Methods and measurement variance for field estimations of coral colony planar area using underwater photographs and semi-automated image segmentation

  • Benjamin P. NealEmail author
  • Tsung-Han Lin
  • Rivah N. Winter
  • Tali Treibitz
  • Oscar Beijbom
  • David Kriegman
  • David I. Kline
  • B. Greg Mitchell


Size and growth rates for individual colonies are some of the most essential descriptive parameters for understanding coral communities, which are currently experiencing worldwide declines in health and extent. Accurately measuring coral colony size and changes over multiple years can reveal demographic, growth, or mortality patterns often not apparent from short-term observations and can expose environmental stress responses that may take years to manifest. Describing community size structure can reveal population dynamics patterns, such as periods of failed recruitment or patterns of colony fission, which have implications for the future sustainability of these ecosystems. However, rapidly and non-invasively measuring coral colony sizes in situ remains a difficult task, as three-dimensional underwater digital reconstruction methods are currently not practical for large numbers of colonies. Two-dimensional (2D) planar area measurements from projection of underwater photographs are a practical size proxy, although this method presents operational difficulties in obtaining well-controlled photographs in the highly rugose environment of the coral reef, and requires extensive time for image processing. Here, we present and test the measurement variance for a method of making rapid planar area estimates of small to medium-sized coral colonies using a lightweight monopod image-framing system and a custom semi-automated image segmentation analysis program. This method demonstrated a coefficient of variation of 2.26 % for repeated measurements in realistic ocean conditions, a level of error appropriate for rapid, inexpensive field studies of coral size structure, inferring change in colony size over time, or measuring bleaching or disease extent of large numbers of individual colonies.


Coral reefs Colony size Colony growth Size structure Planar area Image segmentation 



This study was supported by a funding from National Science Foundation Cyber Enabled Discovery and Innovation Award # 0941760. We wish to thank the Smithsonian Tropical Research Institute and the staff of the Bocas del Toro field station.

Supplementary material

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Online Supplemental Table 1 (DOC 834 kb)


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Copyright information

© Springer International Publishing Switzerland 2015

Authors and Affiliations

  • Benjamin P. Neal
    • 1
    • 5
    Email author
  • Tsung-Han Lin
    • 2
  • Rivah N. Winter
    • 3
  • Tali Treibitz
    • 4
  • Oscar Beijbom
    • 2
  • David Kriegman
    • 2
  • David I. Kline
    • 5
  • B. Greg Mitchell
    • 5
  1. 1.Catlin Seaview Survey, Global Change InstituteUniversity of QueenslandSt. LuciaAustralia
  2. 2.Computer Science and Engineering DepartmentUniversity of California San DiegoLa JollaUSA
  3. 3.Rosenstiel School of Marine and Atmospheric ScienceUniversity of MiamiMiamiUSA
  4. 4.Charney School of Marine SciencesUniversity of HaifaHaifaIsrael
  5. 5.Scripps Institution of OceanographyUniversity of California, San DiegoLa JollaUSA

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