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




6 Conclusions

The Noosa estuary is dominated by bare sand and mud habitats with occasional dense
seagrass beds, rocky reefs and shellfish-dominated reef habitats. In 2020, seagrass covered
a total of 56 Ha throughout the estuary, with the largest continuous remnant patches
occurring at the entrance to Lake Weyba, along Weyba Creek (including around Keyser
Island), in Lake Doonella and along the small bay off the main river channel at Tewantin.
Notable declines in the area of seagrass beds have occurred within the Noosa Estuary,
particularly in Lake Weyba and Lake Cooroibah, with approximately 80% of the total area of
seagrass lost between 1987 and 2020.
Due to the nature of the Noosa River Catchment, different sub-catchments present a good
comparative opportunity to assess the cause of declines in seagrass extent and likely impact
of management actions. For example, impacts in along the main river channel are likely due
to broader scale impacts from the upper catchment, including runoff from catchment clearing
as well as boating activity. In contrast, seagrass in the smaller sub-catchments in Lake
Doonella and Lake Weyba are likely responding to changes in the hydrodynamic regime,
with seagrass in Weyba Creek being particularly susceptible to shifting sand banks.
Further assessment of the potential resilience of seagrass meadows to resist environmental
changes in the Noosa Estuary are considered necessary to understand where to invest in
future management actions for maximum gains. Consideration should also be given to the
potential for natural recovery or assisted restoration of seagrass meadows once key triggers
for past change are known and potential negative inputs have been managed.
Given that the cause of major changes to the extent of seagrass was most likely physical
disturbance during a natural disaster, suitable management of the estuarine habitats in
Noosa should consider an adaptive approach that examines and implements measures that
maximise the resilience of seagrass beds, including the ability to respond to future natural
disasters and human pressures that are predicted to increase in the future.




Assessing Distribution of Seagrass in the Noosa Estuary                                            A-27