Fitoplankton di laut mempunyai peranan penting sebagai pembentuk dasar dari rantai makanan (food-chain) dan bertanggung jawab dalam produksi primer (primary production). Kelimpahan dan jumlah jenis fitoplankton secara tidak langsung akan mempengaruhi tingkat kesuburan suatu perairan. Penelitian ini bertujuan untuk mengetahui  keberadaan fitoplankton ditinjau dari kelimpahan, indeks keragaman, indeks keseragaman, dan indeks dominansi di estuaria Banyuasin, Sumatera Selatan. Penelitian dilakukan pada bulan  September 2017 di sebelas stasiun. Contoh fitoplankton diambil di permukaan perairan dengan menggunakan jaring plankton yang berbentuk kerucut dengan diameter 30 cm, panjang 100 cm dan ukuran mata jaring 30 μm. Hasil penelitian menemukan 17 marga fitoplankton dari kelas Bacillariophyceae, dan terdapat ledakan populasi dari marga Skeletonema, dengan komposisi sebesar 98,71%. Nilai indeks keragaman (H’), indeks keseragaman (E) dan indeks dominansi (D) memperlihatkan adanya kondisi struktur komunitas fitoplankton yang tidak stabil. Nilai indeks keragaman pada penelitian ini berkisar antara 0,02-0,87 yang berarti komunitas dengan keanekaragaman yang rendah,  nilai keseragaman berkisar antara 0,01-0,25 yang berarti komunitas dengan keseragaman tidak merata dan nilai dominansi berkisar antara 0,67-0,99 yang berarti terjadi dominansi jenis fitoplankton.

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Musi Estuary is strongly influenced by various land activities such as plantations, industry, agriculture and others. These activities have a negative effect on the condition of these waters, one of which is sedimentation. Sedimentation is an important factor that must be considered during development such as port construction and reclamation. This study aims to analyzed the dynamics of shoreline changes in the Musi Estuary, South Sumatra associated with sediment characteristics and sedimentation rates in the area. This research was carried out by installing a sediment trap for 14 days. Trapped sediments were taken once a week and calculated the volume and rate of sediment accumulation. The results showed that the dominant sedimentary characteristics in Musi Estuary were dominated by clay and mud with sediment accumulation rates ranging from 86,63-97,97 mg/cm2/day. The results of the dynamics of shoreline changes in the form of abrasion at stations 2, 3, 4, 5 and 6 and sedimentation at Station 1. The highest land change by abrasion was found at station 6 with land changes ± 129, 83 meters in 5 years and land changes by sedimentation at station 1 with a reduction in land ± 13.31 meters in 5 years.  Muara Sungai Musi merupakan perairan muara yang sangat dipengaruhi oleh berbagai aktivitas daratan seperti perkebunan, industri, pertanian dan lain-lain. Aktivitas tersebut memberikan efek negatif terhadap kondisi perairan tersebut, salah satunya adalah sedimentasi. Sedimentasi menjadi faktor penting yang harus diperhatikan pada saat melakukan pembangunan seperti pembangunan pelabuhan dan reklamasi. Penelitian ini bertujuan untuk menganalisis dinamika perubahan garis pantai di Perairan Muara Musi, Sumatera Selatan dikaitkan dengan karakteristik sedimen dan laju sedimentasi di daerah tersebut. Penelitian ini dilakukan pada bulan November 2019 dan pengambilan sampel dilakukan dengan memasang sedimen trap selama 14 hari. Sedimen yang terperangkap diambil seminggu sekali dan dihitung volume dan laju akumulasi sedimen. Hasil penelitian menunjukkan bahwa karakteristik sedimen yang dominan di Muara Musi didominasi oleh tanah liat dan lumpur dengan tingkat akumulasi sedimen berkisar antara 86,63-97,97 mg/cm2/hari. Hasil dinamika perubahan garis pantai dalam bentuk abrasi di stasiun 2, 3, 4, 5 dan 6 dan sedimentasi di stasiun 1. Perubahan lahan oleh abrasi tertinggi ditemukan di stasiun 6 dengan perubahan lahan ±129,83 meter dalam 5 tahun dan perubahan lahan oleh sedimentasi di stasiun 1 dengan pengurangan lahan ±13,31 meter dalam 5 tahun.

Bottom sediments have an essential role, among others, as a habitat for living things, determining waves, turbidity of the waters, and as information on marine development. Determination of the type of bottom waters can be done using the acoustic method. The use of sound waves in the acoustic method can detect objects in the water column using an echosounder instrument. This research aims to analyze the value of acoustic backscatter in finding the type of sediment at the bottom of the water. This research was carried out in October 2018 - January 2019 in the waters of the Banyuasin River Estuary. The results showed that the sediment base corresponds to the acoustic backscatter value, namely clayey sand with an SS value of -16.23 dB. Clay with SS values ranging from -24.09 dB to -21.29 dB. Muddy clay with SS values ranging from -17.88 dB to -15.54 dB, and sandy clay with an SS value of -16.89 dB. Based on multiple linear regression analysis, the three types of sediment fractions strongly influence the formation of acoustic backscatter by 65.3% or 0.81.

Zooplankton is one of the factors that can affect water conditions. The existence and abundance of zooplankton can indicate the level of water fertility. Zooplankton abundance can be observed by using two methods. These are the bongo plankton net and underwater acoustics method. This study aims to determine the abundance of zooplankton using bongo plankton net 250 ?m mesh size and underwater acoustics method using Simrad EK15 200 kHz frequency. This study was conducted in July 2019 in the Banyuasin estuary. The results showed the abundance of zooplankton using bongo plankton net ranged from 7-116 ind/m3, and the zooplankton density in underwater acoustics ranges from 0-2700 ind/m3. It means the ratio between both of the methods is around 1:20. The comparison could illustrate the difference in zooplankton density. It is necessary to adjust the specifications instrument and sampling technique of zooplankton sampling equipment and underwater acoustics instruments to obtain more accurate results.Keywords: Abundance, Banyuasin estuary, hydroacoustics, zooplankton,