Reversing the decline of Bahamian reefs


I recently got in touch with the Cape Eleuthera Institute in The Bahamas to ask about their work on coral reef conservation. I was delighted to “meet” Natalia Hurtado, MSc., Coral Reef Research Associate at PIMS/CEI & Casey Harris, MSc., Coral Reef Research Associate at PIMS/CEI. THis is what they had to say about their important work.

Much like coral reefs worldwide, coral populations in The Bahamas are declining at alarming rates, making coral restoration more vital to preserve marine resources and local economies. The Bahamas Coral Innovation Hub located in Eleuthera, The Bahamas is a collaboration between the Cape Eleuthera Institute (CEI), Perry Institute for Marine Science (PIMS), and The Nature Conservancy (TNC). With our work, we hope to facilitate the recovery of degraded Bahamian reefs and enhance coral population resilience.

One major problem facing coral reefs worldwide is that coral abundance is decreasing due to both local and global threats, making it difficult for corals to maintain genetic diversity on the reef. At the same time, their ecosystem services are deteriorating, affecting human livelihoods and the diversity of marine species that rely on them. At the Coral Innovation Hub, we focus our restoration efforts on 3 main areas of research: nursery-reared coral fragments, larval propagation, and coral microfragmentation. We are also dedicated to student involvement in our research, with the goal of inspiring younger generations to pursue careers in marine conservation.  All projects at the Coral Innovation Hub are led by Natalia and Casey.

Nursery Establishment to Improve Genetic Diversity

Corals can reproduce asexually, in which they undergo a strategic life-history trait called “fragmentation”, where pieces of coral can break off from disturbance and then attach to the substrate to form a whole new colony. We can take advantage of this natural process to grow corals at a much faster rate and plant them back on degraded reefs. We do this by growing corals in a mid-water tree structure, which is made with PVC and tethered to the sea floor, where corals are suspended away from sediment and predators. Below is a picture of Researcher Casey Harris taking notes of coral sizes while an assistant is taking measurements.

The establishment of coral nurseries is an important step to keep coral fragments safe while they grow. Caribbean branching corals grow extremely fast and increase in size about 10-20 cm (4-9 in) per year compared to large boulder species, which only grow about 1-2 cm (<1 in) per year. This is great for restoration efforts because after one year of growing in the nursery, branching corals can be outplanted back on the reef.

We are currently running a project with Dr. Ross Cunning (pictured below) at Shedd aquarium and the Reef Rescue Network, where we are investigating the resilience of staghorn corals by spreading different genotypes across The Bahamas to increase genetic diversity within coral nurseries. We have 19 staghorn genotypes that were collected and moved between existing nurseries and wild populations throughout a few Bahamian Islands in October 2019. Increasing genetic diversity within coral nursery projects is important because some genetically distinct individuals may be better suited to withstand environmental stress than others. Having as many different genotypes as possible is essential to successful restoration outcomes.

During a 15-day expedition onboard the Shedd Aquarium research vessel R/V Coral Reef II, 570 staghorn corals were distributed between newly established nurseries located in Bimini, Nassau, Cat Island, and Eleuthera. In each location, coral growth has been monitored by our partners and they are thriving in their new locations.

Student Involvement as Reef Rescue Divers

The Coral Innovation Hub at CEI works closely with Island School students and visiting educational groups from different ages and backgrounds. These students have a unique opportunity to complete a PADI Reef Rescue Diver Specialty Course. This course was developed by Hayley-Jo Carr, Training Director & Coordinator of the Reef Rescue Network, and Dr. Craig Dahlgren, Executive Director of PIMS. The Reef Rescue Diver Specialty and Reef Rescue Network were both created by PIMS, with the goal of rehabilitating coral reefs by working with various partners to establish a network of coral nurseries around The Bahamas and other parts of the Caribbean.

During the course, students learn about the value of coral reefs and restoration, different types of nurseries, how to maintain nurseries, coral fragmentation, outplanting and monitoring. They work with Critically Endangered species, such as elkhorn and staghorn coral, that were once abundant on Caribbean reefs but have rapidly declined since the 1980s. We target these species for restoration because they play an important ecological role on the reef by providing high rugosity and three-dimensional functionality that protects our shorelines and provides shelter for marine life.

Implementing Larval Propagation as a Restoration Technique

Corals can also reproduce sexually. In sexual reproduction, corals release “spawn” (egg and sperm) and can synchronize their spawning events with colonies of the same species. Pictured below are the gamete bundles of a brain coral, in which the coral releases both egg and sperm (male and female gametes). We can take advantage of these spawning events to collect their spawn and cross fertilize them to increase genetic diversity, and study the vulnerable early life-history stages of corals.

During summer 2019, Coral Innovation Hub researchers collected coral gametes and saw high rates of fertilization and settlement success, with over 5,000 Orbicella faveolata (mountainous star coral) recruits (coral babies pictured below) settled on SECORE Seeding Units (concrete and ceramic substrates).

We are allowing juvenile corals to grow in an offshore nursery tree and outplanted more than 1,000 substrates with coral recruits onto the reef. The goal is to determine if initial and long-term coral survivorship is possible in an offshore nursery and/or on the reef. This research was conducted during SECORE’s International Coral Spawning and Propagation Workshop hosted at CEI with PIMS and TNC. Below is a picture of Researcher Natalia Hurtado carrying substrates to be outplanted on the reef.

A New Restoration Technique for Boulder Corals

Another way to grow corals through asexual reproduction is by using a new restoration technique for slow-growing boulder species called “microfragmentation,” founded by Dr. David Vaughan, Plant a Million Corals. This process consists of cutting fragments of the same colony into small pieces (1-3 cm, pictured below), using a specialized saw. The clone fragments will recognize each other and fuse together, growing 25-50 times faster than normal.

At the Coral Innovation Hub, we plan to run pilot experiments on different coral species to document the most successful microfragmentation methods needed to upscale our efforts. As part of our study, we will examine the survivorship and growth of microfragmented boulder corals (brain corals, star corals, etc.) in our land-based wetlab facility (pictured below). If proven successful, we will grow boulder corals in an offshore table nursery or directly outplant microfragments to the reef.

Want to know more about Reef Rescue Network? Please contact Hayley-Jo Carr. If you have any questions or want to get involved with The Bahamas Coral Innovation Hub project, please contact Natalia Hurtado or Casey Harris.

Nick and Caroline Robertson-Brown

Nick and Caroline Robertson-Brown

Nick and Caroline Robertson-Brown are a husband and wife team of underwater photographers. Both have degrees in environmental biology from Manchester University, with Caroline also having a masters in animal behaviour. Nick is a fellow of the Royal Photographic Society in underwater wildlife photography and he also has a masters in teaching. They are passionate about marine conservation and hope that their images can inspire people to look after the world's seas and oceans. Their Manchester-based company, Frogfish Photography, offers a wide range of services and advice. They offer tuition with their own tailor made course - the Complete Underwater Photography Award. The modules of the course have been written to complement the corresponding chapters in Nick's own book: Underwater Photography Art and Techniques. They also offer equipment sales and underwater photography trips in the UK and abroad. For more information visit

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