Coasts: Distinctive Ecosystems

What are the 4 coral ecosystems of the world?

- Coral Reefs

- Mangroves

- Salt Marshes

- Sand Dunes

What factors effect the coral reef distribution?

- Temperature - needs minimum water temp of 18°C, grow best 23°C and 25°C

- Light - growth

- Water Depth - need for light, shallow, most in sea <25m

- Salinity - only survive in saltwater

What are features of coral reefs?

- Coral reefs are built up entirely of living organisms.

Features of Mangroves

- The roots of mangroves trap mud and sand, and eventually build up the intertidal zone into land.

Distribution of Mangroves

- Salinity of water: can grow in salty water

- Warm temperatures : need water around 19oC

- Inter-tidal: shallow water depths, roots grow above the water

Features of a Salt Marsh

- It is formed when areas of land have been alowed to retreat, allowing natural process to create a salt marsh.

Distribution of Salt Marshes

- Shelter from the sea / protected from wind - prevents erosion

- Salinity: brackish water

- Water regularly flooded by tides: deposits sediment, brings nutrients

- Large expanse of mudflat

Features of Sand Dunes

Coastal sand dunes are accumulations of sand shaped into mounds and ridges by the wind.

Distribution of Sand Dunes

- wide beach: greater area for wind

- large quantity of sand: increases the source of material for the wind to move

- onshore prevailing wind: ensures sand is dry and therefore can be moved inland

What are abiotic and biotic factors (with examples)?

- Biotic: living parts, e.g. plants and animals

- Abiotic: non-living parts that are essential to life (climate, minerals)

Abiotic and biotic characteristics in named ecosystem

The Great Barrier Reef

Abiotic: sea water, litter

Biotic: biomass

Sea Water

• supply of nutrients maintained by on-shore ocean currents.

• coral and other organisms filter and absorb abiotic nutrients, so coral reef grows

• factors needed for coral reef

Biomass

• coral polyps are living creatures, build reef’s limestone skeleton

• seaweeds attached to coral

• huge diversity of fish, crustaceans and invertebrates taking advantage of opportunities provided by reef

• zooxanthellae → algae living within coral convert the energy in sunlight into energy for the coral by photosynthesis

Why are coral reefs valuable?

- biodiversity

- provide protection to low-lying coasts from the impact of tropical storms

- rich fish stocks for food in developing countries

- tourism and recreational opportunities such as snorkelling and scuba diving

How are coral reef ecosystems being threatened?

- Rising water temperatures due to global warming cause coral bleeching.

- Overfishing from tourism and growth of industry removes fish that remove predators of reef-damaging species, fishing methods (bottom trawling and blast fishing) destroy coral

- Pollution of sewage and fertilisers cause eutrophication

Why are mangroves valuable?

- Rich in wildlife (fish and shellfish)

- trap silt, help create new land

- mangrove timber provides fuel and building material

Why are mangroves threatened?

- Shrimp and fish aquaculture: mangroves are deforested to make space for shrimp ponds, embankments and infrasturcture

- Pollution from chemicals, oil spills, and waste: inhibit growth, damage root systems, and kill trees

- Sea-level rise from global warming: increases wave action, causes erosion, roots cannot respire

Why are salt marshes valuable?

- collectors of silt and organic matter: build up beach

- nursery areas for fish and crustaceans: provide food

- protection against wave erosion and sea-level rises: reduce risk of flooding

Why are salt marshes being threatened?

- Creation of farmland, industrial sites, and ports

- Water pollution from ports, power stations and oil refineries

- Eutrophication from fertilisers and pesticided from farmlands

- Global warming, causes more frequent storms and higher water levels

Why are sand dunes valuable?

- provide coastal protection: absorbs wave energy, and provides a reserve of sand to replenish beaches

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How are sand dunes being threatened?

- use as recreational spaces (trail biking and horse riding)

- built over: for urbanisation and industry

- tourism: golf courses, caravan sites