Research

S. Kotzur, C. D. Dürselen, W. Ebenhöh, T. Raabe, U. Brockman

Analysing two mesocosm experiments using an ERSEM-based pelagic Ecosystem model (PEM)

This work is based on data of two mesocosm experiments conducted in Büsum (North Frisian Wadden Sea, Germany) during spring and summer 1999. A multitude of biological, chemical and physical parameters was measured every two hours in control as well as in nutrient enriched enclosures. These data were compared with results from a O-D Pelagic Ecosstem Model (PEM) based on the pelagic part of ERSEM II. The model describes carbon, phosphorus, nitrogen and silicon dynamics in the water column, forced by surface water temperature and global radiation data. The model is able to well reproduce the biogeochemical dynamics of the mesocosm system under differnet nutrient conditions and during different seasons. Concurrently, the simpel one-box structure of the system and the availability of many simultaneously measured experimental data allowed to reveal weaknesses of the model system. The analyses clearly indicated that the decomposition processes such as bacteria dynamics and interactions between dissolved and particulate organic matter need an extensive revision and should be transferred to more complex 3-D ecosystem models.