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-m2 quadrats 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.