This paper presents the characteristics of coastal and marine sediments of the northern part of Obi Island, Molucca. Grain size analyses were conducted on 24 coastal sediment and 32 marine sediment samples. Taphonomy of Homotrema rubrum was studied on three samples from coral reef that grows on the slope off Laiwui to determine current direction. The mean grain size ranges between 0.01 – 2.6 mm, very well sorted to very poorly sorted, and while skewness varies from very finely skewed to very coarsely skewed. While lithic fragments predominate coastal sediments, biogenic fragments form the majority of marine sediment grains. Textural parameters and sediment composition show three distinctive groups that represent: 1) Akeleletango in the west that is characterized by moderately sorted coarse to fine sand; 2) Tabuji – Laiwui that is characterized by poor to moderately sorted fine granules to fine sand that is interpreted as debris flow deposit; and 3) Anggai in the east that is characterized by poorly sorted coarse sand. Linear discriminate function analysis shows the dominance of shallow marine deposits in beach sediments with strong fluvial influence. The taphonomy of H. rubrum indicates that the prevailing current direction off Obi is westward, which is supported by current observation.

Teluk Lampung terletak di bagian selatan Pulau Sumatera yang berhadapan dengan Selat Sunda.  Kualitas ingkungan perairan ini secara perlahan menurun sebagai akibat pertumbuhan berbagai aktifitas manusia di kawasan pesisir.  Tujuan dari studi ini adalah untuk memahami  struktur komunitas ostracoda sebagai komponen sedimen laut terkait dengan perubahan lingkungan perairan ini. Studi ini menggunakan  22 sub-sampel sedimen dari 4 titik lokasi di lepas pantai sekitar PLTU Tarahan dan beberapa sampel sedimen permukaan yang mewakili kondisi lingkungan saat ini. Kemudian sampel sedimen ini dicuci dalam ayakan berbukaan 0.063 mm, dikeringkan dan digunakan untuk studi ostracoda dengan bantuan mikroskop binokuler. Hasilnya menunjukkan bahwa secara vertikal kelimpahan ostracoda menurun atau tidak hadir di beberapa lapisan bawah dasar laut. Hal ini kemungkinan berkaitan dengan erupsi Gunung Krakatau tahun 1883 yang ditunjang oleh keterdapatan material batu apung di lapisan-lapisan sedimen ini. Secara horizontal, ostracoda dari sampel permukaan atau dasar laut cukup bervariasi dan melimpah namun juga menemukan spesimen abnormal seperti rusak dan terisi atau tertutup oleh material berwarna gelap yang mengandung Al2O3 (17,54%) and SiO2 (37,52%). Hal ini kemungkinan berkaitan dengan menurunnya kondisi lingkungan daerah penelitian yang berpengaruh pada habitat ostracoda.Katakunci: ostracoda, spesimen abnormal, perubahan lingkungan, Teluk Lampung Lampung Bay is located in the southern part of Sumatera island that facing to the Sunda Strait. This bay is gradually degradation environment as a result of growing various human activities in the coastal area.  The purpose of this study is to understand the community structure of ostracoda as component of marine sediments related to environmental changes of this area.  This study used 22 sediment sub-samples from four sites in the offshore area of Tarahan power plant and several surface sediment samples represented the present environmental condition. These samples were then washed through 0.063 mm sieve, dried and used for  ostracod study under a binocular microscope. The result shows that,  the ostracoda assemblages, vertically, are decrease or disappear at certain layers below seafloor. It may related to the eruption of Krakatau Volcano in 1883 that was supported by finding of pumice materials in these layers. Horizontally,  ostracod from surface sediments is quite diverse and abundant but we also found abnormal specimens such as abraded and filled or covered by Al2O3 (17,54%) and SiO2 (37,52%).  It may related to decline environment in the study area that likely affect the habitat of ostracoda. Keywords: ostracoda, abnormal specimens, Tarahan power plant.