Coral growth anomalies affect biological function

January 16, 2012  |   |  1 Comment
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coral growth anomalies

Type A, left, and Type B growth anomalies

Two easily discernible types of growth anomalies have been observed on rice coral in Hawaiʻi.

In both types, lesions develop into pale protuberant masses, but Type A looks something like a scoop of cottage cheese while Type B appears more like a ball of mozzarella.

Three people in dive gear in water

Student Makani Gregg with Misaki Takabayashi, center, and John Burns at Waiōpae tide pools

Marine scientists at the University of Hawaiʻi at Hilo wanted to know if the differing morphology indicates underlying differences in the affected tissues and whether they affect the corals’ biological functions.

Associate Professor Misaki Takabayashi and John H. R. Burns, a Tropical Conservation Biology and Environmental Science Program master’s candidate sampled rice corals, or Montipora capitata, from Waiʻōpae tide pools in southeast Hawaiʻi Island, where there is an unusually high prevalence of growth anomalies.

They found that the tissues of growth anomalies had

  • Fewer nematocytes (cells that deliver toxins to entangle prey or repel attackers) and mesenterial filaments (cells involved in digestion and protection)
  • Lower density of symbiotic dinoflagellate algae, particularly in Type B, which impairs corals’ ability to grow
  • Reduced ovum development, particularly Type B, which limits reproductive potential and has genetic implications for coral population and evolution
  • Reduced skeletal density, which likely increases susceptibility of affected colonies to erosion and predation
microscopic samples of healthy and diseased coral tissue with structures stained purple

Under the microscope, developing ova (O), mesenterial filaments (MF) and nematocytes (N) are more evident in healthy coral tissue, left, than in the Type A growth anomaly

“All findings from this investigation support the growing evidence that growth anomalies significantly affects coral’s biological function and is, by definition, a disease,” the authors write in the December 19, 2011 online edition of PLoS One Biology.

While the Type B growth anomaly is less prevalent, the tissue showed the most prominent disease signs, suggesting that it is the more severe and advanced stage of what maybe a progressive disease, they observed.

There was no recovery and only limited tissue regeneration evident in the photo monitoring of affected populations conducted by the researchers over three years at the tide pools.

While growth anomalies represent a threat to coral health and warrant more research to identify causal factors and possible role of environmental stressors, scientists haven’t observed rapid or extensive outbreaks such as that seen recently in Kāneʻohe Bay, where rice coral have been affected by a different disease called Montipora White Syndrome.

The Hilo research was supported by the University of Hawaiʻi Sea Grant program.

Read the article.

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Category: Research

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  1. Sara Brenes says:

    Hello everyone! I think that what you found here is very fascinating and that you guys should keep up the good work! This is just another step to help put our oceans at ease from the harsh and cruelness that we are continually putting into it. Schools dedicated to halp preserving our oceans like UH are very dedicated and hard working and will make a differernce in the world. Whether it’s tagging sharks or taking samples of corals, were all doing our part and the best that we can to help make a better world!

    Thank you and please visit my website!!!

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