Marine Invertebrates of Bermuda Yellow Finger Coral (Madracis mirabilis) Johnna P. Fay Dr. James B. Wood - Editor Taxonomy  Habitat  Ecology  Recent Research  Commercial Importance  Bermuda Laws  Personal Interest  References  Links

Taxononmy


Phylum: Cnidaria
  Class: Anthozoa
    Order: Scleractinia
      Family: Pocilloporidal


Habitat


Madracis mirabilis is found on reefs throughout the Caribbean, South Florida, and the Bahamas. Colonies are fairly common in shallow reef environments and are found at depths ranging from 5 meters to 50 meters (Veron 2000). In fore reef environments,M. mirabilis forms hemispherical aggregations up to 2 meters in diameter, composed of thousands of thin, cylindrical branches (Bruno and Edmunds 1998). In back reef and lagoon environments, the coral colonies can form in larger aggregations, sometimes more than 5 meters in diameter, and have thicker branches with flattened ends (Bruno 1998; Bruno and Edmunds 1998). Colonies of M. mirabilis have been known to form in reef areas where various sponges and algae compete for space, mostly scattered around low diversity reef habitat. Branch spacing varies depending on the reef location and environment (Sebens et al. 1997). Some studies have shown that fish predation may possibly have an impact on the vertical distribution of M. mirabilis on Caribbean reefs (Grottoli-Everett and Wellington 1997).

Ecology


Colonies of the Madracis genus are often described as small and cryptic (Mather and Bennet 1994). Madracis mirabilis appears light yellow, cream or pale brown in color (Veron 2000). The small polyp coral forms dense clumps of small pencil-sized branches with blunt tips (Grottoli-Everett and Wellington 1997). The branches are not connected by tissue, but rather by a common skeleton that the individuals share. As the colony grows, the tissue at the base of each branch diminishes, leaving a segment of bare skeleton. The newly available space on the coral skeleton can then be utilized by sessile invertebrate species and algae (Bruno and Edmunds 1997).

M. mirabilis is a hermaphroditic coral species, meaning that individual colonies have both male and female gametes. The gametes have been observed to develop within mesenteries, which can be hermaphroditic or gonochoric. Methods of reproduction include “pseudo-brooding” and fragmentation; pseudo-brooding involves planulae being released early from colonies without signs of internal brooding, and fragmentation involves fragments becoming detached from parent colonies, attaching to a substrate and becoming a new colony (de Putron 2004). Several factors affect the spawning of M. mirabilis; although spawning varies from year to year, temperature, lunar cycle, photoperiod, and chemical compounds affect the yearly spawning cycle (Dubinsky 1990). Asexual fragmentation requires a low amount of reproductive energy from the coral, but leads to low genetic diversity and low dispersal of new colonies. Usually caused by increased physical activity on the reef, fragmentation can be the primary mode of reproduction for corals in which sexual recruitment is rare (Bruno 1998).

Scleractinian corals have a unique symbiotic relationship with algal zooxanthellae; the dinoflagellate Symbiodinium spp. enhances growth and survival in many coral species (Diekmann et al. 2003). The photosynthetic ability of zooxanthellae supplies the coral with essential sugars, amino acids, and carbohydrates that are used for respiration, growth and calcification. In return, the zooxanthellae use some of the metabolic wastes from the coral, such as carbon dioxide, ammonia, and phosphates. This recycling limits the loss of nutrients and promotes high productivity of corals (de Putron 2004).

