The Flores Sea plays a critical role within the Indonesian Throughflow (ITF) system, functioning as a key transitional pathway where Pacific-derived water masses undergo significant transformation prior to entering the Banda Sea. Despite its importance, scientific understanding of the relationship between water-mass characteristics and water-column stability during the first transition season in this region remains relatively limited. This study was conducted to characterize the water masses present in the Flores Sea and to evaluate water-column stability using conductivity-temperature-depth (CTD) observational data collected from four sampling stations during the Jala Citra III-2023 "Flores" Expedition, carried out between April and May. Vertical profiles of temperature, salinity, and density were systematically analyzed to identify distinct water masses through the construction of temperature-salinity (T-S) diagrams, while water-column stability was assessed by calculating the Brunt-Väisälä frequency at each station. The results revealed a clearly defined vertical hydrographic structure, consisting of a surface mixed layer, a thermocline layer extending from approximately 40 to 300 meters in depth, and a deep layer situated below 300 meters. Analysis of the T-S diagrams identified three major water masses contributing to the hydrographic composition of the Flores Sea: North Pacific Subtropical Water (NPSW), South Pacific Intermediate Water (SPIW), and Antarctic Intermediate Water (AAIW). Furthermore, the highest Brunt-Väisälä frequency squared value, reaching 2.3 × 10⁻² s⁻², was observed at approximately 116 meters depth, indicating that the maximum stratification stability occurred within the thermocline layer. Overall, these findings demonstrate that combining water-mass characterization with Brunt-Väisälä frequency analysis offers a more comprehensive and integrated understanding of water-mass transformation processes and stratification dynamics along the Indonesian Throughflow pathway.
Low-lying coastal regions worldwide face escalating threats from sea-level rise, land subsidence, coastal erosion, and recurrent tidal flooding, underscoring the urgent need for effective disaster management informed by spatial vulnerability assessments. This study evaluates temporal changes in coastal vulnerability within Betahwalang Waters, Demak Regency, Indonesia, over the period 2015–2025, applying the Coastal Vulnerability Index (CVI) integrated with Geographic Information Systems (GIS). Primary data were obtained through field surveys, whereas secondary data comprised Sentinel-2 satellite imagery, digital elevation and bathymetric datasets, and tidal records. Coastal vulnerability was analyzed using a GIS-based weighted overlay approach that combined and quantified multiple physical, geological, and environmental parameters. The results reveal that approximately 69% of the study area falls within the high to very high vulnerability categories, with geomorphology and coastal slope emerging as the two dominant contributing factors, each accounting for 20% of the overall index. A comparison with the 2015 BNPB coastal hazard assessment indicates a pronounced spatial expansion of high-vulnerability coastal zones over the past decade, primarily driven by tidal inundation, aquaculture expansion, and progressive mangrove degradation. This study contributes to coastal disaster management by demonstrating the value of integrating field observations, remote sensing, and GIS for monitoring long-term vulnerability dynamics. The findings offer a robust scientific basis for disaster risk reduction, vulnerability-based spatial planning, and ecosystem-based coastal management. Collectively, they provide a practical and transferable framework for strengthening the resilience of tropical deltaic coasts confronting intensifying climate-related hazards in similarly vulnerable low-lying coastal environments worldwide.
Oysters are cultured using various methods, each with a distinct effect on growth and yield. Understanding the efficacy of these culture methods is essential for optimizing production and ensuring sustainable aquaculture practices. This study aims to compare the growth increment of oysters (Crassostrea spp.) in terms of body weight, shell length, and weight of oyster meat over four months using three culture methods—floating bag, suspended tray, and hanging oyster shell employing a complete randomized design model (CRD) consisting of three treatments with three replications. Findings show that the hanging oyster shell method produces oysters with the highest body weight (21.2 g), indicating that this method might encourage ideal growth conditions. On the other hand, the floating bag method yielded a considerable size of oyster shell length (32.3 mm) and the highest meat weight (6.92 g), indicating that it can produce oysters that are sizeable. Statistical analysis revealed significant differences among the three culture methods for both total body weight (F(2, 42)=11.40 P<.001), and oyster meat weight (F(2,42)=8.056, P=.001. In contrast, there was no significant difference observed in oyster shell length across the different methods (F(2,42)=1.64, P=.206). The findings demonstrate that the hanging oyster shell method yielded the highest overall growth increment, while the floating bag method proved most effective for producing heavier oyster meat. However, as environmental variables were not directly measured during the study, these results should be interpreted as method-specific performance outcomes within the local estuary rather than a definitive assessment of optimal environmental conditions.
