Posidonia australis seagrass meadows of the Manning-Hawkesbury ecoregion

Posidonia australis seagrass meadows of the Manning-Hawkesbury ecoregion is an endangered ecological community, listed under the EPBC Act of the Commonwealth of Australia on 7 May 2015[1] The ecological community is "the assemblage of plants, animals and micro-organisms associated with seagrass meadows dominated by Posidonia australis occurring in the warm temperate Manning Shelf and Hawkesbury Shelf bioregions on the east coast of Australia.

"[2] It occurs subtidal waters at depths from less than 1 m to 10m within the sheltered environments of estuaries on the coastline from Wallis Lake to Port Hacking.

[2] It is found on sand and silty mud and in these estuarine waters the salinity is close to marine levels.

The leaves of Posidonia australis provide a place for many benthic flora, including epiphytes, to grow.

[2] Fauna found within the shelter of the meadows include: protozoans, bacteria, harpacticoid copepods,ostracods, nematodes, polychaetes, bivalves, amphipods, cumaceans, holothurians, phoronids, rotifers, isopods; small decapods, gastropods, pycnogonids, echinoderms, nemerteans, hydroids, bryozoans, sponges; ascidians; serpulid polychaetes, and fish.