Lecture 2 - Mangroves Flashcards
what are mangroves?
> woody tress and shrubs
major vegetation of the intertidal zones of tropical to warm temperate climates
salt and inundation tolerant
ecosystems with specific characteristics
mangroves grow along rivers and into the sea along gradients of salinity
mangroves inhabit the intertidal zone, are tolerant of inundation and salinity
describe water movement in mangrove forests
> water can move fast in mangrove forests with consequences for sediment, leaf litter, fauna, seedling establishment
total inundation with salt water can occur
what are mangroves characterised by?
>strong environmental gradients - salinity - water movement - inundation frequency and severity - sediment > seaward zone > mild zone > landward zone > terrestrial forest
where do mangroves grow?
> tropical and warm temperate regions
intertidal zones
most diverse in species in the Indo-West pacific
What ecosystem services o mangroves provide?
> habitat and nursery
hydrological damping
sediment trapping
nutrient cycling and storage
carbon cycling and storage - sequestration
forest products
bioshields protecting coasts against weather extremes
compare the diversity of mangroves to other alt impacted communities
> Mangroves - woody - 26 families, 69 species > seagrass - herbaceous - 14 families, about 50 species > salt marsh - herbaceous - 18 families (6 dominants) > low diversity compared to rainforest and coral reef
what does mangroves diversity vary with?
> species diversity varies with various factors
estuaries are on essential mangrove habitat
diversity increases from south to north australia
describe how mangroves are taxonomically and structurally diverse
> 46 species in the Indo-east pacific, 12 Atlantic - west pacific
mostly woody trees and shrubs + one fern and palm genus
in Queensland:
Aegiceras = river mangrove, primarily found along river banks
Avicennia = grey mangrove, DOMINANT mangrove of Moreton bay
Rhizophora = red mangrove, typically dominant mangrove in tropics
further species are: Acrostichum speciosum and lumnitzera racemosa
what are some survival strategies mangroves employ to combat the extreme salinity?
> mangroves exclude much salt from water during uptake and several can also excrete salt from leaves
salinity adaptations include specialised water uptake system and efflux of salt ions in roots and salt glands that actively excrete salt from leaves
suberin in root endodermis that is a barrier to salt
what is a survival strategy mangroves employ to breed?
> they have vivipary
bear live young
seeds germinate on the tree, then called propagules
then they drop to the ground, stick into the soft sand substrate and grow
how do mangroves survive anoxic conditions?
> mangroves can grow in anoxic (oxygen depleted) sediment and have different types of roots for anchorage, feeding, aeration
roots = pneumatophores
- act as snorkels
specialised root systems to transport oxygen
aerenchma: tissue for gas exchange to aerate roots and stems
lenticels = small openings gas exchange (here in pneumatophores)
what types of other organisms live within the mangrove community?
> a rich epiphytic algal community on mangrove pneumatophores
snails;
- graze on sediment during low tide and up on trees at high tide
Crabs:
- crabs have central role for leaf litter recycling into soil to maintain nutrient status of sediment
describe the role of supertidal flats and slat marsh associated with mangrove forests
> high evaporation, cencentrates salts and nutrients (silica, phosphate, ammonium)
cyanbacteria mats fix air N2 into reactive N and stabilise sediment
