Enclosure 6 - ESP Letter

                                                           Ecological Service Professionals
                                                                              Sustainable Science Solutions

Weyba Creek and on artificial structures such as jetties outside the fish habitat area). Less
dense aggregations were also found in the main river channel near Tewantin (Figure 8).
We located one oyster bed comprised of dense leaf oysters (Isognomon ephippium) with
some rock oysters and a variety of sessile invertebrate species (this covers approximately
4020m2 of the substrate) (Figure 16). In addition, there were several intertidal and subtidal
rubble areas with sparse oyster aggregations, rocky reefs with oysters predominantly on
intertidal surfaces, oyster beds covered by sediment and extensive seagrass beds recorded
(Figure 8; Figure 16; Figure 17 & Figure 24). Mangroves and saltmarsh were also present
around the perimeter of the lower estuary, although these were not the focus of this
assessment so were not considered further. Based on available data for these habitat types,
mangroves occupy 1.7 km2 and saltmarsh occupies 0.1 km2 of the total 60.8 km2 habitat in
the Fish Habitat Area.

Noosa River - Tewantin Area
The reach referred to in this report as Tewantin area extends from site 1 upstream to site 5
downstream (Figure 8 & Figure 9). There are several large areas of shell and rocky rubble
that have been buried by up to 0.5 m of fine sediment around this area, particularly along
eroding edges (outside bends of the river) (Figure 8 & Figure 9). Oysters were recorded
aggregating in a narrow band in low densities on the rubble (based on visual assessment),
however dense aggregations were limited to intertidal areas (Figure 10) due to the presence
of a high coverage of macroalgae and fine algal turf that trapped a thick sediment layer,
smothering the surface (Figure 11) (a similar issue resulted in recruitment failure on upward
facing horizontal surfaces of settlement tiles in the estuary: ESP & TNC 2015). A low relief
layer of dead oyster shell covered the sediment surface over the rocky reef and intertidally
adjacent to the Tewantin boat ramp, indicating the presence of live oysters at some point,
although turbid conditions at the time of assessment prevented a more detailed assessment
of the density of live oysters found in those areas (Figure 12).
A large area of soft sediment had smothered oyster and rubble banks (shown in pink on
Figure 8) was discovered adjacent to Tewantin through direct observation and probing
(Figure 8a). The depth of sediment covering oyster shell in these areas was between 10 and
30 cm. These shallow oyster reefs and beds likely supported a large proportion of the
intertidal and shallow subtidal oysters, as is evidenced by their proximity to a substantial
indigenous midden site where oyster shell up to 4 m deep was discovered (Thurstan 2015).
The reefs likely covered most of the small bay near the current Council Chambers, although
this area is currently covered with sediment.
Probing of the soft sediment along the western bank of the river to the north of Tewantin
(around sites 2 and 3) found that there was a coarse shell grit or rubble bank approximately
30-50 cm below the current sediment surface. The extent of shell beds in this area requires a
more detailed assessment although none were found on the surface at these locations.
Burial is likely related to past mobilisation of sediment.




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