Pitcairn Islands Expedition Photos: Strange and Beautiful Algae

By Andrew Howley & Kike Ballesteros

With all our emphasis on charismatic fish and stunning coral formations, boring old algae tends to get skipped over by most observers of the underwater world. Being out here in the South Pacific with an algae expert though, it doesn’t take long to be won over by these intriguingly important life forms.

Kike Ballesteros of the Centre d’Estudis Avançats de Blanes, CSIC, is NG Explorer-in-Residence Enric Sala’s long-time mentor and collaborator. He is also the master of all things algal for the Pitcairn Islands expedition, and he agreed to enlighten me about the wonders of algae.

Algae Great and Small
First off, there are two major kinds of algae in a coral reef. One is the tiny microalgae living inside the coral itself and providing a food source (and coloration) for these ancient animals. The other is macroalgae, which includes seaweed, and can be either soft and fleshy or hard and crusty (calcareous).

Basis of the Food Chain
In shallow temperate areas huge plains of seaweed and other macroalgae are the main components of the seascape. Here in the tropics the main component is coral. But don’t be fooled—macroalgae are still hard at work making life at the coral reefs possible.

Algae, both soft and crusty, provide the only food source for plant-eating fishes (such as parrotfishes, chubs, damselfishes or surgeonfishes) and invertebrates (some sea urchins, small crustaceans, and snails). Together with the microalgae that live inside the coral colonies, these algae provide the basic food and energy source much of what lives on the reef.

Builders of the Reef
Crusty algae are also active builders of the reef structure itself.

Red algae (such as Hydrolithon and Lithophyllum in the gallery above) produce limestone which cements together the coral pieces into a solid chunk. Without this ever-rising base, the corals themselves would not be able to build up vertically.

The algae then is what allows the reef to build up towards the ocean surface and cause waves to break off shore, at once forming the lagoon and protecting the interior island’s beaches from the full power of the ocean.

Where Tropical Beach Sand Comes From
Finally, other crusty species of green algae (Halimeda in the gallery) are important sand producers. Beaches along the reef and sand flats under the water are made up of many components, including coral debris and the skeletons of several marine invertebrates (like molluscs, sea urchins, and tiny shelled foraminiferans) but far and away, the biggest contributors are broken up Halimeda.

So next time you’re sipping mai-tais on a tropical beach, raise your glass to algae, the workhorses that make paradise possible.


More From the Pitcairn Islands Expedition

Read All Blogs


  1. […] in the South Pacific, Kike reveals some of his most colorful and finely detailed images yet of the strange and beautiful creatures that call the bottom of the ocean […]

  2. […] Kike’s Strange and Beautiful Algae Photos […]

  3. […] Kike’s Strange and Beautiful Algae Photos […]

  4. sepide
    iran , kish but Island
    December 11, 2013, 8:27 am

    wow , these are very nice….tnx

  5. […] Accompanying Enric in the research will be two veteran Pristine Seas team members: Alan Friedlander of the University of Hawaii will join as the fish specialist, and Kike Ballesteros of the Centre d’Estudis Avançats de Blanes will join from Spain as the benthos (ocean floor) specialist. (See a gallery of Kike’s “Strange and Beautiful Algae Photos.”) […]

  6. Pitcairn Islands - Facebook Statistics
    September 24, 2012, 11:18 pm

    […] Schubring shared a link. Pitcairn Islands Expedition Photos: Strange and Beautiful Algae Read more about National Geographic explorer Enric Sala's […]

  7. […] Read a whole story during National Geographic […]

  8. […] Photo Gallery: Strange and Beautiful Algae […]

  9. […] Photo Gallery: Strange and Beautiful Algae […]

  10. […] Photo Gallery: Strange and Beautiful Algae […]

  11. […] and leafy brown algaes are extremely well represented according to a new survey highlighted in National Geographic this week. If you stop to think about it, we as aquarists know a heckuva lot more about nasty, […]

  12. […] fish and corals that inhabit the undersea and overlook other inhabitants…like algae. A recent National Geographic Explorer’s Journal post has some stunning pictures and details on the various algae being studied in the Pitcairn […]

  13. More to see than just fish and coral...
    April 11, 2012, 9:40 am

    […] to see than just fish and coral… Pitcairn Islands Expedition Photos: Strange and Beautiful Algae – News Watch If I gotta have 6-foot above me — Let it be liquid. When I die, make me fish poop! […]

  14. janab ali
    ksa riyadh
    April 10, 2012, 11:24 pm

    hi geo friends,
    thanks for discover the new world for 3g when we past away from erth the people ar rember us with good words.

    thanks for the people who run ng chanal ,
    janb ali amn ki asha.

  15. Colin
    April 10, 2012, 7:50 pm

    I got some of that stuff in my fish tank! 🙂

  16. […] Read more about National Geographic explorer Enric Sala’s recent expedition to the Pitcairn Islands. For more on his trip:… […]

  17. Rozhan
    April 10, 2012, 5:00 pm


  18. Gabriela
    April 7, 2012, 3:21 am

    Thanks for explaining what algae do. I thought parrotfish created all the sand. Great pics!