Ocean Acidification

Numerous studies have found that elevated CO₂ levels in marine waters induced significant physiological and behavioral effects in fish. In an earlier study of coho salmon (Oncorhynchus kisutch), we observed that elevated CO₂ exposure impaired signaling in the olfactory bulb, through a mechanism likely involving interference of gamma-aminobutyric acid (GABA) signaling. However, the effects of elevated CO₂ may be species-specific, and there have been few studies addressing the effects of elevated CO₂ on benthic fish. In the current study, we investigated the effects of elevated CO₂ exposures on the deep-water benthic species, sablefish (Anoplopoma fimbria). Sablefish were exposed to three different levels of CO₂ (700, 1600 and 2700 µatm) for two weeks, followed by behavioral, neurophysiological and gene expression analysis of the olfactory system. Analysis of behaviors mediated by food odors, including swimming activity and food strikes did not differ between fish maintained under elevated or control CO₂ conditions. Similarly, electro-olfactogram recordings of odorant signaling did not differ among treatment and controls. mRNA expression patterns of olfactory bulb genes that were altered in coho salmon exposed to elevated CO₂ levels, were similarly examined in sablefish. Sablefish mRNAs encoding genes involved in GABA-mediated olfactory bulb signaling were generally unaffected by high CO_2, but aldh9a1, an enzyme involved in the synthesis of GABA, was elevated by high CO₂. The results of our study contrast other studies demonstrating adverse effects of elevated CO₂ in pelagic fish, but support differences among fish species to susceptibility to elevated CO₂, potentially associated with life history traits.

Williams C. R., Gallagher E. P., McElhany P., Busch D. S., Maher M. T. & Dittman A. H., in press. Tolerance to future elevated CO₂ conditions in sablefish (Anoplopoma fimbria), a deep-water benthic dwelling fish species. Journal of Comparative Physiology A. Article.