Editing Manila Bay (section)

==Water quality==
Successive changes in and around Manila Bay are largely due to the intertwining impacts of continued industrialization, unrelenting increase in population, and incessant human activities catering to livelihood and habitation. These factors are directly degrading the overall environment of Manila Bay and these impacts are manifested in the continued deterioration of the [[water quality]] within the bay. Several industries operate along the bay in the highly urbanized Metro Manila area, while there are shipyard facilities in Cavite and<ref name="pemsea 2001">Programme on Building Partnerships in Environmental Management for the Seas of East Asia-PEMSEA. (2001). Manila Bay:
Initial risk assessment. PEMSEA Technical Information Report No. 2001/01, 112 p. Global Environment Facility/United Nations Development Programme/International Maritime Organization Regional PEMSEA, Quezon City, Philippines.</ref><ref name="bajet">Bajet, C.M. (2003).
Ecotoxicology of pesticides in Philippine aquatic ecosystems. In: Taylor MD, Klaine SJ, Carvalho FP, Barcelo´ D, Everaarts J, editors. Pesticide residues in coastal tropical ecosystems. Distribution, fate and effects. London: Taylor & Francis/CRC Press. pp 271–310</ref> in Bataan, several more heavy industries, refineries and a power plant are present. At the shipping ports and ferry terminals, an average of 30,000 ships arrive and depart annually to transport passengers, manufactured goods and raw materials.<ref name="mbemp 2001" /> Industrial waste discharges<ref name="pemsea 2001" /> and discharges of untreated domestic wastes from drainage and sewer outlets<ref name="acorda">Acorda, L. (1985). "Manila Bay Study". EMB-DENR. Quezon City, Philippines.</ref> have contributed to the severe decline in the quality of water and sediments in the bay as well as impacted on the existing marine habitats.<ref name="Jacinto et al (B)" />

=== Salinity ===
According to a 2011 study by Jacinto et al.,<ref name="jacinto 2011">Jacinto, G., Sotto, L., Senal, M., San Diego-McGlone, M., Escobar. M., Amano. A. and Miller, T. (2011) Hypoxia in Manila Bay, Philippines during the northeast monsoon. Marine Pollution Bulletin. 63: pp 243–248.</ref> Manila Bay has an average surface [[salinity]] of 32.6 psu (practical salinity unit). Due to the river influx, the areas near the coasts have low salinity especially in the vicinity of the mouth of the Pasig River in the eastern part of the bay. The bay's salinity is also affected by strong seasonal variations.<ref name="Jacinto et al (B)" />

=== Effects of soil erosion ===
As indicated by the exposed roots of the coconut trees, continuing [[soil erosion]] has been a major factor in the changing shoreline of Manila Bay. Apart from soil erosion, other environmental processes such as siltation and [[sea level rise]] have also contributed to changing the bay's coastline. In some parts of the bay, however, erosion are prevented by seawalls and breakers particularly in areas where land has been reclaimed.<ref name="Jacinto et al (B)" />

=== Pollution ===
With the presence of ports, sea-based sources of pollution around the bay are from ships and motorized boats. Twelve oil spills were recorded in 1995, but it was in 1999 where the highest total volume of oil spill occurred in the Manila South Harbor and Limay, Bataan.<ref name="Jacinto et al (A)" /> Increased presence of oil and grease in the waters are attributed to maritime activities at the harbors, together with the presence of oil terminals and the discharges from industries.<ref name="PEMSEA" /> These factors directly impacted the health of Manila Bay's waters.

Aside from oil spills, trace metals such as [[copper]], [[cadmium]] and [[zinc]] at the surface of the water<ref name="velas">Velasquez I., Jacinto, G.S., and Valera, F.S., (2002). The speciation of dissolved copper, cadmium and zinc in Manila Bay, Philippines. Marine Pollution Bulletin 45, pp 210-217</ref> were found at the bay coming from sea-based and land-based (e.g., domestic sewage, industrial effluents, runoff, combustion emissions, and mining operations)<ref name="Jacinto et al (A)" /> sources.

In 1996, concentrations of 16 commonly used [[pesticide]]s in surface sediment<ref name="Jacinto et al (A)" /> was found including dichloro-diphenyl-trichloroethane ([[DDT]]). [[Polycyclic aromatic hydrocarbon]]s (PAH) found in Manila Bay sediments have been influenced by human activities. PAH come principally from petrogenic sources (e.g., oil discharges from ships, refineries and industries) and pyrolytic sources (from combustion sources).<ref name="santi">Santiago, E.C., (1997). The levels and distribution of polycyclic aromatic hydrocarbons (PAH) contamination in bottom sediment in Manila Bay. Science Diliman 9, pp 16-28</ref>

Pesticide residues from rice paddy water draining into irrigation canals, which later on empty into river systems and eventually flowing into the surrounding lakes reaches the waters of Manila Bay.<ref name="carvalho">Carvalho, F.P., Villeneuve, J.P., Cattini, C., Tolosa, I., Bajet, C.M. and Calingacion, M.N. (2009). Organic Contaminants in the Marine Environment of Manila Bay, Philippines. Arch Environ Contam Toxicol. 57:348-358</ref> Compounds from these pesticide residues find themselves in food items with metamidophos, [[endosulfan]], [[chlorpyrifos]] and [[diazinon]] among the common contaminants.<ref name="carvalho" /> While chronic toxic effects on inhabitants of the bay are not found, impairment of marine [[biota (ecology)|biota]]<ref name="carvalho" /> were more evident.

In 1997, [[polychlorinated biphenyl]] congeners, compounds common in transformers, [[hydraulic fluid]]s, paint additives and pesticides were determined in sediments and oysters sampled from Manila Bay.<ref name="ville">Villeneuve, J.P., Cattini, C., Bajet, C.M., Navarro-Calingacion, M. and Carvalho, F.P. (2010). PCBs in sediments and oysters of Manila Bay, the Philippines. International Journal of Environmental Health Research. 20(4): pp 259-269</ref> The increase in the nutrient concentration and presence of [[nitrate]], [[ammonia]] and [[phosphate]] in the bay, from the 1980s, through to the 1990s and beyond are not only attributed to agricultural runoff and river discharges but also on fertilizers from fishponds.<ref name="Jacinto et al (B)" />

On July 25, 2024, the oil tanker MT ''Terra Nova'', carrying around {{convert|1.5|e6L|sp=us}} of industrial fuel, capsized in Manila Bay during [[Typhoon Gaemi]], causing an oil spill with a length of {{convert|4|km|sp=us}}.<ref>{{cite web |last1=Guinto |first1=Joel |title=Race to contain oil spill after ships capsize as typhoon hits Taiwan and Philippines |url=https://www.bbc.co.uk/news/live/ce98pq4e3d1t |website=BBC News |access-date=25 July 2024 |language=en |date=25 July 2024}}</ref>