Mangrove habitats Flashcards
Mangroves
Tropical inshore communities dominated by species of tree and shrubs that grow in permanently salty water
How many Species, genera and families
70 described species, 28 genera and 20 families
Taxonomically diverse, adaptations enabling survival evolved 16 times
Most dominant families
Avicenniaceae and Rhizophoraceae are the dominant families throughout the world with 23 species between them
Mangrove growth environment
Mangrove roots grow in a hostile soil environment
Soil is oxygen deficient and often has a higher salinity than open ocean due to evaporation
Typical redox potential of aerated soil is 300mV and mangrove around -200mV
In the absence of oxygen, anoxic reactions take place sequentially as organic material is broken down
Root adaptations for anoxic soil
Shallowing root system that is widespread or perpendicular to trunk
Elongation in rhizophora can be as much as 9mm a day
There are several species specific adaptations to cope with oxygen deficient soil, most of these consist of arial roots that can represent up to 24% of above ground biomass
Mangrove root adaptations
Aerial roots of rhizophora are often known as stilt roots
Branching increases anchorage points also securing plant during wave action
The height of pneumatophores is a response to tidal cycles of water submergence
Root adaptations for saline soils
Like with brackish organisms, dealing with osmotic changes in the cell requires adaptations
Water must be drawn against
This water can also be hypersaline so adaptations are required to counter this
How do root systems counteract the uptake of salt water
Build negative hydrostatic pressure by transpiring salts at the leaves through salt glands
Species such as Avicennia and Acanthus often have clearly visible salt crystal deposits on their leaves
Leaves have hairs to precipitate the droplets of salty water.
