Validation of a hydrodynamic-ecosystem model simulation with time-series data collected in the western English Channel

Evaluation is essential if ecosystem models are to be used to simulate short-term and climate scale forecasts. A three-dimensional hydrodynamic-ecosystem model (ERSEM-POLCOMS) simulation of the western English Channel for the period 2003–2005 has been validated with a series of univariate and multivariate tests using physical, biological and chemical data collected routinely at time-series station L4 (50° 15′N, 04° 13′W). Our assessment indicates a varying confidence in model ability to simulate different variables: In terms of high frequency variability there is a high level of confidence in temperature, some confidence in nutrients, especially nitrate, but much development needs to be done before there will be confidence in the model ability to simulate phytoplankton, zooplankton and bacteria at sub weekly timescales. In terms of seasonal timescales, the model captures the phytoplankton succession when diatoms and flagellates dominate the system, but performs less well when dinoflagellate blooms are dominant. The evaluation provides a benchmark for future model development, and highlights the importance of data collection for model validation and the need to expand the range of biological variables sampled. The potential for coastal observatories to play a key role in the future development of marine ecosystem models is discussed.