A Better Understanding of Coral Reef Ecosystems

Pelagic predators such as these barracuda, Sphyraena qenie, are part of the coral reef ecosystem in the U.S. Line Islands (NOAA Photo by Kevin Lino).
A team of scientists have embarked from Hawai'i on a three-month survey of coral reef ecosystems at Johnston Atoll, the U.S. Phoenix Islands, the islands of American Samoa, and the U.S. Line Islands in the tropical Pacific Ocean. The overarching objective is to better understand the coral reef ecosystems of these areas, many of which are seldom explored. The research expedition is part of a regular monitoring program, conducted by the Coral Reef Ecosystem Division (CRED), headquartered in Honolulu, Hawai'i. The expedition is supported by NOAA's Coral Reef Conservation Program and involves extensive cooperation among NOAA scientists and research partners, including the University of Hawaii Joint Institute for Marine and Atmospheric Research (JIMAR), the U.S. Fish and Wildlife Service, San Diego State University, and the Papahānaumaokuākea Marine National Monument.

The research expedition will be carried out from February 27 to May 24, 2012 aboard the NOAA ship Hi'ialakai. Under the leadership of Chief Scientists Dr. Jill Zamzow, Dr. Bernardo Vargas-Angél, and Jamison Gove, a diverse team of researchers will be conducting multidisciplinary coral reef ecosystem surveys, assessing the status of fishes, corals, algae, marine invertebrates, and the oceanographic conditions in which these organisms exist. The scientific data collected during the three-month research expedition will enable informed and effective implementation of ecosystem-based management and conservation strategies for coral reef ecosystems, helping to ensure their protection for generations to come.

Sunday, April 19, 2009

A little more about corals

by Jean Kenyon, photo by Cristi Richards

While on the expedition we have received some excellent questions from students following the expedition.  From time-to-time we will try our best to answer as many of your questions as we can.  For Mr. Hill's period one class, here is a brief discussion on corals by Dr. Jean Kenyon:

Corals can reproduce in two major ways. One is by "sexual reproduction" in which an egg is fertilized by a sperm, which then develops over a period of time into an adult coral. Another way used by some, but not all, types of coral is "asexual reproduction", which usually involves a piece of the adult colony breaking off, becoming re-attached to the bottom, and continuing to grow. Sexual reproduction produces a genetically distinct individual, while asexual reproduction produces offspring that are identifical genetic copies of the parent.

More than 200 species of corals are known from Guam. Wake has been less well studied, but at least 80 species have been documented.

Corals get their color from two sources. Some of the color actually comes from colored pigment in microscopic algae (zooxanthellae) that live inside their tissue. Some, but not all, corals, have additional colored pigment inside their own cells.

For more information on corals, you might want to head over to this coral biology page put together by the Bermuda Biological Station for Research.  Corals exist all around the world in warm tropical waters and while the BBSR deals mainly with Atlantic corals, the basic biology remains the same.


  1. Mr. Hill's Period 6,

    When a coral fragment breaks off the parent coral is the parent coral harmed or can that branch or portion of the coral regenerate?

    Thanks so much for your resonses.

  2. Mr. Hill's Period 2,

    1. If corals are fixed to the bottom how do the sperm and egg from two individual corals combine?
    2.What would happen if the sperm and egg of two different species of coral combine?

  3. Great Questions! To answer your questions I asked Drs. Jean Kenyon and Bernardo Vargas-Angel, two of the coral specialists on our expedition. Here is what they said:

    Regarding Period 6's question on fragmentation:
    Corals have the ability to break easily. It is actually part of their life strategy to reproduce by fragmentation (asexual reproduction). In general terms, if a fragment breaks off the parent colony, both the parent colony and the fragment will regenerate. That is unless the parent colony is smashed into many small pieces. If this happens, it will most likely result in death of most of the fragments as they roll back and forth on the bottom of the reef. Fragmentation particularly common to the branching corals, which can readily propagate and cover extensive reef areas by means of this strategy. Often natural events, such as storms, can cause corals to break and although this is part of a natural cycle strong storms, such as hurricanes, can cause considerable damage on reefs, taking coral populations many years to recover.

    Regarding Period 2's questions on coral reproduction:
    The most frequent pattern is for the eggs and sperm to be released into the water column, where the sperm fertilize the egg. Many colonies of the same species time the release of their sperm and eggs to natural events such as the lunar or tide cycles. The release of millions of eggs and sperm at the same time increases the chances for the gametes to find (or bump into) each other as they drift with the waves and currents.

    There is still much that is not known about the ability of the eggs and sperm of seemingly different species to combine. When reproductive products of two different species combine successfully the result is a hybrid (such as the cross between a horse and a donkey giving rise to a mule). Hybrids are not sexually reproductive; therefore, mules are sterile. However, since corals can grow and reproduce by fragmentation, hybrid corals can successfully populate a reef. There is at least one known coral hybrid. It's name is Acropora prolifera and it is produced by the combination of gametes from two Caribbean coral species: Acropora cervicornis and Acropora palmata. Like mules, this coral does not reproduce by means of eggs and sperm. However, unlike a mule, it can reproduce by asexual reproduction (fragmentation).

    Experiments show that some species form "hybrids" quite readily while others do not. For the ones that do, the degree to which these hybrids subsequently develop into mature adults varies greatly. This ability of some "species" to form hybrids has challenged our ideas about what defines a species. Also, it is poorly know to what degree the results of laboratory experiments on the ability to hybridize actually translates to the natural world.

    Keep your questions coming! We love hearing from you!