Journal of Plankton Research Vol.23 no.10 pp.1081-1093, 2001
© Oxford University Press 2001
Modelling and the monitoring of mesocosm experiments: two case studies
School Of Environmental Sciences, University Of East Anglia, Norwich Nr4 7tj, Uk
* To Whom Correspondence Should Be Addressed
Mesocosm experiments have played an important role over the last decade in increasing our understanding of marine ecosystems. Many studies use these controlled environments to examine ecosystem responses to factors such as nutrient addition and light limitation. A few studies have been able to successfully model mesocosm experiments using carefully designed and comprehensive models and experimental design. Nevertheless, it is rare for such models to be compared with oceanic studies, and to consider the sulphur cycle as well as the carbon and nitrogen budgets. Here we take an ecosystem model, including a dimethylsulphide loop, that has been successfully used in modelling the evolution of the planktonic system in a Lagrangian field experiment in the North Atlantic—the PRIME cruise of 1996—and apply it to two mesocosm experiments. These were operated by two different groups of scientists, but in the same field station in a Norwegian fjord. The experiments were not explicitly designed with the data requirements of any model in mind. We show that the model is best able to simulate mesocosm data using model parameters taken from the real ocean. However, most sensitivity tests are significantly less successful in the mesocosm environment than the real ocean, especially if the model parameters are allowed to vary in a best fit sense. The limitations of the model–mesocosm match highlight the importance of comprehensive monitoring of mesocosms if they are to be useful for validating models suitable for the open ocean.