Mangrove ecosystem

What are mangroves? Mangroves consists of different kinds

of plants living on protected soft shores

Northeast New Territories

Environment

Tidal zone

Soil in anaerobic condition

Distribution In tropical region between 20ºN and

20ºS where the annual temperature is above 20 degrees

Environment Highly unstable environment as

sedimentation is active but the soil is not consolidated

Waterlogged soil, so aeration is poor In high salinity environment

Plants Plants adapt to the soft sea shore

where mud and sand are deposited Root buttresses and stilt roots develop

Mai Po Marsh

Common mangrove plants

Kandelia candel Avicennia marina Lumnitzera Racemosa Bruguiera gymnorrhiza Heritiera littoralis Aegiceras corniculatum

Salt released on leaves

Avicennia marina

Lumnitzera Racemosa

PneumatophoresAvicennia marina

PneumatophoresAvicennia marina

Knee roots

Buttress roots

Derris trifoliata in Lai Chi Wo

Heritiera littoralis

Droppers

Cerbera Manghas

Animals Crabs - fiddler crabs and sesarmine

crabs Oysters and barnacles Gastropods

Animals Mudskippers live between the high-

tide and low-tide level. They can live without water for days

Fish and shrimps larval

Mudskipper

Mudskipper

Mudskipper

Fiddler Crab (Uca borealis)

Crab

Crab

Fish

Egret

Energy flow Warm tropical climate provide a lot of

solar energy for photosynthesis Mangrove litter dropped on the ground

is consumed by crabs, shrimps and fish

Energy flow The small animals are then eaten by

larger fish and then by resident and migrant birds (egrets and spoonbills)

The litter that is not consumed is decomposed in the soil

Example The fish ponds and gei wais in South

China The marsh provides shelter for

juvenile and larval animals such as shrimps and fish

Litters, small plants and animals provide food for these animals in the ponds

The animal wastes and litter enrich the soil with nutrient

Nutrient cycling The sea and rivers carry nutrients to

the shore The nutrients are absorbed by

mangrove plants and seagrasses and algae.

The nutrient is then transferred to the consumers such as crabs, fish and shrimps

then transferred to human beings, birds and large fish

Nutrient cycling

Nutrient cycling The dead bodies and litter are

decomposed by micro-organisms in the soil

Nutrient is released to the soil and sea water

Utilization and threats Marsh lands have been dredged and

vegetation removed to form fish ponds They have been developed into

recreational grounds for fishing and barbecue

This provides income and can make better use of mangrove resource.

Threats Increase in demand for land in coastal

areas.– For industrial and residential development– Recreational use

Environmental pollution around the wetland

Other threats?

Tin Shui Wai

Yuen Long Industrial Estate