Science-based approach to using growth rate to assess coral performance and restoration outcomes

Abstract

One response to the coral reef crisis has been human intervention to enhance selection on the fittest corals through cultivation. This requires genotypes to be identified for intervention, with a primary basis for this choice being growth: corals that quickly grow on contemporary reefs might be future winners. To test for temporal stability of growth as a predictor of future performance, genotypes of the coral Porites spp. were grown in common gardens in Mo'orea, French Polynesia. Growth was measured every two to four months throughout 2018, and each period was used as a predictor of growth over the subsequent period. Area-normalized growth explained less than 29% of the variance in subsequent growth, but for biomass-normalized growth this increased to 45–60%, and was highest when summer growth was used to predict autumn growth. The capacity of initial growth to predict future performance is dependent on the units of measurement and the time of year in which it is measured. The final choice of traits to quantify performance must be informed through consideration of the species and the normalization that best capture the information inherent in the biological processes mediating variation in traits values.

Colony-Level 3D Photogrammetry Reveals That Total Linear Extension and Initial Growth Do Not Scale With Complex Morphological Growth in the Branching Coral, Acropora cervicornis

“…This suggests that post-outplant growth, rather than nursery growth, can more reliably project the performance of A. cervicornis transplants. However, the moderate correlations seen here, which are similar to the correlations between initial and subsequent growth previously reported for massive species (Edmunds and Putnam, 2020), imply that colony growth is determined by more than just intrinsic growth rate.…”

“…Early growth rate in TLE for Acropora cervicornis was found to be a poor predictor of future growth rate for nurserygrown (O'Donnell et al, 2018) and wild corals (Edmunds, 2017). Similarly, early growth rates for two massive coral species as measured in nurseries explained only a portion of future performance, and the predictive power of these metrics varied over sampling points and traits (Edmunds and Putnam, 2020). The utility of higher order traits, such as SA, V, and V inter , for predicting subsequent growth remains unknown because handling or destructive sampling of outplants is not possible in a restoration context.…”

“…However, the ultimate success of these efforts has been hampered by the inability to predict the performance of coral outplants, given that both genetic and environmental variables can influence survival and growth (Drury et al, 2017;O'Donnell et al, 2017). The ability to use early, non-invasive indicators to quantify outplant success would be beneficial in restoration settings that aim to optimize efforts to repopulate Caribbean reefs (Edmunds and Putnam, 2020;Parkinson et al, 2020).…”

Bleaching resistant corals retain heat tolerance following acclimatization to environmentally distinct reefs

“…Such differences driven by GxE effects within this cohort of bleaching resistant corals create critical challenges in the selection of individuals with desired climate change resistant traits for coral reef restoration efforts, while also accounting for future performance in other important traits. Growth in particular showed a strong GxE effect, and our findings align with recent work cautioning against using growth alone as a predictive trait for future coral performance as it can vary between seasons (Edmunds and Putnam 2020;Edmunds 2017) and heat tolerance in a stressful environment does not correspond with rapid growth in a less stressful environment . In summary, this study indicates that bleaching resistance is not plastic in these species and is thus an informative trait for predicting future coral performance.…”

Applying model approaches in non-model systems: A review and case study on coral cell culture

“…Coral growth, for example, has long been considered as an important performance metric so, traditionally, the rate of linear extension was considered a measure of coral fitness because coral reproduction is based on size [ 155 ]. However, growth has also been demonstrated as highly variable according to parameters such as seawater temperature [ 156 ] and pH [ 155 ], and recent studies have identified limitations of tracking growth as a primary indicator of performance [ 125 , 157 ], with multiple metrics likely a necessity.…”