What is a lagoon, how it is formed and examples

A lagoon is a coastal lagoon that forms when a strip of land, such as a range of dunes or a sandbank, separates a portion of the sea. This barrier prevents salt water from entering directly, although there may continue to be some exchange depending on the tide, rainfall or natural or artificial openings made in that strip.

The lagoons are usually connected to the sea by channels or floodgates, which generates a very particular balance between the fresh water that comes from the rivers or rain, and the salt water from the sea. Therefore, one of the most common questions is: are the lagoons fresh or salt water? The answer is that, in reality, they are brackish water, that is, a mixture of both. However, this proportion can change with the climate or human activity, becoming sweeter or saltier depending on the case.

The formation of a lagoon is a natural process that can take centuries.

1. It all starts in flat coastal areas, where the sea deposits sand and sediment over time, especially in places with little waves and gentle slopes.
2. These sediments accumulate and form a barrier or coastal range that little by little encloses a part of the sea.
3. When this cord closes completely or leaves just a small connection with the sea, the lagoon that we know as the lagoon is formed.
4. In that enclosed space, the water begins to change: it receives contributions from rain, runoff or even nearby rivers, which reduces its salinity. However, if the connection to the sea remains open, even partially, the water may still have some salt.
5. Sometimes, humans also intervene in the formation or maintenance of a lagoon, opening and closing gates or channels to control the flow of water, whether for agricultural, fishing or environmental conservation reasons.

Let’s see some of the most famous examples of lagoons in the world and from different parts:

Lagoons in Spain

Spain is one of the countries with the most tradition in the protection and sustainable use of lagoons. Among them stands out:

• Albufera de Valencia: it is probably the most famous in the country, a natural park located a few kilometers from the city of Valencia. In fact, if you are wondering which lagoon is the largest in Spain? The answer is this: the Albufera de Valencia, since it has about 2,800 hectares of lagoon surface and more than 20,000 hectares if the entire ecosystem of the natural park is counted.
• Albufera de Adra (Almería): a small coastal wetland that is very valuable for waterfowl.
• Albufera de Mallorca: it is an extensive and protected wetland, ideal for bird watching. It is a protected natural area in the Balearic Islands.

Lagoons in Argentina

Although the word “albufera” is not used as much in Argentina, there are similar ecosystems:

• Mar Chiquita Albufera: located in the province of Buenos Aires, it is a coastal lagoon very similar to the Mediterranean lagoons. It is separated from the sea by a sand barrier and has brackish water. It is recognized as a Biosphere Reserve by UNESCO.

Other lagoons in the world

• Venice Lagoon (Italy): known as the Venetian Lagoon, it is an extensive coastal ecosystem that is home to the famous city of canals. Its natural dynamics are very similar to that of a Mediterranean lagoon.
• Izmir Lagoon (Türkiye): This coastal wetland in western Turkey functions as a lagoon and provides habitat for hundreds of bird species. It is separated from the Aegean Sea by a sandy strip.
• Kerala Lagoon (India): On the southwestern coast of India, the well-known Kerala backwaters are interconnected coastal lagoons, some of them formed by processes similar to those of lagoons.

The flora and fauna of the lagoon is very varied and depends largely on the type of water (fresh, brackish or salty) and the degree of conservation of the environment. These coastal ecosystems are a refuge for numerous species, many of them threatened or protected.

lagoon fauna

Birds are the most visible and diverse group. Many lagoons are located on migratory routes, which is why they are home to species such as herons, flamingos, stilts, mallards, marsh harriers and grebes. There are also fish adapted to salinity, such as eel, mullet or fartet (Aphanius iberus), an endemic fish in danger of extinction in the Iberian Peninsula. In addition, it is common to find amphibians such as the spotted toad and reptiles such as leprous turtles or water snakes. Aquatic invertebrates, such as dragonfly larvae, crustaceans and mollusks, play an essential role in the food chain.

Flora of the lagoon

The vegetation is also very characteristic. On the banks, reeds, reeds and cattails predominate, which help stabilize the soil and filter the water. Inside the lagoon, submerged aquatic plants grow, such as Maritime Ruppia or Zannichellia, essential for the balance of the ecosystem and the refuge of small animals. In areas with greater salinity, halophilic species such as salicornia appear, well adapted to saline and nutrient-poor soils.

A lagoon is a coastal lagoon separated from the sea by a sandy barrier. Its water is brackish, a mixture of fresh and salt water, and is connected to the sea by channels that allow water exchange and affect its biodiversity.

On the other hand, a lagoon is a more general body of water that can be found both in coastal areas and inland. Lagoons can be fresh, salt or brackish water, and are not always connected to the sea. Some lagoons are permanent, while others may be temporary, depending on weather conditions.

In summary, all lagoons are coastal lagoons with specific characteristics, but not all lagoons are lagoons.

Lagoons play a fundamental ecological role in coastal ecosystems. Let’s see what some of the most important ecological functions are:

• Biodiversity refuge: it is home to fish, amphibians, insects, aquatic plants, crustaceans and migratory birds. Many birds use lagoons as resting and feeding areas during their long migrations.
• Natural water filter: lagoons filter sediments and pollutants carried by rivers before they reach the sea. The aquatic plants and microorganisms present help clean the water, improving its quality and avoiding contamination of nearby marine waters.
• Flood control: thanks to their ability to store large volumes of water, lagoons help cushion the effects of heavy rains or river flooding.
• Regulation of local climate: by containing large masses of water, lagoons influence the microclimate of coastal regions.
• Coastal protection: the strip of land that separates a lagoon from the sea acts as a natural barrier against coastal erosion.

Visiting a lagoon is a highly recommended experience for those who enjoy nature, tranquility and observing unique landscapes. In fact, many lagoons are protected as natural parks, biosphere reserves or wetlands of international importance, which ensures that your visit is safe and respectful of the environment.

These are some of the activities that can be done in a lagoon:

• Boat or kayak rides.
• Bird watching.
• Hiking and cycling routes.
• Nature photography.
• Environmental education and responsible tourism.
• Enjoy local cuisine.

Being delicate ecosystems, they face multiple threats: urbanization, pollution, mass tourism, overexploitation of water resources and climate change. For this reason, many countries have developed legal frameworks and specific programs to protect them and guarantee their long-term conservation.

• Many lagoons have been declared natural parks, which implies a high level of environmental protection. This is the case of the Valencia lagoon, which since 1986 has had this legal status in Spain. Thanks to this, access can be regulated, human activities controlled and degraded areas restored.
• In the case of lagoons in Spain and other countries in the European Union, many are included in the Natura 2000 Network, a European ecological network of protected areas. Its objective is to conserve the most valuable and threatened habitats on the continent, and guarantee the survival of the species that inhabit them.
• Globally, lagoons can be recognized as Wetlands of International Importance under the Ramsar Convention, a treaty signed by more than 170 countries. This designation implies a commitment to conserve and rationally use these wetlands, with the collaboration of governments, NGOs and local communities.
• In addition to laws, social awareness plays a key role in protecting lagoons. More and more people participate in environmental volunteer activities, collective cleanups, species monitoring or educational workshops.

If you want to read more articles similar to What is a lagoon, how it is formed and examples, we recommend that you enter our Ecosystems category.