Enclosure 6 - ESP Letter

                                                                                 Ecological Service Professionals
                                                                                                           Sustainable Science Solutions

Water quality was assessed at 10 sites throughout the Noosa River Estuary in October 2016
to determine potentially suitable conditions for oyster growth. The location of sites surveyed
and reaches in the estuary are shown in Figure 7. Salinity was lowest (21.54 psu) at the most
upstream site (site 1), and highest in Lake Weyba (sites 16 & 17 approximately 35.5 psu;
Figure 24). Salinity at the site closest to the mouth of the estuary (site 10) was only
29.82 psu (Figure 8). Decreased salinity in the estuary could be due to complex hydrological
interactions between tidal and freshwater surface and groundwater flows. The other water
quality parameters measured were typically more similar among the sites assessed (Table
3). Oysters were found growing at turbidity concentrations less than 15 NTU, although
resuspension of fine sediment particles reduced oyster aggregation density at those sites
(i.e. site 17).
     Table 3        Water quality results from the Noosa Estuary

Parameter            Units       Site

                                 1        2         3        5         6        10        11       12        16          17

Time sampled                     1536     1550      1608     1625      1506     1321      1358     1347      1103        1024

Date sampled                     26/10    26/10     26/10    25/10     25/10    25/10     26/10    26/10     26/10       26/10

Tidal state                      flood    flood     flood    flood     flood    flood     flood    flood     ebb         ebb

Temperature          °C          25.6     25.4      24.9     25        26.1     24.6      25.1     25.8      26.8        24.1

Salinity             PSU         21.54    22.73     23.46    29.51     26.72    29.82     33.07    33.21     35.58       35.53

Conductivity         µS/cm       34325    36050     37076    46100     41701    45949     50471    50670     53913       53766

Dissolved Oxygen     mg/L        7.8      7.7       7.55     7.53      7.81     7.3       7.33     7.67      7.22        6.79

Dissolved Oxygen     % Sat.      108      106.7     104.1    107.7     112.1    104       107.2    113.6     110.2       99.6

Turbidity            NTU         7.1      10.8      4.3      1.9       4.4      2         2.3      10.4      5.7         15

pH                   pH units    8.03     8.04      8.03     8.06      8.07     8.01      8.06     8.07      8.07        8.04

Grey cells indicate current ambient conditions in October 2016 that were below current optimal oyster growth limits, although
adult oysters can tolerate salinity this low and were found growing in low densities on nearby coffee rock reefs which indicates
that oysters can grow there if suitable habitat is provided.

An assessment of the accommodation space in the Noosa River (based on measurements
taken in October) demonstrates that there are current ambient environmental conditions
(temperature, salinity and depth) suitable for oyster growth; however, the availability of hard
substrate (dead shell beds, rubble, bedrock) is lacking, particularly in areas that would allow
the natural formation of oyster beds or reefs due to smothering from sediment, among other
factors.

Current Distribution of Oyster Reefs
Based on field observations in October 2016, the predominant habitat in the lower Noosa
Estuary is soft sediment (a mix of sand, mud and clay to varying proportions depending on
the position in the estuary). In the Noosa Estuary, naturally occurring oyster aggregations
were only currently found where hard surfaces protrude from the soft sediment to a sufficient
height and orientation where fine sediments cannot accumulate, therefore allowing oysters
avoid being smothered and survive (i.e. aggregations on Rocky Point in Lake Weyba, along




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