Coral Reefs: The World Beneath the Waves

Picture the most beautiful place on earth. Maybe you
envisioned a beach of pristine sand and white-capped
waves. Or maybe you saw yourself on a
boat with nothing but turquoise water stretching
in all directions. While the beach and ocean are
indescribably alluring, some of the most incredible
sights lie beneath the water’s surface.

In the tropical ocean waters fringing many of
the continents lie vast stretches of colorful structures
resembling underwater gardens. These vivid
structures are not constructed of plants but living
animals. We know them best as coral reefs and can
find them in shallow and deep water all around the
world. The most well-known reef, the Great Barrier
Reef off the coast of Queensland, Australia, covers
over 130,000 square miles. This reef system is visible
from space. In 2020, oceanographers found a
reef in Australian waters that was 1,640 feet tall—taller than the Eiffel Tower in Paris.

Coral reefs occupy less
than 1% of the entire ocean
floor, yet are home to 25% of all marine species.

Even more impressive than the area that reefs
occupy is the variety of life that calls them home.
We use the term biodiversity to provide a measure
of the diversity of lifeforms living in an ecosystem.
More species typically means higher biodiversity.
Coral reefs are the most biodiverse ecosystems on
earth. Not even tropical rainforests can compete
with the variety of life in coral reefs. Coral reefs
occupy less than 1% of the entire ocean floor, yet
are home to 25% of all marine species. Over 4,000
species of fish—including some of the most visually
vibrant such as clown fish, tangs, parrotfish,
seahorses, and butterfly fish—live in coral reefs.
Around 3,000 species of other animals have been
documented to spend all or most of their lives in
reefs, including some sea turtles, moray eels, and
marine mammals.

With such a diversity of life dwelling in coral reefs, it’s no
surprise that humans rely heavily on these ecosystems for
resources. Nearly 500 million people derive1 a significant portion
of their food and/or revenue from reefs, mostly through
the fishing industry and tourism. In the tourism industry, the
world’s coral reefs are worth billions of US dollars per year.2

Coral reefs also provide coastal protection, absorbing wave
action that would erode the coastline of areas that tens of millions
of people call home.3 Additionally, corals are a source of
medicine used to treat diseases such as cancer, arthritis, and
Alzheimer’s.

But often in the news, we read reports claiming that climate
change is heating the world’s oceans, threatening the
survival of coral reefs. Some scientists even predict that coral
reefs might disappear entirely in the coming decades. Political
philosophy related to the climate change issue must be
carefully dissected from actual evidence related to climate
change concerns. However, God made us stewards of the world,
even the world beneath the waves. Given the extent to which
humans and animals rely on corals, we should educate ourselves
on these essential ecosystems and the actual threats
to their survival so we can exercise discernment and steward
coral reefs well.

What Are Corals?

Many animals, and even algae, contribute to the construction
of these biological reefs, but no animals play a bigger role
than corals. While corals come in many shapes, sizes, and types,
stony corals (scleractinians) are the primary organisms responsible
for building coral reefs. The individual corals, called polyps,
often live in colonies comprised of thousands of organisms. The
coral colonies grow in size as the polyps pull calcium from the
sea water and use it to build an exoskeleton to recede into. Periodically,
the polyps will separate from their skeletons and build
another layer on top of the previous one. When a coral polyp
dies, its skeleton remains as a scaffold on which other corals can
build. Over time, these coral colonies grow into enormous reefs.

Corals display one of the best examples of mutualism found
anywhere on earth. Mutualism is a symbiotic relationship
between two or more species where all organisms benefit from
their interactions. Corals are mutualistic with single-celled
photosynthetic algae known as zooxanthellae (pronounced zoe-uh-zan-THEH-luh). These tiny creatures live inside coral tissues
and pay their rent by making sugars from sunlight and carbon
dioxide, giving the coral a nearly limitless supply of food. The
zooxanthellae benefit from the protection the coral provide and
the materials the coral pull out of sea water. Mutualistic relationships
require a very careful, well-designed balance of give
and take, but when disturbed, they can break down.

In response to high temperatures, corals become stressed
and evict their zooxanthellae tenants who produce toxins in
response to this thermal stress. If the heat wave is short, this
breakdown can be reversed. However, if the heat persists for
an extended period, the corals will die from lack of nutrients.
Because the color of coral comes from their tiny partners, these
dead corals look bleached (inspiring the term coral bleaching).

Over the past few decades, the world has experienced more
prolonged periods of heat compared to historical records dating
back to the late 1800s, leading to the extensive loss in corals and
the reefs they build. Most scientists accept the idea that this rise
in heat is attributable to climate change caused by human activity.
But according to the fossil record, corals have played this disappearing
game before.

Corals Worldwide

Coral reefs cover around 110,000 square miles
(284,300 km) around the world. Of course, you might
be familiar with the Great Barrier Reef in Australia,
but coral reefs show up scattered throughout the
Caribbean (including the Florida Keys), off the coast
of Central America, along the east coast of Africa, and
even in the Red Sea.

Indonesia has the most area with coral reefs at nearly
18%. Roughly 80 countries host coral reefs in their
waters. Many reefs grow in an area called the “coral
triangle” among the Indonesian and Philippine Islands.

Some corals grow in deep, cold water, such as
along South America, because they do not need
zooxanthellae (algae) to survive.

