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
These physical parameters influence key physical processes such as light, water flow and
sedimentation, and biological processes such as foraging and recruitment (Connell 2007).
Shallow subtidal reefs are often dominated by canopy forming algae. Deep reefs, where light
penetration is limited, are often dominated by large sessile invertebrates such as massive
sponges (Figure 38), whip corals, soft corals and colonial ascidians. Biotic assemblages can
form habitat and food sources for invertebrates and fish. The biota of the Cape Howe MNP
comprises both southern and eastern Australian temperate species. Assemblages vary
according to the location, depth and exposure (Williams et al. 2007).
Flora
The inshore reef is dominated by a mixture of crayweed Phyllospora comosa and bull kelp
Durvillaea potatorum, the reef further offshore tends to be dominated by P. comosa (Ball and
Blake 2007; Williams et al. 2007). The algal understorey (Figure 34) at Cape Howe is
dominated by encrusting coralline algae, with only sparse cover of erect fleshy understorey
species (Williams et al. 2007). The brown algae Carpomitra costata, Zonaria turneriana and
Halopteris spp, red algae Delisea pulchra, Phacelocarpus peperocarpus, Rhodymenia
linearis, Galaxaura marginate are the common fleshy understorey species (Williams et al.
2007). Arthrocardia wardii and Haliptilon roseum are the common erect coralline algae. The
Phyllospora canopy is particularly dense in places, with little light at the reef surface which is
covered by sponges rather than algae (Williams et al. 2007). Deeper waters have
macroalgal beds on sand covered reef, including large beds of the green algae Caulerpa in
the north-east of the MNP (Holmes et al. 2007b; Figure 36).
Invertebrate fauna
An important invertebrate of the Cape Howe MNP and the eastern Twofold Shelf bioregion is
the long-spined black sea urchin Centrostephanus rodgersii (Williams et al. 2007; Edmunds
et al. 2010b). Centrostephanus forms large grazing aggregations which denude the reef of
erect algal species, forming ‘urchin barrens’. Urchin barrens have been observed in Cape
Howe MNP (Ball and Blake 2007; Holmes et al. 2007b; Williams et al. 2007; Edmunds et al.
2010b). The occurrence of urchin barren habitat at this location reflects the influence of
species from the east coast of Australia on the Twofold Shelf bioregion. Removal of large
seaweeds by Centrostephanus causes substantial changes to subtidal reef community
structure on reefs in eastern temperate Australia (Williams et al. 2007; Edmunds et al.
2010b).
There are high abundances of large herbivorous invertebrates on shallow subtidal reefs in
Cape Howe MNP including the sea urchin Centrostephanus rodgersii, blacklip abalone
Haliotis rubra, the warrener Turbo undulatus and another turban shell Astralium tentoriformis
(Williams et al. 2007). Other common invertebrate grazers are the eastern temperate
gastropod Astralium tentoriformis, and purple sea urchin Heliocidaris erythrogramma.
Predatory invertebrates include dogwhelks Dicathais orbita, eastern rock lobster Jasus
verreauxi, 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 and ascidians (Williams et al. 2007). Sessile invertebrates such as sponges,
asicidians, seawhips and gorgonian corals dominate the reef in 30 to 40 m (Holmes et al.
2007b).
Fish
Common subtidal reef fish at Cape Howe MNP are herring cale Odax cyanomelas,
leatherjacket Meuschenia freycineti, striped mado Atypichthys strigatus, banded morwong
Cheilodactylus spectabilis and the damselfishes Parma microlepis and Chromis hypsilepis
(Williams et al. 2007). Herring cale is an abundant large species of fish. It feeds on kelp and
can be an important structuring agent of algal communities when present in high numbers
during breeding aggregations. The other kelp feeding species, rock cale Crinodus lophodon
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