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Seagrasses are true plants that flower and need light for photosynthesis. As a consequence seagrass meadows are restricted to quite shallow water and are most often found in sheltered bays.
The most common seagrasses found in Sydney harbour are, Eel-grass Zostera capricorni found in very shallow water often on mudflats that are occassionally exposed during the low tide; Strap-weed Posidonia australis which prefers slightly deeper water and Paddle-grass Halophila.
The largest concentrations of seagrasses occur in the lower reaches of Sydney Harbour in the sandy bays of Middle Harbour and various shallow bays in the outer harbour such as Manly, Double Bay, Clifton Gardens and Rose Bay.
Seagrasses provide an important 'nursery habitat' for the juveniles of many fishes such as Luderick Girella tricuspidata, Tarwhine Rhabdosargus sarba, Eastern Blue Groper Achoerodus viridis and Yellow-finned Leatherjacket Meuschenia trachylepis. The young fish feed on small animals living on seagrass leaves and use the seagrasses to hide from larger predators. Most of these fish will leave the seagrass meadows and migrate to other habitats, such as kelp beds and rocky reefs, as they get older.
For many other fishes such as pipefishes, White's Seahorse Hippocampus whitei, Southern Pygmy Leatherjacket Brachaluteres jacksonianus, Leaf Fish Ablabys taenionotus and Blue-spot Goby Pseudogobius seagrasses provide lifelong habitat.
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