Damages on arctic seabird feathers: Exposure to low sulphur fuel oils is comparable to exposure to conventional oil.

New fuel oils with low content of sulphur are entering the market due to recent international regulations on the sulphur content. These oils show large variations in properties, but many have high pour points, low dispersibility and low evaporation, important for oil spill consequences. Though oil spills may be mitigated by e.g. in-situ burning, remaining residues may still be harmful for wildlife, particularly seabirds. Here, we quantified weight increase and clumping of barbules using the Amalgamation Index [AI] on seabird feathers following exposure to three different low sulphur fuel oils (ULSFO - Ultra Low Sulphur Fuel Oil, WRD - Wide Range Diesel and HDME - Heavy Distillate Marine ECA) and related burn residues. The results were compared to damages from a traditional oil type (Arctic Gas Oil [AGO]) and controls. Only oil film exposures ≥2.6 μm resulted in weight increases significantly (p < 0.05) higher than the controls. For these exposures the most severe weight increases were seen for ULSFO, ULSFO residue and WRD residue. From the measurements of feather microstructure damages, we found that AGO and HDME resulted in the lowest AI and the residues resulted in the highest AI. Overall, within the experimental exposure range we did not find clear indications that the negative effects on feathers of the new low sulphur fuel oils are particularly worse than AGO. We found that the tested burn residues will most likely cause most severe damage, whereas WRD and ULSFO produce intermediate damage and AGO and HDME result in the least damage.