Field measurements of turbulent mixing south of the Lombok Strait, Indonesia.

The Indonesian seas, with their complex passages and vigorous mixing, constitute the only route and are critical in regulating Pacific-Indian Ocean interchange, air-sea interaction, and global climate events. Previous research employing remote sensing and numerical simulations strongly suggested that this mixing is tidally driven and localized in narrow channels and straits, with only a few direct observations to validate it. The current study offers the first comprehensive temporal microstructure observations in the south of Lombok Strait with a radius of 0.05° and centered on 115.54oE and 9.02oS. Fifteen days of tidal mixing observations measured potential temperature and density, salinity, and turbulent energy dissipation rate. The results revealed significant mixing and verified the remotely sensed technique. The south Lombok temporal and depth averaged of the turbulent kinetic energy dissipation rate, and the diapycnal diffusivity from 20 to 250 m are ε  = 4.15 ± 15.9) × 10-6 W kg-1 and K ρ = (1.44 ± 10.7) × 10-2 m2s-1, respectively. This K ρ is up to 104 times larger than the Banda Sea [ K ρ  = (9.2 ± 0.55) × 10-6 m2s-1] (Alford et al. Geophys Res Lett 26:2741-2744, 1999) or the "open ocean" K ρ = 0.03 × 10-4 m2s-1 within 2° of the equator to (0.4-0.5) × 10-4 m2s-1 at 50°-70° (Kunze et al. J Phys Oceanogr 36:1553-1576, 2006). Therefore, nonlinear interactions between internal tides, tidally induced mixing, and ITF plays a critical role regulating water mass transformation and have strong implications to longer-term variations and change of Pacific-Indian Ocean water circulation and climate. Supplementary Information: The online version contains supplementary material available at 10.1186/s40562-024-00349-3.

Vertical distribution of microplastic along the main gate of Indonesian Throughflow pathways.

Even though Pacific - Indian Ocean exchange [Indonesian Throughflow (ITF)] has been measured for the last three decades, the measurements of microplastic in the region is very limited. This study was the initial investigation of the vertical distribution of microplastic in the deep-sea areas across the ITF Pathway. Niskin water samples were utilized to obtain the samples from a water column in a range of 5 to 2450 m. A total of 924 microplastic particles with an average abundance of 1.062 ± 0.646. n/L were found in the water column. Our findings indicate that water temperature and water density are the most significant factors correlated to the microplastic concentration. This study will be the first report discussing the distribution of microplastics in the deep-sea water column that could be highly significant in determining the fate and transport of microplastic within Indonesian waters that exits into the Indian Ocean.

Present status of 137Cs in seawaters of the Lombok Strait and the Flores Sea at the Indonesia Through Flow (ITF) following the Fukushima accident.

Due to thermocline and surface water from the western equatorial Pacific Ocean, which are transported to the Indian Ocean, Indonesian marine waters play an important role in the global ocean circulation. The objective of this study was to assess the spatial distribution of 137Cs in the Lombok Strait as part of a national monitoring program concerning the possible impacts of radionuclides released as a result of the Fukushima accident. Sampling was conducted in the Flores sea and Lombok Strait on 15 to 24 November 2013. Measurements for the Lombok strait showed that 137Cs concentrations at surface layer, thermocline layer and 1000m depth were 0.27Bqm-3; 0.42Bqm-3 and

Genetic relationship of Sardinella lemuru from lombok strait with fish rich in omega-3 fatty acid.

Lombok Strait has abundance of Sardine, Sardinella lemuru, which contains such high amount of omega-3 fatty acid (omega-3). However, the genetic relationship of S. lemuru with other commercial fish rich in omega-3 has not been widely studied yet. Studies on genetic proximity of S. lemuru with the other marine fish using 12S rRNA gene is very important in order to obtain genetic information of the Sardine to develop an appropriate strategy for future conservation of the fish in Lombok Strait. The aim of this study was to find out the genetic relationship of Sardinella lemuru living in Lombok Strait with the economically valuable fish and its correlation with omega-3 production. Sardinella lemuru were collected from Lombok Strait, the phylogenetic tree was done based on 12S rRNA gene through a neighbor-joining method to identify the relationship of Sardines and fish rich in omega-3 fatty acid. The phylogenetic tree showed that Sardinella lemuru is similar to Sardinella aurita and has a close similarity with Sardinella maderensis. However, the relationship did not correspond to omega-3 production. Based on the results of the study, it is suggested that the production of omega-3 is not specifically based on the proximity of the species, but it is more associated with conserved domain of Δ6-desaturase. Nevertheless, detailed mechanisms still need to be elucidated.