Abstract
Few species in the Swedish fauna cause stronger reactions among the general public as cormorants, and these problems have been accentuated with the strong increase in cormorant population during recent decades. Cormorants are often accused of reducing fish populations and destroying the vegetation on nesting islands. While the effect on fish populations have received considerable research interest, little research have been aimed at examining ecosystem effects on nesting islands in the Baltic. In this project we aim to study how the nutrient inflow on cormorant nesting islands affects (i) the flow and accumulation of nutrients (mainly N & P), (ii) the density, diversity and food web structure of plants and arthropods, and (iii) the dynamics of plant-herbivore interactions. To cover the range of effects, we will perform studies on islands without colonies, on active colonies of various nesting density and on abandoned islands. As a framework for interpreting density responses, following the increased nutrient inflow, we will use recent advances in ecological stoichiometry, which is a method for independently describing the resource demand of species based on their elemental composition. To study dynamics, we will quantify density response across multiple years for herbivore species associated with Lythrum salicaria. We will also use experiments, both in the field and in the lab, to establish connections between the nutrient content of plants and life history characteristics.
Sweden