Upwelling-level acidification and pH variability moderate effects of
ocean acidification on brain gene expression in black surfperch
(Embiotoca jacksoni), a temperate fish with no pelagic larval stage
Abstract
Acidification-induced changes in cognitive function and behavior have
recently been documented in tropical marine fishes, raising concerns
about related shifts in species interactions. Here, we investigate
whether similar patterns of broad neurological impacts are observed in a
temperate Pacific fish that experiences regular and often large shifts
in environmental pH due to upwelling events and other natural phenomena.
In two manipulative laboratory experiments, we tested the effect of
acidification, as well as pH variability, on gene expression in the
brain tissue of a common temperate kelp forest/estuarine fish, Embiotoca
jacksoni. We found that patterns of global gene expression in brain
tissue differed significantly across pH level treatments. Additionally,
differential gene expression analysis and gene set enrichment analysis
identified significant differential expression of specific genes and
gene sets both in comparisons of static pH level treatments as well as
in static vs. variable pH treatment comparisons where mean pH was
consistent. Enriched gene sets included those related to ion transport,
signaling pathways, mRNA processing and splicing, and epigenetic
regulation of gene expression, among others. Importantly, we found that
pH variability decreased the number of differentially expressed genes
detected between high and low pH treatments, and that the
inter-individual variability in gene expression was significantly
greater in variable pH treatments than static treatments of the same
mean pH. By demonstrating a broad shift in brain gene expression, these
results provide important confirmation of neurological impacts of
acidification in a temperate fish species, which are likely to translate
to shifts in behavior. This study also provides critical insight into
the potential of natural environmental variability to mediate the
impacts of ocean acidification.