Composition and diversity of prokaryotic communities sampled from sponges and soft corals in Maldivian waters

Abstract

In the present study, prokaryotic communities from nine sponge species, two octocoral species, sediment and seawater were assessed from Maldivian coral reefs. All host species contained prokaryotic communities, which were distinct from those found in sediment and seawater. Certain host species, however, contained relatively high abundances of environmental OTUs, that is, OTUs recorded in sediment and/or seawater. This was particularly the case for the sponge species Svenzea novo sp. and Stylissa carteri with respect to seawater and Liosina paradoxa with respect to sediment. The sponge species Svenzea novo sp., S. carteri, L. paradoxa, Jaspis splendens and Ptilocaulis cf. spiculifer all had relatively high abundances of Proteobacteria, Cyanobacteria and Planctomycetes and relatively low evenness compared to the remaining sponge species. They also housed distinct subsets of highly abundant OTUs, which were rare or absent in other hosts, a trait they shared with the octocoral species. The aforementioned compositional traits suggest LMA status for these sponge species. The remaining species (Hyrtios erectus, Luffariella variabilis, Neopetrosia chaliniformis and Plakortis cf. kenyensis) had high relative abundances of Chloroflexi, Actinobacteria, Acidobacteria, Gemmatimonadetes, PAUC34f (or SAUL; sponge-associated unclassified lineage) and Poribacteria, high evenness and limited compositional variation among samples, traits associated with HMA status. Our results, furthermore, confirmed the previously established classification of H. erectus as an HMA and S. carteri as a LMA species. Both octocoral species (Melithaea maldivensis and Paraminabea sp.) housed prokaryotic communities, which were compositionally distinct from sponge species and included significantly discriminating OTUs assigned to the Tenericutes, Spirochaetae and Proteobacteria phyla and the genera Mycoplasma (Tenericutes), Spirochaeta 2 (Spirochaetae) and Endozoicomonas (Proteobacteria).