Common Eider and Herring Gull as Contaminant Indicators of Different Ecological Niches of an Urban Fjord System

Abstract

Seabirds like gulls are common indicators in contaminant monitoring. The herring gull (Larus argentatus) is a generalist with a broad range of dietary sources, possibly introducing a weakness in its representativeness of aquatic contamination. To investigate the herring gull as an indicator of contamination in an urban-influenced fjord, the Norwegian Oslofjord, we compared concentrations of a range of lipophilic and protein-associated organohalogen contaminants (OHCs), Hg, and dietary markers in blood (n = 15), and eggs (n = 15) between the herring gull and the strict marine-feeding common eider (Somateria mollissima) in the breeding period of May 2017. Dietary markers showed that the herring gull was less representative of the marine food web than the common eider. We found higher concentrations of lipophilic OHCs (wet weight and lipid weight) and Hg (dry weight) in the blood of common eider (mean ± SE ∑PCB = 210 ± 126 ng/g ww, 60 600 ± 28 300 ng/g lw; mean Hg = 4.94 ± 0.438 ng/g dw) than of the herring gull (mean ± SE ∑PCB = 19.0 ± 15.6 ng/g ww, 1210 ± 1510 ng/g lw; mean Hg = 4.26 ± 0.438 ng/g dw). Eggs gave opposite results; higher wet weight and lipid weight OHC concentrations in the herring gull (mean ± SE ∑PCB = 257 ± 203 ng/g ww, 3240 ± 2610 ng/g lw) than the common eider (mean ± SE ∑PCB = 18.2 ± 20.8 ng/g ww, 101 ± 121 ng/g lw), resulting in higher OHC maternal transfer ratios in gulls than eiders. We suggest that the matrix differences are due to fasting during incubation in the common eider. We suggest that in urban areas, herring gull might not be representative as an indicator of marine contamination but rather urban contaminant exposure. The common eider is a better indicator of marine pollution in the Oslofjord. The results are influenced by the matrix choice, as breeding strategy affects lipid dynamics regarding the transfer of lipids and contaminants to eggs and remobilization of contaminants from lipids to blood during incubation, when blood is drawn from the mother. Our results illustrate the benefit of a multispecies approach for a thorough picture of contaminant status in urban marine ecosystems.

Differences in Trophic Level, Contaminant Load, and DNA Damage in an Urban and a Remote Herring Gull (Larus argentatus) Breeding Colony in Coastal Norway

“…The prepared samples were analyzed using high‐resolution gas chromatography/high‐resolution electron ionization mass spectrometry (GC/EI HRMS; Waters Autospec; HP6890 GC coupled to VG AutoSpec). Further details on the analysis have been described in the supporting information of Thorstensen et al ( 2020 ).…”

“…The instrumental analysis of PFOS was conducted as described by Hanssen et al ( 2013 ) using ultrahigh‐pressure liquid chromatography triple‐quadrupole mass spectrometry (UHPLC‐MS/MS). At NIVA Oslo, the samples were analyzed as described in the supporting information of Thorstensen et al ( 2020 ). Briefly, samples were extracted with acetonitrile, cleaned using graphitized carbon and acetic acid, diluted with ammonium acetate buffer, and analyzed by acquity ultra‐performance liquid chromatography coupled to a Xevo G2‐S Q‐ToF‐HRMS instrument (UPLC; Waters Corporation).…”

Advancing exposure assessment approaches to improve wildlife risk assessment

“…Contaminant concentrations measured in these matrices are extrapolated to whole body concentrations or doses to match the units of available toxicity data to enable risk predictions. However, because species differ in physiology, dietary ecology, and reproductive strategies, conclusions regarding exposure risks vary depending on the matrix sampled and physicochemical properties of the contaminant (Thorstensen et al, 2021). Therefore, it is important to consider multiple proxies of contaminant exposure.…”

Towards Resolving Three Problems in Ecological Parasitology: Parasite Aggregation, Determinants of Parasitism, and Parasite Detoxification of Contaminants

“…The diet of these eider consists primarily of mollusks (mostly bivalves), though also includes arthropods (crabs) and some fish (Hanssen et al, 2003;Laursen and Møller, 2022). Common Eider have been studied extensively; for example, they have been used as a study system for research into foraging ecology (Smith et al, 2023), environmental monitoring of contaminants (Thorstensen et al, 2021), and -perhaps most of all -breeding ecology (Mosbech et al, 2006;Love et al, 2010;Sénéchal et al, 2011;Descamps et al, 2011). Their value as a study system for these and other research questions concerning arctic nesting birds is in part due to their relative ease of capture and marking, allowing individuals to be tracked across years (Provencher, 2016).…”