Lecture 9 - Mangroves Flashcards Preview

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Flashcards in Lecture 9 - Mangroves Deck (22):

What are mangroves?

Coastal communities, tropical equivalent of salt marshes, sheltered habitats sediment accumulation, found on 60-75% of tropical coastline


What are the six conditions needed from mangrove growth

> water needs to be shallow (intertidal)
> Sedimentation deposition occurs (low energy)
> Adequate light (photosynthesis)
> Water temperature >5oC
> Air temp high
> High rainfall, controls salinity


Explain the type of biota in mangroves

Mangrove trees are exposed to tidal emersion and partial immersion, due to the specialised habitat associated life has a low diversity, not totally marine some organisms are terrestrial. Water column and sediments are truly marine


Explain zonation on the mangrove shore

Zonation is a function of tollerance to tidal regime, salinity, anoxic sediments, stability and the main adaptions and roots are mechanisms of salt loss goes from (sea to shore)
Red magrove
black mangrove
white mangrove


How can zonation vary from location to location

Its though to be due to environmental conditions such as tide (macrotidal they can be dench) and other factors such as rainfall etc


Explain the four factors of the tidal regime

> Landward areas dry out resulting in desiccation and high salinity
> Tidal flushing washes away salt crystals and hydrates the sediment, less effective inshore
> tidal immersion also provides suspending nutrients
> anoxic sediments release sulphides, removed by tide


Explain how anoxic sediments form in mangroves

Colonisation by plants stabilise sediment, immersion by tide limits O2 exchange, high detrital input from plants leads to high bacterial mineralisation rates, which leads to anoxic sediment


what are the four root forms mangroves have to deal with anoxic sediments

> Pneumatophores
> Prop roots
> Kneed roots
> Plank roots


Pnuematophores explantation

-ve geotropic, roots grow up to 3m in length and go under the substrate and emery protruding out vertically, can take oxygen out of the air


Prop roots explanation

These hold the tree base out of the sediment and therefore can be emmersed allowing for oxygen absorption


What are Lenticles

Pores which allow gas exchange but not water and solutes enable oxygen to be transported through channels in the Aerenchyma tissues (found in both prop and pneumatophores)


Knned roots explanation

Look like little knees coming out of the sand, no lenticles


Plank roots explanation

minimise amount of tree under the ground like the ones you see in the rainforest, no leticles


What are the tree mangrove adaptations to saline environment

> Salt secretions
> root membranes
> Non-salt secretions


Explanation of salt secretions

Salt is taken in by the plant roots and is transported to the leaves in the sap, the sap is normally at 1/10th of the water column, sap is then excreted through glands in the leaves


Root membranes as an adaption again saline environments

Semi-permeable membrane excludes most salt ions, limiting uptake


Explanation of non secretors

Complex ultra-filtration system that is not fully understood in the following order in the root system (radial filtration)
a. Na+ / K+ ions pumps in the xylem (active transport)
b. Na+ / K+ ion pumps in the leaves (active transport)
c. Salt is stored in ion saturated cells, sealed of by suberin coating
d. These cells are lost when leaves are shed and are pushed back down by plant growth


Mangrove reproduction stages (3)

1. Viviparous seeds (germinate before detachment) develop onto the parent plant - vivipary
2. Embryo grows out through the seed coat and fruit wall - Cryptovivipary
3. Embryo only grows out through the seed coast and not the fruit wall before it splits open


what occurs after germination of the vivipary

Seed drops out of fruit and is already ready to grow in a suitable habitat, it is either washed away of falls straight into the mud - has competition with parent plant in that case


Explain mangal fauna

Similar to other soft shore sediment communities in types of organisms, i.e molluscs, decapods etc..


What are the five key types of mangal fauna

Crustaceans (decapods and cirrpidiia)
Chelicerates (spiders and horseshoe crabs)


What are the human uses of mangrove swamps?

Timber, paper, cattle fodder, tobacco substitute, wine etc...