8 research outputs found
Abrupt regime shifts in space and time along rivers and connected lake systems
Regime shifts between clear and turbid water states are commonly found in shallow lakes. These shifts are attributed to a positive feedback between water clarity and submerged macrophytes (underwater plants). Altering the retention time of the water may influence these interactions and thus potentially reduce the probability of alternative stable states. Here we assessed the effect of water retention time on the occurrence of alternative states in water quality of flushed lakes, chains of lakes and rivers using a spatially explicit simple model. Our results indicate that increased flushing of lakes rapidly decreases the range of parameters with alternative stable states up to their total disappearance at a flushing rate of about 50% the algal growth rate. Similarly, in a chain of lakes or in rivers with low flowing velocity, our model predicts that alternative stable states can only occur for systems with a high retention time. Despite the lack of hysteresis at lower water retention times, we predict that abrupt changes between clear and turbid states are still possible both in time and in space. Over a wide range of parameters, the equilibrium state of the chain of lakes shows a steep gradient of vegetation cover. Further, the transient dynamics of the model often include rapid shifts in time. For example, a local regime shift that occurs upstream may propagate through the whole lake chain or river due to a domino effect. All results of the simple model could qualitatively be reproduced with a more mechanistic model. The abrupt rather than gradual response of submerged macrophytes to reduced turbidity levels still makes river systems rather resilient to management measure. The importance of the initial turbidity and the observed domino effect suggest that restoration measures should start upstream and that these measures should eventually trigger regime shifts downstrea
Abrupt regime shifts in space and time along rivers and connected lake systems
Regime shifts between clear and turbid water states are commonly found in shallow lakes. These shifts are attributed to a positive feedback between water clarity and submerged macrophytes (underwater plants). Altering the retention time of the water may influence these interactions and thus potentially reduce the probability of alternative stable states. Here we assessed the effect of water retention time on the occurrence of alternative states in water quality of flushed lakes, chains of lakes and rivers using a spatially explicit simple model. Our results indicate that increased flushing of lakes rapidly decreases the range of parameters with alternative stable states up to their total disappearance at a flushing rate of about 50% the algal growth rate. Similarly, in a chain of lakes or in rivers with low flowing velocity, our model predicts that alternative stable states can only occur for systems with a high retention time. Despite the lack of hysteresis at lower water retention times, we predict that abrupt changes between clear and turbid states are still possible both in time and in space. Over a wide range of parameters, the equilibrium state of the chain of lakes shows a steep gradient of vegetation cover. Further, the transient dynamics of the model often include rapid shifts in time. For example, a local regime shift that occurs upstream may propagate through the whole lake chain or river due to a domino effect. All results of the simple model could qualitatively be reproduced with a more mechanistic model. The abrupt rather than gradual response of submerged macrophytes to reduced turbidity levels still makes river systems rather resilient to management measure. The importance of the initial turbidity and the observed domino effect suggest that restoration measures should start upstream and that these measures should eventually trigger regime shifts downstrea
Entwicklung von Methoden zur Messung der Partikelsedimentation in Gewaessern unter der Wirkung der Bodenschubspannung Abschlussbericht
SIGLEAvailable from TIB Hannover: F00B255 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung und Forschung (BMBF), Bonn (Germany)DEGerman
Untersuchungen zu Stoffeintraegen in Oberflaechengewaesser sowie zu Stoffumsetzungsprozessen in Fliessgewaessern im Einzugsgebiet der Unteren Spree als Grundlage fuer Sanierungskonzepte Abschlussbericht
SIGLEAvailable from TIB Hannover: F96B1215+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman
The role of micro-organisms in the ecological connectivity of running waters
Pusch M, Fiebig D, Brettar I, et al. The role of micro-organisms in the ecological connectivity of running waters. Freshwater Biology. 1998;40(3):453-495