Two research projects were initiated in 2013 and 2017 with the aim of investigating whether otoliths from shorthorn sculpin can be used as a pollution archive with heavy metals in Arctic areas. Otoliths are small calcareous structures in the inner ear of fish that function as an important part of the sensory system and consist of more than 96% calcium. However, small amounts of heavy metals, such as lead, zinc, cadmium and copper, can be incorporated into the calcium structure. The otoliths grow in step with the fish's growth, like the annual rings on a tree, and thus information can be stored about the heavy metal load in the environment where the fish has lived.

New analytical techniques have made it possible for even very small concentrations of heavy metals to be measured in such solid calcareous materials with a fine spatial resolution. The most commonly used analysis method for doing this is called Laser Ablation Inductively Coupled Mass Spectrometry. Using this method, a precise section through the annual layers in the otolith is scanned with a thin laser beam. The laser beam continuously brings a quantity of material into the gas phase, which is immediately analyzed for elemental composition using a mass spectrometer. Measuring the heavy metal concentrations in the annual layers of the otolith combined with dating the annual layers makes it is possible to determine both the age of the fish and probably also at what point in time it may have been exposed to heavy metal pollution.

The project is focused on otoliths from shorthorn sculpins, as the shorthorn sculpin is considered the most stationary fish in the Greenland fjords and, thus, the most suitable for monitoring pollution from point sources such as mines. Shorthorn sculpins were collected at the former lead-zinc mine at Maarmorilik and in Nuuk Fjord in 2012, 2013 and 2017. The results show that particularly lead is embedded in the annual layers of the otoliths and, thus, the method can be useful for investigating year-to-year variation in the fish's lead uptake and when any lead contamination has occurred back in time during the fish's life span. Thus, the otoliths constitute a valuable supplement to other sample types from fish, such as liver, muscle and blood, each of which can contribute to knowledge about the fish's exposure and absorption of environmental pollutants and, thus, the pollution in the area. Two scientific articles have been published in connection with projects (DOI 10.1007/s11270-015-2605-1 and https://doi.org/10.1016/j.envres.2020.109194, respectively).