Elevated CO₂ levels did not induce species- or tissue-specific damage in young-of-year salmonids

The broad objective of our study was to use a histological approach to examine possible tissue-level effects of exposure to elevated CO₂ in freshwater young-of-year salmonids.

To study these effects, young-of-year Arctic Char Salvelinus alpinus, Rainbow Trout Oncorhynchus mykiss, and Brook Trout S. fontinalis were exposed to either control levels of CO₂ (1400 μatm) or elevated levels of CO₂ (5236 μatm) for 15 days. Fish were then sampled for gill, liver, and heart tissues and histologically analyzed.

A species effect was observed for the length of secondary lamellae, as Arctic Char had significantly shorter secondary lamellae than the other species. No notable changes within the gills and livers of Arctic Char, Brook Trout, or Rainbow Trout exposed to elevated CO₂ were observed.

Generally, our results indicated that elevated CO₂ levels over 15 days do not induce catastrophic tissue damage and it is unlikely that fish health would be seriously impacted. Ongoing research dedicated to examining how elevated CO₂ long-term may affect internal tissues of fish will allow for a more comprehensive understanding of how fish may fair with ongoing climate change and in aquaculture facilities.