Camper Trailer Australia — December 2017

BENEATH THE SURFACE

homes in the nearby mangroves, which hold 54

per cent of the world’s mangrove diversity.

In the water can be found 1625 species of fish

and 450 species of hard coral plus much more in

the way of sea life.

WHAT IS CORAL?

Coral, as we see it, is a colonial structure built

by myriads of genetically identical organisms,

know as cnidarians (pronounced ni-darians),

which means they are related to jellyfish and

anemones. Each individual organism, or polyp,

is a small sac-like creature a few millimetres in

diameter and up to a couple of centimetres in

length. For their protection each polyp builds

a hard structure around itself from calcium

carbonate extracted from the ocean’s water. This

collection of hard structures builds the larger

coral formation that contributes to an overall

reef.

While some corals have tentacles around a

central mouth and can capture small marine

organisms with stinging cells, most corals derive

all or much of their energy from a symbiotic

relationship with internally housed small single

cell algae that function by photosynthesis. In a

symbiotic relationship both parties benefit from

THREATS TO THE REEF

The Great Barrier Reef is under threat from

a number of sources. Significantly rising sea

surface temperatures have resulted in coral

bleaching, in which the polyps eject their

symbiotic algal cells. This can be a temporary

solution to stress, but if the stress is sustained

the polyp will die. If the stress is removed the

polyp can usually take in fresh algae, though

this can take some years and requires optimum

conditions. The visible effect of this is the loss of

colour from the reef.

This has been most marked in the more

northerly areas of the reef, where temperatures

are highest. Since 1910 sea surface temperatures

have risen by an average of 0.68 degrees but

localised significant rises can cause severe

localises impacts. In 2016 a report in the science

journal Nature detailed an 800km stretch of the

northern reef which had died in that year. A 2017

survey found that in total as much as two-

thirds of the reef has suffered from severe

coral bleaching.

Otherthreatstothereefcomesfrom

agricultural run-off, with dissolved fertilisers

encouraging surface algal growth over the coral,

sedimentation due to industrial and other run-off

from human activity on land, the loss of coastal

wetlands, overfishing, ship wrecks and periodic

outbreaks of crown of thorns starfish which eat

the coral polyps.

TAKEALOOKFORYOURSELF

InNovember2014,GooglelaunchedGoogle

Underwater Street View in 3D of the Great

Barrier Reef, as part of a project which similarly

coversotherreefsystemsaroundtheworld.You

areabletoseethewondersofthereefsaround

Heron Island, Lady Elliot Island and Wilson

Island.

For more:google.com.au/maps/about/behind-

the-scenes/streetview/treks/oceansCTA

It's little wonder the Great Barrier

Reef is one of the Seven Natural

Wonders of the World

Six of the world's seven species of sea

turtle call the Reef home

You can find Nemo among the

1625 species of fish in the Reef

the association, in this case the algae benefit

by being provided with a safe hard structure

in which to live while the polyp benefits by

receiving surplus food from the algae and

having its waste and carbon dioxide consumed.

The photosynthetic process requires

sunlight, so this limits coral growth to a

maximum of about 60m in depth and with

clear water.

Most corals, such as those seen in the

Barrier Reef, survive only in waters with an

average temperature higher than 18 degrees

Celsius. However, there are some deeper

water and colder climate corals which can

survive in water up to 600m deep and at

much lower temperatures.

Snorkelling the Reef is a popular
tourist attraction