2022-11-08 P&E Agenda - Item 6 - Attachment 1 - Current & Historical Distribution of Seagrass in the Noosa Estuary (40 pages)

                                                              Ecological Service Professionals
                                                                                  Sustainable Science Solutions




    Figure 3.4 Small patch of Zostera muelleri growing along the Goat Island in the main Noosa
               River Channel in November 2020

3.2 Seagrass Condition
The seagrass growing in the Noosa Estuary was showing signs of stress, as a result of
sedimentation in some areas. Further, many of the seagrass beds growing in the relatively
clear and shallow water of the estuary were covered in a high load of epiphytic algae. The
dense Z. muelleri was typically in moderate condition, with long blades up to 50 cm long that
had a high coverage of epiphytic algae (greater than 40% of the blade) (Figure 3.5). In some
areas of Weyba Creek around Keyser Island, and along the main creek channel further
upstream, the coverage of epiphytic algae on the Z. muelleri blades was extremely dense
(> 80%) and in some cases it completely smothered the seagrass (Figure 3.5). The coverage
of epiphytic algae was particularly high in dense beds around freshwater inputs such as
stormwater drains.
Elsewhere, the coverage of epiphytic algae was sparser, particularly in areas where the
coverage of Z. muelleri was also lower (Figure 3.6). The coverage of epiphytic algae on
H. ovalis was typically very low, although this seagrass species was typically observed along
the fringes of Z. muelleri beds and in areas of increased turbidity such as in Lake Doonella.
There were also instances where seagrass patches were being smothered by shifting
sediment. This was particularly the case along sections of the channel in Weyba Creek and
at the entrance to Lake Weyba (Figure 3.6 & Figure 3.7). The non-vegetated intertidal and
subtidal habitat within the study area was generally characterised by coarse, sandy

Assessing Distribution of Seagrass in the Noosa Estuary                                                    10