The implementation of the ecosystem module of a coastal environmental model: Port Phillip Bay, Australia

When implemented as a computer program, an ecosystem model is only a part of a larger programming environment. This programming environment includes other programs, non-model program components, program design rules, data files, and associated analysis analytical tools. These components should be divided to allow programmers to focus on their areas of expertise, but must then be rejoined in such a way as to minimise debugging and execution overheads. We describe this larger programming environment as it surrounds a model of the ecosystem of Port Phillip Bay, Australia. The ecosystem model requires a transport model to allow spatial modelling; this transport model uses currents from a computationally intensive hydrodynamic model. Implementation of the ecosystem model also requires non-model code, such as routines to initialise parameters or the integration method. Their design determines program reliability and performance. A modular structure allows different parts of the model to be independently modified; this makes for efficient programming. We describe formal design rules used to enhance readability and information content of the model’s parameter names. To execute, the model must access data files and a record of the run must be kept — a Unix shell program serves both these functions. The data files may require software tools for generation or manipulation. Output from the model also requires post-processing for visualisation and analysis. The model is thus only a part of a network of software, whose development must be coordinated to ensure reliability and efficiency. Ó 2000 Published by Elsevier Science Ltd. All rights reserved.