Mangroves and Seagrasses

Overview• Ecosystem Interactions

• Mangroves– What are Mangroves– Distribution– Adaptations– Associated Animals– Dispersal & Reproduction– Life Cycle

– Importance of Mangroves– Uses of Mangroves– Threats

• Seagrasses– Seagrass Beds– Morphology– Importance

Reduce wave action

Act as juvenile nursery ground / Source of leaf litterReduce coastal

erosion Freshwater buffer

Act as juvenile nursery ground

Trap sediment

Trap sediment

Slow wave action and currents

Ecosystem Interactions

Mangroves

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

Distribution

• Almost exclusively tropical.• Coastal zones and estuarine mouths• Correlates with sea temp.• Extend only a few km inland.

Adaptations

• Waterlogged soil

• Low oxygen environment

• Aerated roots called Pneumatophores

Adaptations

•High / changeable salinity

•Salt excretion glands

•Sacrificial leaf

Adaptations

•Soft sediment

•Wave action

•Butress root system

Associated animals

Dispersal and Reproduction

• Vivipary

• Spear shaped fruits called Propagules

• Fall and take root in the soil

• Increases chance of survival

Dispersal and ReproductionHydrochory:

• Dispersal by water

• Propagules dry out to enable them to float.

• Can travel great distances from the parent tree.

Life Cycle

Importance of MangrovesCoastal protection• Prevents soil erosion• Trap excess

sediments and nutrients

Fisheries• Nursery • Spawning

• Fuel• Construction• Fishing• Domestic uses• Agriculture• Medical

Uses of Mangroves

Threats

40% of Mangroves lost during the 20th Century

Seagrass

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

• 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

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

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