Evaluating the Adaptation of a Predictive Model

An ecologist models the sudden collapse of a fish population after a certain level of river pollution is reached. They base their model on an economic concept originally used to describe a situation where a small change in market sentiment triggers a rapid, self-reinforcing crash in asset prices. In this adaptation, what does the 'river pollution level' that triggers the collapse correspond to in the original economic model?

An economist's model for a speculative market bubble, which describes a rapid, unsustainable increase in asset prices followed by a sudden collapse, is being adapted to explain a sudden algal bloom in a lake. Match the key component from the economic model (Term) with its analogous component in the new environmental model (Definition).