Coastal ecosystems

Question 1

What is a coral reef?

Answer 1

Coral reefs are large deposits of calcium carbonate built entirely of living organisms called coral polyp

Question 2

Where do you find coral reefs?

Answer 2

Corals are scattered throughout the tropical and subtropical Western Atlantic and Indo-Pacific oceans, generally within 30°N and 30°S latitudes

Question 3

What factors affect coral reefs

Answer 3

Temperature
Light
Water depth
Salinity

Question 4

What are the optimal conditions for a coral reef?

Answer 4

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%

Question 5

What are the types of coral reef?

Answer 5

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

Question 6

Where do you find mangroves?

Answer 6

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

Question 7

What are the characteristics of mangroves?

Answer 7

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

Question 8

What are sand dunes?

Answer 8

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

Question 9

What causes sand dunes to form?

Answer 9

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

Question 10

How are dunes eroded?

Answer 10

Wind and rising tidal levels can erode dunes as well as human activity

Question 11

Describe the dune formation process

Answer 11

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

Question 12

What do pioneer species have to deal with?

Answer 12

High salinity
Lack of moisture as sand drains quickly
Wind
Temporary submergence by wind blown sand
Rising sea levels

Question 13

Describe an embryo dune

Answer 13

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

Question 14

Describe a fore dune

Answer 14

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

Question 15

Describe a yellow dune

Answer 15

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

Question 16

Describe a grey dune

Answer 16

Grey dunes are more stable, with less than 10% of exposed sand and have a good range of biodiversity

Soil acidity and water content increase as more humus is added

Shrubs and bushes begin to appear

Height is between 8 - 10 metres

Question 17

Describe a mature dune

Answer 17

As the name suggests, these are the oldest and most stable of the dunes

They are found several hundred metres or more from the shoreline

The soil can support a variety of flora and fauna such as oak trees and alders (climax vegetation)

This is the final stage in succession which is known as the climax community stage

Question 18

What are the characteristics of a salt marsh?

Answer 18

They are found all over the world and are not temperature dependant
They are typically very flat, with numerous channels running through them

They form in:
Coastal areas that are well sheltered, such as inlets and estuaries where fine sediments can be deposited

Areas behind spits and artificial sea defences where tidal waters can flow and gently and deposit fine sediments

Question 19

What are the features of salt marshes?

Answer 19

Salt marshes are communities of nonwoody, salt-tolerant plants

They begin as tidal mud flats, gaining height as more sediment is deposited

This builds up to and above the level, and frequency of tidal flooding ensuring that the soil never dries out and remains muddy and sticky

Pioneer species of halophyte plants begin to colonise
As these plants die and add nutrients to the soil, sediment builds up.
This makes the conditions more favourable and other species start to develop.

The lower marshes are flooded daily by the rising tide.
They are good coastal defences in some areas, acting as a natural buffer against coastal erosion and flooding
However, in many areas they have been reclaimed for agriculture or development, and are threatened by human activities