Hawkesbury-Nepean River Environmental Monitoring Program
Hawkesbury-Nepean River Environmental Monitoring Program
Hawkesbury-Nepean River Environmental Monitoring Program
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Dam to Wisemans Ferry. The results of this study are reported by Thiebaud and<br />
Williams (2008) and included in Appendix 9.<br />
Native as well as exotic species were encountered in each of three categories:<br />
submerged, emergent, and floating vegetation. Macrophytes in the submerged<br />
category included the native plants Ceratophyllum demersum, Hydrilla verticillata,<br />
Najas tenuifolia, and Vallisneria gigantea. Two exotic species in this category, Egeria<br />
densa and Elodea canadensis, were also encountered, the former being widespread<br />
in occurrence and of particular concern as it has spoiled the recreational amenity of<br />
the waterway.<br />
Emergent macrophytes included Bolboschoenus fluviatilis, Juncus usitatus,<br />
Phragmites australis, Schoenoplectus validus, Triglochin procerum, and Typha<br />
orientalis. Gymnocoronis spilanthoides and Sagittaria graminea ssp. platyphylla, two<br />
introduced species, had a limited distribution, being found only within the central<br />
portion of the study area.<br />
Native floating macrophytes included Azolla spp., Lemna spp., and Ludwigia<br />
peploides ssp. montevidensis, whereas the introduced Alternanthera philoxeroides,<br />
Eichhornia crassipes and Salvinia molesta were confined to the upper and central<br />
portions of the study area. The latter three species have been of particular concern in<br />
the past.<br />
Figure 6.34: Egeria densa stranded after minor flooding in June 2007 (Photos courtesy<br />
of DPI Fisheries—Thiebaud and Williams 2008)<br />
Major conclusions from Thiebaud and Williams’s (2008) study were:<br />
• Much of the shoreline of the <strong>Hawkesbury</strong>-<strong>Nepean</strong> <strong>River</strong> from Warragamba Dam<br />
to Wisemans Ferry was vegetated with emergent or submerged macrophytes.<br />
• The distribution of the floating macrophytes was restricted to the more central<br />
section of the study area.<br />
• The introduced submerged species Egeria densa was present throughout much<br />
of the study area.<br />
• The introduced submerged species Cabomba caroliniana was not found in the<br />
study area.<br />
64 <strong>Hawkesbury</strong> <strong>Nepean</strong> <strong>River</strong> <strong>Environmental</strong> <strong>Monitoring</strong> <strong>Program</strong>: Final Technical Report