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What is seagrass
Seagrasses form the 'meadows' of coastal waters.
They are vascular, flowering plants with roots, making them quite different from seaweed, which is an alga. Their large root system is essential for the uptake of nutrients and for anchoring them to the sand.
It is estimated that seagrasses cover 5,000 km² of the sheltered waters of Gulf St Vincent. The dominant seagrasses are ribbon-weed (Posidonia spp.) and wire-weed (Amphibolis spp.) and in the shallower regions, paddle-weed (Halophila spp.) and eel-grass (Zostera and Heterozostera spp.).
Seagrass provides habitat for a large variety of marine animals, including fish, and stabilises the sand, reducing erosion. Seagrasses also reduce wave energy, which can help to stop coastal damage during storms.
What is happening to seagrass
Seagrass is commonly lost when nutrient levels in the water increase.
These nutrients cause a large number of epiphytes to grow on the seagrass leaves, causing them to become too heavy and to break off.
The nutrients also encourage more microscopic algae to grow in the water, reducing the amount of light getting to the seagrass, particularly in the deeper regions.
Over 50 km² of seagrass have been lost from the Adelaide metropolitan coastline. This has been attributed to the effects of discharges such as sewage effluent and sludge and also stormwater.
Reports
Links
- Adelaide Coastal Waters Study
- Coast and Marine Branch, Department of Environment and Natural Resources
Last modified: 02/11/2011 03:59 pm
