2019-01-14 General Committee Agenda - Attachment 2 to Item 2 - Aquatic Restoration and Management Options

Rapid field assessment
In addition to the expert workshop, TNC undertook a rapid preliminary field assessment in
Noosa Estuary. The assessment was facilitated by the Noosa Parks Association. The purpose
of this assessment was to look at potential locations for habitat restoration activities, with
an emphasis on oyster reef restoration. The people involved in this field assessment were
Bryan DeAngelis (a coastal habitat restoration expert with TNC’s North America program),
Dr Simon Walker (a Brisbane based marine ecologist with many years’ experience working
on habitat restoration in South East Queensland estuaries), and Dr Eddie Game (marine
biologist and TNC’s lead scientist in the Asia-Pacific region).
Although there has been substantial modification of aquatic habitats in Noosa Estuary (e.g.,
the development of Hayes Island), the remaining contribution of mangrove, seagrass, and
unstructured benthic habitats (e.g., sandy bottom) is high. While the relative contributions
from each of these habitats to estuary productivity may be reduced because of external
stressors (e.g., sedimentation or pollution), there appears to be limited opportunity for
active restoration of those habitats. Regarding these mangrove and seagrass habitats,
effort would likely be better spent managing existing habitat for improved health and
resiliency, and thus ecosystem services, by reducing anthropogenic impacts.
The most noticeable lack of habitat was structured, biogenic habitat from reef-forming
bivalves. In this regard, Noosa contrasts to other nearby systems such as Pumicestone
Passage which has rather extensive intertidal shellfish reef habitat. Saccostrea glomerata
(Sydney rock oyster) was regularly observed in much of the southern portions of the
estuary, particularly in the slower moving, backwaters. Nearly all hard substrate showed
evidence of oyster settlement (Figure 5). From a restoration planning perspective, this is a
very positive sign. It hints at the possibility of potentially eliminating the need for hatchery-
derived oysters to increase reproductive output beyond recruitment-limiting
conditions. While settlement (and apparent recruitment) of oysters was observed in
multiple locations where hard substrate existed, in most instances it was restricted to the
intertidal zone (e.g., top and middle panel Figure 5). This effect may be the result of
predation pressure of oysters that are fully sub-tidal such that oysters are found in greatest
densities in a band near the upper limit of their exposure tolerance. Should this be the case,
it is unlikely to be a limiting factor to potential oyster reef restoration works in Noosa
Estuary because many of the candidate areas for oyster restoration are intertidal.
One small sub-tidal reef was observed, being comprised on the oyster species Isognomon
ephippium (Rounded Tooth pearl oyster, see Figure 6). This was found in a deep section of
Weyba Creek and although heavily impacted by sediment, it is suggestive of the possibility
that reconstructed oyster reef may ultimately be comprised of multiple species.
Based on our field assessment, the most promising candidate sites for pilot oyster reefs
restoration are likely to be sites in Weyba Creek and Lake Weyba.




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