At increased depths, symbiotic zooxanthellae cannot meet the coral’s energy requirements. Therefore, particle feeding is necessary to provide energy for growth and maintenance and to supply nutrients that may be limited. Zooplankton capture by corals is influenced by the mechanism of particle capture, the polyp’s ability to adhere to the prey, and by any selectivity for particular types of prey (Sebens et al. 1996). Feeding ability is also affected by flow, which is affected by the branching morphology of the coral colonies. M. mirabilis is a passive suspension feeder and feeds primarily by using tentacle capture (Sebens et al. 1996). Although mucus is produced in the polyp mouth, the mucus strands are not used in the capture mechanism (de Putron 2004). Direct interception is the most likely mode of particle capture for M. mirabilis; branches commonly capture zooplankton ranging in size from less than 200 µm to more than 300 µm (Sebens et al. 1996; Sebens et al. 1997). Zooplankton captured in the polyps of M. mirabilis commonly consists of polychaete, chaetognath and crustacean larvae. Other prey consists of zooplankton from the open water planktonic community and benthic invertebrates. When invertebrates interact with M. mirabilis on a close level, the colony captures they prey and ingests it. In addition, the swimming ability of zooplankton has an impact on coral prey capture rate (Sebens et al. 1997). The polyps of M. mirabilis are generally expanded throughout the day and night for feeding purposes (Veron 2000). One would generally assume that a small polyp coral, such as M. mirabilis, would capture a smaller amount of prey than a coral with a larger polyp size, such as Montastrea cavernosa. However, recent studies have shown that M. mirabilis captures up to 36 times the amount of zooplankton than M. cavernosa does. The reason for this success is explained by the increased surface area of M. mirabilis due to branching, thus increasing the encounter rate (Sebens et al. 1996).



Recent Research


Since it is a fairly common coral species on reefs around the world and fairly easy to collect, Madracis mirabilis is used as a model organism for a wide variety of research experiments. The majority of research focuses on coral morphology, fluid dynamics, and physiological processes such as prey capture, gas exchange, and photosynthesis of symbiotic zooxanthellae (Sebens et al. 1997; Sebens et al. 1998).

Coral reef degradation is an exponentially increasing problem affecting the world’s oceans. The effects of pollution from oil terminals, oil tanker traffic and oil refineries are speculated to have a grave long term impact on reef habitats. One tactic used to study the ecotoxicology effects of pollution on a reef ecosystem is the analysis of xenobiotics, in coral tissue. Xenobiotics can commonly be described as foreign, biologically active compounds that can be found in oil and pesticides. In order to carry out experimental processes, numerous coral species were examined, one of which was M. mirabilis. Although no correlation has been found between species specificity and the amount of radioactivity taken up, the use of M. mirabilis has lead to the understanding that Bermudian corals take up xenobiotics from sea water (Solbakken et al. 1984).

Varying stress levels have decreased the amount of coral cover on reefs over time; one such stressor is high temperature. The combination of pollution, habitat destruction and elevated temperatures results in lower ecological reliability. M. mirabilis has been used to study the immunological response of heat shock in scleractinian corals and the progress of developing a biomarker for stress in corals (Branton et al. 1999).

Commercial Importance


The International Ecotourism Society defines ecotourism as “responsible travel to natural areas that conserves the environment and improves the well-being of local people” (ecotourism.org 2004). The survival of coral reefs worldwide is essential to ecotourism in the majority of tropical islands. Geographically speaking, there are 80 countries and locations with coral reefs world wide (Spalding 2001). Not only do coral reefs contribute to the success of tourism through activities such as snorkeling and SCUBA diving, but reefs create a habitat for thousands of vertebrate and invertebrate marine species. Many commercially important fish and shellfish are supplied with feeding and breeding grounds that would normally not exist in absence of coral reefs.

Bermuda Laws


The Coral Reef Preserve Act (1966) act was established in order to protect the world’s coral reef ecosystem; among other reefs, it covers the majority of Bermuda’s fringing reef. Therefore M. mirabilis is protected under this act. Marine plants and animals are protected within the South Shore Coral Reef Preserve and the North Shore Coral Reef Preserve. Under this act, it is illegal to remove, damage, or be in the possession of plants or animals attached to the coast, the benthic community or any reef in the two preserve zones (www.fantasea.bm/diving/law.htm; November 14,2004).

