Characteristics of Coastal Ecosystem (Edexcel IGCSE Geography)

Characteristics of Coral Reef Ecosystems

• An ecosystem is a community of interacting biotic and abiotic organisms

• All ecosystems, whether on land or in water function in the same way

• All survive by nutrient cycling around three stores:

  • Biomass

  • Litter

  • Sea Water

Nutrient Cycle of Coastal Ecosystems

Overview of Coastal Nutrient Cycling

Biotic Components of a Coral Reef

• A coral reef is a well-organized food web comprising of:

  • Producers

  • Consumers

  • Scavengers

  • Decomposers

• Producers in a coral reef include seaweed, seagrass, and phytoplankton. zooxanthellae are also producers that provide the nutrients from photosynthesis to coral

• Consumers are organisms that eat other organisms to gain energy. There are three main types of consumers in a food web: primary, secondary, and tertiary

  • Primary consumers only eat producers - the green sea turtles graze on seagrass

  • Secondary consumers eat primary consumers - stingrays, octopuses, squid, and larger fish for example

  • Tertiary consumers, also called apex predators, are carnivores that do not prey upon themselves.  These consumers help maintain the balance of the ecosystem -  sharks, dolphins, tuna, barracuda, etc. 

• Scavengers feed on dead and decaying plants and animals - crabs and lobsters scavenge for food 

• Decomposers bring nutrients back into the ecosystem to support another cycle - examples include bacteria, sea cucumbers, and fungi

Abiotic Features of a Coral Reef

• Light: Corals need some sunlight to survive:

  • Too little, then the zooxanthellae will not be able to photosynthesize and produce food for corals.

  • Too much may cause corals to expel zooxanthellae, causing bleaching 

• Depth: As corals need light, they are typically found at approximately 25 meters

• Water temperature:  Corals thrive in the warm waters of the tropics. They prefer a temperature range of 23-25°C but will survive at lower and higher temperatures for short periods of time 

• Salinity: Corals need salty water

• Air: Can survive out of water for very short periods of time

• Water: Corals need clean, clear water

Characteristics of Mangrove Ecosystems

Biotic Components of a Mangrove

• Mangroves are the producers of their own ecosystem

  • Many organisms feed on the detritus created from falling leaves 

  • Phytoplankton can float on the surface of the water and algae grow on the mangroves' roots

• Primary consumers are usually the decomposers (e.g. the mangrove tree crab). Small fish, crabs, clams, and shrimp feed off of the detritus. Very few consumers directly feed on the mangroves 

• Secondary consumers are the larger predatory fish, turtles, and crabs

• Tertiary consumers include birds (e.g. herons and ospreys), eels, saltwater crocodiles, tigers, and humans

• Scavengers include shrimp, crabs mussels and mullet

• Decomposers include worms, bacteria and fungi

Abiotic Features of Mangroves

• Temperature: Mangroves typically grow in areas where the temperature does not drop below 19°C

• Oxygen: Just like other plants, mangroves need oxygen to survive. Complex root systems allow the mangroves to receive the oxygen they need by sticking out of the water 

• Salinity: Mangroves have adapted to live in salt water with some removing excess salt through their leaves

• Soil: Mangroves can grow within the intertidal zone of a coast. The soils are made up of sand, silt, and mud 

• Wave Energy: Mangrove vegetation cannot develop on exposed coasts with a lot of wave energy or currents that move sediments which would stop seeds from colonising

• Ocean Currents:  These distribute mangrove seeds and help keep the areas full of trees 

Characteristics of Sand Dune Ecosystems

Biotic Components of Sand Dunes

• Producers that provide the initial beach fuel for dunes include:

  • phytoplankton, microscopic algae (green scum found on a beach), detached seaweeds such as kelp and seagrass and blown-in seeds.

  • These support the growth of pioneer species such as couch grass, and lyme grass. As succession continues, multiple species of vegetation begin to colonize - marram grass, gorse, sea buckthorn, heathers, red fescue, etc.

• Primary consumers: beetles, butterflies, moths, bees, wasps, flies, rabbits, etc

• Secondary consumers: sand lizards, snakes, spiders, frogs, bats, etc

• Tertiary consumers: seagulls, waders, hawks, swans, bats, etc 

• Scavengers: crabs, beetles, flies, wasps, crows, rats, etc

• Decomposers:  flies, fungi, bacteria, weevils, etc

Abiotic Features of Sand Dunes

• Wind - an onshore prevailing wind is needed to blow dried sand into ridges

• Tidal Range - needs to be large to allow sand to dry

• Water - a mix of fresh and saline to support pioneer spices

• Sand - large quantities needed

• Beach - needs to be wide 

• Obstacles - needed for sand to accumulate behind

Characteristics of Salt Marsh Ecosystems

Biotic Components of Salt Marshes

• Producers - algae, seaweed, rushes, samphire, cord grass, salt marsh hay etc

• Primary consumers - fish, insects, mussels, crabs, bees, oysters, shrimp etc

• Secondary consumers - fish, mice, frogs, herons, lizards, sandpipers, bats etc

• Tertiary consumers - harriers, sea eagles, gulls etc

• Scavengers - snails, rats, crows, flies, crabs etc

• Decomposers - fungi, bacteria, worms, etc

Abiotic Features of Salt Marshes

• Waves - sheltered away from the open sea & destructive waves, usually behind a spit or in sheltered bays

• Water - brackish (mix of fresh and salty)

• Tidal Range - large tidal range with occasional flooding. Mud flats need to be exposed to colonise

• Mud - sediment needed to build up mud flats

• Elevation - needs variation in height to build up mud flats and stabilise marshes