Physiological and Molecular Responses Suggest Local Adaptation of the Lobe Coral Porites lobata to the Nearshore Environment

Corals in nearshore marine environments are increasingly exposed to reduced water quality, which is the major local threat to coral reefs in Hawaii. Corals surviving in such conditions may have acclimatized and/or adapted to withstand sedimentation, pollutants, and other environmental stressors. Lobe coral () populations from Maunalua Bay, Hawaii showed clear genetic differentiation along with distinct cellular protein expressions between the ‘polluted, high-stress’ nearshore site and the ‘low-stress’ offshore site. To understand the driving force of the observed genetic partitioning, reciprocal transplant and common-garden experiments were conducted using the nearshore and offshore colonies of from Maunalua Bay to assess phenotypic differences of stress-related physiological and molecular responses between the two coral populations. Physiological responses (tissue layer thickness, tissue lipid content, and short-term growth rates) all showed differences between the populations, revealing more stress resilient traits in the nearshore corals. Proteomic responses highlighted the inherent differences in the cellular metabolic state and activities between the two populations under the same environmental conditions; nearshore corals did not significantly alter their proteome between the sites, while offshore corals responded to the nearshore transplantation with increased abundances of proteins associated with detoxification, antioxidant, and various metabolic processes. The response differences across multiple phenotypes suggest that the observed genetic partitioning was likely due to local adaptation of nearshore corals to the nearshore environmental conditions.