Abstract:
The main purpose of this study was to determine the distribution patterns of benthic foraminifera and the relative sedimentation rate. Bottom sediment samples were collected at 7 stations in the Bengkais Strait using gravity corers.
Sediment samples were taken approximately 2 cm on the top of 7 core samples, which is 10 cc wet sediments, was utilized for foraminiferal study. The number of individuals of benthic foraminifera at 7 stations in the Bengkalis Strait range from 98 to 374 individuals consisting of 33 species. Based on analysis index morisita, distribution of the benthic foraminifera dominantantly to clumped, allegedly is closely related with the substrate and environmental conditions. The results of cluster analysis of benthic foraminifera at 7 stations showed 3 groups of distribution: group I, located in the middle of the Bengkalis Strait, group II is located near the island of Bengkalis, which received the influence of the supply of the Siak river, group III is located on the coastline, this station is the first point that influenced the flow. The relative sedimentation rate (L/TL) ranges from 2.7% to 8.8%. Based on L/TL values, the study area can be divided into three areas : 1.) L/TL high which is in the north of the Bengkalis Strait, 2.) L/TL rather high are located in the south of the Bengkalis Strait, and 3.) L/TL low, and in the middle of the Bengkalis Strait (mangrove area). Judging from the distribution pattern and sedimentation rate, Bengkalis Strait is influenced by the flow velocity, sediment types and characteristics of the area in the Bengkalis Strait.
