CORAL Video & Highlights: Coral Reef Resilience

25 Feb, 2014

Transcript of RESILIENCE, narrated by Bruce Carlson, Ph.D.

Few places on earth captivate our sense of wonder as much as coral reefs.

Screen capture from "Resiliance", coral reef video by Bruce Carlson

But how stable and enduring are coral reefs? Violent tropical storms frequently destroy fragile coral skeletons, but broken branches quickly sprout new growth. Coral reefs are resilient and adapted to recover from these natural events, but what happens when humans tip the balance? Let me show you two examples in Fiji.

For centuries Fijians have harvested marinelife without serious harm to their reefs, but near the capital city of Suva there are may more people fishing. Let’s look more closely at this reef.

Screen capture from "Resiliance", coral reef video by Bruce Carlson

This is an area I studied 40 years ago. Constant fishing over decades has reduced the populations of many herbivorous animals.

Screen capture from "Resiliance", coral reef video by Bruce Carlson

In 1973, this was a vibrant shallow reef with a good diversity of corals and fishes.

Screen capture from "Resiliance", coral reef video by Bruce Carlson

By the 1990s, I saw evidence of net fishing, and macroalgae were beginning to dominate.

Screen capture from "Resiliance", coral reef video by Bruce Carlson

By 2001, the tipping point had been surpassed, and corals gave way to algae.

Screen capture from "Resiliance", coral reef video by Bruce Carlson

Resilience was lost when key herbivores were removed.

Higher than normal sea surface temperatures are becoming more frequent worldwide, and cause corals to bleach. In 2000, a catastrophic bleaching event occurred in Fiji. My friends and I immediately headed to the Beqa Barrier Reef to document this event.

Screen capture from "Resiliance", coral reef video by Bruce Carlson

What would happen if all the corals died? Would the reef recover? Would it remain barren?  Or, would it become an algal reef?

The seaward side of the Beqa Barrier Reef is remote, rarely visited by divers, and untouched by pollution. As I recorded this video, I remember thinking how beautiful it was, but in reality it was a catastrophe for the corals and for the animals that coexist with them. When corals bleach, they are actually losing the golden brown algae that live in their tissues.  The polyps are then transparent.

Screen capture from "Resiliance", coral reef video by Bruce Carlson

When the algae are gone, pastel pigments may persist, but otherwise only the white skeleton is visible, making the coral appear bleached.

Screen capture from "Resiliance", coral reef video by Bruce Carlson

Corals usually die after significant bleaching, and they are quickly overgrown by algae.

Screen capture from "Resiliance", coral reef video by Bruce Carlson

As a biologist, I wanted to carefully record observations, so I set up four 30-meter transects along the barrier reef.  On this transect, at the height of the bleaching event, 99% of the reef was covered by corals, but when I returned in 2003 corals had all but vanished.

Screen capture from "Resiliance", coral reef video by Bruce Carlson

By all appearances it was a dead, gray-colored reef.  Many species of fishes that depend on corals for food or shelter had disappeared.

After four years, the reef was still barren, but I noticed pink coralline algae now covering much of the reef.

Screen capture from "Resiliance", coral reef video by Bruce Carlson

Finally, eight years after the bleaching event corals were returning; I counted 960 small coral colonies within 30 square meters.

Screen capture from "Resiliance", coral reef video by Bruce Carlson

After a decade, this resilient reef was on its way to full recovery.

Screen capture from "Resiliance", coral reef video by Bruce Carlson

Coral cover had increased to 48% and coral-dependent fishes were back.

Images are valuable to document change over time.  Freeze-frame shots can be examined in detail using software developed by the National Coral Reef Institute.

Screen capture from "Resiliance", coral reef video by Bruce Carlson

I could calculate the size of every coral colony and describe with precision how coral cover changed over a decade.

Screen capture from "Resiliance", coral reef video by Bruce Carlson

It took years to transform the Suva reef from corals to algae. By contrast, the bleaching event in 2000 was like a forest fire; it quickly changed exquisite coral gardens into barren fields of rock and rubble. It took 10 years, but the Beqa reef did recover; this time, it was a happy ending.

Coral reefs can recover from major storm damage and even severe bleaching events, but full recovery can take many years and human disturbances can tip the balance. Ocean warming and acidification, over-fishing and pollution, must all be reduced to ensure that coral reefs continue to remain resilient.

Screen capture from "Resiliance", coral reef video by Bruce Carlson

 All images, screen captures and video by Bruce Carlson.

Credits
Dr. Bruce Carlson’s video channel on YouTube: Exallias

Bruce Carlson, Ph.D. is a marine biologist and former chief science officer of the Georgia Aquarium. He is also a former director of the Waikiki Aquarium and now lives and does research in Hawaii with his wife and fellow marine scientist Marj Awai.

References
National Coral Reef Institute (NCRI)

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About the author

Matt Pedersen
Matt Pedersen

Matt Pedersen is a Sr. Editor and Associate Publisher with Reef To Rainforest Media, LLC, including AMAZONAS & CORAL Magazines. Matt has kept aquariums for 34 years, has worked in most facets of the aquarium trade, is an active aquarist and fish breeder (both marine and freshwater), and was recognized as the 2009 MASNA Aquarist of the Year.

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