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After installation of phosphorus elimination plants at the inflows of the eutrophic Lake Tegel and Schlachtensee, phosphorus (P) loading declined by a factor of 40 and 100, respectively. This resulted in a pronounced reduction of phosphorus concentrations in the lake water, followed by a decline of chlorophyll-a concentrations. However, for many years P release from sediments due to mineralization and desorption of sedimentary P continued. In Schlachtensee, the presence of nitrate above the sediment suppresses P release, because the Fe/P ratio is sufficient to provide enough aerobic sorption capacity. In Lake Tegel, some P release occurs even under aerobic conditions because of the low aerobic P sorption capacity of the sediments. There, nitrate could moderate the P release peaks which occur when the Fe-P cycle at the sediment water interface is disturbed by precipitation of iron sulfide after reduction of sulfate during times of high mineralization intensity. The potentially mobile P pool in the sediments of both lakes is rather small, indicating that the P release could subside after sufficient reduction of the external P load in Lake Tegel and the disruption of the internal P cycle in Schlachtensee.

Purpose – This paper aims to propose a collaborative approach toward an integrated vulnerability assessment to climate change in Germany that attempts to bridge the gap between scientific output and policy demand. Design/methodology/approach – Conceptually, the approach follows the definition of vulnerability as used by the Intergovernmental Panel on Climate Change, but it has modified this basic concept. It clearly distinguishes between three time slices (presence, near and remote future) not only regarding the change in the climatic conditions but also socio-economic development trends. Findings – The paper concentrates on the selected methodological framework, the collaborative research design and those preliminary results of the nationwide vulnerability assessment that are transferable to other settings. Practical implications – A Vulnerability Network (“Netzwerk Vulnerabilitaet”) emerged from an applied research project commissioned under the Adaptation Action Plan of the German Strategy for Adaptation to Climate Change by the Federal Ministry for the Environment, Nature Conservation, Building and Nuclear Safety and the Federal Environment Agency. The assessment serves as evidence basis for the implementation of the German Adaptation Strategy. Thus, all relevant federal authorities and agencies are represented in the Vulnerability Network. Originality/value – The approach is the first really integrative vulnerability assessment for the whole Germany, as it considers not only 16 sectors but also interconnections between these sectors and cumulative effects for three different time slices. Moreover, the normative component of the assessment was clearly separated from the analytic one. The Vulnerability Network as a whole has been responsible for all normative decisions to be taken during the assessment procedure thus ensuring a wide understanding and acceptance of commonly achieved results.

No abstract

Schauser, I. and I. Chorus. 2007. Assessment of internal and external lake restoration measures for two Berlin lakes. Lake and Reserve. Manage. 23:366-376. Two previously highly eutrophic lakes, Lake Tegel and Schlachtensee in Berlin, Germany, were subjected to similar external but different internal restoration measures during the last 20-25 years. External phosphorus (P) load was reduced in both lakes by P-stripping their main inflows using P-elimination plants; internal P load was treated by aeration in Lake Tegel and by hypolimnetic withdrawal in Schlachtensee. Loads before and after treatment are compared with the targets using the Vollenweider model and a modified One-Box model. The results indicate that external load reduction was the main cause of the pronounced lake water quality improvements. The hypolimnetic withdrawal in Schlachtensee was effective only in the initial years. No significant positive effect can be identified for the aeration of Lake Tegel.