Erik Jeppesen

The defence took place on December 11, 1998 at The Freshwater Centre, Silkeborg, Denmark. Officiel opponents was Prof. Jürgen Benndorf, University of Technology, Dresden,Germany and Prof. Dag Hessen, University of Oslo, Norway . The defence was led by Lektor Leif Lau Jeppesen, Zoological Institute, University of Copenhagen. The Doctor's dissertation (excluding the 25 original papers) is available in Danish entitled: Lavvandede søers økologi - biologisk samspil i de frie vandmasser. Doktordisputats. Faglig rapport fra Dmu nr. 248. 60 s. The thesis is a summary of 25 selected original scientific publications. The thesis was in June 1998 approved by The Faculty of Natural Sciences at the University of Copenhagen for defence for the doctor´s degree in Natural Sciences (D.sc). This thesis describes how biological interactions in the pelagial of lakes change across both nutrients and depth gradients in freshwater as well as brackish lakes. Particular importance is paid to the role that fish and submerged macrophytes play in determining the structure and function of shallow lakes . Other points of discussion include factors responsible for resilience when nutrient loading changes.and the potential of utilizing biomanipulation as a restoration tool. The research strategy combines cross-analysis of data from a vast number of lakes with whole-lake experiments as well as mechanistic enclosure studies and paleoecological analysis of sediments.