Aquatic Ecosystem Simulator (AES) — a learning resource for biological science students

Project Leader	Dr Peter Randerson
Organisation	Cardiff University
Contact	randerson@cardiff.ac.uk
Partners
Grant type	Teaching Development
Completed	Summer 08
Screen shot of AES

Description

AES provides a flexible learning aid for experimental study in aquatic ecology, separate from the process of mathematical modelling. It simulates the physico-chemical and trophic dynamics of freshwater systems containing functional groups (guilds) of organisms forming planktonic and benthic food webs. Primary production is limited by solar radiation (varies seasonally and spatially) and nutrient supply (via inflow and recycling). Producer organisms comprise green algae, cyanobacteria, diatoms, and aquatic macrophytes, limited by silicate, nitrate, phosphate, and carbon dioxide. Herbivorous and carnivorous zooplankton, benthic invertebrates and fish comprise higher trophic levels. Temporal and spatial variations in conductivity, pH, and dissolved oxygen are also included. The model is calibrated by default to emulate alternative scenarios (mesotrophic-temperate, eutrophic-temperate, hyper-eutrophic tropical, and oligotrophic-arctic systems), and a range of experiments can be performed by manipulating the realistic system variables (e.g. eutrophication, competitive exclusion, climate change, flood impact, and biomanipulation).

AES is operated by on-screen option buttons connected by a flow diagram to assist navigation. Instructions on how to perform hypothesis-driven experiments are presented in text boxes and help windows, so that a conventional handbook is not necessary. Simulation proceeds by numerical integration of 27 differential equations with respect to time. Values of state variables, driving variables, rate processes, and other simulated data at daily intervals for up to five years are output numerically in tables, and graphically as line-graphs, bar-charts, and pyramid-rcharts. Data can be saved as text files and Microsoft Excel spreadsheets for further analysis. Graphs and charts can be saved as bitmap files to be added to Microsoft Word documents. Photographs of typical ecosystems and organisms are included (in response to student demand). AES is pre-calibrated with values of 121 parameters (36 fixed constants; 85 of which can be changed by the user). Randomness, associated with natural biological variation and analytical error is a primary characteristic of all biological data; AES includes an option for some parameters to vary randomly around deterministic values.

We have developed AES with the aim of motivating students and enriching their existing knowledge of ecology as well as developing generic skills (hypothesis testing, problem-solving, enquiry learning, and critical evaluation of quantitative data). It shows the value of a computer model for demonstrating fundamental ecological concepts (biomass pyramids, food chain efficiency, competitive exclusion), and for predicting the impact of anthropogenic activities on a complex aquatic ecosystem (manipulation of trophic status, climate change, and trophic cascades).

Peter Randerson and David Bowker

Get the model

Download the Aquatic Ecosystem Simulator (as .exe file ~17.5 MB)

Download the Help and Suggested Exercises file (as pdf)

Further Links

Article Aquatic Ecosystem Simulator - a full length version with complete references of the article that appeared in Bulletin 23.

Handout from the Swapshop presentation Peter gave at the e-learning event in December 2007.