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Coastal ecosystems
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Some of the world's richest ecosystems are found where land meets sea. They are also some of the most threatened.
Four coastal ecosystems
Coral reefs: in warm, clear, shallow tropical seas. Built by tiny animals (polyps).
Mangroves: salt-tolerant trees on muddy tropical coasts. Their roots trap sediment, protect the coast from storm surges and shelter young fish.
Sand dunes: ridges of sand above the high-tide line, held together by plants such as marram grass with long roots.
Salt marshes: in sheltered estuaries, where mud builds up and salt-tolerant plants grow.
Mangroves: salt-tolerant trees on muddy tropical coasts. Their roots trap sediment, protect the coast from storm surges and shelter young fish.
Sand dunes: ridges of sand above the high-tide line, held together by plants such as marram grass with long roots.
Salt marshes: in sheltered estuaries, where mud builds up and salt-tolerant plants grow.
A named ecosystem: the Great Barrier Reef
Off the coast of Queensland, Australia, it is the world's largest coral reef system and a UNESCO World Heritage Site.
Abiotic: warm water, strong sunlight, clear and shallow sea.
Biotic: corals contain tiny algae that live inside them and provide food by photosynthesis; thousands of species of fish, turtles and sharks live there.
In very warm water corals expel their algae and turn white: coral bleaching.
Abiotic: warm water, strong sunlight, clear and shallow sea.
Biotic: corals contain tiny algae that live inside them and provide food by photosynthesis; thousands of species of fish, turtles and sharks live there.
In very warm water corals expel their algae and turn white: coral bleaching.
Threats
Industrialisation: ports, dredging and pollution.
Agriculture: fertiliser and soil washing into the sea; mangroves cleared for shrimp farms.
Tourism: trampling dunes, damaging coral and building resorts.
Deforestation: clearing mangroves for timber and land.
Climate change: warmer seas causing bleaching and rising sea levels.
Agriculture: fertiliser and soil washing into the sea; mangroves cleared for shrimp farms.
Tourism: trampling dunes, damaging coral and building resorts.
Deforestation: clearing mangroves for timber and land.
Climate change: warmer seas causing bleaching and rising sea levels.
Explain why mangroves are important to people.
- Their roots trap sediment and absorb wave energy, protecting the coast from storms.
- They are nurseries for young fish, supporting fishing.
- They provide timber, fuel and food.
Answer: Coastal protection, fishing and resources.
Coastal ecosystems: coral reefs (warm, clear, shallow seas), mangroves (salt-tolerant trees), sand dunes (marram grass) and salt marshes (sheltered estuaries). The Great Barrier Reef is the largest reef system, threatened by bleaching and pollution. Threats include industry, farming, tourism, deforestation and climate change.
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