Personal Interest


I have always been interested in coral reefs throughout my life. Last fall I took a writing class at my home university that required the composition of a fairly substantial review paper at the end of the semester. It was advised that we choose a topic somewhat appealing to us, since we would be examining our subject in depth. Having always been a big environmentalist throughout my life and wanting to be a marine biologist, I chose to write my paper on “Solutions to coral reef degradation”. However, it was not until recently this semester that I have had the opportunity to study them in such great detail. While participating in the Coral Reef Ecology class here at BBSR, I had the opportunity to work with Madracis mirabilis on several accounts. M. mirabilis is a fairly common species throughout the Bermuda platform. Over the next four weeks, I will be examining the effects of stress on the feeding of M. mirabilis and Favia fragum for my individual research project.

References

Branton, M., T. MacRae, F. Lipschultz, P. Wells. 1999. Identification of a small heat shock/ a-crystallin protein in the scleractinian coral Madracis mirabilis (Duch. And Mitch.). Canadian Journal of Zoology. 77(5): 675-682.

Bruno, J. and P. Edmunds. 1997. Clonal variation for phenotypic plasticity in the coral Madracis mirablilis. Ecology. 78: 21177-2190.

Bruno, J. and P. Edmunds. 1998. Metabolic consequences of phenotypic plasticity in the coral Madracis mirabilis (Duchassaing and Michelotti): the effect of morphology and water flow on aggregate respiration. Journal of Experimental Marine Biology and Ecology. 229: 187-195.

Bruno, J.F. 1998. Fragmentation in Madracis mirabilis (Duchassaing and Michelotti):how common is size-specific fragment survivorship in corals?. Journal of Experimental Marine Biology and Ecology. 230: 169-181.

de Putron, S.J. 2004. Coral Reef Ecology Lecture notes.

Diekmann, O.E., J.L. Olsen, W.T. Stam, R.P.M. Bak. 2003. Genetic variation within Symbiodinium clade B from the coral genus Madracis in the Caribbean (Netherlands Antilles). Coral Reefs. 22: 29-33.

Dubinsky, Z. Ecosystems of the World 25, Coral Reefs: Elsevier Science Publishing Company Inc. 1990.

Fantasea Bermuda. November 14, 2004. www.fantasea.bm/diving/law.htm.

Grottoli-Everett, A.G. and G.M. Wellington. 1997. Fish predation on the scleractinian coral Madracis mirabilis controls its depth distribution in the Florida Keys, USA. Marine Ecology Progress Series. 160: 291-293.

Sebens, K. P., K. S. Vandersall, L.A. Savina, K. R. Graham. 1996. Zooplankton capture by two scleractinian corals, Madracis mirabilis and Montastrea cvavernosa, in a field enclosure. Marine Biology 127: 303-317.

Sebens, K. P., J. Witting, B. Helmuth. 1997. Effects of water flow and branch spacing on particle capture by the reef coral Madracis mirabilis (Duchassaing and Michelotti). Jornal of Experimental Marine Biology and Ecology. 211: 1-28.

Sebens, K.P., S.P. Grace, B. Helmuth, E.J. Maney Jr., and J.S. Miles. 1998. Water flow and prey capture by three scleractinian corals, Madracis mirabilis, Montastrea cavernosa, and Porites porites, in a field enclosure. Marine Biology. 131 (2): 347-360.

Solbakken, J.E., A.H. Knap, T.D. Sleeter, C.E. Searle, K.H. Palmork. 1984.Investigation into the fate of 14C-labeled xenobiotics (naphthalene, phenanthrene, 2,4,5,2’,4’,5’– hexachlorobiphenyl, octachlorostyrene) in Bermudian corals. Marine EcologyProgress Series. 16: 149-154.

Spalding M.D., C. Ravilious , E.P. Green. World Atlas of Coral Reefs. University of California Press, Berkeley, USA. 2001.

Veron, Jen. Corals of the World, Volume 2. Australian Institute of Marine Science, Townsville, Australia. 2000.

Links

NOAA’s Coral Health and Monitoring Program