Coastal ecosystems Flashcards
What is a coral reef?
Coral reefs are large deposits of calcium carbonate built entirely of living organisms called coral polyp
Where do you find coral reefs?
Corals are scattered throughout the tropical and subtropical Western Atlantic and Indo-Pacific oceans, generally within 30°N and 30°S latitudes
What factors affect coral reefs
Temperature
Light
Water depth
Salinity
What are the optimal conditions for a coral reef?
Temperature - Corals grow best at 23°C – 29°C.
Light - Corals need light for photosynthesis due to the algae, called zooxanthellae, that live in their tissue
Water - Corals are generally found at depths of less than 25m where sunlight can penetrate. The water must also be clear (low turbidity)
Salinity - 32-42%
What are the types of coral reef?
Fringing reefs - reefs that form around a land mass
Barrier reefs - found parallel to the shore but are separated by a channel of water
Atolls - horseshoe shaped rings consisting of a coral ring which encircles a lagoon
Where do you find mangroves?
Mainly found in warm tropical waters and coastal swamps within 30° N and S of the equator
Some have adapted to more temperate conditions and have colonized as far south as New Zealand’s North Island
What are the characteristics of mangroves?
They are trees which grow in water on the coastline between 0.5 and 2.5m high
They range in size from small shrubs to 60m high
They have lots of roots
They need high humidity 75-80% and high rainfall
Ideal temperature around 27%
Snorkel like roots that stick out of the mud to help them take in air
What are sand dunes?
Costal sand dunes are found all over the world and are mounds of sand shaped into ridges by the wind
Found at the back of beaches above the maximum reach of the tide
What causes sand dunes to form?
Wide beach with lots of sand
The prevailing wind is onshore
Large tidal range so sand can dry
Suitable place for the sand to accumulate
How are dunes eroded?
Wind and rising tidal levels can erode dunes as well as human activity
Describe the dune formation process
Wind blown sand is deposited against an obstruction - pebble or driftwood
As more sand particles are caught, the dunes grow in size, forming rows at right angles to the prevailing wind
Over time, the ridges of the dunes will be colonized and fixed by vegetation in a process called succession
What do pioneer species have to deal with?
High salinity
Lack of moisture as sand drains quickly
Wind
Temporary submergence by wind blown sand
Rising sea levels
Describe an embryo dune
Wind blown dried sand is trapped by debris and deposition begins
Pioneer species such as Lyme Grass and Sea Couch Grass begin to colonise
Embryo dunes are very fragile and reach a maximum height of 1 metre
Describe a fore dune
The embryo dunes bring some protection against the prevailing wind
This allows other species of plant to grow such as Marram Grass
Marram grass begins to stabilise the dune with its root system
These plants add organic matter to the dunes making the dunes more hospitable for plants that later grow
A microclimate forms in the dune slack
Maximum height is 5 metres
Describe a yellow dune
These are initially yellow but darken as organic
material adds humus to the soil
Marram grass still dominates the vegetation, but more delicate flowering plants and insects are found in the dune slacks
20% of the dune is exposed, down from 80%
Height does not exceed 8 metres