Nitrogen from coastal cities are predicted as one of the largest sources of N loading into oceans. Jakarta is an example, with its adjacent bay suffering massive algal blooms, hypoxia and extensive fish kills due to excess nutrient loading. Despite this fact, water quality standards of Indonesia does not consider total N load. Without adequate management, the problems likely will continue and will be exacerbated by climate change and the construction of Giant Seawall.

This study estimates N budgets for Jakarta city for the years 2011‑2015 to identify sources and assess possible factors affecting N retention, including population density, precipitation, and land cover. By quantifying N inputs and outputs within Jakarta city using mass balance approach, N retention was estimated as the difference between them. N inputs were riverine N input, net N in food and feed, atmospheric N deposition, N fertilizer, and N fixation; and N outputs were riverine N export, solid waste exported, and manure volatilization. The dominated N sources to the city came from the riverine input, and rivers were also responsible for the largest export.

The average of N retention approximately ‑8,800 kg N km^‑2 year^‑1, but trending to be negative (+15 to ‑24%) for years 2011–2014. The estimate for N retention drastically decreased in 2015, and although based on few data points for total nitrogen, appears to be a result of a dredging project. The possible drivers for N retention were precipitation and population density.

However, to investigate the relationship between parameters was difficult, mostly because of urban dynamics happened within the fast-growing city which greatly influenced observed data. While the results are acquired from the specific case of Jakarta city, the information can be used as a reference regarding N budget in urban ecosystem elsewhere.