Sentinels of plastic: Monitoring plastic pollution in the sub-Arctic ecosystem through fin whales off Iceland

In this study, we investigate the occurrence and magnitude of plastic pollution in the Sub-Arctic ecosystem through the monitoring of several indicative variables in a sentinel organism, the fin whale (Balaenoptera physalus) from the waters off western Iceland. We followed two approaches. The first was the analysis of microplastics in fin whale’s stomach content (n=25, collected in 2018). The second was the analysis of two sets of plastic additives: phthalates in fin whale muscle (n=31, collected along the period 1986-2015), and organophosphate flame retardants (OPFR) in both fin whale muscle (n=20, collected in 2015) and stomach contents (n=10, collected in 2009-2013). We found that the stomach contents, which were composed of krill (Meganyctiphanes norvegica), the mean concentration of microplastics was 0.057 particles per gram of krill, suggesting a fin whale daily intake of 38,646 to 77,292 particles per day. Regarding phthalates, we found that the most abundant compounds were: di-n-butylphthalate (DBP), diethylphthalate (DEP), and bis(2-ethylhexyl) phthalate (DEHP). We did not observe any significant trend in the phthalate concentrations over the 29-year period studied. Regarding organophosphate flame retardants (OPFR) we found the occurrence of seven OPFRs compounds in the fin whale muscle and five in krill, being tri-n-butyl phosphate (TNBP), Isopropylated triphenyl phosphate (IPPP), and Triphenylphosphine oxide (TPPO) the most abundant compounds in both matrices. Our results also support the absence of OPFR krill-to-whale biomagnification as well as the bioaccumulation of these compounds in fin whale tissues. These findings highlight the need for continued monitoring of plastic pollution and its associated chemicals in marine wildlife, particularly in large filter-feeding species such as the fin whale.