Molecular response of a coral reef fish (Acanthochromis polyacanthus) to climate change

Abstract

Marine ecosystems are already threatened by the effects of climate change through increases in ocean temperatures and pCO2 levels due to increasing atmospheric CO2. Marine fish living close to their thermal maximum have been shown to be especially vulnerable to temperatures exceeding that threshold, and even relatively small increases in elevated pCO2 levels have led to behavioral impairments with amplified predation risks. These ongoing threats highlight the need for further understanding of how these changes will impact fish and if any potential for adaptation or acclimation exists. The coral reef fish, Acanthochromis polyacanthus, has been well studied in response to singular environmental changes both through its phenotype and molecular expression profiles within and across generations. However, key questions regarding transgenerational heritability and molecular responses to multiple environmental changes have not been addressed. To further understand A. polyacanthus I examined the mechanisms behind heritability of behavioral tolerance to elevated pCO2 in an attempt to determine the maternal and paternal contributions to this phenotype. There was a strong impact of parental phenotype on the expression profiles of their offspring regardless of environmental exposure. Offspring from both parental pairs expressed mechanisms involved in tolerance to ocean acidification suggesting this phenotype is reliant on input from both parents. Creation of a new proteomic resource, a SWATH spectral library, delivered a closer examination of the link between phenotypic and expression changes. Analysis on different constructed libraries led to the use of an organism whole library combined with study specific data to analyze proteomic changes in A. polyacanthus under the combined environmental changes of ocean acidification and warming. With direct comparisons to transcriptomic changes in the same individuals I identified an additive effect of elevated pCO2 and temperature associated with decreases in growth and development. However, a strong role of parental identity on the expression profiles of offspring reinforced the high genetic variability of this species. This thesis provides novel insights into the heritability of phenotypic traits and the molecular responses to combined stressors in A. polyacanthus, as well as presenting a new resource for proteomic studies in this fish and other non-model species.