Coral Reefs- The Great Barrier Reef

2.2 Hydrological Processes

The hydrosphere is all about flows and storages of water. The different types of flows of water have an impact on the development of Coral Reefs.

The flow of water in the form of waves impacts coral reefs in a number of ways.
Firstly, the millions of tiny air bubbles in waves that crash on the edge of reefs provides the necessary oxygen for optimal coral growth.
Secondly, the powerful force of waves especially after cyclones are responsible for the breaking off and movement of large coral pieces (transport) and the placement in other parts of the reef deposition)

Currents affect Coral Reefs in a number of ways.

They help move sediment weathered and eroded from other areas to be deposited onto the reef to form islands, cays etc. Stradbroke Island is a classic example of sediment moved from NSW to create this sand island.
Currents also bring to the reef the tiny organisms called zooplankton to help feed the variety of life
Currents also help bring plant life and seeds that colonise newly exposed sand bars.
Currents are used by many marine organisms to migrate for breeding.
easterly winds and the currents determine water movements in the Great Barrier Reef region. Around 7000 cubic kilometres of water a day is flushed through the system by tides and currents.
There are two currents which affect the Great Barrier Reef: The Trade Wind Drift Current and the East Australian Current (the EAC out of Finding Nemo!)
For about nine months of the year, the south easterly trade winds make the water flow in a northerly direction (trade wind drift current).
During the summer months, the dominant wind comes from the north-east and this reverses the direction of the current to flow to the south. In the southern parts of the Great Barrier Reef, the influence of the East Australian Current moves water in a southerly direction. The Figure below shows the main currents in operation in the region.

Source: http://www.marine.csiro.au/LeafletsFolder/37eac/