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Seaweek 2010: Oceans of Life - ours to explore; ours to restore


• Algae act like aquatic plants (although are not classified as plants) capturing sunlight and transforming it into energy through the process of photosynthesis to produce organic matter (carbon). Their shapes, sizes and colours vary greatly; from small single-celled to multicellular and complex structures that range widely in colour.

• Algae are found in many different habitats growing on hard structures such as rocks, dead corals and shells. Red and brown algae dominate the inshore part of coral reefs while red and green algae dominate offshore areas. A special type of calcareous (i.e. has a limestone skeleton) algae exists called coralline algae that grows over the coral reef structure like orange, red or purple cement helping to bind the reef structure together.

• Algae are primary producers. All life on earth is dependent directly or indirectly upon primary producers who produce organic compounds form atmospheric or aquatic carbon dioxide primarily via photosynthesis. Primary producers form the foundation of most food chains and are mainly plants on land and algae in the water. Algae are therefore a keystone in the ecology of coral reefs. • Tiny single-celled algae that live in the water column (called phytoplankton) produce a large quantity of the oxygen present in the Earth’s atmosphere, around half of that produced by all plant life.

• Algae require nutrients to grow such as nitrogen and phosphorous. If there are excessive nutrients in the water from human activities such as agricultural runoff, algae may proliferate on coral reefs smothering coral and out-competing it for space.

• Tiny microscopic algae actually live inside coral in a symbiotic relationship providing the coral with energy in return for a safe place to live. These algae are called zooxanthellae.

• Humans use algae in many different ways; such as a food source, for making cosmetics and even ice cream.

• Reef Check Australia identify and monitor Nutrient Indicator algae. We record the following types of categories; Nutrient Indicator Algae (NIA), Halimeda algae (OT), Coralline Algae (RCCA), Turf Algae (RCTA), Macro algae (MA) includes sargaaaum, padina and turbinaria sp. High cover of NIA indicates high nutrient levels in the water and/or the removal of herbivores from the reef.

Interesting Fact: Some species of fish that eat algae keep small algae farms to feed on.

Further links:

• ReefED:

• Wikipedia: (also gives useful information on primary production and oxygen production).






Clump of pink Coralline algae in shallow waters
from GBRMPA Image Collection

Algae growth on bleached Acropora coral
from GBRMPA Image Collection

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Marine and Atmospheric Research


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