Kerang Bakau (<em>Geloina coaxans</em>) merupakan salah satu jenis gastropoda yang diduga memiliki komponen bioaktif yang dapat digunakan sebagai antibakteri. Tujuan penelitian ini yaitu mengeksplorasi potensi kerang bakau (<em>G. coaxans</em>) sebagai sumber bahan alami antibakteri terhadap Vibrio parahaemolyticus. Aktivitas antibakteri ekstrak <em>G. coaxans</em> di uji dengan metode difusi pada konsentrasi 10, 50 dan 100 mg/mL, serta identifikasi senyawa aktif. Hasil penelitian menunjukan rendemen ekstrak etanol <em>G. coaxans</em> yaitu 8,50%, senyawa fitokomia ekstrak etanol <em>G. coaxans</em> terdiri dar alkaloid, tanin, flavonoids, saponin, triterpenoid dan steroid. Aktivitas antibakteri menunjukkan ekstrak etanol <em>G. coaxans</em> memiliki zona hambat sebesar 25,05 pada konsentrasi 100 mg/mL terhadap <em>V. parahaemolyticus</em>.
Pulau Bunyu di Propinsi Kalimantan Utara memiliki sumberdaya hayati ekosistem perairan laut yang berlimpah dan bernilai ekonomis yang tinggi, dimana masyarakat pulau Bunyu memanfaatkan potensi ekosistem perairan laut digunakan sebagai potensi perikanan dalam hal penangkapan dengan menggunakan alat tangkap bubu dasar (bottom fish pot). Hasil tangkapan yang bernilai ekonomis berupa ikan kakap merah dan ikan kerapu yang terdapat di perairan ekosistem laut pulau Bunyu. Tujuan penelitian adalah menganalisis pertumbuhan dan struktur ukuran ikan kakap merah (Lutjanus argentimaculatus) serta ikan kerapu lumpur (Epinephalus malabaricus) yang berasal dari perairan pulau Bunyu. Data yang diteliti berupa parameter pertumbuhan yaitu panjang total dan panjang standar, berat total, jenis kelamin, tingkat kematangan gonad, dan berat gonad. Hasil penelitian ikan kakap paling banyak tertangkap ukuran panjang 40,49-47,61 cm dan bobot 990,05-1.451,68 gram. Pada ikan kerapu lumpur dengan ukuran panjang 43,73-50,13 cm dan berat 800,94-1.308,70 gram. Sifat pertumbuhan pada ikan kakap merah adalah allometrik negatif. Nilai indeks kondisi berbentuk kurus pada sampel ikan kakap merah. Sifat pertumbuhan pada sampel ikan kerapu pada variabel panjang total dengan berat total bersifat allometrik positif dan pada variabel panjang standar dan panjang cagak dengan berat total bersifat allometrik negatif.
Bahan organik fosfor (P) dalam sedimen memainkan peranan dalam fotosintesis, penggunaan gula dan Pati, dan pengalihan energi yang dibutuhkan oleh tanaman dan organisme dalam sedimen. Kajian ini bertujuan untuk menentukan kandungan fosfor (P) dalam sedimen berdasarkan kedalaman 10 cm, 20 cm dan 30 cm di kawasan hutan bakau Mamburungan Tarakan. Studi ini dimulai pada bulan Februari sampai dengan Juli 2018 metode yang digunakan dalam studi ini adalah kuantitatif deskriptif dengan menjelaskan isi dari fosfor berdasarkan kedalaman pada setiap stasiun penelitian. Pengambilan sampel sedimen dilakukan di 3 titik Stasiun, yaitu daerah akuakultur, pemukiman dan mulut Sungai dengan 3 pengulangan. Dari hasil kajian yang diperoleh nilai bahan organik fosfor dalam sedimen daerah hutan mangrove Mamburungan berdasarkan kedalaman 10 cm berkisar dari 10,11-101,15 mg/L, 20 cm berkisar dari 7,04-141,98 mg/L dan 30 cm berkisar dari 29. 41-66,88 mg/L.
Dinoflagellates are a class of phytoplankton and are divided into two groups, namely autotrophs and heterotrophs. This research aims to analyze the structure of the phytoplankton community, especially from the dinoflagellate class, namely in terms of the number of species, and the abundance of dinoflagellates in the waters of Tarakan, Juata Laut Village, Tarakan City. There are 7 types of dinoflagellates found in waters, namely: Ceratium spp., Noctiluca sp., Protoperidinium spp., Prorocentrum spp., Gymnodinium sp., Gonyaulax sp., and Dinophysis sp. This research was conducted for 2 months by using descriptive analysis. The results showed that the index values for diversity, uniformity, and dominance of dinoflagellates ranged from 0.06 to 1.53, uniformity from 0.09 -0.80, and dominance from 0.23 -0.95. The highest diversity index value is at Station 3 of 1.63 and the lowest diversity index is at Station 5 of 0.07, the highest uniformity index value is at Station 3 of 0.90 and the lowest diversity index is at Station 5 of 0.10, while The highest dominance index is at Station 3 of 0.97 and the lowest dominance index is at Station 9 of 0.23. Water quality parameters still show the optimum value with temperatures ranging from 27-30°C, brightness 53-63 cm, salinity 16-2 4 ppt, and Ph 7.2 -7.4. Optimum concentrations of chlorophyll a, b, and c from morning to afternoon with sampling at 08.00 -12.00 with chlorophyll a value of 0.3447 µg.L-1, chlorophyll b 0.2081 µg.L-1 and chlorophyll c 0.03 µg.L-1.
Margalefidinium polykrikoides blooms resulted in massive fish mortality in many countries around the world. The prevalence of booms is believed to be associated with the eutrophication of the coastal area. Therefore, this study aims to determine the effects of different nitrogen (N) and phosphorus (P) concentrations on the growth of M. polykrikoides. Experiments were conducted on M. polykrikoides isolated from the affected area by exposing the cell to various N and P ratio: seawater without the addition of N and P (SW), equal N:P ratio (NP), trial ratio of N and P (TR), F/2 medium (+NP), deficient N (–N), and deficient P (–P). The experiments were carried out in triplicates for 20 d in similar environmental conditions with the determination of density, specific growth rate, and cell size during the study period. Furthermore, nutrient concentrations nitrite+nitrate (NO2 –+NO3 –), phosphate (PO4 3–), and ammonia (NH4 +) were measured initially in the medium and both nutrients and chlorophyll were determined at the end of the experiment. The results revealed that M. polykrikoides grew in all the experiments, but the growth patterns differed between the treatments. The highest specific growth rate (0.1901 ± 0.017 d–1) with the highest cell density (1709 ± 68.21 cells mL–1) with a long chain of cells was observed in TR during the exponential phase. However, cell size was significantly smaller in SW compared to other nutrient conditions during the exponential phase. This study shows that M. polykrikoides a flexible species in nutrient uptake, thus allowing the species to survive in different nutrient conditions. The understanding of this bloom mechanism is important in monitoring and management of this harmful species, particularly in Sabah coastal waters.
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