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 Description. 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." 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. It is found on sand and silty mud and in these estuarine waters the salinity is close to marine levels. The meadows of the community occur as both monospecific meadows (of "P. australis") or as multispecies meadows (with, for example, "P. australis" together with "Zostera muelleri" subsp. "capricorni", "Halophila ovalis"). The macrophyte, Ruppia, may also be found growing within the ecological community (Creese et al., 2009). The leaves of "Posidonia australis" provide a place for many benthic flora, including epiphytes, to grow. These epiphytes photosynthesise and their proportion within the meadows is largely dependant on the  nutrients available in the water. 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.