2022-05-16 GC Agenda - Item 7 - Attachment 2 - Noosa Oyster Ecosystem Restoration Project - Project Restoration Plan

                 5.5 Composite substrate

                 A small portion (<20 percent) of the restoration substrates will be a mixture of rock and cured oyster
                 shell as per the specifications. This composite is being used to further explore whether oyster
                 recruitment is enhanced by mixing oyster shell with the rock or not. Restoration scientists generally
                 expect that oyster shell provides chemical cues that may attract oyster larvae to settle on a particular
                 restoration site, but this has not yet been fully tested.

                 The composite mix will comprise up to 10 percent shell. In lower flow locations, such as in Noosa Sound,
                 the proportion of shell may be increased to 20 percent, subject to confirmation of the stability of the
                 structure by engineers. A higher proportion of shell may be considered subject to constructability and
                 monitoring outcomes, as per the specifications.

                 When used as a composite, the cured oyster shell will be evenly mixed through the rock to achieve
                 good interlocking. The shell will not be placed in alternating layers with rock. Mixing will occur in small
                 volumes on the barge immediately prior to placement to avoid shell damage due to rehandling. An
                 example of a rock oyster restoration substrate displaying a mix of rock and shell is given in Figure 5.5.




                 Figure 5.5: An example of rock oyster restoration substrate (augite) augmented with oyster cultch
                 (unseeded) in Port Stephens, NSW. Source: Craig Bohm, TNC.




                                                                                                                         47




Document Set ID: 21802641
Version: 1, Version Date: 31/01/2022