear-sky SSR series, especially during winter and autumn. Overall, these results confirm a tendency towards a decrease of SSR in the TP during the last five decades. The comparisons with reanalysis show that both NCEP/NCAR and ERA-40 reanalyses do not capture the decadal variations of the all-sky and clear-sky SSR. This is probably due to a missing consideration of aerosols in the reanalysis assimilation model. The SSR simulated with the ECHAM5-HAM global climate model under both all-sky and clear-sky conditions reproduce the decrease seen in the surface observations, especially after 1980. The steadily increasing aerosol optical depth (AOD) at 550 nm over the TP in the ECHAM5-HAM results suggests transient aerosol emissions as a plausible cause.     

Multi-proxy reconstruction of the Holocene vegetation and land use dynamics in the Julian Alps,north-west Slovenia

Small mountain lakes are natural archives for understanding long-term natural and anthropogenic impact on the environment. This study focused on long-term (last ca. 13 000 years) vegetation changes and sedimentary processes in the catchment area of Lake Planina pri jezeru (1430 m a.s.l.) by using mineralogical, geochemical and palynological methods. Palynological results suggest that regional vegetation between 12 900 and 11 700 cal a bp was a herbaceous–forest tundra (Pinus, Artemisia, Poaceae ). Climate warming at the beginning of the Holocene (ca. 11 700 cal a bp ) caused the transition from a wetland (Cyperaceae) to an eutrophic lake with alternating anoxic (pyrite) and oxic conditions (gypsum). In addition, the surrounding area became forested (Picea, Larix, Ulmus). Fagus expanded at 10 200 cal a bp and Abies at 8200 cal a bp. Between 7500 and 4300 cal a bp , human impact on the environment was barely noticeable and mostly limited to grazing. During 4300–430 cal a bp human impact became more evident and gradually increased. The greatest influence was observed from 430 cal a bp onwards, when excessive exploitation of the surrounding area (logging and grazing) severely eutrophicated the lake.     

Susceptibility of fish to Chattonella marina is determined by its tolerance to hypoxia

The harmful alga Chattonella marina has caused massive fish kills and economic losses worldwide. However, the fish kill mechanisms by C. marina have not been identified. The present study has confirmed that a significant elevation of blood osmolality is the universal response in moribund fish exposed to C. marina and the possible reasons leading to contradictory reports were identified. Both osmotic distress and respiratory impairment are important mechanisms leading to fish kill by C. marina. The susceptibility of marine fish to C. marina appears to be inversely related to their tolerance to hypoxia, with the hypoxia intolerant goldlined seabream being the most susceptible, and the hypoxia tolerant green grouper being the most tolerant to C. marina. Further studies in the marine medaka (Oryzias melastigma) showed that fish susceptibility to C. marina is directly related to susceptibility of the fish to hypoxia, but not related to its tolerance to hypersalinity stress.