Are we restoring coral reefs for today or for tomorrow?

Elise Keister wrote this post as a final project for Stacy Krueger-Hadfield’s Science Communication course at the University of Alabama at Birmingham. Elise studies the impact of climate change on coral as a PhD student in Dr. Dustin Kemp’s lab. Elise completed a B.S. in Biology and Marine Science at the University of Miami’s Rosenstiel School of Marine and Atmospheric Science (RSMAS) and then was involved in a myriad of research projects ranging from damage assessment for the Deepwater Horizon Oil Spill to the impact of thermal stress on Floridian coral species. Elise is passionate about working with these susceptible invertebrates that play such a foundational role in coral reef ecosystems. She hopes to determine some mechanisms coral utilize to promote resiliency to high temperatures, as this will only become more common in the decades to come. Elise tweets at @elise_keister.

Coral reefs are in trouble.

Headlines reveal dire situations. Alarmingly, this will only become more challenging in the coming decades with extreme temperatures and increasing ocean acidity.

The predicament coral reefs find themselves in has been recognized around the world with hundreds of organizations playing a more active role assisting coral restoration.

Such restoration efforts utilize methods that facilitate rapid growth and then out-plant those coral fragments to nearby reefs to encourage proliferation. Fig. 1 shows one such method: a restoration ‘tree’.

Fig. 1. A restoration ‘tree’ of Acropora cervicornis, common to Floridian reefs. © Wikipedia

Acropora cervicornis, commonly known as staghorn coral, historically played an essential role as a framework species. It literally lays the foundation of coral reefs in the Florida Keys. Sadly, this species has suffered a 95% loss since the 1970s (Weil et al., 2003) as a result of a combination of disease, pollution, and high temperatures. The role of disease negatively impacting this species is still not fully understood and more work needs to be done. Due to the rapid decline and reduced populations throughout the Caribbean, A. cervicornis was listed as Critically Endangered by the International Union for Conservation of Nature and Natural Resources (IUCN)

Three restoration nurseries in south Florida are trying to increase A. cervicornisabundance on local degraded reefs: Miami Nursery, Upper Keys Nursery and the Lower Keys nursery (Fig. 2). In a recently published article, Parkinson and colleagues (2018) investigated differential transcriptional responses between nurseries and genotypes within these three nurseries to heat and cold stress. The goal was to try to identify biomarkers of individuals that have increased resilience to warm or cold temperature extremes and potentially use these to enhance restoration efforts.

Fig. 2.  A. cervicornis Floridian nurseries utilized by Parkinson et al., 2018 

Overall, a high degree of variation in gene expression was observed within and among genotypes, which can be attributed to nursery of origin, host genotype, stress type and time point sampled. Furthermore, there were inconsistencies in correlations between gene expression and overall coral performance over the sampling period. Only genes that have been previously annotated were included in this study, which may explain why this study was unable to identify many reliable biomarkers. Four biomarkers were identified as being capable of indicating heat stress, which also appeared to be upregulated consistently in hot conditions across all nurseries.

Additionally, adding genotypes with biomarkers that indicate less heat stress to restoration programs has the potential to expand the impact of these efforts by focusing on more resilient genotypes; however, four biomarkers is likely not enough to have a significant impact.

The next big question: Is this enough to revitalize reefs of today when corals have been around for thousands of years and only recently started to collapse? Will coral restoration allow for already stressed ecosystems to withstand more drastic changes predicted for the coming century and beyond?

We may only have definitive answers to these questions in 100 years, but asking these questions and remaining cautiously optimistic may be the best approach. There is still so much we don’t understand about coral resiliency to rapid environmental change, as this is change is occurring at rates unprecedented in the geologic record.    

References

Weil, E. et al. (2003) Distribution and status of Acroporid coral (Scleractinia) populations in Puerto Rico. Acropora Workshop: Potential Application of the US Endangered Species Act as a Conservation Strategy.

Parkinson, J.E. et al. (2018) Extensive transcriptional variation poses a challenge to thermal stress biomarker development for endangered corals. Molecular Ecology 27: 1103-1119

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About Stacy Krueger-Hadfield

I am a marine evolutionary ecologist interested in the impacts of seascapes and complex life cycles on marine population dynamics. I use natural history, manipulative field experiments and population genetic and genomic approaches with algal and invertebrate models in temperate rocky shores,estuaries and the open ocean.
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