ABSTRACT
This chapter deals with importants of water quality assessment and for understanding the cycling of nutrients in the aquatic ecosystem. In many ecological models of complex aquatic ecosystems, the concentration of nutrients has been based on chemical analyses, but the difference between bulk concentration and its bioavailable fraction is often overlooked, though only the latter is relevant for the characterization of water quality. The chapter discusses the modelling of constructed wetlands, involving both structural modelling and parameter estimation, and, finally, a lagoon ecosystem will be considered from several viewpoints, including modelling and management. It describes a method for diagnosing the state of the aquatic ecosystem from the observed Dissolved oxygen (DO) variations, using a method based on wavelet denoising. DO data are normally affected by noise in many ways, and a dyadic wavelet decomposition, with its multi-scale property, can reveal data trends that other signal analyses.
