Why is diving so alluring? Why are coral reefs so colourful? What is a pristine reef? And what exactly does a coral symbiosis with algae entail? Coral expert Oded Degany has spent the last two decades trying to find answers, while exploring the secrets of tropical coral reefs. In this interview, he discusses his most important findings and might just change your perception of coral reefs.
Oceanographic Magazine (OM): How has your deep love for coral reefs developed throughout your life?
Oded Degany (OD): I was born in a city near Tel Aviv, Israel, on the sandy shore of the Mediterranean Sea. The sea has always been part of me. My adventure with corals began when my family took me to the Sinai Peninsula, an awe-inspiring place known for its reefs. During this trip, I was introduced to the incredible world of coral reefs and had the chance to snorkel in this breathtaking habitat. That first moment, when I was surrounded by the beauty of the reef, is etched into my memory. I eventually took scuba diving courses and began exploring dive sites worldwide, with a particular focus on the Coral Triangle. This region, between the Philippines, Indonesia, and Papua New Guinea, is famous for its unrivalled marine biodiversity. At first, I was captivated by the physical sensations of diving: the weightlessness, crystal-clear waters, stunning beauty. But it wasn’t just about the physical experience – I was also entranced by the intellectual aspect of marine life and developed a deep fascination for its intricate ecosystem. Academically, I have a Bachelor’s degree in Physics, a graduate degree in Biological Thought, an MBA, and a partially completed Doctorate in Religious Studies. In my business career, I focused on corporate development, particularly mergers and acquisitions in hi-tech.
OM: What makes coral reefs so special in your eyes?
OD: For me, coral reefs are special because of their incredible beauty and complexity. They represent a unique combination of aesthetic, sensual, and intellectual experiences. This distinct combination is the underlying theme of my new book. By nature, I have a deep desire to understand and engage with the world around me; coral reefs gave me a perfect medium for pursuing my passions.
OM: One of the more fundamental questions to begin with is: What are corals? Are they animals? Are they plants? Are they both?
OD: Until late antiquity, corals were often classified as plants, minerals, or somewhere in between, perhaps due to their sessile nature. Although many people surprisingly think of them as a type of plant, they are actually animals. Broadly speaking, corals are made up of tiny, individual animals called polyps. The mouth of each polyp is encircled by a ring of stinging tentacles, which allows them to catch small floating organisms. One of the topics my book explores is the question of whether coral colonies can be considered superorganisms. Basically, a superorganism is a group of organisms that work together, functioning as though they were a single organism. How should we consider massive brain coral that measures several meters in size? Is it a single organism? A huge aggregate of polyps? It’s actually a bit of both, and I dive into this more in my book.
OM: Your latest book is a ‘multidisciplinary exploration of coral reef wonders’ – what can readers look forward to?
OD: Readers can look forward to seeing coral reefs from an entirely new perspective. My eclectic book covers several seemingly unrelated topics, including evolution, zoology, psychology, philosophy, mathematics, art, physics, and more. It’s not a singularly focused zoological book. The basic idea was to interweave scientific and humanistic ideas, centred around coral reefs, sparking readers’ intellectual curiosity and giving people ways of thinking about coral reefs. Structurally, the book is made up of nine self-contained chapters, so people can dive into the topics that pique their interest first. No need to read the book in a linear fashion, from start to finish. Each chapter and subchapter begins with a story: a myth, folk tale, historical episode, or personal experience from my travels. It then delves into scientific aspects of the reef in a way that’s meant to make people curious.
OM: Who is this book for exactly?
OD: The book is for anyone who loves nature and has an intellectual interest in coral reefs. It offers an intellectually stimulating and engrossing experience, particularly for people who love coral reefs. It’s great for seasoned divers who want to enrich their diving experience, amateur snorkelers, or anyone who loves to learn. It’s perfect reading before, during, or after a diving vacation.
OM: What’s your favourite finding or the most interesting topic of the book?
OD: Wow! That’s a challenging question. This book is the culmination of years of research, writing, and revision, and everything in it interests me. That’s why it’s in the book. Some of the questions that I explored include: Why is diving so alluring? Why are coral reefs so colorful? What is a pristine reef, anyway? And, of course, the question of marine animal consciousness. During my research, I encountered several unresolved puzzles. For example, how is it that octopuses, which often use bright colours as mating displays and can accurately mimic colours to blend into their surroundings, are technically colourblind? In my book, I present a recently published theory that resolves this puzzle by utilising an optical effect that enables them to see colours despite their colour blindness. One particularly surprising finding was a theory about the extraterrestrial origin of octopuses. I’m not saying that I was convinced (even though it was published by a scientific publication), but the idea was unexpected, to say the least.
OM: The book covers, amongst many other things, coral symbiosis with algae. Could you elaborate on what exactly this entails?
