You, Me, and the Sea: Our Life with Coral Reefs

Picture, if you will, a clear blue sea.

You’re going snorkeling along a coral reef. This is biodiversity on over-drive: Every square centimeter is covered with hundreds of little creatures. You see millions upon millions of tentacle-rimmed mouths—each feeding a tiny individual coral polyp—guarded savagely by resident crabs, fish, and shrimp. Right next door, a myriad of other coral species, with added choice residents and predators, sway in the waves. Algae—the sugar-producing pals of corals—grow in and around these polyps, exchanging sugars, oxygen, and other nice things.

Long story short, even if you spent your entire life only looking at coral reefs, you’d see tens of thousands of species.

snorkel by Yodyodyo
Photo by Yodyodyo

But coral reefs are in danger. Many have died completely. Seventy five percent of the remaining coral reefs are threatened.

The threats to coral reefs are massive. Climate change is making waters warmer, stressing corals and their tiny resident algae. As oceans absorb the carbon dioxide we are putting into the air, the water becomes more acidic and breaks down the bony skeleton on which corals make their home. There are countless other challenges—like people fishing with cyanide or dynamite, invasive species, and exploitation for coral trade.

But let’s focus on just one threat: the crown-of-thorns starfish.

Crown of thorns starfish by Matt Kiefer
Crown-of-thorns starfish eating coral by Matt Kiefer

The savage-looking crown-of-thorns starfish is a coral eater. It cruises over entire areas of coral, turns its stomach inside out, and swallows the digested food. Each month, it can eat a meter squared of coral.

You might say that starfish are just part of nature’s scheme. Humans didn’t put them there. And you’d be right, for the most part. Crown-of-thorns starfish play an important role in keeping fast-growing corals in check, allowing other coral species to grow. This keeps the biodiversity high and the ecosystem healthy.

In a balanced reef, corals grow and starfish and other predators eat some of the coral. Both stay in relative balance (even though they may fluctuate with time). But imagine if you make it harder for the coral to grow (for the reasons we’ve already mentioned), and easier for the starfish to multiply. Things lose their balance.

Lately, these starfish have been getting out of hand. In some areas, crown-of-thorn starfish were responsible for almost half of coral decline. And—guess what—humans are a big part of the problem. Here’s why:

  • We’re giving crown-of-thorn starfish more food. By allowing dirty urban water runoff to go into rivers and flushing fertilizers from our farms and yards, we are making water more nutritious for plankton, the baby crown-of-thorn’s choice food. If the spike in plankton populations coincides with the starfish’s spawning season, more starfish survive into adulthood than would under natural conditions.
  • We’re helping them grow. By warming oceans through climate change, we are potentially speeding up the growth of larval starfish into adults. Shortening the time it takes for these babies to grow into adults means we may be increasing their probability of survival by 240 percent!
  • We’re killing their predators. Once a crown-of-thorns starfish is mature, it has very few predators. Of the predators it does have, the giant triton—a half-foot marine snail—is caught and killed for its shell, often sold to tourists visiting tropical areas. The humphead wrasse, another predator, is illegally fished or collected for the aquarium fish trade.
Triton snail (Charonia tritonis) attacking crown-of-thorns starfish, by ARKive; KurtAmsler
Triton snail (Charonia tritonis) attacking crown-of-thorns starfish, by ARKive; KurtAmsler

So our everyday choices have very real impacts. Our decision to add fertilizer to our yards and eat foods that are grown with too many chemicals impacts coral reefs by shifting nutrients in the water. Our decision to skip an election where we could have voted for politicians who support taking action against climate change impacts coral reefs. Even the decorative trinkets from our last vacation and the fish in our aquaria and on our plates impact coral reefs. And, remember, that’s just focusing on one part of the coral problem.

But why does any of it matter?

Because without coral reefs, we’re in deep, deep trouble.

The obvious problem is that losing coral reefs means losing sea turtles, mollusks, and one third of fish species. Less obvious is the danger we are causing our own wellbeing: even though coral reefs cover less than 1 percent of the Earth’s surface, they provide goods and services worth USD 375 billion each year!

In some countries, one out of four fish catches depends on coral reefs, providing food for tens of millions of people. In the U.S., fisheries that depend on coral reefs are worth USD 100 million.

Many drugs for cancer, arthritis, and infectious diseases are being developed from reef animals and plants. Coral reefs protect us from wave action, controlling erosion and safeguarding our businesses, homes, and lives during extreme weather. Healthy reefs provide millions of jobs through tourism, fishing trips, hotels, restaurants, and other businesses. In the Florida Keys alone, reefs are estimated to have an asset value of USD 7.6 billion!

Photo by Unsplash
Photo by Unsplash

Here’s what we can do.

When you see the connections we have to natural systems, it gets easy to make better choices. There are small things we can do every day to make it easier to live in balance with coral reefs. Thank you, Nature Conservancy, for these 10 easy steps to protect coral reefs:

  1. Conserve water: Using less water means having less runoff and wastewater in our oceans.
  2. Help reduce pollution: Reducing your carbon footprint by walking, biking, or using shared transportation helps slow down the warming of oceans.
  3. Use only ecological or organic fertilizers: Fertilizers flow thousands of kilometers down rivers and into oceans. These chemicals throw off the balance of nutrients in the water, changing which species survive.
  4. Dispose of your trash properly: Plastic bags, six-pack rings, unwanted fishing lines, and other trash can kill sea life. If you see trash, pick it up and toss it in a bin.
  5. Support reef-friendly businesses: Ask your fishing, boating, hotel, aquarium, dive and snorkeling operators how they protect the reef.
  6. Plant a tree: Trees reduce runoff and contribute to reversing the warming of the planet.
  7. Practice safe and responsible diving and snorkeling: Don’t touch or anchor your boat to the reef. Contact with corals can kill them.
  8. Volunteer for a coral reef cleanup: Whether you live or vacation close to a coral reef, groups are always looking for help. Find an organization here.
  9. Contact your government representatives: Demand that they take steps to address climate change, stop sewage pollution, and expand protected marine areas.
  10. Spread the word: I don’t know about you, but when I learned about the importance of coral reefs, I wanted to share my excitement with everyone. Share your enthusiasm with others and get them involved.

These seem like small actions but, trust me, the more people make the change, the safer our reefs (and our economies and societies) will be.

Keep an eye out for our biodiversity mini-series to learn more about easy steps to bring our planet toward sustainability!

Gaelle Gourmelon is director of communications at the Worldwatch Institute. She has a background in biology and environmental public health.

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