() Seabirds as transport vectors for persistent organic pollutants (POPs) to Lake Ellasjoen, Bjornoya (Bear Island), Norway.
Evenset, A1, Christensen, G.N.1, Kallenborn, R.2, Herzke, D.3, 1 Akvaplan-niva, Tromsoe, Norway2 The Norwegian Institute for Air Research, Kjeller, Norway3 The Norwegian Institute for Air Research, Tromsoe, Norway
ABSTRACT- High concentrations of persistent organic pollutants (POPs) have been measured in sediment and biota from Ellasjoen, a lake located on Bjornoya (Bear Island) in the Barents Sea. In Lake Oyangen, located only 6 km north of Ellasjoen, levels of POPs are several times lower. There are several differences between the lakes that may have led to the differences in contamination status. One of the most important differences is the number of seabirds occurring around the lakes. Large colonies of seabirds (mainly kittiwake (Rissa tridactyla), little auk (Alle alle) and glaucous gull (Larus hyperboreus) are situated close to Ellasjoen, while there are few seabirds around Oyangen. The seabirds feed in the marine environment, and deposit large amounts of guano (excrements) directly into Ellasjoen or in the catchment area of the lake. There are two ways in which input from seabirds can lead to higher levels of POPs in Ellasjoen: 1) a change in trophic state as a result of nutrient loadings or 2) direct input of POPs through allochthonous material (mainly guano). The effect of guano on the Ellasjoen food-chain has been demonstrated through analyses of stable isotopes of nitrogen. The d15N-values are significantly higher in biota from Ellasjoen than in corresponding samples from Oyangen. This is probably caused by utilisation of nitrogen originating from seabird guano. Analyses of guano from the three seabird species that are important around Ellasjoen have revealed elevated levels of POPs, and the seabirds will therefore transport contaminants from the marine to the limnic ecosystem. Contaminants that are transported by seabirds have gone through one or more bioaccumulation cycle before they are deposited in the limnic ecosystem. Bioaccumulation processes alter the contaminant pattern (increase concentrations of the most persistent compounds) and increase concentrations. Organisms from Ellasjoen have a higher share of the most persistent POPs than organisms from Oyangen. In Oyangen the composition of POPs in the whole lake system seem to reflect atmospheric deposition as a contamination source. The high levels of POPs in Ellasjoen, the differences in contaminant patterns and stable isotope ratios between Ellasjoen and Oyangen, as well as the elevated levels of POPs in guano indicate that input from seabirds represent a significant source for POPs to Ellasjoen.
Key words: guano, Bjornoya, persistent organic pollutants, stable isotopes