Sampling
The sampling strategy was designed to facilitate tests of the effect of time and shore on mobile invertebrates to species level of Echinoids, Gastropods, Asteroids (Acanthaster and Culcita only) of the fringing, backreef, and fore reef habitats of Moorea. For the purpose of this analysis, fringing communities were defined as reefs adjacent to the shore and within ca. 50 m of the land. The backreef is located within the lagoon and may be synonymous with lagoon habitats in other studies. Fore reef habitats were censused at 10 and 17-m depth in order to sample habitats that are representative of the fore reefs of Moorea, and within the depth range tractable to diving research.
The project was designed with twenty 1-m2quadrats along a 50-m transect at each site/depth combination. To facilitate field sampling, the 50-m transect was repeated in 5 contiguous sectors that are not independent (one begins where the previous ends) and are not intended to be a factor in the statistical design. Quadrats were initially set-up randomly, but were then fixed in time. Data are collected for 4 quadrats per sector and 5 sectors per habitat.
Beginning in 2009, Acanthaster are noted when one meter away, by including the note '(1 m away)' in the species field. Beginning in 2013, Culcita are similarly noted when one meter away. And beginning in 2018, Linckia are so noted.
In 2005-2006, where none of this set of invertebrates were observed within a quadrat, the words 'No invertebrate observed' appear in the taxonomy field with a count of zero. In 2007 and later, where none of this set of invertebrates were observed within a quadrat, all species observed elsewhere on the transect are listed with a count of zero.
The “year one” survey spread between 2005-2006 to cover all locations. Each subsequent year contains a complete survey.
*In 2021 fore reef 10 m and 17 m surveys were not conducted due to Covid border closures in French Polynesia.
Statistical Analysis
The original design was established to support a nested, factorial ANOVA experimental approach, but the sampling strategy is amenable to many other designs to meet the users needs. In the factorial construct, shore (north, southeast, or southwest) is treated as a fixed factor, site (LTER 1-6) as a random factor nested within shore, and time as a repeated measures factor based on individual quadrats that are relocated. In the case of the fore reef, depth (10 or 17 m) also was used as a fixed factor to contrast the effects of time and shore between depths. All census methods were designed to quantify mobile invertebrates to species level.
