Artificial substrate

Sampling recruits is achieved using artificial substrate as described by Mundy (2000). In each station, 20 metallic fixings are randomly and permanently set on the substrate over an approximate surface of 100 m². Each fixing has a central stainless steel screw where a pierced terra cota plate (11 x 11 x 1 cm) can be attached. While the fixings are permanent, the plates which serve as recruiting substrate can be changed easily.

After recovering the plates, they are whitened using bleach, dried in the sun and examined using a binocular magnifier. The recrutes present on the plates are counted and identified to the family level for the Acroporidae, Pocilloporidae and Poritidae and two additional categories are defined: « autres familles » for other family and « cassés » for broken.

Belt-transect

At each of the nine stations, three belt-transects of 10 m² (1 x 10 m) are delimited. These belt-transects are set parallel to the reef crest and set at least 2m wide apart. All the belt-transects of a station represent a zone of roughly 100 m². Two permanent stakes are installed at both ends of the median line of each belt-transect. A tensed string between these stakes and a 1m wide frame is used to pin point the exact location each year with a precision of 5cm.