Mangroves: Biome


Mangroves Introduction

  • Mangroves are forests in tropical areas
  • They are adapted to coastal conditions, with saline water
  • Challenges: high salinity (affects osmoregulation), anaerobic conditions (low oxygen availability where soil is waterlogged), stormy (tropical cyclones threaten stability), as well as extremes in temperature and water availability (they are in the inter-tidal range)

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Features of Mangroves

- Symbiotic Relationship with Tropical Corals: mangroves are found in similar areas as tropical coral reefs, as the mangroves trap sediment with their long roots and reduce turbidity for the corals, and the coral reefs protect the mangroves somewhat

- Obtaining Oxygen: the mangroves have lenticels (pores) on roots for gas exchange, and pneumatophores which poke up out of the sediment to access the air

- Halophytes: the mangrove plants are adapted to salty conditions. They even have leaves which are 'sacrificial' - they secrete salt then drop and die

- Water Retention: important in saline conditions. They have a thick waxy cuticle layer on the leaves, which are rounded to reduce water loss

- Reproduction: frequent flooding at high tide means the mangroves use the water as a seed dispersal mechanism. Propagules (small shoots) fall from the trees and float in water until they can take root in sediment

- Prop Roots: these are adaptations to withstand the stormy conditions, as the long roots anchor the coastal trees

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1. Coastal Erosion Protection - trapping sediment between roots helps to stabilise the coast

2. Fisheries - commercially important fish like groupers as well as shrimps use mangrove roots as nursery grounds for juveniles, due to the provision of food (algae, bacteria) and protection. This also is an important source of income and sustenance for coastal communities

3. Timber Supplies - resources like timber for construction and fuel have been important in local communities. Use of mangroves commercially for wood pulp and charcoal is also important

4. Trap Suspended Solids - enables the symbiotic relationship with tropical coral reefs. Therefore it could be argued that mangroves have the same importance as this ecosystem.

5. Carbon Sequestration - being photosynthetic organisms, mangrove trees remove carbon dioxide from the atmosphere and store the carbon in woody biomass

6. Medicinal Resources - traditional herbal medicines linked with lowering blood pressure

7. Tourism - the biodiversity supported by mangroves is important in attracting tourists

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Threats to Mangroves

1. Coral Reef Destruction - loss of the reefs means that the storms reaching mangroves are much stronger, and they are unable to be stable in such conditions

2. Overfishing - imbalances food webs and can cause trophic cascades

3. Global Climate Change - increases in storm frequency and severity can destabilise mangrove trees and cause larger fluctations in sea level as it continues to rise. Changes to temperature and sea level are also threatening tropical coral reefs

4. Pollution - as mangroves are commonly found at estuaries and on coastlines, any pollutants (fertilisers, pesticides, etc) from upstream reach them. These can harm the roots themselves, deplete oxygen, or affect the food webs. Oil pollution also blocks the lenticels and prevents gas exchange

5. Land Use Change - conversion and development of land for tourism (hotels, etc), urban developments, port expansion and aquaculture destroy the habitats

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Threats Summary

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Destruction of Mangroves

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Conservation Efforts


Re-planting mangrove trees in areas where loss has occurred. Projects are funded by international NGOs and carbon credit schemes. UN has 'Blue Forest' projects which take part on reforestation. Recolonisation of magroves can be rapid


Preventing coastal development - e.g: the Coastal Aquaculture Act, 2005, in India protects areas of mangroves


Like the Sundarbans region in India, which is a World Heritage site as it is the largest area of mangrove forests in the world

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