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The rapid development of Indonesia over the past 20 years and also its increasing negative impact on the environment are by far best to be seen at the metropolitan area and the corresponding coastal ecosystems of Jakarta. All the information and facts reported in this chapter regarding the environmental state of Jakarta Bay demonstrate impressively the huge anthropogenically induced pressure and stress this ecosystem is exposed to. Additionally, an intact ecosystem is a basic precondition for many aspects directly impacting human beings around the Bay covering, e.g., seafood health, drinking water accessibility, or recreation needs. Noteworthy, the investigations reported here do not remain on the description of the environmental status but explored also the relevant processes behind inducing the pollution problems and, consequently, point to potential solutions. Abstrak Pesatnya pembangunan di Indonesia selama 20 tahun terakhir, termasuk dampak negatifnya pada lingkungan dapat dilihat pada kawasan metropolitan Jakarta maupun ekosistem pesisir di sekitarnya. Data dan informasi yang ditampilkan pada chapter/bab ini menunjukkan adanya ancaman dan cekaman antropogenik yang serius pada lingkungan Teluk Jakarta. Sementara itu, sebuah ekosistem yang terpelihara dengan baik merupakan faktor penting bagi berbagai aspek yang berpengaruh langsung pada kehidupan masyarakat di sekitar pesisir, seperti keamanan produk perikanan, akses air bersih, maupun kegiatan rekreasi. Oleh karena itu, hasil penelitian ini tidak hanya menjelaskan kondisi lingkungan Teluk Jakarta, tetapi juga melihat lebih dalam faktor-faktor yang menyebabkan terjadinya pencemaran serta memberikan alternatif solusinya.

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.

Large amounts of waste water are discharged from the Jeddah Metropolitan Area into the Red Sea. Daily loads of total nitrogen (TN) and phosphorus (TP) amount to 6564 kg and 2241 kg, respectively, comprising 83% of dissolved inorganic nitrogen and 33% of dissolved phosphate. Steep gradients prevail nearshore, ranging from 2000 μM TN and 250 μM TP in the hypertrophic city lagoons to 6 μM TN and 0.4 μM TP in the adjacent oligotrophic water. Sewage inputs from Al Khumra, Jeddah’s main outfall, cause a widespread but moderate increase in surface nutrient concentrations due to the submerged diffuser. The nutrient pool in the oligotrophic water is dominated by dissolved organic and particulate forms, with nitrate frequently below the detection limit, indicating rapid transformation of inorganic nutrients. N:P ratios, as well as half-saturation constants for phytoplankton growth, suggest that nitrogen is the limiting factor restricting primary production in the area.

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 20 km2 can be identified in the eastern part of Jakarta Bay where oxygen levels decrease to 60% saturation, equaling a noxiously low concentration of 4.0 mg·dm− 3 O2. The absolute minimum detected was 51% O2 or 3.2 mg·dm− 3 O2. The observed oxygen concentrations fail Indonesian quality standards for seawater.