Genevieve is from upstate New York, where she grew up in the Finger Lakes Region. She obtained her BSc in Biology from Haverford College, studying chemical mediation of bacterial-phytoplankton dynamics. Genevieve is working towards her MSc in Marine Biology at James Cook University, where she is studying genetic diversity of seeded corals to inshore macroalgae dominated reefs.

Genotypic diversity of corals seeded to macroalgae dominated inshore reefs

2022 to 2024

Project Description

The aims of this experiment are to (i) develop a world first method to measure genetic diversity within sexually propagated coral larvae in restoration programs, inclusive of chimerism, and to (ii) utilize this methodology to determine the genetic diversity of corals seeded to inshore reefs.

Project Importance

Coral reefs worldwide are facing rapid decline, necessitating the development of innovative conservation efforts. While much restoration work has been focused on labor-intensive asexual propagation methods—such as fragmentation or colony transplantation, for a limited number of mainly branching taxa —attention has shifted toward sexual propagation of coral larvae, to reduce the risk of genetic diversity loss through asexual propagation of limited genotypes. Restoring or maintaining genetic diversity in coral reefs is a common restoration objective, but often lacks explicit monitoring strategies or standardized methods to accomplish this goal.
Recent advances have attempted to harness the potential of coral sexual reproduction. Seeding corals onto engineered devices, aimed at mitigating the early life bottleneck faced by coral juveniles, has demonstrated significant potential for improving survival. These devices incorporate microhabitats that seek to protect coral larvae from threats such as grazing and sedimentation, contributing to their enhanced chances of survival. Another factor that has been demonstrated to mediate the success of these devices is the surrounding environment, and yet this approach remains untested on degraded, macroalgae-dominated reefs.
One intriguing aspect of larval seeding is the potential for chimerism. When coral larvae settle in aggregations, they often (~50%) fuse with conspecifics to form larger colonies containing multiple genotypes. This phenomenon, likely underestimated in the wild (~5%) due to paucity of study, can result in colonies that have reached size-escape thresholds sooner by growing larger faster, have higher survival rates, and even potentially produce genetically distinct gametes. Additionally, because reproductive output and maturity is linked to size, rather than age, in clonal organisms, chimerism could facilitate earlier gene pool contribution. Chimerism has been suggested as a rescue mechanism to safeguard the genetic diversity of reefs, due to their possession of multiple genotypes, which confers a higher potential for adaptability. Moreover, chimeras might exhibit enhanced resilience to climate change, as they have demonstrated not only higher survival rates but also greater retention of symbiont infection under warming conditions.

Project Methods

This project commenced in 2021 with the collection from Yunbenun (Magnetic) island of gravid adult Acropora kenti (formerly acropora tenuis) colonies, which were spawned in the SeaSim in October 2021. The coral gametes were collected, fertilized in tanks, reared until settlement competency, and settled onto aragonite plugs, six of which were inserted into seeding devices with engineered protrusions to reduce grazing mortality. These devices were deployed to reefs currently within a macroalgae removal reef restoration experiment at Yunbenun island in November 2021 on stainless steel rods and were surveyed for survival until retrieval in August 2023. Surviving seeded corals were measured and sampled for processing DaRTseq genome wide SNP sequencing at SeaSim. These resulting data will be used to facilitate parentage analysis to determine which and how many members of the brood stock contributed to the surviving generation, to ascertain if surviving corals are genetically distinct within macroalgae removal/ control plots, and to determine if chimeric individuals are present in the surviving population. These data will be combined with size measurements in order to evaluate and compare the qualities of chimeric individuals when compared with homogenous seeded corals. Furthermore, these results will be compared between macroalgae removal and control plots to ascertain if chimerism has a differential prevalence and therefore contribution between these treatments.

Project Results

It is expected to see that the trait of chimerism is common among the surviving corals, as it is suspected that chimerism helps corals to reach size escape thresholds of juvenile mortality at an earlier age. It is also suggested that chimerism could have other beneficial traits, such as the ability of a coral colony to have an earlier and more diverse contribution to the gene pool and increased tolerance to temperature stress, but their incidence within restoration programs is unknown. Our ability to restore reefs is inhibited by the lack of knowledge of the successful traits at the genetic level that contribute to establishing a healthy, reproductively viable population. This experiment aims to strengthen this knowledge, and as such, will benefit our understanding of how to develop and maintain sexually propagated coral restoration projects under climate change and other anthropogenic stressors.

Keywords

Algae,
Climate change,
Coral reefs,
Field based,
Genetics