Piniak, G. A., Foarty, N. D., Addison, C. M., Kenworthy, W. J. E.

Fluorescence census techniques for coral recruits

2005

Coral Reefs

24

3

496-500

Recruitment processes influence coral population dynamics as well as reef community structure. Coral recruitment is generally determined by one of three methods: artificial settlement plates, small-scale macro photography, or painstaking visual searches in the field. These methods can be labor-intensive or time-consuming, as they require microscopic examination of the settlement surface or enough time for the coral to grow large enough to be visible to the naked eye. Corals and their symbiotic zooxanthellae both contain fluorescent pigments that absorb light at a certain wavelength and re-emit it at a different wavelength. Chlorophyll in the zooxanthellae harvests light for photosynthesis and fluoresces red at about 685 nm. The coral host also contains fluorescent pigments, which could provide photoprotection or amplify the light available for photosynthesis; however, other research suggests fluorescent proteins have no effect on photon absorption and have no photosynthetic function. Host pigments typically exhibit fluorescence peaks between 480 nm and 590 nm. When excited with blue or ultraviolet light, corals often fluoresce green or orange. This distinguishes corals from other chlorophyll containing reef organisms such as algae, which appear red. Fluorescence is a relatively weak effect and is difficult to observe during the day, but is easily seen at night because of increased contrast and reduced backscatter. Recent advances in the use of fluorescence imagery allow photographic detection of reef invertebrates as small as 1 mm diameter. The authors evaluated the capability of fluorescence technologies to identify and enumerate scleractinian coral recruits, and to compare this technique with current methods used to quantify coral recruitment. The working hypothesis was that the increased contrast and reduced backscatter of fluorescence techniques would facilitate the observation of coral recruits. If fluorescence can be developed as a rigorous tool to count coral recruits, it can potentially be a simple, sensitive tool for rapid estimates of the distribution and abundance of scleractinian recruits at a variety of spatial scales. This could be a valuable tool to guide coral reef ecosystem management; for example, fluorescence could provide rapid, non-invasive, site-specific estimates coral recruits needed as input data for spatially explicit coral recovery models.

fluorescence; coral; recruitment; scleractinian corals

10.1007/s00338-005-0495-1

2002 NOAA Coral Reef Conservation Program grant. ASFA

Coral Reef Conservation Program