Just as the land has grass so does the sea. Although the sea grass is related to the land based grass it only returned to the sea in recent evolutionary history.
Sea grasses are flowering plants that grow along the coast in well-lit quiet waters sheltered by bays and inlets. They form into lush grass meadows and are a hiding ground for small crustaceans, fish and anything wanting to hide from a predator. These are also feeding grounds for dugongs (manatees) and green turtles. Black swans also like to feed on the seagrass. Australian waters have the world’s highest diversity of sea grass species:
- 22 species found in temperate (cold) waters
- 15 species found in tropical waters.
Australia has about 51 000 sq. km. of sea grass meadows. The largest of these are in Western Australia and Queensland. Western Australia is home to the most diverse number of sea grass species in Australia. One square meter of sea grass can generate up to 10 litres of oxygen per day. Sea grass meadows capture and store carbon at a rate forty times faster than a tropical rain forest – and they can store that carbon for thousands of years. On the other hand when the seagrass is destroyed the carbon is released back into the atmosphere. Cyclones are responsible for some of this destruction as well as loss of light due to sedimentation and algae growth due to increased nutrient levels in the water. These plants flower in autumn or summer and their roots absorb nutrients but unlike land plants do not take up water. They are more closely related to terrestrial lilies and gingers than to true grasses, they grow in sediment on the sea floor with erect, elongated leaves a buried root-like structure (rhizome).