This mass-balance model predicts trophic magnification factors (TMFs) in aquatic food webs for up to 7 species (Excel version) or 9 species (VB version). The species present represent pelagic and demersal species from a Lake Ontario food web. The Excel spreadsheet version includes three models present in separate sheets to represent a pelagic food web, a demersal food web, and a combined pelagic and demersal aquatic food web. Users can input chemical properties for a particular chemical as well as its concentration in the water and sediment. Properties related to the water, metabolism and growth rate constants, species properties including size, lipid content, and Q (i.e., ratio of input diet rate constant to output egestion rate constant) can be inputted or altered from default values. Diet preferences for all species can be inputted as desired and trophic levels (TL) can be assigned for the lowest level species, which are in equilibrium with the surrounding environment. The dietary preference of each species is expressed in the form of a predator/prey matrix. Species and environmental properties can be edited or replaced.
The output gives the prevailing concentrations throughout the foodweb as well as detailed uptake/clearance data for each species. The Excel version features new TMF calculations for the food web. This model can be used to calculate TMFs and also to explore implications that various environmental factors may have on TMFs. Some examples include a chemical's log KOW value, organism size, lipid content, Q, dietary preferences and food web branching, metabolism, growth rate, differences between sediment and water concentrations, and spatial differences in feeding.
Features of the Aquatic FoodWeb and TMF Model
- Permits temporary additions/changes of each item and their properties to a simulation
- Permits permanent additions, changes and deletions of items and their properties in each database
- Displays and prints the FoodWeb model calculations, as performed by the program
- Allows the printing of simulation tables and the summary diagram
- Allows the program results to be saved as a comma separated value text file, easily viewed with standard spreadsheet software
- Provides a species list and predator-prey feeding matrix based on data from Lake Ontario
- Provides default values for environmental and species properties
- Treats any neutral organic chemical
- Accounts for uptake and loss due to respiration, diet, metabolic biotransformation, and growth dilution
- Includes guidance for choosing input values, and more in-depth information available in the publications
- Wet-weight and lipid-normalized concentrations and biomagnification factors (BMFs) allows for comparison between values
- Includes pelagic-only, demersal-only, and pelagic/demersal combined food web models (Excel version only)
Based on the following publications:
- Mackay, D., Celsie, A.K.D., Arnot, J.A., Powell, D.E. “Processes influencing chemical biomagnification and trophic magnification factors in aquatic ecosystems: Implications for chemical hazard and risk assessment”. Chemosphere. 154, 99-108, 2016.
- Mackay, D., Celsie, A.K.D., Powell, D.E., Parnis, J.M. “Bioconcentration, bioaccumulation, biomagnification and trophic magnification: a modelling perspective”. Environ. Sci.: Processes Impacts. 20, 72-85, 2018.
- Campfens, J., Mackay D. 1997. Fugacity-Based Model of PCB Bioaccumulation in Complex Aquatic Food Webs. Environ. Sci. Technol. 31: 577-583.
The required input data are:
Chemical Properties
- Chemical name
- Molar mass
- Henry's law constant (an arbitrary value is acceptable if unknown)
- Log KOW
- Sediment/water fugacity ratio (default value supplied)
Lake Properties
- Suspended particulate matter content in water
- Volume fraction sediment solids
- Organic carbon content of suspended matter and sediment particles
- Densities of solids
Food Web Properties
- Organism name, volume, lipid volume fraction
- Organism biotransformation half-life, digestion rate, growth rate
- Organism feeding rate, fractional respiration rates (water and sediment), gut absorption efficiency parameters (water and lipid)
- Dietary preferences as a feeding matrix
Environmental Concentrations
- Chemical concentration in the water column and the sediment
Model output includes:
- Water, sediment, and organism fugacities
- Organism Z-values and D-values
- Organism rate constants
- Organism concentrations (wet-weight and lipid-normalized)
- Bioconcentration Factors (BCF)
- Bioaccumulation Factors (BAFs)
- BMFs (wet-weight and lipid-normalized in Excel version)
- Organism trophic levels
- TMFs (wet-weight and lipid-normalized in Excel version)
- Graph of organism fugacity vs. TL used to calculate TMF (in Excel version)
Please read the Software License before downloading the software. Use of the software constitutes your agreement to abide by the terms and conditions set out in the license agreement. Please report any problems to Prof. Mark Parnis.