Persistent chemicals that are also toxic, such as organochlorines, may affect all aspects of an ecosystem. For instance, the reproduction of seabirds may be affected by eggshell thinning, making them vulnerable to damage, or embryos may die. Some of these chemicals have been banned, and their content in seabird eggs may reflect the rate at which the level of these persistent chemicals in the marine environment decreases. The aim is to reduce the levels of organochlorines in the marine environment, and as such in seabirds.
The level of organochlorines in seabird eggs can serve as an indicator since the level can demonstrate results of efforts to reduce environmental inputs.