Mangroves are a collection of tree species that live along shores, rivers and estuaries in tropic and subtropical regions. Most thrive on muddy soil, but some others grow on peat, sand and between coral rocks. They live in environments considered extreme for terrestrial trees. They evolved to cope with high salinity, extreme tides, strong winds, high temperature and anaerobic soils. Their presence within the inter-tidal zone provides healthier ecosystems and a source of food for several organism living within their community, creating a special sanctuary for juveniles and larvae. Scientists believe that there might not be other trees with such highly developed morphological and physiological adaptations to such an extreme combination of conditions, combining salinity and soil anoxia.

How peculiar is this? An ecosystem based on the extreme capacity of trees adaptation can produces such a sanctuary for other organisms living in the surrounding area.
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Figure 1: Mangroves in Los Haitises National Park (Dominican Republic) Autor: Anton Bielousov

Exceptional adaptations: Mangroves are considered unique organisms due to their adaptations to the environment in which they live. Although salinity is a challenging  factor for terrestrial trees, they are capable to tolerate high concentration of salinity, hosting a great biodiversity around their ability of adaptation. These adaptations vary among genus and with the physico-chemical nature of the habitat. Some are tolerant to high salt levels and they developed mechanisms to actively pump fresh water into their roots against a strong osmotic gradient. Some also absorb salt, but expel the salt through specialized glands in the leaves. Whereas, others, transfer salt into senescent leaves or store them in the trunk/wood.  Their morphological specializations of mangroves is incredibly precise and accurate, including profuse lateral roots that anchor the trees in the loose sediments, aerial roots for gas exchange, and viviparous water-dispersed propagules. Perhaps the most remarkable adaptations of the mangroves can be seen among: the stilt roots of Rhizophora, the pneumatophores of Avicennia, the root knees of Bruguiera, and the buttress roots of Heritiera.

Why do they matter? Mangroves have been greatly exploited and studied in the past , resulting “keystone” systems. They contribute to soil formation and help stabilize coastlines, they act as a filter for upland runoff protecting the coastline from floods and reducing storms and hurricanes impacts. Also, mangroves produce large amounts of detritus that contribute to productivity in offshore waters- helping nearby ecosystem with lower productivity.

Living Oceans Foundation created a video explaining why mangroves are one of the most productive ecosystems on the planet.

Account: Khaled bin Sultan Living Oceans Foundation

Mangroves as supporting services:

It’s a surprise how good mangroves are as ecosystem services but what is really outstanding, is their productivity in terms of nursery services.

A nursery is an area or habitat where, on average, juveniles make a larger contribution per unit area to the recruitment of the adult population, and overall contribute more recruits to the population than other areas where juveniles occur (Dahlgren et al. 2006)”.

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Figure 2: Up: Underwater view of Silverside fish swimming through a Mangrove in Cuba

Mangroves serve a nursery habitat to the marine micro and macro-fauna. The muddy sediments, where their roots tangle, is home for ephibenthic, infaunal and meiofaunal invertebrates (Fig2), whereas the channels within the Mangal support phytoplankton, zooplankton and fish. Mammals, birds and reptiles also live among Mangroves, where the area plays special role as a nursery habitat for juveniles (Fig.3) , while the adults occupy other habitats nearby such: coral reefs and sea grass. Despite the complexity on quantify how valuable a ecosystem is, especially when part of the value comes from underwater activities, mangrove forests have been valued at US$ 194.000 per hectare each year. The nursery service provides an abundance of food, protection from predators and shelter increasing ecosystem productivity.

They produce positive influence on survival and recruitment of juvenile fish and crustaceans and, to some species that are commercially important. Due to the fact they provide shaded areas and oxygenated water, when compared with other ecosystems, mangroves provide advantages in the growth and the survival of juveniles.  Even though only few species use mangroves as a nursery are mangrove-dependent i.e. require estuaries at some stage of their life such as the Banana prawns  Penaeus merguiensis, others, still prefer using mangroves rather than the nearby alternative habitats. As shown in (Fig 2),the biodiversity created on the surface of the roots, show the quantity and quality of the life under a mangrove tree.

Therefore, the healthier the juveniles are, the better the animal population will do. The biodiversity produced by mangroves creates a magical sanctuary that provides all the necessary facilities to both marine and terrestrial animals to release pulps/ juveniles/ larvae. The high abundance of organisms living in the substratum and around the community provides a important rate of dissolved organic matter (DOM) production. This, indirectly helps nearby ecosystems providing a higher production of (DOM), which is greatly important for the enrichment of the sediment. It assists with the recycling of nutrients in the mangrove community and the adjacent habitats, supporting coastal sea productivity and fishery resources. This helps to increase nutrient concentration to clear tropical waters where their concentration is normally low i.e. coral reefs.

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Fig3: Underwater view of Silverside fish swimming through a Mangrove in Cuba. Author: National Geographic.

Help Mangroves to remain in this planet:  In the video below are summarised the multiple reasons why Mangrove do matter for our entire ecosystem and indirectly for human. Without investing in mangroves we do not invest on ourselves and on our welfare. They do need protection and further respect. If you want to know more about the ecosystem service they provide watch the upcoming video below and sign in the website, clicking here … Find your local conservation and government organizations around your area that are conserving mangrove forests, and support them.

Account: Mangrove Action Project

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