Mercury tends to accumulate through the foodweb, causing high levels in birds for instance. Since seabirds feed close to their breeding colony (during the period of egg formation), prolonged monitoring of mercury levels in seabird eggs can reveal trends in local contamination.
Regulatory action to reduce discharges, emissions and losses of mercury to the environment has been taken. Therefore levels of mercury in sea birds should begin to decline towards background levels.
The aim is to achieve a low level of mercury in sea bird eggs by reducing mercury inputs to the sea.