Physiological temperature adaptations and climate change: an integrative approach in fish.

Important results from the project

The objectives of this project were to provide unique information on physiological and metabolic adjustments to chronically elevated temperature in fish expected to result from ongoing global warming. We used two different approaches to achieve these objectives: a laboratory acclimation and a field work in an experimental facility (the Biotest enclosure at Forsmark). We then performed several experiments on these fish at the cell level including oxygen consumption by mitochondria, enzymatic activities of several metabolic pathways as well as genetics and genomics experiments.

Expected long term effects

We found that fish from the Baltic sea living at around 16 degrees celsius, have depressed mitochondrial respiration when maintained at 23 degrees celsius for 8 months in the laboratory when compared to fish from the Biotest put at their natural temperature (23 degrees celsius). However, our in situ experiments on fish collected in the field at Forsmark showed that fish from the Baltic sea (at 16 degrees) have the same depressed mitochondrial respiration and this decrease was not related to differences in mitochondrial DNA, in gene expression or in enzymatic activities.

Approach and implementation

This suggests that fish from the Biotest might have adapted their mitochondrial metabolism to higher temperature. When migrating from the Baltic sea at 16 degrees to the Biotest at 23 degrees, the fish will undergo a remodeling of their mitochondrial metabolism. This remodeling is not related to genetic or genomic changes and seems to affect only the mitochondrial metabolism, suggesting that the ability of mitochondria to tolerate different temperatures is a crucial limitation for the organism and might drive adaptations in the context of climate change.