. Atoll research bulletin. Coral reefs and islands; Marine biology; Marine sciences. 26 ZOOBENTHOS BIOMASS IN SEDIMENTS : FIRST RESULTS A survey of 20 random stations was realised in the lagoon by A. Intes to provide a first assessment of the macro-zoobenthos of the soft bottoms. These unpublished data have to be considered as preliminary results. Taxonomic structure - results (Fig. 14) In terms of abundance, the Molluscs and the Polychaetes dominate the endofauna with a mean density of and ind nr2 respectively. The crustaceans count for less than 2 ind nr2 and the Echinoderms as wel
. Atoll research bulletin. Coral reefs and islands; Marine biology; Marine sciences. 26 ZOOBENTHOS BIOMASS IN SEDIMENTS : FIRST RESULTS A survey of 20 random stations was realised in the lagoon by A. Intes to provide a first assessment of the macro-zoobenthos of the soft bottoms. These unpublished data have to be considered as preliminary results. Taxonomic structure - results (Fig. 14) In terms of abundance, the Molluscs and the Polychaetes dominate the endofauna with a mean density of and ind nr2 respectively. The crustaceans count for less than 2 ind nr2 and the Echinoderms as well as the lancelets less than 1 ind nr2. The abundance of the Crustaceans is probably under estimated as only large apparent Invertebrates were counted and no digging operations were carried out. Large Invertebrates burrowing in the sediment are not taken into account and their biomass remains unknown. However, the average density of the big burrowing species can be estimated to stand around ind nr2 as revealed by hole density. Regarding the epifauna, the Sponges clearly dominate with around colony nr2. The other organisms are generally scarce except in some very localised areas harbouring high densities of holothuroid (Halodeima atra). 2 -\ g AFDW TAXONOMIC STRUCTURE. 0 Epifauna I Endofauna SW ML CR ED Fig. 14: Taxonomic structure of zoobenthos biomass in sediment (SW : Sea weeds; ML: Molluscs; SP : Sponges ; SC : Sipunculids; PL : Polychaetes; CR : Crustaceans; ED : Echinoderms) expressed in Ash Free Dry Weight (AFDW). In terms of biomass, the global structure is not very different: the Molluscs remain at first rank with 36% of the animal organic matter (AOM), followed by the Sponges with 27% of AOM. The third class includes the Sipunculids, but also all the fauna living in the dead shells and in all probability some micromolluscs. This represents about 25% of AOM. The other groups stand far behind in importance : the Polychaetes are mainly small animals and contribute
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