Fact Sheet

The NPBL includes a wide variety of marine habitats that range from sandy bottoms to rocky reefs, in open areas and in small bays or protected areas. The marine habitats found in Loreto that are most vulnerable to the impacts caused by a desalination plant are rocky coasts, slat marshes, estuaries and lagoons, and seaweed beds. These habitats are important because of their high biodiversity levels and/or because they represent nursery habitats.

1. Seagrass beds
   Beds of the brown seaweed Sargassum are common on the shallow rocky shores of the Loreto region. This architectural alga grows seasonally and creates a unique habitat for many species that use it to find food or shelter.
2. Mangrove forests
   Mangrove forests are very productive systems that harbor a great variety of species, and they can be found in some areas of the region. They form small patches on some islands but are more abundant along the coast in places like Puerto Escondido, Nopoló and San Bruno.

Important species found in those habitats

The leopard grouper (Mycteroperca rosacea) is a very important species in the local fishery. Sargassum beds are critical nursery habitat for this species and a decrease in abundance of Sargassum beds will cause a decrease in the recruitment of the leopard grouper. This decrease in recruitment will be reflected years later in smaller adult populations. Also, when the Sargassum fronds detach they drift with the current carrying and attracting many organisms. Among the species that use these floating habitats are species like finfish who feed on smaller fish aggregating below the drifting algae.

Mangrove forests are also considered critical habitat for many commercially important species. Some fish species like snappers, mojarra and some groupers use this habitat as nursery habitat. Mollusks also live in these habitats and, in the case of birds, they represent nesting or feeding grounds for many species.

Impacts to marine systems from a desalination plant

• The extraction of large quantities of water has an impact on marine habitats and organisms. Water suction can cause organisms to collide with the mesh protecting the intake pipe. Smaller organisms (phytoplankton, zooplankton, eggs and larvae) can be pulled into the plant’s system leading to a decrease in recruitment to the local habitat, as well as a decrease in the overall productivity of the ecosystem.
• The concentration of brine can be up to double that of natural seawater and the magnitude of the impact depends on environmental factors as well as the concentration of the brine, the discharge rate, bathymetry, wave action, currents, among others.
• Sensitivity to high salinity levels varies from species to species; larvae and young adults, as well as benthic organisms, in particular sessile species, are among the most vulnerable.
• Changes in community structure can result in a change in the entire ecosystem.

Research and monitoring needs if desalination is to be considered

• Planning, construction and operation of desalination plants should include an environmental impact assessment and monitoring programs that record impacts to the natural environment.
• The best place to locate a desalination plant would be on an open coastal area where water circulation is strong enough to allow rapid mixing of the brine discharge. Information on water circulation in the region was not found and it is crucial information that needs to be available in order to choose the best location of a desalination plant.
• The NPBL lacks basic information on types of habitats and their extension. Gathering this information, including characteristics of each habitat as well as a map, should be considered a priority for the near future if sustainable development is to be achieved.
• Desalination seems to be a possibility in the region so monitoring programs should begin as soon as possible. This will allow researchers to gather information before and after the construction and operation of a desalination plant.

Fact Sheet in Spanish