OD: This is an essential question, as it represents a critical factor in understanding the complex nature of reef life. Coral reefs rely on a symbiotic relationship between their fundamental unit, the polyps, and tiny single-celled algae called zooxanthellae. These algae use sunlight to produce food through photosynthesis, with up to 95% of this food is transferred to the coral host. In return, the algae receive protection from predators and some nutrients. This mutually beneficial relationship is crucial to the success and proliferation of coral reef systems. However, the ongoing problem of global warming is disrupting this delicate symbiosis, leading to the breakdown of the coral-algal relationship. This stress can cause corals to eject the symbiotic algae, resulting in coral bleaching, where their white calcium carbonate skeleton is visible. Many corals depend on these algae for their energy, so without them, they are at risk of starvation, disease, and even death. Interestingly, this type of symbiosis is not unique to corals and also occurs in other marine invertebrates, such as jellyfish, sea anemones, bivalves, sponges, nudibranchs, flatworms, and hydra. There are many other symbiotic relationships I explore in the book. One example that amazes me are cleaning stations. These are very common in coral reefs, and the question I explore is how this mutually beneficial association, which seems based on an inherent conflict of interest, started, evolved, and became imprinted. For the fish coming to get cleaned, it seems natural selection would prefer defection, getting cleaned, and then eating the cleaner. But this isn’t what happens.
OM: What are the reasons behind the exceptional biodiversity of coral reefs?
OD: Darwin was the first to identify this exceptional biodiversity and the puzzle behind it, now known as “Darwin’s Paradox.” Imagine him, sitting on the deck of the HMS Beagle, amazed by the vibrant diversity of life on the atoll reefs, in stark contrast to the relatively poor diversity of the fauna and flora of the Cocos (Keeling) Islands, just a few meters from the reef. The paradox of rich diversity in a seemingly hostile environment puzzled Darwin and has continued to intrigue scientists ever since. Despite being surrounded by low-nutrient ocean water akin to a desert, coral reefs thrive and support an astonishing array of life forms. The biomass produced by coral reef ecosystems is 20 times higher than that of the open ocean, making them a true wonder of nature and an “oasis in the desert.” Broadly speaking, I would say that two major factors can explain this. Firstly, symbiotic algae convert a massive amount of sunlight energy into food, which is later consumed by the coral polyps. In other words, the sun’s energy feeds the reef creatures. Secondly, coral reefs form a complex system whose unique characteristics enable a great number of interdependent interactions between reef creatures. An example is the recovery of the reef from an acute natural disaster such as a tsunami or volcanic eruption. The reef system recovers and achieves new system equilibrium without any master plan. This character of a complex system is called self-organisation.
OM: You write about our ‘biased perspectives of the healthy reef myth’. What is this and why does it matter?
OD: Our perception of what a pristine coral reef should look like is influenced by how we view coral reefs today and by photos or movies that have been created since the development of recreational scuba diving in the 1960s. Unlike terrestrial areas, coral reefs have been relatively protected from human impact due to the natural barrier of the sea. However, ecological degradation began as early as the seventeenth century, with the rise of colonial occupation. This represents a significant amount of time in terms of potential accumulated damage, and raises the question of what pristine coral reefs looked like before human disturbance. Intrigued by the concept of pristine reefs, I have looked for an intuitive approach to assess the health of the reefs I encounter. One theory I discuss in my book proposes that a healthy reef’s spatial biomass structure is distributed in an inverse pyramid pattern, with 85 percent of the biomass attributed to large predators, such as sharks and large snappers, instead of herbivores and planktivores, which people typically assume account for most of the biomass. This suggests that a reef with a significant number of large predators is likely to be healthier.
OM: Why are coral reefs so colourful?
OD: I’m sure most divers have asked themselves this question at some point during their life, and there are many reasons for it. The first reason is communication or signalling, which includes things like reproduction and warning coloration. A good example is the bright colours of nudibranchs that serve as a warning to potential predators. The second reason relates to the unique properties of light and the colour spectrum in an underwater environment, which differs from that on land. Because of light and colour attenuation in water, some mechanisms of colour production are more prevalent in marine creatures. Two primary mechanisms common in the coral reef are fluorescence and bioluminescence, both of which can generate colours that are attenuated in deep water. The third reason relates to the guiding principles of camouflage, some of which may seem counterintuitive. The fourth reason comes from cognitive psychology and suggests that our perception of these habitats as “colorful” may differ from how reef animals perceive them. In my book, I discuss these reasons in detail, and in connection with the brilliant, non-scientific view of the British essayist Aldous Huxley, who argued that our attraction to colorful forms and views results from our desire to visit and enjoy colorful, unmapped, unconscious experiences in the antipodes of human consciousness.
OM: You’ve been researching coral reefs for years. What’s your favourite encounter to date? Any species behaving unusually? Any coral behaviour that really stands out?
