Table Of ContentC O R A L
R E E F S
A NATURAL HISTORY
C O R A L
R E E F S
A NATURAL HISTORY
Charles Sheppard
Consultant Editor
Russell Kelley
PRINCETON UNIVERSITY PRESS
PRINCETON AND OXFORD
Published by Princeton University Press
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Library of Congress Control Number 2021930492
ISBN 978-0-691-19868-2
Ebook ISBN 978-0-691-21862-5
Publisher James Evans
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Commissioning Editors Kate Shanahan, Natalia Price-Cabrera
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Printed in Singapore
10 9 8 7 6 5 4 3 2 1
CONTENTS
6 Foreword
8 Introduction
CHAPTER 1
12 THE CORAL ANIMAL
CHAPTER 2
60 DIFFERENT KINDS OF REEFS
CHAPTER 3
96 HOW A CORAL REEF WORKS
CHAPTER 4
150 LOCAL AND REGIONAL
DISTURBANCES TO REEFS
CHAPTER 5
180 CLIMATE CHANGE AND REEFS
CHAPTER 6
200 PEOPLE AND REEFS
232 Glossary
234 Further Reading
236 Index
240 Picture Credits
FOREWORD
Imagine swimming in a warm, tropical sea. Through your
face mask you peer down into an infinite azure abyss. All
you can see are shafts of light plunging into the depths like
lightsabers, and iridescent, sapphire-like flashes reflecting
from invisible plankton somewhere below. Now you hear
something between the lazy splashes of the torpid sea. A
non-stop crackling hiss rises and falls like someone tuning a
distant radio station. You kick your fins and turn 180 degrees
and a vertical reef wall looms, draped in a wriggling tapestry
of color and movement. Fish teem around hundreds of
other kinds of reef creatures. You swim closer and gawp
at the hallucinogenic patterns while the entire coral reef
carnival carries on without a care for an alien visitor as
clumsy as yourself.
For me, there is nothing as ineffably beautiful as a coral
reef on a calm, sunny day—such scenes sear vivid memories
that last a lifetime. Remarkably, the story of reefs—their
origins, adaptations, and achievements in the great pantheon
of evolution and Nature—is equally breathtaking.
From the study of modern reefs, we know corals are
not just beautiful biological baubles, but an innovative force
in Nature. Corals have solved the problem of how to create
something from nothing in the middle of empty,
nutrient-poor oceans using an ecology based on symbiosis
and collaboration. And not just a modest “something,” —a carnivore by night and a solar farm by day. Now corals
but the richest marine ecosystem on Earth. had energy to burn, energy to build!
The coral reef innovation derives from an extraordinary Their larvae dispersed on ocean currents to settle on the
advent in biology—the ability for a plant to live inside an edges of sterile volcanoes where, with nothing but sunlight
animal, the best known example being the algae cells laced and microscopic planktonic meals, they combined their
through the tissues of every reef-building coral polyp. construction prowess with another great evolutionary
Somewhere in the mists of geological time, shallow-water achievement—cloning. In this way the arrival of a single
corals became infected with plant cells that not only survived coral larva, transforming into a polyp, could build great
but thrived within the coral animal. These tiny plant cells coral colonies. I like to think of them as colonial castles
did what plants do: photosynthesise. Using sunlight, excess conjured from nothing in the middle of empty oceans.
CO, and animal waste products, they flourished inside On coral reefs recycling is a way of life, as is finding a
2
their host. In return the plant cells released sugars and the home on, or inside, another species. Over many millions of
humble coral polyp suddenly had two engines for growth years coral reefs have attracted thousands of species to come
6 | FOREWORD
along for the ride, weaving an evolutionary fabric so organically page 186) that attacks the evolutionary bond between coral
intricate it inspires, and deserves, the term living art. and algae, the very engine of the ecosystem’s existence.
This book explores the natural history of reefs in a Coral Reefs; A Natural History is a portrait of the wonders
human context. Written plainly and richly illustrated, it is and dilemmas facing the richest of marine realms. If we
a guide to the good, the bad, and the ugly of the coral reef want our children to see Nature’s great gifts, and if millions
story. Around the world Nature is in retreat and so it is with of people are to avoid displacement and hardship, then it is
reefs. In the tropical world around 500 million people depend time for humanity to take our collective foot off the carbon
on reefs for shelter, protein, and employment. Yet in many emissions accelerator.
regions reef decline is accelerating due to the impacts of
growing populations of people without options.
Even more pressing is the threat of climate change and
the ocean warming it causes. Underwater heatwaves are Russell Kelley
triggering mass coral bleaching, a “disease” (described on Townsville, Queensland, Australia
7
INTRODUCTION
Coral reefs mean different things to different people. To
a sea captain they are potentially hazardous, often poorly
marked on the chart, and always lying just beneath the
surface of the water. To people living in the tropics beside
a reef, or on a small island perched on one, they provide
both a home and food. To many divers and snorkelers who
visit tropical coasts they are a kaleidoscopic wonderland
of colorful fish that circle and dart above the strangest of
living structures, and these tourists bring significant revenue
and foreign earnings to such regions. The scientist sees
something different again, a place of huge diversity in a
relatively small space, of apparently chaotic pattern and
movement, something to try to make sense of. A reef is all
of these things and more.
Coral reefs occupy only about one percent of the
Earth’s surface but they contain a high abundance of
marine species, and they concentrate huge densities of it
too, like an oasis. Not only this, but they also construct the
reef itself. A reef is made by corals and other organisms as
they extract limestone from the seawater to deposit as solid
rock to make their own skeletons. They have been doing
this for millennia so that now some reefs are a couple of
kilometers thick in parts of the Earth that have been slowly
subsiding over the ages, such as in the atolls scattered across
tropical parts of the Indian and Pacific oceans. The parts
of the reef that are now living form only a veneer on the Yet there are fewer than 1,000 species of reef-building
top. Yet that small quantity has built the structure that coral—a thousandfold fewer than the number of species
supports all the rest, from the thousands of species of that live among the structures they have built. Corals are
simple animals to the swarms of fish above, and to several the key animals that deposit the limestone rock, which they
entire oceanic nations. do because of help from captive, symbiotic algae, in a close
Few of us realize that around half a billion to a association between animal and plant that has lasted for a
billion people are now wholly or largely dependent on couple of hundred million years. The far greater numbers
coral reefs, because they live on them or are dependent of invertebrates on reefs include many that are hidden,
on the protein that they produce, or perhaps because they and this is unsurprising given the huge whirls of predatory
provide sheltered waters for a mainland settlement. That fish above them. Many animals are gaudily colorful. All
number does not include many millions more who use are hunting for food and mates, and many use astonishing
them for recreation. methods of hunting while avoiding being eaten themselves.
8 | INTRODUCTION
