Great Barrier Reef’s Outer Reef

Our last full day in Port Douglas Australia was on a snorkeling trip to the Outer Reef of the Great Barrier Reef. On previous Australian trips, we dove and snorkeled a few section of the Great Barrier Reef. Each of these have been off of islands (Lizard, Heron and Wilson) to which we had to fly from the mainland. This day trip, with Wavelength Reef Cruises, explored some of the coral and fish in the inner and outer reefs off the coast from Port Douglas—no flying required.

Getting Educated on the Way

During the  hour-and-a-half cruise to just inside the outer edge of the reef, the excellent resident biologist began with an overview of the nature of the reef and the most effective ways of approaching fish. For example, don’t stare at them (move your head and eyes from side to side, as if you were navigating rather than focusing on a particular animal); approach them from the side (swim alongside them and gradually move closer rather than from the rear); and paddle slowly while keeping your arms at your side (rather than using them for propulsion).

He then asked the 30 snorkelers what we were most anxious to experience on the reef. While most were game for anything, a few people had special requests for sharks, turtles, manta rays, octopi and clownfish. He then discussed each one, identifying the environments and times of day in which we would find them, how best to look for each, the behaviors to look for and how best to approach each so as to get the best look. For example:

  • Sharks. We were most likely to see small reef sharks that primarily eat crustaceans. While they are harmless to humans, he explained that all sharks are motivated primarily by protecting themselves from injury (since injury would limit their ability to hunt and indeed, turn themselves into potential prey). Therefore, they will avoid creatures that are larger than themselves and those with which they are not familiar or do not understand. They will attack only if provoked. If we saw them, it would likely be in deeper water and most likely, outside the reef.
  • Turtles would most likely be green turtles. He applied the general rules for approaching all marine life to turtles, and specifically, how to tell when they are preparing to breathe and how to clear a spot for them to do so (to reduce the chance that they will speed away to get their own space).
  • Manta rays. We unlikely to see them in waters that were shallow enough for us to see coral or reef fish, but if we wanted to even try to find them, we must take time for our eyes to adjust to the limited light of deeper waters, rather than the shallow reef. We may, however, see smaller sting rays.
  • Octopi are seldom out in the day. Best chances to find them areto look for indirect signatures of these extremely intelligent, extremely versatile animals. These include an “octopus garden”, which consists of a semi-circular ring of shells or coral that octopi use to decorate the front of their lairs. The second is to look for coral trout that are suspended vertically in the water, either toward a garden in an effort to entice the octopus to participate in a cooperative hunt for food, or, after a cooperative hunt has already been arranged, to point the octopus to the hole where the trout has chased potential prey.
  • Clownfish are increasingly rare after the movie “Finding Nemo” created a huge market for capturing them for private aquariums. As a result, protected sites are the best place to find these fish.

Snorkeling The Outer Great Barrier Reef

Then we went to 3 different dive sites—each as or more spectacular than the other. Once at each site we were free to snorkel anywhere we wished However, many of us spent much of our water time with our guide, who was able to find and identify creatures that we would have otherwise missed. We saw:

  • Sharks. Most of us saw a roughly five-foot reef shark and some even a much more unusual seven-foot tiger shark, which happened to be stalking a turtle until he spotted us and fled.
  • Turtles. We enjoyed watching a green turtle with whom some of us swam for perhaps ten minutes;
  • Sting rays;
  • Octopus garden. Not the actual octopus unfortunately;
  • Clownfish. Four of them were cavorting in a stand of soft coral.

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Then there were the:

  • Dolphins who were riding the bow of our boat to get a push by swimming just ahead of the boat’s pressure wave;
  • Crown of thorns starfish (which our guide found after spotting a recently denuded patch of coral that the starfish devoured the previous night);
  • Dozens of lovely anemone fish that we saw in addition to the clownfish (which is also a member of the anemone family);
  • Huge Mauri wrasse that greeted us when we entered the water for the second of our two swims on the outside edge of the outer reef (for which we technically in the Coral
    Sea, rather than on the Barrier Reef;
  • Parrotfish, of many different species and colors. Parrotfish play a critical role in maintaining the health of the ecosystem, both by eating excess algae that accumulates on coral which clears the limestone substrate on which baby coral can land and survive, and even by their continual scratching of the limestone, which creates sound waves which guide baby coral from their nursery in mangrove swamps, out to the reef.
  • Dozens of other pretty or otherwise interesting fish including triggerfish, wrasses, angel fish, tang, surgeonfish, butterfish, damselfish and needlefish

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While the sea life was amazing, we also saw endless blankets of beautiful coral of virtually every type (brain, staghorn, elkhorn and especially elaborate plate) and of virtually every color (other than red and yellow). The colors (especially the brilliant blues) are particularly pronounced in the crystal clear waters outside the reef (the water was so calm that we were able to do a drift snorkel in this area). And we also saw a small handful of dramatic giant clams (although most of these had relatively monochromatic black mantles).

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The guide also told us how to distinguish coral that is healthy (usually some shade of brown or burnt orange), stressed (typically a bright green, yellow, or blue) and bleached (grey) and the synergistic biological relationship between the coral and algae as the coral is stressed. He explained how the reef can create its own weather and continually rejuvenate the itself by creating updrafts of warm, moisture-laden air. These form into clouds that waters (both via rain and “cloud striping”, which occurs when trees pull moisture directly from low clouds and fog) the rainforest, carrys the nutrients from decomposing plants down to the mangrove swamps, and serves as a nursery for baby fish and coral that continually repopulates the reef. (Crocodiles also play a vital role in this cycle by eating and otherwise controlling the number of predator fish (barramundi, coral trout, etc.) that would otherwise eat the babies in the mangrove swamp nursery.

And we learned how changes in global and water temperatures and El Nino and La Nina patterns disrupt this complex cycle in ways that, while impossible (at least with current levels of climatic understanding) to fully predict, are particularly dramatic in this fragile, interconnected ecosystem. This is particularly true for the future of a reef in which many coral thrive in temperatures between 27 and 29 degrees (Celsius), but die in temperatures above 30 degrees.

This was, by far, the most educational of all of the snorkeling tours—and indeed of most of the many nature tours we have taken (with the notable exceptions of one-to-two week tours of the Galapagos and Antarctica). It was also one of the most beautiful of our many snorkeling trips. But for all the superlatives we can lavish on this tour, it was, for us, a preview to the main act—a three-day revisit to Lizard Island, one of our favorite spots in the entire world. And that is the topic of our next blog.

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