Kappaphycus alvarezii is an important seaweed for various industries. Indonesia, as one of the largest producers, cultivates it extensively in South Sulawesi, particularly on Tanakeke Island. However, because the adoption of aquaculture technologies among local farmers remains limited, the quality and quantity of production are not yet optimal, making the use of biofertilizers one solution to increase cultivation yields. Biofertilizers are necessary because they are environmentally friendly and can be made from industrial waste to improve productivity. However, their effectiveness is not yet known, and the basic materials are very limited. Therefore, this study aims to evaluate the effectiveness of using biofertilizers made from black soldier fly frass (BSFF) and K. alvarezii in increasing the specific growth rate and carrageenan content of K. alvarezii. Water-quality parameters were also measured to support the interpretation of the experimental results. Samples were collected in Mallasoro Bay, South Sulawesi, and laboratory analysis were conducted at Pangkajene Pangkep Island State Polytechnic Laboratory. This research used four treatments: treatment A (BSFF-based biofertilizer), treatment B (K. alvarezii-based biofertilizer), treatment C (combination of BSFF and K. Alvarezii-based biofertilizer), and treatment D (control). The results showed that treatment C had the highest average specific growth rate of 5.41 ± 0.84%. Treatment C also had the highest carrageenan content of 56.61 ± 0.63%. This study highlights the potential of a combination of biofertilizer based on BSFF and seaweed as an environmentally friendly and cost-effective alternative to chemical fertilizers for increasing K. alvarezii cultivation productivity while utilizing BSFF waste. However, commercial use of these biofertilizer combinations requires further study.
This study aims to develop an integrated framework for disaster mitigation and coastal carrying capacity assessment by combining the Coastal Vulnerability Index (CVI) with trophic status analysis in Betahwalang Waters, Demak. Unlike previous studies that primarily evaluate physical vulnerability or ecological conditions separately, this study integrates both approaches to identify areas where high physical susceptibility coincides with ecological pressure, thereby providing a more comprehensive basis for sustainable coastal management. Seven physical parameters, including geomorphology, slope, elevation, land use, distance from the shoreline, distance from rivers, and tidal range, were analyzed using a weighted overlay approach in ArcGIS based on field observations, Sentinel-2 imagery, Digital Elevation Model (DEM), and tidal data. Ecological carrying capacity was assessed using trophic status derived from chlorophyll-a and nitrate concentrations following the EPA trophic classification. The results indicate that 69.01% of the study area falls within the high (42.96%) and very high (26.05%) coastal vulnerability classes, primarily due to low elevation, gentle slopes, and extensive aquaculture replacing natural mangrove protection. Chlorophyll-a concentrations ranged from 2.19 to 36.19 µg.L-1, while nitrate concentrations ranged from 43.62 to 126.52 µg.L-1, indicating mesotrophic to eutrophic conditions with moderate to high nutrient enrichment. The integrated assessment revealed that physically vulnerable areas generally coincide with nutrient-enriched coastal waters, indicating increasing environmental pressure and reduced ecological carrying capacity. These findings demonstrate that integrating CVI with trophic status provides additional spatial insight beyond conventional vulnerability assessments by simultaneously identifying priority areas for ecosystem restoration, disaster risk reduction, and sustainable aquaculture management. The integration of CVI and trophic status provides additional spatial insight by identifying areas where high physical vulnerability coincides with ecological pressure, thereby supporting ecosystem-based disaster mitigation and sustainable coastal management. The proposed framework supports evidence-based coastal planning through ecosystem-based disaster mitigation strategies, including mangrove restoration, spatial zoning, and adaptive coastal management under climate change.
