Food Webs
Conceptual Models
A Food
Web model describes the interconnected feeding relationships between plants and
animals in a particular area. Food Web models are often combined with
contaminant bioaccumulation data, in order to estimate contamination in members
of the food web. A common goal of a Food Web modeling is to predict contaminant
levels in top-level organisms (predators) from known measurements of
environmental contamination.
Figure 1: An example food web model for
aquatic and terrestrial ecosystems. (Copied from the Baseline Ecological Risk
Assessment for the Kalamazoo Superfund Site)
Food Web
models may differ in complexity. A model may seek to characterize all the
potential interactions between species, while other models may limit themselves
to the primary pathways.
Mathematical Models
Mathematical
food web models seek to quantify the transfer of a chemical between members of
the food web. Similar to conceptual models, mathematical models vary in how the
member interrelationships are characterized.
An
explicit food web model seeks to characterize the behavior of every member of
the food web. Often this is difficult to do, because the movement and feeding
behavior of all organisms are not always well understood, and may change over
time due to ecosystem changes. Furthermore, the bioaccumulation of a
contaminant in an organism depends on the specific chemical properties of the
contaminant.
An
alternative to the explicit model is to model a simpler empirical relationship
between the source and the organism of interest. For example, simple
relationships may be used to estimate the occurrence of PCB in carp base on
measurements of PCB in river water or river sediments.
References
- Camp Dresser & McKee, I. (2003). Final (Revised)
Baseline Ecological Risk Assessment: Allied Paper, Inc./Portage
Creek/Kalamazoo River Superfund Site, Michigan Department of Environmental
Quality, Remediation and Redevelopment Division.
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