Please see the following link, You may find useful :

http://link.springer.com/content/pdf/10.1007%2Fs10661-008-0303-9.pdf

Thanks a lot for your answer. I still looking for another information that explain the relation between the tissues of root (especially the cortex and aerenchyma structures) with their capability to filtering saline water become fresh water.

I advise you to read these articles " Agricultural and Forest Meteorology, Volume 153, 15 February 2012, Pages 54-66Jordan G. Barr, Vic Engel, Thomas J. Smith, José D. Fuentes" and " Journal of Experimental Marine Biology and Ecology, Volume 171, Issue 2, 15 October 1993, Pages 201-223Daniel M. Alongi, Paul Christoffersen, Frank Tirendi" and "Global Environmental Change, Volume 19, Issue 2, May 2009, Pages 227-239Beatrice I. Crona, Patrik Rönnbäck, Narriman Jiddawi, Jacob Ochiewo, Sam Maghimbi, Salomão Bandeira" and " Aquaculture, Volumes 362–363, 28 September 2012, Pages 72-79Eleonor A. Tendencia, Roel H. Bosma, Jurgenne H. Primavera, Johan A.J. Verreth"

As you know well that mangrove plants can tolerate and grow with high salinity. it does not mean that it is filter and drink water water. Mangroves have all xerophytic features and has salty glands where excess salt would be stored. Further, mangroves are found in areas where water periodically diluted by frequent flushings and mixing of fresh water from inland. like deserts plants it certain special adaptations to face adverse conditions. this can grow well in fresh water as like other plants but rate.

Mangrove forests are vital for protecting farmland from salt water intrusion and buffeting the effects of tropical storms. The great tsunami of 2004 demonstrated how they can save thousands of lives by blunting the force of tsunami waves.

With regards to water purification (toxicant-wise) mangrove have been documented to be prone to anthropogenic waste products, and significantly altered habitat quality due to pollution.

Dear Hery

Mangroves are well known for their ability to treat effluents. In addition to the sediment pollution, mangroves also help to control other forms of pollution, including excess amounts of nitrogen and phosphorous, petroleum products, and halogenated compounds (rhizofiltration). The lenticels that are there on the mangrove’s root systems let the surrounding area around the root to remain aerobic even in anaerobic, saturated soils. Microbes that can break down and make stable the potentially dangerous substances flourish in here, thus treating the effluent that flushes through the mangrove system. In the big cities of the world, mangroves swamps filter the runoff water; making use of the nutrients, absorbing pollutants and leaving the water cleaner in turn.

Some references:

1. Hennig, R.C., 2009. The mangroves, an undervalued ecosystem. Afrol News.

2. Mitsch, William J., and James G Gosselink, Wetlands, Third Edition, John Wiley and Sons, Inc. New York, NY, 2000

3. http://www.mangrove.org/sect1.htm

4. http://ocw.unu.edu/international-network-on-water-environment-and-health/unu-inweh-course-1-mangroves/Biology-of-mangroves.pdf

5. http://link.springer.com/article/10.1007%2FBF00029138

6. http://hal.archives-ouvertes.fr/docs/00/55/97/59/PDF/Text_V4_JSSS.pdf

Mangrove trees and thier biological associates add dissolved organic matter, especially fulvic acids, and nutrients to estuary and tidal flat sea water which help make this ecosystem a highly fertile environment for a wide specrtum of marine especies. The shading effect of the mangroves is critical in lowering the water temperature, thus increasing the level of dissolved oxigen. The tidal flows are critical in maintaining biological diversity and in constantly renewing the complex physical, chemical and biological interactions. See....http://www.sciencedirect.com/science/article/pii/S0304420303001397