Coral Comeback

From the fossil record, we infer an interesting
story regarding coral reefs. The Great Barrier Reef
was one of the first modern reef systems to develop.
After studying the coral thickness, some creation
scientists believe this reef appeared just 3,700 years
ago.4 This reef and other modern reefs are restricted
to a small portion of the earth’s sea floor. But the
distribution of reefs has been far more extensive
during other periods of earth history, with large
deposits of fossil reefs in Australia and all over the
Northern Hemisphere, including the United Kingdom
and the Great Lakes region of North America.
In fact, hundreds of thousands of visitors to Michigan
take home a piece of these fossilized reefs as a
souvenir each year in the form of Petoskey stones.
Petoskey stones are pebble-shaped, fossilized coral
that have been worn smooth over time.

Many species of coral appear all at once in the
fossil record, disappear all at once, and reappear
in later deposits. Six entire families of coral disappear
from the fossil record during the global flood
of Noah’s day.5 Corals reappear in post-flood deposits
a couple hundred years after the flood, only
to completely disappear from the fossil record. It
seems that corals have a history of becoming common
enough to leave fossils and then becoming too
rare to leave a record.6 Modern coral reefs may be
repeating this cycle.

In no other period of history has the climate
varied so extremely than the time of the flood and
the following ice age. During the flood, Scripture says the “fountains
of the deep” broke open, releasing hot water from inside
the earth and causing violent volcanic activity. For the first few
centuries after the flood ended, this gradually waning volcanic
activity would have continued to keep the oceans warm and fill
the atmosphere with particles of ash. These particles would have
deflected sunlight, causing cooler temperatures. Additionally, the
heated waters would have caused higher levels of evaporation,
resulting in heavy rainfall in equatorial regions and heavy snowfall
in higher latitudes. Rapid climate fluctuation during the volatile
post-flood period may have caused coral to disappear from
the fossil record and reappear later.

Presently, coral reefs seem to be staying true to this cycle as
they become less common around the globe. Some reefs have lost
over 50% of their reef area. While new reefs are forming
in some areas and some reefs have experienced far
less loss than others, the total area of sea floor covered
with coral seems to have decreased by nearly 50% in
the last five decades. Some forecasts predict 90% of all
coral reef areas will be gone by 2050.

We recognize that the climate fluctuates in a normal
pattern of variability. Regardless of the extent to
which human activities might be contributing to climate
change, corals seem to be responding to current
rising temperatures by fading away. But as to whether
they will disappear completely, only time will tell. We
do not know that the earth’s temperature will continue
rising, but we do know that God is in control of
his creation.

Since corals made a comeback following their most
recent disappearance during and after the global
flood, some individual corals must have survived the
last disappearance, giving us hope for corals struggling
to survive today.

Taking Care of Themselves

Corals are not at the mercy of rising temperatures
without any mechanisms for defense. God created corals
and all animals with the genetic variation to change
in response to stress in a dynamic post-fall world.
Like all organisms, corals have some individuals that
are more tolerant to rising ocean temperatures than
others. As the stress becomes more intense, the less
resilient coral individuals bleach, leaving the stronger
individuals to reproduce and pass on their resiliency.
Eliminating the weaker individuals can actually
make the entire population more tolerant to high
temperatures.

In addition to variation of individuals within a
species, some species of coral are more comfortable
than others at handling the increased temperatures.
The principal fear of some scientists,
however, is that ocean waters might heat more
quickly than what any coral individual or species
can handle without human intervention. This
fear does not seem to be justified by the data, as
corals survived a rapid heating period soon after
the flood7 and some coral species are extremely
heat tolerant.

Stewarding Coral Reefs

Scripture states in Genesis 1 that God created humans in his
image and placed us in a position to steward his creation. We
have the unique responsibility to care for the present and future
needs of the earth and all mankind, while also ensuring that we
never put the cares of animals above the cares of man. But to
ensure the welfare of the people and creatures that depend upon
this underwater ecosystem, maintaining coral reefs will require
some creativity and healthy management.

Scientists have tried to use artificial selection to accelerate
the rate at which coral populations adjust to increased ocean
temperatures. By applying heavy pressure on corals in the laboratory,
they can eliminate the least tolerant individuals and produce
more hearty corals. Introducing more resilient individuals
into areas where reefs have experienced significant bleaching
can repair and regrow reef systems.

Scientists are also trying to mitigate reef loss by monitoring
the species that prey on corals. The quantity of these predators,
including the crown-of-thorns sea stars, have exploded in recent
years. Because these organisms feed extensively on coral, Australia
and other countries have developed programs for reducing
their numbers in delicate reefs.

Finding solutions to conserving coral reefs allows us to exercise
our God-given creativity to help these animals adapt to a
changing world.

Getting Close to Corals

Good stewardship starts by understanding and appreciating
God’s creation. Consider planning a vacation in an area close to a
coral reef. With some snorkeling gear, you can catch a glimpse of
these underwater wonders. Study the animals that make and live
in the reefs and talk to people directly impacted by coral reefs.8

The world of coral reefs beneath the waves deeply impacts our
world here on land. God created these intricate ecosystems to
provide a home for many kinds of life and to provide resources,
enjoyment, and protection for mankind. May we manage these
reefs well so that their biodiversity will continue to inspire awe
and point to the Creator who filled the earth with life.

Dr. Matthew Ingle is an associate professor and assistant chair of biology at The Master’s
University. He is a graduate of The Master’s College and Loma Linda University (MS, PhD). His
research interests vary from disease to marine biology.