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2N - Field Studies (MOP/129) Comparison of free-ranging zooplankton and zooplankton sampled from seabirds stomachs: organochlorine concentrations and patterns. Borga, Katrine1, Gabrielsen, Geir1, Skaare, Janneche 2, 3, 1 Norwegian Polar Institute, Tromsoe, Norway2 Norwegian School of Veterinary Science, Oslo, Norway3 National Veterinary Institute, Oslo, Norway ABSTRACT- To investigate the use of predators stomach contents to measure the load of chlorinated pesticides and PCBs in free-ranging prey, the two zooplankton species Thysanoessa inermis (euphausiids) and Parathemisto libellula (amphipods) were collected simultaneously from the water column and from the seabird Brunnichs guillemot/thick-billed murre (Uria lomvia)s stomach (from crop to proventriculus). The organochlorine compounds concentrations and relative proportion of PCB-153 generally did not differ between the two sampling methods (p>0.01), indicating that the organochlorines in stomach-sampled prey were not yet affected by mechanical, chemical and bacterial degradation. In addition, similar organochlorine concentrations and pattern in free-ranging and stomach-collected prey suggest that Brunnichs guillemots feed randomly on the zooplankton population, and that the contaminant level in Barents Sea zooplankton does not influence their behaviour to change the vulnerability to predation. In conclusion, the organochlorine concentrations and pattern in zooplankton collected from seabirds stomach correspond with levels in free-ranging prey. Key words: predation vulnerability, diet, digestion, Arctic |
