Abstract
Humans have profound effects on the structure and functioning of biological communities, and these are often manifested at the scale of the food web. We propose to manipulate a well characterised quantified food web for which we have highly resolved data, by altering the availability and quality of the food at the base of the web. This complements the data we have already obtained on a top-down manipulation of the same system where we introduced a new top predator. The proposed research will stimulate algal production in the steam by ameliorating light limitation thereby increasing the relative (and absolute) importance of autocthonous pathways in the food web. We will explore a range of responses across multiple levels of biological organisation, from population dynamics of individual species to ecosystem processes and whole stream metabolism. Further we will use these empirical data to inform and develop new theoretical models that link metabolic theory and ecological stoichiometry in food webs.