Geographic and temporal variation in persistent pollutants in Australian humpback and snubfin dolphins

We investigated between 2014 and 2016 the concentrations of PCBs, DDTs and HCB and trace elements in blubber and skin samples of Australian humpback and snubfin dolphins collected from the Fitzroy River estuary and Port Curtis, Queensland, Australia. The concentrations of PCBs, DDTs and HCB from this study were compared with results from samples collected in 2009 and 2010 from the same areas. Our results showed that the concentrations of PCBs, DDTs and HCB have increased over time. A large proportion (~68%) of the sampled population accumulated organochlorines contaminants above thresholds over which immunosuppression and reproductive anomalies are known to occur. Results also suggest a general enrichment of some trace elements above natural levels in humpback and snubfin dolphins from the Fitzroy River estuary and Port Curtis. Extensive flooding in adjacent catchments is the most likely primary factor responsible for increased distribution and bioavailability of these contaminants into coastal waters. Land-based pollution from the adjacent catchments is an ongoing threat to coastal systems and particularly for top predators such as dolphins in the Great Barrier Reef. Climate change models predict increasing frequency and intensity of extreme rainfall events that will impact coastal Queensland and the Great Barrier Reef. Reduction of land-based persistent pollutants into coastal waters of the Great Barrier Reef will be critical for the health and survival of humpback and snubfin dolphins in this region.