COASTAL ECOSYSTEMSMANGROVES

MANGROVE WETLANDS Mostly dicots—Myrtales

and Rhizophorales (representing about 50% of the species)

Families: Avicenniaceae, Rhizophoraceae, Combretaceae, Sonneratiaceae.

Palmae- One monocot Nypa fruticans

SPECIES OF MANGROVES-60 species worldwide

Black MangroveRed Mangrove

Sweet Mangrove

White Mangrove

Viviparous propagule

ORIGIN OF MANGROVES Indo-Malayan region. Spread westward by

ocean currents during the Late Cretaceous and Lower Miocene.

Seeds and propagules.

Characteristics of Mangroves

Evergreen plants with thick leathery leaves designed to minimize transpiration.

Viviparous germination where the seed germinates on the tree and falls down in the germinating condition with a long radicle- characteristic of Rhizophoraceae .

Root system has many unique types of roots. 1. Stilt-roots, 2. Pneumatophores, 3. Root knees. 4. Plank Roots

ROOTS STILT ROOTS--looping roots

arise from the trunk and lower branches

PNEUMATOPHORES-Erect roots that are extensions of the underground root system. These roots are exposed at least part of the day and not submerged underwater, the root system can obtain oxygen in an otherwise anaerobic substrate.

                                                                  

ROOTS KNEED ROOTS-

the horizontal roots growing vertically upwards and forming loops downwards to resemble a bent knee.

PLANK ROOTS-wavy, snake-like roots that radiate outwards from the trunk base.

                                                                 

Stilt roots are characteristic of Rhizophora but also occur in Brugeria and Ceriops.  They may also occur in Avicennia alba and A.officinalis.  They grow downwards from the trunk and branches, providing gas exchange in the exposed sections and water uptake in the sections below the sediment.  They also provide support in older trees.  

Knee roots are raised loop sections of cable roots, with thickening on the upper exposed side, forming 'knees'.  These are characteristic of species of Brugueira and Ceriops.  Some species of Xylocarpushave knee roots that grow from the upper surface of horizontal roots, forming extended blade-like structures.  Lumnitzera develops knee roots without the thickening of secondary growth, which are structurally intermediate between kneeroots and pneumatophores. 

Pneumatophores project through the sediment surface from underlying cable roots and function primarily in gas exchange.  They are characteristic of Avicennia spp and Sonneratia spp.  Pneumatophores inAvicennia usually project less than 30cm above the sediment surface.  Those of Sonneratia species are bark-covered and may reach heights of 3 metres.  Some other genera may also develop pneumatophores.  In some circumstances, Laguncularia may develop pneumatophores, which are often branched, unlike those typical of Avicennia and Sonneratia.

Lenticels Lenticels—small

pores present on aerial roots.

Lenticels are susceptible to clogging by crude oil and other pollutants, and attacks by parasites.

COPING WITH SALT Exclude Salt (no

intake) Extrude salt (take

salt in and dispense it through glands in their leaves).

IMPORTANCE--ECOLOGICAL

Habitats, nurseries, and nesting sites. Root systems –harbor many organisms that

trap and cycle nutrients and other chemicals.

Contribute to higher water quality. Protect shorelines from erosion.

IMPORTANCE --ECONOMIC Food--- edible fruits and honey from flowers of

some species. River mangrove—source of best honey.

Medicines- Treatment of skin disorders and sores including leprosy. Headaches, rheumatism, snakebites, boils, ulcers, diarrhea, and many more conditions are traditionally treated with mangrove plants.

Hard wood -- used for boat building and cabinet timber.