Mangroves are a collection of halophytes 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 have evolved to cope with high salinity, extreme tides, strong winds, high temperature and anaerobic soils. Their presence within the intertidal zone provides healthier ecosystems and a source of food for a multitude of organisms living within their community, creating a sanctuary for juveniles and larvae. Scientists believe that these might be a collection of tree species with the most highly developed morphological and physiological adaptations to such an extreme combination of  environmental conditions.

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. These adaptations vary among genus and with the physico-chemical nature of the habitat. Mangroves are well known for their specially developed mechanisms to actively pump fresh water into their roots against a strong osmotic gradient. Some also absorb salt, which is then expelled through specialised glands in the leaves. Others, transfer salt into senescent leaves or store them in the trunk or wood.  The morphological specialisations of mangroves have lead to the formation of  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 (Figure 2A), the root knees of Bruguiera(Figure 2B), the pneumatophores of Avicennia(Figure 2C),and the buttress roots of Heritiera (Figure 2D).

Figure2: A The stilt roots of the red mangrove Rhizophora. Image: Jonathan Wilkins; B The root knees of Bruguiera. Image: www.mangrove.at ; C The pneumatophores of the black mangrove Avicennia. Image: Botanical Gardens, South Rd, Paget. D The buttress roots of Heritiera. Image: www.mangrove.at

 

Why do they matter? Mangroves have been the focus of much scientific attention since they were first described by Georg Eberhard Rumphius. They have been termed “keystone” due to their contribution to soil formation and help stabilise coastline, they also act as a filter for upland runoff protecting the coastline from floods and reducing storms and hurricane impacts. Mangrove forests support the conservation of biodiversity of several terrestrial and marine species by offering spawning grounds, nurseries and food. 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 at providing 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 3: 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 sediment, where their roots tangle, is home to ephibenthic, infaunal and meiofaunal invertebrates (Figure 3), whereas the channels within the mangrove support phytoplankton, zooplankton and juveniles fish and the adults occupy habitats nearby e.g. coral reefs and sea grass. Despite the complex in nature quantifying the value of a ecosystem, 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 to species that are commercially and non-commercially important, increasing ecosystem productivity and value (Figure 4).

They produce positive influence on survival and recruitment of juvenile fish and crustaceans, providing shaded areas and oxygenated water. When compared with other ecosystems, mangroves provide advantages in the growth and the survival of juveniles. Even thought this requirement could ontogenitically change as for the Lemon shark pulp, Negaprion acutidens ,only few other species are mangrove-dependent in their life cycle i.e. require estuaries at some stage of their life  e.g. the Banana prawns  Penaeus merguiensis, others, still prefer using mangroves rather than the nearby alternative habitats when the choice is available. As shown in Figure 3 ,the biodiversity created on the surface of the roots, show the quantity and quality of the life under a mangrove tree.

The ecosystem created by mangroves provides all the necessary facilities to both marine and terrestrial animals to release pulps/ juveniles and larvae, consequently, the healthier the juveniles are, the better the animal population will do.

The high abundance of organisms living in these communities and, particularly, in the substratum lead to a high rate of dissolved organic matter (DOM) production. This, indirectly helps nearby ecosystems providing more DOM, which is important for the enrichment of the sediments; it assists with the recycling of nutrients  for the mangrove community and the adjacent habitats, supporting coastal sea productivity of fishery resources. This helps to increase nutrient concentration to clear tropical waters where their concentration is normally low.

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Figure 4: Underwater view of Silverside fish swimming through a Mangrove in Cuba. Author: National Geographic.

Help Mangroves to remain on this planet:  In the video below are summarised the multiple reasons why mangrove habitats are important for tropical ecosystem health and function as well as for human livelihood. Without investing in mangroves we do not invest on ourselves and on our welfare. They 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 organisations around your area that are conserving mangrove forests, and support them.

Account: Mangrove Action Project

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