What is an Estuary?

What is an Estuary?

An estuary is a coastal area where fresh water flowing from rivers and streams mixes with salt water from the ocean, bays, lagoons and channels. This combination creates a different and unique ecosystem, where many different species live (and grow) (fish, reptiles, birds and mammals such as the manatee).

The Puerto Rico Department of Natural and Environmental Resources classifies estuaries into five types: river mouths, semi-enclosed bays, open bays, coastal lagoons and saline estuaries.

Healthy estuaries are indispensable for humans, as well as for wildlife, for the following reasons:

  • They provide food that supports both commercial and recreational fishing.
  • They clean waste and runoff, so they maintain water quality.
  • They protect coastal areas from natural hazards.
  • They connect bodies of water for transportation and marine operations.
  • They promote the balance of the food web on which all forms of life depend.

Where is the Estuary?

When you hear about the San Juan Bay Estuary, many think it is a park or a visitor center. In reality, it is a large ecosystem where fresh waters mix with the sea, all along the coast, from Toa Baja to Loíza. This zone includes the rivers and streams that pass behind houses and under bridges, from the mountain to the beach.

Endangered species, such as the “tinglar” and the manatee, live in its waters.

In addition to its immense ecological value, the ecosystem is fundamental for economic development and food security. This, due to the fact that food arrives by boat. A great part of the island’s commercial activity is carried out there.


What is required to visit the Estuary?

If you wish to visit the San Juan Bay Estuary, you can request the services of small companies that offer environmental interpretation tours on foot, by bicycle or by boat.

Bodies of water that make up the San Juan Bay Estuary

The San Juan Bay is connected by the Martín Peña Channel to San José Lagoon and the Corozos Lagoon. These, in turn, are connected by the Suárez Channel to the La Torrecilla Lagoon and the Piñones Lagoon. The Bay is also connected to the Condado Lagoon, through the San Antonio Channel.

Another important part of the Estuary system is the Ciénaga Las Cucharillas, which, among other things, works like a gigantic sponge to prevent floods.

The Estuary’s ecological importance

The San Juan Bay Estuary offers food and shelter to:

  • 8 species of animals and 17 plants in danger of extinction, such as the Antillean manatee and several species of marine turtles, including the hawksbill and the “tinglar,”
  • 160 bird species, such as the brown pelican and the gray heron,
  • 19 species of reptiles and amphibians, such as the coquí and the Puerto Rican boa,
  • 124 species of fish, such as shad and bass, and
  • 300 species of wetland plants


The following reasons stand out among those that support the importance of this estuarine system:

  • It houses 33% of the total mangrove acres in Puerto Rico.
  • It supports resident, migratory and external species, that leave through one of the three outlets the system has to the sea.
  • It is a natural barrier against storms.
  • Avoids and controls floods.
  • Includes protected systems such as: mangroves, wetlands and seagrass meadows.
  • Provides unique conditions in pH, nutrients, temperature due to the mixture of fresh and salt water.
  • It is a settlement and sediment retention area; material that does not pass to the sea, where it could affect corals.

The Estuary’s economic importance

The San Juan Bay Estuary annually receives 80% of the products imported into Puerto Rico.

The docks and ports located in the Estuary water system play a crucial role in the process of exporting all kinds of products.

  • The port of San Juan Bay is number 17 in size worldwide.
  • It is visited by 1.3 million tourists on cruises and 9.8 million passengers by plane per year. It receives an average of 700 cruises annually.
  • More than 1,000 fishermen use the SJBE system every year, with an average catch of 350,000 pounds of fresh fish.
  • It works as one of the main resources to prevent floods in the Metropolitan Area.
  • Includes the development in construction of 67% of the lands in the watershed. Some of these are the most expensive real estate areas in the island, both commercial (the entire banking area in the Golden Mile) and residential (Condado, Miramar, Isla Verde, Punta las Marías, among others).
  • The central offices of most of Puerto Rico’s government agencies are located in the Estuary system. The Santa Catalina Palace or La Fortaleza, located in one of the salt water inlets to the Estuary system.
  • The Estuary comprises some of the island’s most important parks, such as: The Central Park (Parque Central), which includes the Enrique Martí Coll Linear Trail, located in part of the Martín Peña Channel; the Muñoz Marín Park and the Muñoz Rivera Park.
  • Some of Puerto Rico’s most important historical monuments and sites are also located in the Estuary, among them: The San Felipe del Morro castle, the San Cristóbal castle and Old San Juan.