Here, we communicate a point of departure in the development of aquatic ecosystem models, namely a new community-based framework, which supports an enhanced and transparent union between the collective expertise that exists in the communities of traditional ecologists and model developers. Through a literature survey, we document the growing importance of numerical aquatic ecosystem models while also noting the difficulties, up until now, of the aquatic scientific community to make significant advances in these models during the past two decades. Through a common forum for aquatic ecosystem modellers we aim to (i) advance collaboration within the aquatic ecosystem modelling community, (ii) enable increased use of models for research, policy and ecosystem-based management, (iii) facilitate a collective framework using common (standardised) code to ensure that model development is incremental, (iv) increase the transparency of model structure, assumptions and techniques, (v) achieve a greater Handling editor: Boping Han understanding of aquatic ecosystem functioning, (vi) increase the reliability of predictions by aquatic ecosystem models, (vii) stimulate model inter-comparisons including differing model approaches, and (viii) avoid 're-inventing the wheel', thus accelerating improvements to aquatic ecosystem models. We intend to achieve this as a community that fosters interactions amongst ecologists and model developers. Further, we outline scientific topics recently articulated by the scientific community, which lend themselves well to being addressed by integrative modelling approaches and serve to motivate the progress and implementation of an open source model framework.

The reduction of macronutrients to levels that limit primary production is often a critical element of mitigating eutrophication and reducing the potential for algal blooms. Lake Okaro has remained highly eutrophic despite an intensive catchment and in-lake restoration programme, including implementation of a constructed wetland, riparian protection, an alum application and application of a modified zeolite mineral (Z2G1) to reduce internal nutrient loading. A onedimensional process-based ecosystem model (DYRESM-CAEDYM) was used in this study to investigate the need for further nutrient loading reductions of both nitrogen (N) and phosphorus (P). The model was calibrated against field data for a 2-year period and validated over two separate 1-year periods. Model simulations suggest that the trophic status of the lake, measured quantitatively with the Trophic Level Index (TLI), could shift from highly eutrophic to mesotrophic with external and internal loads of both N and P reduced by 75Á90%. The magnitude of the nutrient load reductions is indicative of a major challenge in being able to effect transitions across trophic state categories for eutrophic lakes.

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