parks victoria technical series marine natural values study vol 2 ...

Parks Victoria Technical Series No. 79
Flinders and Twofold Shelf Bioregions Marine Natural Values Study
An abundant and diverse range of invertebrates is present on the subtidal reef (Plummer et
al. 2003; Figures 47 and 48). The invertebrate fauna of the Twofold Shelf bioregion
comprises both southern and eastern Australian temperate species. Common invertebrate
grazers found at Beware Reef MS include the tent shell Astralium tentoriformis and elephant
snail Scutus antipodes (Williams et al. 2007). Predatory invertebrates include the triton
Cabestana spengleri, octopus Octopus moarum and a wide variety of seastar species
(Williams et al. 2007). Other large reef invertebrates include mobile filter feeding animals
such as feather stars Cenolia trichoptera and sessile (attached) species such as sponges,
corals, bryozoans, hydroids (see Figure 48) and ascidians (Williams et al. 2007). The
holdfasts of E. radiata are encrusted with sponges, worms and the brittle stars Ophiothrix
spongicola and O. caespitose (Plummer et al. 2003).
Beware Reef invertebrate fauna is similar to both the Point Hicks and Cape Howe monitored
sites. It has large numbers of the mobile filter feeding feather star Cenolia trichoptera like
Point Hicks and high densities of the black sea urchin Centrostephanus rodgersii and
blacklip abalone Haliotis rubra like Cape Howe (Edmunds et al. 2010b). The purple urchin
Heliocidaris erythrogramma is also abundant at the MS (Williams et al. 2007). The
abundance of legal sized abalone appears to have increased in the MPAs of Twofold Shelf
bioregion since declaration (Edmunds et al. 2010b). The black sea urchin C. rodgersii can
form large grazing aggregations which denude the reef of erect algal species, forming ‘sea
urchin barrens’ and these have been observed in the MS (Edmunds et al. 2010b). The
occurrence of urchin barren habitat reflects the influence of species from the east coast of
Australia on the MS (Williams et al. 2007). Removal of large seaweeds by Centrostephanus
causes substantial changes to subtidal reef community structure (Williams et al. 2007).
Deep on the subtidal reefs (> 20 m) sessile invertebrates dominate with ‘gardens’ of massive
erect sponges, encrusting sponges, gorgonian coral, sea-whip coral, zooanthids and basket
stars (ECC 2000; Edmunds et al. 2005). The northern side of the reef has steep drop-offs,
with urchin-modified habitat and sessile invertebrate wall fauna below the kelp zone
(Edmunds et al. 2005). The sea urchins C. rodgersii and H. erythrogramma, and the feather
star C. trichoptera were particularly prominent on the northern side (Edmunds et al. 2005).
Anemones Anthothoe albocincta and Balanophyllia bairdiana, encrusting sponges and large
finger sponges, colonial Botrylloides sp. and stalked ascidians are abundant on deeper
vertical faces and in shaded gutters on the reef where limited light penetration reduces algae
cover (Plummer et al. 2003). Crinoids Cenolia trichoptera and C. tasmaniae of green, orange
and white colour morphs are common in cracks (Plummer et al. 2003). Hydroids, gorgonians
Mopsella sp. and Capnella sp. and sea whips Primnoella australasiae are common towards
the base of the reef (Plummer et al. 2003). The jewel anemone Corynactis australis and the
nudibranch Hypselodoris bennetti are also found on the reef (Plummer et al. 2003).
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