Accumulation of Cd and Pb in sediments and Asian swamp eels (Monopterus albus) from downstream area of Cisadane River, Indonesia.

This study examined the presence of two heavy metals (Cd and Pb) in the sediments and Asian swamp eels (Monopterus albus) in the downstream area of Cisadane River. The average concentrations of Cd and Pb in the sediments from all sampling locations were 0.594 ± 0.230 mg/kg and 34.677 ± 24.406 mg/kg, respectively. These concentrations were above the natural background concentration and the recommended value of interim sediment quality guidelines (ISQG), suggesting an enrichment process and potential ecological risk of studied metals to the ecosystem of Cisadane River. The increase in contamination within this region may be attributed to point sources such as landfill areas, as well as the industrial and agricultural land activities in surrounding area, and experienced an increasing level leading towards the estuary of Cisadane River. Meanwhile, the average concentrations of Cd and Pb in the eels from all sampling locations were 0.775 ± 0.528 µg/g and 28.940 ± 12.921 µg/g, respectively. This study also discovered that gill tissues contained higher levels of Cd and Pb than the digestive organ and flesh of Asian swamp eels. These concentrations were higher than Indonesian and international standards, suggesting a potential human health risk and therefore the needs of limitations in the consumption of the eels. Based on the human health risk assessment, the eels from the downstream of Cisadane River are still considered safe to be consumed as long as they comply with the specified maximum consumption limits.

Roles and interrelation between variables : a study case of plastic waste management in Jakarta Bay.

The accumulation of plastic waste in the marine environment has increased the global risk of marine pollution due to its negative impact on land, ecosystems, and especially the food chain and marine organisms. Ineffective plastic waste management has reduced the quality of the coastal environment including community sanitation and health, landscapes, and coastal views, and influenced economic sectors such as tourism, fisheries, and shipping. The economic and public activities within coastal areas have consistently as the source of plastic waste leakage either directly or indirectly. Various variables involved and connected each other, some influential and other existing variables were not working effectively and do not support each other optimally in the system. The policy without limitation on the plastic production and certain type of plastic such as packaging or single-use, bags, and a lack of management capacity have led to the establishment of a burden on current plastic waste management within the coastal and marine of Jakarta Bay. Therefore, the study aims to analyze the roles and interrelation of variables that influence plastic waste management in Jakarta Bay. Public participation through group discussion, interview, and Micmac analysis method was used to identify, map, and analyze their interrelationships, roles, and hierarchy in the plastic waste management system. The results showed that the dynamics of variables' interaction affect their level of performance and contribution. The variables with strong influence have the potential to strengthen others, while some had a high dependence which was vulnerable to have ineffective performance in the waste management system as their stability relied on other variables' performance. A group of variables were greatly affected by others and indicates that they had lower influence and higher dependence, while the rest of the variables were relatively disconnected from the system. The key to better waste management is to improve the performance and the quality of relationships of variables that were found in the influential and intermediate quadrants. Furthermore, the indirect influence variables also need to be considered as they have the potential to contribute to the future system strategy or scenario planning.

Numerical simulations of river discharges, nutrient flux and nutrient dispersal in Jakarta Bay, Indonesia.

The present application of numerical modelling techniques provides an overview of river discharges, nutrient flux and nutrient dispersal in Jakarta Bay. A hydrological model simulated river discharges with a total of 90 to 377m(3)s(-1) entering Jakarta Bay. Daily total nitrogen and total phosphorus loads ranged from 40 to 174tons and 14 to 60tons, respectively. Flow model results indicate that nutrient gradients are subject to turbulent mixing by tides and advective transport through circulation driven by wind, barotropic and baroclinic pressure gradients. The bulk of nutrient loads originate from the Citarum and Cisadane rivers flowing through predominantly rural areas. Despite lower nutrient loads, river discharges from the urban area of Jakarta exhibit the highest impact of nutrient concentrations in the near shore area of Jakarta Bay and show that nutrient concentrations were not only regulated by nutrient loads but were strongly regulated by initial river concentrations and local flow characteristics.

Pressure on oxygen levels of Jakarta Bay.

Jakarta Bay is subject to inputs of large amounts of dissolved inorganic nutrients and organic matter deriving from the Jakarta Metropolitan Area and its hinterland. As a consequence, inorganic and organic nutrient concentrations in the nearshore area are considerably increased. The hydrographic pattern inside the bay fosters phytoplankton bloom formation due to pronounced vertical density gradients. High Biomass Blooms (HBB) of phytoplankton are observed recurrently, representing an additional source for oxygen consuming degradable organic matter. An oxygen deficiency area of 20km(2) can be identified in the eastern part of Jakarta Bay where oxygen levels decrease to 60% saturation, equaling a noxiously low concentration of 4.0mg·dm(-3) O2. The absolute minimum detected was 51% O2 or 3.2mg·dm(-3) O2. The observed oxygen concentrations fail Indonesian quality standards for seawater.