Effects of contaminants on seabirds
Research has revealed that the effects of a contaminant load on glaucous gulls involve changes in the liver enzyme activity, vitamins, hormones, immune system, metabolism and temperature regulation, regulation of genes, egg size, reproduction, behaviour and survival.
Birds with a high content of contaminants suffer disturbances in their hormones which change their breeding behaviour and thus affect the survival of their chicks. In addition, it has been found that the egg itself may be affected by the contaminant load in the mother, resulting in the egg being smaller and having less yolk, thus affecting the chick at the start of its life.
All told, the effects are a great burden for glaucous gulls, particularly in the breeding season. The glaucous gull population on Bjørnøya (Bear Island) has shown a negative development, declining by 60 % since the 1990s.
The ivory gull is even more exposed than the glaucous gull since it feeds at several levels in the food chain, eating zooplankton, small fish and carrion from marine mammals. It therefore consumes fat from marine mammals with high concentrations of contaminants. Studies have shown that eggs containing a large amount of contaminants have thinner shells than normal and therefore break more easily.
As the contaminant level in ivory gulls exceeds that measured in glaucous gull eggs, it is possible that deleterious effects may also occur in ivory gulls, but this has not been investigated.
MOSJ (Environmental Monitoring in Svalbard and Jan Mayen) indicators: