2016-12-12 General Committee - Attachments 1, 2, 3 to Item 10 - Oyster Restoration Project

                                                            Ecological Service Professionals
                                                                                Sustainable Science Solutions

The presence of oyster spat, optimal salinity, temperature, good tidal/water movement, and
suitable surfaces for oyster spat to settle are key drivers of the distribution of oyster
dominated habitats in an estuary (Volety et al. 2014). Suitable substrate includes hard
surfaces (old shell, rubble/gravel, coffee rock, bedrock) areas with complex three-
dimensional structure with various small spaces for oyster spat to settle, with over, hanging
and vertical surfaces shown to maximise oyster spat settlement (TNC & ESP 2015). Healthy
functional estuaries in Florida on the east coast of the USA (that also have everglades and
occur at a similar latitude in the northern hemisphere) have between 1-5% oyster coverage
of the accommodation space (i.e. the area within the estuary with suitable conditions for
oyster growth) (Volety 2013). Due to the degradation of oyster dominated habitats, this value
provides a good estimate of the potential area historically occupied by oyster habitats in the
Noosa Estuary prior to commercial harvesting.
In terms of habitat provision, oyster reefs provide three-dimensional habitat that can have up
to 50 times more surface area than an equivalent size of bare sand or mud (MDCA 2006).
The crevices and spaces between oysters create important places for a variety of small
organisms to live away from competition with fast growing algae (including oyster spat,
crabs, worms, snails, sea squirts, sponges and fish). The productivity of restored oyster
habitats can also drive increased diversity and biomass of commercially and recreationally
important species such as fish and crabs relative to bare sediment (Grabowski et al. 2005;
Peterson et al. 2003). The positive benefits that oyster reefs provide has led to the
recognition of shellfish reefs as an important wetland habitat type in the Convention on
Wetlands of International Importance (The Ramsar Convention – habitat type ‘Ga’) (Kasoar
et al. 2015). Oyster reefs provide a variety of ecosystem functions include providing habitat
for recreationally and commercially important fisheries; stabilisation of sediment and
shoreline protection, diversification of habitat types in the seascape, water quality
improvement, carbon sequestration and oyster production (Grabawski et al. 2012). A key
function of restored oyster reefs and beds may be local stabilisation of soft sediment habitats
and filtering of estuarine water. Oyster reefs have the potential to provide substantial
benefits worth up to US$99,000 ha-1 year-1, through the ecological functions they provide
(Grabawski et al. 2012).
Estuarine habitats such as oyster reefs and beds, seagrass beds and mangrove forests can
regrow naturally following disturbance where conditions are suitable and there are sufficient
recruits/propagules/seeds available. Unfortunately, due to the removal of conch (dead shell)
beds in the Noosa Estuary (references cited in Thurstan 2015), current conditions limit
natural regrowth of oyster reefs primarily due to a lack of suitable substrate within the
accommodation space. Areas that may be suitable for oysters to grow are now dominated by
mobile sediments which can smother oyster spat before they can grow to a size large
enough to survive. A similar issue occurs for mangrove habitats where bank erosion creates
unfavourable conditions for propagule survival. Restoration of mangroves on eroding banks
usually requires human intervention to stabilise banks and remove wave action, followed by
natural or assisted reseeding by mangrove propagules.
Marine plant restoration within a Fish Habitat Area is well established and community driven
projects can be achieved through self-assessable codes and various exemptions of the
legislation. However, currently the mechanisms to facilitate holistic restoration of seascapes
or the natural restoration of oyster habitat are not recognised within this legislation (despite
shellfish being recognised as a wetland habitat type under Ramsar Legislation in the same
way as mangroves, seagrass and saltmarsh). Sixteen sites have been identified as potential
areas for oyster reef restoration throughout the lower Noosa River Estuary (which is subject


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