Foraminifera assemblages were studied in marine surface sediments from shallow open marine, reefal, mangrove and sandy coastal near Serasan, Riau Islands Province. The twelve deposits (sand, silty sand and clay)contain microorganism shell fragments. This study is conducted to identify foraminifera in study area, as well as determine abundance, dominant and typical of assemblages in this area based on quantitative data analyses. The study was done in several stages: literaturestudy, field work and samples collection, laboratory analyses, identical and overview of the taxonomy of each taxon.
The fifty nine genera of benthic foraminifera were identified in the sediment samples, in low to high abundance. The assemblages was dominantly composed of Suborder Rotaliina, the calcareous forms, reached more than 54% of total assemblages (average 78%). Reusella,Cancris, Eponides, Neoeponides, Orbitina,Neoconorbina, Rosalina, Siphoninoides, Discorbia, Lobatula, Planorbulinella, Gypsina, Cymbaloporetta, Epistomaroides, Amphistegina, Nonion, Nonionoides, Heterolepa, Gyroidina, Hanzawaia, Pararotalia, Rotalia, Ammonia, Asterorotalia, Pseudorotalia, Baculogypsinoides, Calcarina, Elphidium, Parrellina, Assilina, Heterostegina and unidentified rotaloidforam are classified intothis group. Porceleneous shells that typified by subordo Miliolina and Lagenina, occur less than 29% (average 17%). Genera Adelosina, Spiroloculina, Agglutinella, Ammomasilina, Lachlanella, Massilina, Quinqueloculina, Miliolinella, Pseudomassilina, Pyrgo, Triloculina, Peneroplis, Archaias, Marginopora, and young miliolidae are classified intosuborder Miliolina; whereas Lagena, Guttulina, Oolina, and Glandulina are Lagenina. SubordoTextulariina and Spirillinina with arenaceous shells are appears rarely in samples. Suborder Textulariina is represented by genera Ammobaculites, Spiroplectinella, Spirotextularia, Dorothia, Karreriella, Bigerina, Sahulia, Textularia, and Clavulina. Spirilina is the only genus of Suborder Spirillinina.
The most frequently encountered genera are Eponides, Amphistegina, Heterolepa, Ammonia, Elphidium, and Assilina(suborderRotaliina), Quinqueloculina (Miliolina) and Textularia (Textulariina). The most abundant benthic foraminifera is Asterorotalia(represented by A. trispinosaThalmann) that recorded in open marine and near reef samples. It was found that high abundance and diversity of benthic foraminifera assemblages were recorded in open marine.