Manila Bay is a natural harbour which serves the Port of Manila (on Luzon), in the Philippines. Strategically located around the capital city of the Philippines, Manila Bay facilitated commerce and trade between the Philippines and its neighbouring countries, becoming the gateway for socio-economic development even prior to Spanish occupation. With an area of 1,994 km2 (769.9 sq mi), and a coastline of 190 km (118.1 mi), Manila Bay is situated in the western part of Luzon and is bounded by Cavite and Metro Manila on the east, Bulacan and Pampanga on the north, and Bataan on the west and northwest. Manila Bay drains approximately 17,000 km2 (6,563.7 sq mi) of watershed area, with the Pampanga River contributing about 49% of the freshwater influx. With an average depth of 17 m (55.8 ft), it is estimated to have a total volume of 28.9 billion cubic metres (28.9 cubic km). Entrance to the bay is 19 km (11.8 mi) wide and expands to a width of 48 km (29.8 mi). However, width of the bay varies from 22 km (13.7 mi) at its mouth and expanding to 60 km (37.3 mi) at its widest point.
The islands of Corregidor and Caballo divides the entrance into two channels, about 2 miles (3.2 km) towards the North and 6.5 miles (10.5 km) wide on the South side. Mariveles, in the province of Bataan, is an anchorage just inside the northern entrance and Sangley Point is the former location of Cavite Naval Base. On either side of the bay are volcanic peaks topped with tropical foliage: 40 km to the north is the Bataan Peninsula and to the south is the province of Cavite.
Across the entrance to Manila Bay are several islands, the largest of which is Corregidor, located 3 kilometres from Bataan and, along with the island of Caballo, separates the mouth of the bay into the North and South Channels. In the south channel is El Fraile Island and outside the entrance, and to the south, is Carabao Island. El Fraile, a rocky island some 4 acres (1.6 ha) in area, supports the massive concrete and steel ruins of Fort Drum, an island fortress constructed by the United States Army to defend the southern entrance of the bay. To the immediate north and south are additional harbors, upon which both local and international ports are situated. Large number of ships at the North and South harbors facilitate maritime activities in the bay. Being smaller of the two harbors, the North Harbor is used for inter-island shipping while the South Harbor is used for large ocean-going vessels.
Manila Bay was connected to Laguna Lake (or Laguna de Bai) approximately 3,000 years ago. Recurring episodic uplifts along the West Marikina Valley Fault caused the two to break up. Interaction between Manila Bay and Laguna Lake occurs only through Pasig River.
Today, Manila Bay still remains important for commerce and industry, including fishing, although rapid urban growth and industrialization are contributing to a decline in water quality and deteriorating marine habitats. It also serves a focus for recreation for Metro Manila and is a popular destination for walks and for viewing the sunset. Much of the land fronting the bay along Metro Manila is reclaimed land which now includes important sites such as the Philippine Senate and the Mall of Asia.
On 27 September 2011, The sea walls of Manila Bay were destroyed by the storm surge caused by Typhoon Pedring. Even the US Embassy, Museo Pambata and Sofitel Philippine Plaza were submerged into flooding. It was estimated that the damage would cost P30 million. On April 2012, the sea walls were once again opened to public and it was also designed to become stronger to withstand strong storm surges.
Coastal and marine habitats in the area include upland forests, mangrove, mudflats, sandy beaches, sea grass and coral reefs.
A total of 19,139 birds belonging to 33 families and 99 species were observed at various monitoring sites along the bay area. The endangered Chinese Egret (Egretta eulophotes) and Black-winged cuckoo-shrike were sighted in the area. A large number of migratory birds use the intertidal mudflats, fishponds and saltpans in winter and during the migration seasons.
Large number of commercial fish species such as snappers, sea catfish and mackerels were once abundant in these waters. Their decline ushered in the appearance of squid, shrimp, and small pelagic species such as herrings and anchovies.
The mangrove ecosystem around Manila Bay has both ecological and socioeconomic uses with its association of unique plant and animal species. Of the original 54,000 hectares of mangroves existing at the turn of the 20th century, only 794 hectares are remaining as recorded in 1995. A few of the mangrove swamps remaining in Pampanga Bay are of considerable value for research and conservation education. As natural habitats, mangroves considerably help in acting as a protective buffer against cyclones and storms.
Predominant in the bay area are Avicennia marina (gray or white mangrove) together with 15 species of mangroves belonging to 9 families that grow there. In the Bataan area, species of mangrove swamps that are found thriving include:
- Rhizophora apiculata (bakhaw lalaki in Filipino)
- Rhyzophora mucronata (no common name found)
- Avicennia marina (gray or white mangrove)
- Nypa fruticans (nipa palm)
- Sonneratia alba (no common name)
- Scyphiphora hydrophyllacea (nilad in Filipino)
- Sonneratia acida (pagatpat in Filipino)
- Acanthus ilicifolius (holly-leaved acanthus)
- Excoecaria agallocha (milky mangrove)
Plantations of Cocos nucifera (coconut palm) co-exists with the mangroves found in these areas.
Covering about 4,600 hectares, wetlands around Manila Bay are useful in:
- providing food and habitat for fish, shorebirds and wildlife;
- maintaining and improving water quality of rivers, lakes and estuaries,
- acting as reservoir for watersheds, and
- protecting adjacent and downstream properties of the area from potential flood damage
Mudflats, sand flats, swamps, beaches and rocky shores form part of the wetlands in Manila Bay. Found mostly along the coast of Bataan and Pampanga, mudflats are suitable habitats for shellfish.
Contributing to the balanced functioning of the ecosystem around Manila Bay, coral reefs in the area provide sanctuary for fishes. Consequently, its decline through the years has directly affected the fish yield.
As a diverse ecosystem, seagrass beds provide shelter for fishes and other marine life forms. Like the coral reefs, most of the seagrass beds in Manila Bay are found near its mouth, most notably in the areas of Malolos,Orion, Marivels, Bataan and Corregidor.
Within the watershed of Manila Bay upland forests abound which are sources of food, timber, fuel wood and other products, as well as habitats for wildlife. These forests provide protection from soil erosion and help maintain the water levels and water quality in rivers and streams. Mount Makiling, Angat Dam watershed, La Mesa Dam watershed, Mount Palay-Palay, Mataas na Gulod National Park, Mount Arayat, and other portions of national parks located in Bataan, Bulacan, Rizal and Tarlac form part of these upland forest ecosystem.