5. What are Mangroves?
• Woody, seed bearing halophytes
adapted for life in brackish and
waterlogged soils that are acidic
and often anoxic
• Shrubs to tall trees
• Found along sheltered tropical
mudflats
• 54 species across 20 genera
6. Distribution
• Almost exclusively tropical.
• Coastal zones and estuarine mouths
• Correlates with sea temp.
• Extend only a few km inland.
18. What is seagrass?
• Firstly it is not a seaweed nor is
it a true grass.
• The only marine flowering
angiosperm.
Where is it found?
• In both tropical and temperate
climates
Seagrass Beds
19. • Highest diversity is in Australia
with 23 species found. The
second highest area is in the
Philippines with 13 species
present.
• Tend to be found in the
intertidal region but can be
found to depths of 30m +
• Thalassia testudinum &
Syringodium filiforme are the
dominant species in the
Caribbean.
Seagrass Beds
20. The Morphology of
Seagrass
• Flowering plants
• Root system to withstand
wave action
• Reproductive system that
distributes pollen by water
• Normally found in areas
with high light penetration
• Often found between
mangroves and coral reefs
21. Importance of
Seagrass• Nurseries for juvenile fish
• Food source – manatees,
turtles,
• Feeding grounds for
predators
• Reduce currents and
erosion
• Improve water quality and
visibility
• Commercial uses
• Increase oxygen levels in
the water column
Hinweis der Redaktion
Mutualistic symbiosis of ecosystems
What is a mangrove?
A mangrove is.......
54 species across 20 genera
Mangroves did not evolve just once and then allow rapid diversification by a common ancestor but probably evolved independently at least 16 times in 16 separate families. The common features have evolved through convergence not common descent.
Distribution
Mangroves are found almost exclusively in tropical areas, although they can be found in areas where the air temp falls as low as 5 degrees Celsius. They are however intolerant of frost. There position correlates most closely with sea temperatures and as such follow the winter position of the 20 degree isotherm. The closer you move towards this boundary the less species are found.
Waterlogged soil:
Underground tissues of plants require oxygen for respiration. In normal non-waterlogged soil gas diffusion can supply this need. However, in waterlogged soil, even when the water is saturated with oxygen, the concentration is still far below that of air and the diffusion rate is approx 10,000 less than in air. Therefore waterlogged soils are considered to be low in oxygen. When water movement is limited this oxygen is soon depleted by aerobic respiration of soil bacteria which leads to an anaerobic environment.
Roots need air – absent in waterlogged anoxic mud, so…
Most mangroves have at least some aerial roots- directly exposed to the air
Surface of roots perforated with pores called lenticels
Air passes into lenticels, then along root through honeycombed sponge-like tissue – aerenchyma – which accounts for upto 40% total volume
Pneumatophores – grow vertically in air to act as snorkel
Rising tide pushes old air out of roots, and when it receeds, fresh air flows in again through lenticels and pneumatophores – thus roots of mangroves effectively breathe, using sea as their diaphragm
Avicennia – pencil-like; other species secondarily thicken to develop into tall, substantial cones
Anoxic bacteria are toxic to the mangrove so the roots secrete a small layer of oxygen to protect it and act as a barrier.
High/Changeable Salinity
Salt excretion
Soft sediment and wave action
BUTRESSES
Tree canopy
Birds, bats, insects
Trunks and aerial roots
Snails, crabs, barnacles, rock oysters, sponges, anemones, tunicates, mussels, worms, hydroids, bryozoans
Axial of branches and rot holes
Mosquitoes
Soil surface
Snails
Burrows
Fiddler crab, mud lobster, mud skippers
Surrounding water
Fish, dugongs/manatees, crocodiles
To establish themselves in unstable substrate, have large, often spear-shaped fruits that implant themselves rapidly upon reaching the mud
Some can disperse propagules, which hang from branches of mature trees
These may fall and take root in the soil surrounding the parent tree or float away
Rhizophora has fruit that germinates on the tree
Vivipary: After pollination the growing embryo remains on the parent tree and is dependant on it for a period that often stretches to many months: 4-6 months and grow 25-30cm
Propogation by water
Coastal Protection
Fringe of mangrove prevents soil erosion from land and sediment removal by sea
Removal of mangroves leaves coasts unprotected – may require construction of breakwaters
Coasts then more exposed to damage by natural events, e.g. 1992 Hurricane Andrew, Florida
Corals are vulnerable to sedimentation and eutrophication – mangroves may protect reefs by trapping excess sediments and nutrients
Fisheries
Mangroves are often the basis for thriving local fisheries
Species richness is generally high
Nursery areas – provide nutrition, shelter and protection e.g. shrimps, juveniles of pelagic species
Spawning areas
40% of mangroves lost during C20 - few forests are now pristine
Destroyed for building, agriculture (e.g. rice), municipal rubbish dumps, commercial logging and aquaculture
Apart from exposing the coast to erosion, extraction removes material which would have contributed to ecosystem
Selective removal of large trees for timber affects age structure
Removal of certain species affects community structure and decreases diversity
.since 1985 25% of mangroves in quintanaroo have been removed....data 3 years old....get pic of cancun...used to be a wetland.