Acclimatization Drives Differences in Reef-Building Coral Calcification Rates

Abstract

Coral reefs are susceptible to climate change, anthropogenic influence, and environmental stressors. However, corals in Kāneʻohe Bay, Hawaiʻi have repeatedly shown resilience and acclimatization to anthropogenically-induced rising temperatures and increased frequencies of bleaching events. Variations in coral and algae cover at two sites—just 600 m apart—at Malaukaʻa fringing reef suggest genetic or environmental differences in coral resilience between sites. A reciprocal transplant experiment was conducted to determine if calcification (linear extension and dry skeletal weight) for dominant reef-building species, Montipora capitata and Porites compressa, varied between the two sites and whether or not parent colony or environmental factors were responsible for the differences. Despite the two sites representing distinct environmental conditions with significant differences between temperature, salinity, and aragonite saturation, M. capitata growth rates remained the same between sites and treatments. However, dry skeletal weight increases in P. compressa were significantly different between sites, but not across treatments, with linear mixed effects model results suggesting heterogeneity driven by environmental differences between sites and the parent colonies. These results provide evidence of resilience and acclimatization for M. capitata and P. compressa. Variability of resilience may be driven by local adaptations at a small, reef-level scale for P. compressa in Kāneʻohe Bay.

Gene expression plasticity facilitates acclimatization of a long-lived Caribbean coral across divergent reef environments

“…Of the surviving corals in this experiment, FR-sourced corals transplanted to the NS exhibited reduced calcification (Fig. 2B), which is consistent with previous work transplanting corals to more marginal sites 28,81 . This suggests that while some corals may be able to survive in these NS environments, it may come at a physiological cost 71 .…”

Corals that survive repeated thermal stress show signs of selection and acclimatization

“…Signs of coral acclimatization are widespread, having been documented in Australia [ 42 , 43 ], Hawai‘i [ 44 , 45 ], Kenya [ 46 ], the Maldives [ 47 ], Malaysia [ 48 ], Palau [ 35 ], the Persian Gulf [ 49 ], and the Red Sea [ 50 ]. However, the cumulative stress of repeated bleaching is non negligible, and can reduce coral physiological performance over time [ 51 , 52 ] rather than induce acclimatization.…”

From the microbial to the mechanical : environmental impacts on coral nitrogen cycling, microbial communities, and skeletal properties

“…Future insights into skeletal properties and mechanisms of biomineralization and will likely improve our ability to use coral skeletons as proxies of environmental change and reef health across a range of disciplines. Bulk skeletal properties, such as density and linear extension, are often used as metrics of coral health (Barnhill et al, 2020;Ferrari et al, 2017;Lough and Cooper, 2011). However, such measurements do not account for the structural quality of the skeletal material, such as changes in crystal organization, porosity, or organic content, and may not be reliable metrics (Fantazzini et al, 2015;Edinger et al, 2000).…”