New article published! - Urban seabirds as contaminant indicators
In a new publication, our former master student Helene Thorstensen compared concentrations of legacy persistent organic pollutants (POPs), per- and polyfluoroalkyl substances (PFASs), and Mercury (Hg) in blood and eggs of the herring gull and common eider to assess their roles as contaminant monitoring species in urban environments.
Figure 1: Lipophilic POPs, PFAS, and Hg in urban common eiders and herring gulls. Figure credit: Helene Thorstensen
In the project Environmental Contaminants in an Urban Fjord (Urbanfjord), our group focuses on the monitoring of contaminants in urban seabirds. In our newest article, we study the roles of two seabird species as contaminant indicators in urban marine food webs: the herring gull, a generalist predator, and a commonly used seabird indicator, and the common eider, a benthic-feeding diver.
The publication is written by group member Helene Thorstensen, together with co-authors Anders Ruus (NIVA), Morten Helberg (Østfold University College), Kine Bæk (NIVA), Ellen Katrin Enge (NILU), and Katrine Borgå.
We compare the ecological niche and occurrence of legacy POPs, PFASs, and Hg in blood and eggs of the species from the Norwegian Oslofjord, and find that the common eider represents a mid-trophic predator in the marine food web. The herring gull has a more terrestrial dietary signal than the common eider and likely forages on a mix of marine and terrestrial and anthropogenic items.
Our main discussion points are summed up here:
- The common eider, a benthic mid-trophic predator, represents marine contamination in the urban Oslofjord marine food web better than the opportunistic herring gull, but cannot replace the gull as indicator species.
- The herring gull feeds from terrestrial and anthropogenic sources in addition to the marine food web, and shows lower blood organohalogen contaminants (OHC) concentrations than the common eider, but is an interesting indicator species for the urban environment.
- Egg: blood OHC concentration ratios were >0 in the gull and <0 in the eider, likely resulting from remobilisation of contaminants to the bloodstream during incubation fast in eiders, providing challenges for interpreting results, and illustrating that the matrices should be used in combination.
- There was no clear species difference in PFAS concentrations, with higher concentrations of PFDA, PFUdA and PFHxS in common eider, higher PFTrDA concentrations in herring gull, and no difference between the species for PFOS and PFDoA.