Powerful analysis tools for conducting system-wide budgets and interrogating controls on process variabilities.
World-leading phytoplankton, pathogen and geochemistry sub-modules.
Overview
CAEDYM (Computational Aquatic Ecosystem Dynamics Model) is a process-based model of the major biogeochemical processes influencing water quality. It optionally models inorganic particles, oxygen, organic and inorganic nutrients (C, N, P and Si), multiple phytoplankton and zooplankton groups, fish and bacteria. Recent developments also include optional modules for benthic organisms (e.g. clams, macroalgae), pathogens and microbial indicator organisms, and a generic geochemical module capable of simulating pH, aqueous speciation (including metals), precipitation/dissolution reactions and sediment diagenesis. Configuration is flexible so that the modeller can focus on the processes of interest. CAEDYM has been applied to a variety of aquatic systems including wetlands, lakes/reservoirs, rivers, estuaries and the coastal ocean; it is currently coupled to three hydrodynamic drivers, but may be coupled to other hydrodynamic codes through a common interface module.
CAEDYM can be configured as a 'N-P-Z' (nutrients-phytoplankton-zooplankton) type, but it also includes comprehensive process representation of the cycles of carbon, oxygen, nitrogen, phosphorus and silica. Further, suspended solids, phytoplankton, the microbial loop and other optional benthic and pelagic biological state variables can be configured. Hence, CAEDYM is more advanced than traditional N-P-Z models, as it is a general biogeochemical model that can resolve species- or group-specific ecological interactions. CAEDYM is presently linked to three hydrodynamic models including the Dynamic Reservoir Simulation Model (DYRESM), the Estuary, Lake and Coastal Ocean Model (ELCOM), and the Dynamic River Model (DYRIM). DYRESM is a one-dimensional model used for predicting vertical density stratification in lakes and reservoirs. ELCOM is a three-dimensional hydrodynamic model applicable to lakes, reservoirs and estuaries. Recently, CAEDYM has been coupled to DYRIM (Lagrangian river-floodplain model) to simulate biogeochemical processing in rivers. Time and space scales of interest dictate the selection of the hydrodynamic driver (DYRESM, ELCOM, DYRIM). CAEDYM can potentially be linked to a simple non-steady state Vollenweider-type model (i.e. no spatial dimension) or two-layer model (e.g. mixed layer and hypolimnion) for lakes and reservoirs, in addition to 1D, 2D or 3D hydrodynamic drivers.
One of the objectives during CAEDYM development was flexible ecological configuration capability that could be tailored for specific applications. CAEDYM operates on any sub-daily time step to resolve algal processes (diurnal photosynthesis and nocturnal respiration), but is generally run at the same time interval as the hydrodynamic model. Algorithms for salinity dependence are included so that a diverse range of aquatic settings can be simulated.
Recent CAEDYM developments include a sophisticated geochemistry module. This allows the user to input any inorganic species of interest (eg. ions, metals) and account for any pure phases (ie. mineral precipitates), and CAEDYM will solve the complete system based on a thermodynamic equilibrium. The geochemistry is dynamically influenced by biology, such that nutrient uptake and organic matter mineralization will dynamically effect the aqueous speciation and pH. In addition, a comprehensive sediment diagenesis model has been included within CAEDYM, which will allow for dynamical prediction of nutrient and metals fluxes at the sediment water-interface. A further development currently implemented and being tested is the inclusion of heavy metals in the organic cycles (in particular for Zn and Cd, and eventually Hg), such that metals may be cycled through phytoplankton, and then recycled during detrital breakdown. The metals also toxically impact on biological growth rates. Other developments include development of detailed sub-models for benthic organisms (eg. macroalgae, bivalves), and a model of fish egg and larval fate.
News
2/6/2007
New online CAEDYM parameters database for phytoplankton - Click on the 'Parameters' link in the menu for details
1/6/2007
CAEDYM v3.1 nears completion - New developments as part of the new CAEDYM release are currently being finalised. Developments include a dynamic sediment diagenesis model, geochemical model, fish eggs and larave dispersion model, a new model for Cldophora, and numerous other enhancements. Contact Matt Hipsey for more info.
