Using Atlantic haddock (Melanogrammus aeglefinus) as bioindicators in sea disposal mining impacted fjords

Sea disposal of mine tailings in fjords is a controversial issue. The Arctic fjord Repparfjorden is a historic, sub-marine deposit site for mine tailings (1972-1978) and is currently at risk of being one again. Sea disposal of mine tailings has potential effects on concentrations of toxic elements in marine biota. Therefore, we mapped concentrations of elements from biota in the impacted Repparfjorden and a reference fjord, Revsbotn, without a sea disposal point source of pollution. Atlantic halibut (Hippoglossus hippoglossus), Atlantic haddock (Melanogrammus aeglefinus), Atlantic cod (Gadus morhua), and blue mussel (Mytilus spp.) were sampled at all stations. Based on our sampling, Atlantic haddock had the most pronounced differences in element concentrations between the impacted and reference fjord ecosystems. Concentrations of lead, chromium, arsenic, iron, copper, and selenium were significantly higher in both Atlantic haddock muscle and liver, manganese was only higher in muscle, and nickel, silver, and zinc were higher in liver from Repparfjorden, compared to the reference fjord. Chromium, nickel, and lead reached concentrations of concern according to the Norwegian PROREF system, and less systematic differences were observed between sampling stations for other species. Consequently, we suggest that Atlantic haddock can be used as an effective bioindicator in mining waste sea disposal impacted fjord ecosystems. Atlantic haddock element concentrations may also be used as a baseline to track legacy pollution impacts and pathways including climate change effects. Our study also underscores the importance of using organ-specific sampling approaches to understand and estimate recent and long term pollution exposure dynamics.