OD: The behaviour of reef creatures never ceases to amaze me, and I find that exploring life underwater breaks the conventional borders created by our ‘mammalian thinking’. For example: mating octopuses. For many octopuses, mating means the beginning of the end of their lives, as both the female and male die afterward. On the face of it, this doesn’t make sense from an evolutionary perspective, and in my book, I discuss the scientific controversy about this unique controlled death mechanism. Another example is the mantis shrimp. Firstly, its eye has a remarkable visual system, with 16 types of photoreceptors that provide complex color reception and linear and circular polarisation sensitivity. Each eye can move independently, allowing for a broad angular range of movement that includes up-down, side-to-side, and torsional movements. Secondly, the mantis shrimp (smasher shrimp) has a powerful strike that generates a force equivalent to a 0.22 caliber bullet and produces a temperature close to that of the sun’s heat for a fraction of a second. A coral behaviour that stands out is coral spawning. An incredible phenomenon, sometimes described as the greatest orgy in the world, usually occurs only once a year and takes just a few minutes. Within seconds, a huge number of corals of a given species, spanning a vast area simultaneously release their reproductive material, creating a colorful underwater snowstorm.
OM: You also dedicate a chapter on mathematics. How does that tie in with coral reef conservation and research?
OD: The chapter on mathematics in coral reefs explores two major themes. First, the ancient connection between beauty and mathematics is discussed in the context of the golden ratio and the manifestation of symmetry in coral reefs. Second, the theory of complex dynamic systems provides a modelling and explanatory framework for understanding various phenomena in reef systems, including topics related to reef conservation.
OM: How do corals reproduce? And what other fascinating things did you find when researching reproduction in the coral reef?
OD: As an author who is deeply fascinated by coral reproduction, I am constantly in awe of the incredible diversity and complexity of these beautiful animals. It is a topic that never fails to fascinate me. One fascinating thing about coral reproduction is the amazing variety of strategies they use to propagate. It can be classified into two major categories: sexual and asexual reproduction (budding). While some species of coral have separate sexes, meaning that every individual colony is either male or female, in others, each coral serves as both male and female, producing both sperm and eggs. Some corals can even change their sex from one reproductive season to the next. Most coral species reproduce via broadcast spawning, where they release both sperm and eggs simultaneously. The fertilised eggs (planula larvae) swim at the ocean surface for days or weeks before eventually falling back to the seabed and attaching themselves to a hard surface. Then they metamorphose into polyps, begin to grow by budding (asexual reproduction), and form a coral colony. As the coral colony grows and matures, it reproduces sexually through broadcast spawning. Another fascinating topic is hybrids, a long-standing controversial issue in biological thought. In some cases or localities, a few or even many coral species may release their reproductive material simultaneously, leading to fertilisation between the eggs and sperm of different species and the development of hybrids. These hybrids can continue to grow and reproduce via budding, forming a new coral colony. The reproduction of reef creatures is highly diverse. Some animals change their sex during their lifetime; some animals, such as nudibranchs, are both female and male at the same time. In other words, when it comes to marine sex, there is no such thing as “normal.” An example of sex change can be found in some species of sea goldies. All sea goldies are born female. In the absence of a male, the largest female will transform into a male, a process that takes several weeks.
OM: What are the main threats to coral reefs across the globe?
OD: Coral reefs are subject to both acute and chronic perturbations. They seem to recover well from acute perturbations, like the tsunami of 2004, but not from chronic disturbances like rising sea temperatures, pollution, and overfishing. Chronic problems like these are taking their toll on coral reefs worldwide, seriously threatening their ability to survive and reproduce. I am deeply concerned that without significant efforts to reduce these risk factors, future generations may be unable to enjoy the privilege of experiencing this magnificent habitat.
OM: What needs to change to preserve coral reefs in the future? What can individual do? And what should be done on an international level?
OD: Historically, the first attempt to address the issue of nature conservation was to promote ‘shallow ecology’, which involved fighting pollution and resource exploitation to benefit the health and wealth of people, mainly in developed countries. However, this approach has largely failed, and most people remain indifferent to the ongoing destruction of natural habitats. I think we need a paradigm shift, perhaps in the form of a new environmental movement that unites people and inspires action. One potential avenue is to increase public awareness of animal consciousness. We need to recognise that sentient animals, including those in the ocean, deserve a place within humanity’s moral boundaries. Many animals have the ability to experience pleasure and pain, and we often ignore this due to cultural conditioning. By including animals within our moral boundaries, we can create a turning point in how we view our relationship with nature. There are already signs that this is happening. For example, a report published in 2021 by the London School of Economics (LSE) found strong evidence of sentience in two groups of invertebrates: cephalopods (these include octopuses, squid, and cuttlefish) and decapod crustaceans (these include crabs, lobsters, and crayfish). These results could have practical implications, such as having included in the UK animal welfare law.
OM: With many negative news on coral reefs bombarding us on a daily basis, how do you stay positive?
OD: I try to stay optimistic. There are signs of a paradigm shift, but the question is about the pace of change. Encouraging indications suggest that contemporary attitudes are shifting towards a more comprehensive perspective on the connection between humans and nature. The younger generation is definitely more attuned to conservation issues, with many of them adopting a vegan or vegetarian lifestyle. Furthermore, Eastern concepts related to the relationship between humans and nature are gaining wider acceptance. I have faith in the younger generation’s ability to effect positive change and rectify the damage caused by previous generations.
Oded Degany’s book Reflections Underwater – A Multidisciplinary Exploration of Coral Reef Wonders is out now.
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