Creating a more Resilient Coral
Madison Churchill
Liv Williamson is a marine biologist working to improve the health and longevity of our coral reef ecosystems. Rising ocean temperatures threaten sensitive reef ecosystems all around the world. Liv studies intervention techniques to help corals become more resilient to climate change. In this interview she tells us about about what these Florida-based scientists are doing to preserve biodiversity.
Photo: Liv Williamson.
Hey! Tell us a bit about yourself and what first drew you to the ocean.
Hey there! My name is Liv Williamson, and I just began the fourth year of my Ph.D. at the University of Miami’s Rosenstiel School of Marine and Atmospheric Science. I grew up on a small island north of Boston, MA, where I spent my summers sailing, paddling, fishing, hunting for tide pool critters along the shore, and taking walks on the beach. These activities throughout my childhood drew and bonded me to the ocean, and I can’t imagine ever living away from it.
I didn’t realize that marine biology was my passion and desired career path until I went snorkelling and SCUBA diving for the first time on the coral reefs of Bocas del Toro, Panamá in 2016. When I took my first breath out of a regulator and saw the beautiful, bewildering, swirling diversity of life around me on a coral reef, I was instantly hooked.
Please outline a basic description of your work with corals, and what outcomes you hope to achieve with this work.
Briefly, I work with several “foundation” species of reef-building corals here in the Caribbean, testing strategies to enhance climate resilience during their early life stages. Specifically, I inoculate, or combine, newly-settled coral “recruits” (juveniles) with heat-tolerant symbiotic algae in hopes of increasing their resistance to bleaching.
I also work to “cryopreserve” coral sperm, which involves freezing it for long-term storage. This helps us to create a genetic bank to preserve existing diversity. Cryopreserved sperm can be carefully thawed in the future for selective breeding, which allows us to create offspring from novel combinations of parents in hopes of generating resilience in the next generation of corals.
In your opinion, what is the most interesting part of coral propagation?
It is totally fascinating to me that corals reproduce both asexually and sexually. When a coral colony breaks or is fragmented, all the resulting pieces can each continue to grow and become their own new colonies. This is the strategy widely used for coral gardening, in which a few pieces sourced from wild colonies can eventually be fragmented, grown, and planted over and over again to help repopulate reefs.
Photo: Liv Williamson.
Corals also reproduce sexually through coral spawning, but this only happens on a few nights a year with very specific, closely synchronized timing. Coral colonies use environmental cues, such as the lunar cycle and water temperature, as well as chemical cues, to precisely time their release of eggs and sperm with one another. This process is spectacular to witness.
For divers, it feels like being inside a snow globe, with thousands of tiny pinkish blobs of coral gametes floating lazily around you in the darkness. These spawning events result in many new larvae, tiny planktonic baby corals that drift with the ocean currents for days or weeks until they find a suitable spot on the ocean floor to settle down.
Photo: Liv Williamson.
How does your work contribute to the health of coral reefs?
Coral reef ecosystems are declining at an alarming rate, with over 80% of coral cover lost in the Caribbean since the 1970s. With this huge loss, there has been a considerable reduction in genetic diversity, which enables populations to adapt and evolve in the face of change. Therefore, ensuring the success of new generations of coral juveniles is crucial. By helping to optimize the survival, fitness, and climate tolerance of Caribbean coral juveniles, I hope I can contribute to meaningful reef restoration efforts here in Florida and beyond.
Why is it important to preserve coral reefs? What are some potential outcomes of mass coral die-offs?
Coral reef ecosystems support one-quarter of all marine species, making them biodiversity hotspots. In addition to this ecological significance, humans benefit immensely from coral reefs. Reefs support the fisheries we depend on for sustenance and livelihoods. Reefs act as natural breakwaters, reducing wave action and protecting our vulnerable coastlines from storm damage and erosion. Reefs hold great cultural and aesthetic value for coastal communities around the world.
Without reefs, we risk losing the immense array of marine species that depend on these animals, many of which humans rely on for seafood and protein. Directly and indirectly, humans derive extraordinary value from coral reefs, which we cannot afford to lose.
You’ve mentioned that you’re working with acclimation of corals to combat rising ocean temperatures, can you walk us through how you hope to achieve this?
Corals host tiny single-celled algae called zooxanthellae inside their tissues in a symbiotic relationship, where both partners benefit. These algal symbionts photosynthesize, turning sunlight into energy that the coral animals use to grow and build their calcium carbonate (limestone) skeletons. Marine heat waves destabilize this symbiosis, causing the corals to eject the algae from their cells in a process we call coral bleaching.
Without their symbionts, coral tissue is transparent, so it looks white because you can see through it to the limestone skeleton beneath. If the heat wave subsides and temperatures cool, corals can re-establish symbiosis and become colourful and healthy once more. However, if high temperatures linger, bleached corals are likely to die without their main source of nutrition.
Photo: Liv Williamson.
As ocean temperatures rise due to climate change, bleaching events are becoming more and more frequent and intense, resulting in mass mortality of reef corals worldwide. Combining a variety of interventions will probably buy coral reefs the most time.
I focus on 2 types of interventions:
Giving corals more heat-tolerant algae as symbiotic partners, as this association may be less vulnerable to marine heat waves and thus prevent corals from bleaching.
Breed more thermally-tolerant corals themselves, so the next generation of corals may be more resilient to warming oceans.
Reef ecosystems are incredibly interconnected from the smallest micro to the biggest macro. How does this interconnection help to support biodiversity on a global scale?
Coral reefs rival tropical rainforests as the most biodiverse ecosystems on earth. Although reefs cover less than 0.1% of the ocean, more than one quarter of all marine species rely on coral reefs at some point during their lives. They play a huge role in creating “hotspots” of productivity in otherwise nutrient-poor, unproductive tropical seas. Marine life uses the corals for everything from shelter to hunting grounds to nurseries. Larger species like sharks eat these smaller ones, and so the entire food web depends on corals. In turn, these larger predators such as sharks help balance the ecosystem by regulating prey populations.
What do you see as the greatest threats to coral? Are they predominantly human caused, or are there natural ecosystem functions at play as well?
Based on what I see in south Florida and the Caribbean where I mainly work, I see human-caused climate change as the primary threat to coral reefs. This comes mostly in the form of ocean warming, which causes coral bleaching and mortality, and ocean acidification, which hinders a coral’s ability to calcify and build its limestone skeleton. Additionally, nutrient pollution, disease, overfishing, and invasive species are all major threats to coral reefs in the Caribbean and worldwide, and all these stressors have a human element.
So, where do you go from here?
I have 2 years left in my Ph.D. program, so I will be working to make lots of strong, healthy coral juveniles and helping to put them onto south Florida’s reefs. After my Ph.D., I hope to stay in the world of coral conservation, ideally working with an NGO to optimize and implement novel coral restoration techniques around the world. I also hope to actively engage members of communities directly impacted by coral reef health, to include local citizens and stakeholders in reef restoration efforts.
If you’ve enjoyed this interview with Liv Williamson, you can follow her here @liv_in_the_moment
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