Geographic differences in organic contaminants and stable isotopes (δ13C, δ15N) in thick-billed murre (Uria lomvia) eggs from Alaska

Abstract

The contents from thick-billed murre (Uria lomvia) eggs collected at four Alaskan colonies in 2002 were analyzed for organic contaminants and carbon (δ¹³C) and nitrogen (δ¹⁵N) stable isotopes. Contaminant concentrations in the eggs varied from below detection limits to 230 ng g⁻¹ wet mass for 4,4′-DDE in one egg from St Lazaria Island in the Gulf of Alaska. Eggs from this colony generally contained higher levels of contaminants and exhibited significantly different patterns compared to eggs from the Bering and Chukchi seas. Stable isotope values also varied geographically; however, these differences appeared to be related to differences in C and N baselines in the food webs instead of differences in prey. Contaminant and stable isotope correlations were inconclusive, suggesting that better information on regional food web differences and differential offloading of contaminants and stable isotopes to the eggs must be obtained before these kinds of data can be fully incorporated into seabird egg contaminant monitoring programs.