P. Frouin et P. Hutchings, Macrobenthic communities in a tropical lagoon (Tahiti, French Polynesia, central Pacific), CORAL REEF, 19(3), 2001, pp. 277-285
Soft bottom communities were sampled quantitatively in Tahiti lagoon (Frenc
h Polynesia) at 18 stations in five zones around the island over 1 year. In
addition, various environmental parameters (silt/clay fractions, organic c
ontent, chlorophyll and phaeopigment content) were sampled at the same stat
ions over 2 years. The temporal and spatial variabilities of the macrobenth
ic communities are described and related to these environmental parameters.
Each zone ran from the fringing reef to the inner flat of the barrier reef
. The macrofauna exhibited a high richness (392 taxa) with an average mean
biomass of 1.8 g AFDW m(-2) (grams ash-free dry weight per square metro). T
hese communities exhibited temporal but not seasonal fluctuations. The biom
ass of the macrofauna increased from the fringing to the barrier reefs, and
the density of individuals was significantly higher on the fringing reefs.
Ordination techniques highlighted four groups of stations characterised by
distinctive species composition, density and biomass. The first group incl
uded stations located on the inner flat of the barrier reef and in the shal
low lagoon area and was characterised by highly diverse communities dominat
ed by polychaetes. The second group primarily included stations from the in
dustrial and hotel zones. This group had the lowest diversity and was also
dominated by polychaetes, especially the capitellid Dasybranchus sp. 1. The
third group was dominated by gastropods and bivalves. The final group of s
tations was represented only by station 51, in zone 5, which was characteri
sed by mobile soft sediments and wave action and was dominated by the decap
od Hippa cf. pacifica. Presumably, these mobile sediments facilitate the de
velopment of this benthic community, which does not occur elsewhere in the
lagoon. The diversity and biomass of these benthic communities are low comp
ared with most other areas in the South Pacific.