Ecosystem analysis and ecological modelling is a rapidly developing interdisciplinary branch of science used in theoretical developments in ecology and having practical applications in environmental protection. In this book, the authors introduce new holistic, particularly cybernetic, concepts into ecosystem theory and modelling, and provide a concise treatment of mathematical modelling of freshwater ecosystems which covers methods, subsystem models, applications and theoretical developments. Part I begins with a brief introduction to the principles of systems theory and their applications to ecosystems, and provides a summary of various methods of systems analysis. In Part II emphasis is laid on the pelagic processes in standing water, characterised by relatively uninvolved structures from which models can be readily developed. Part III describes applications of the technique of modelling to solutions of theoretical and practical problems, with different modelling methods and objectives being used in the various chapters. More recent developments in the methods and theory of ecosystem modelling are covered in Part IV which also includes a discussion of future trends. The book is addressed to practising ecologists and engineers in the fields of ecology, limnology, environmental protection, and water quality managements, as well as to graduate/post-graduate university students in science and engineering. Students and researchers involved in environmental applications of mathematics and cybernetics will also find the book of interest.