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
2.4.2 MARINE HABITAT DISTRIBUTION
Mapping of habitats is important for understanding and communicating the distribution of
natural values within Marine National Parks and Sanctuaries, particularly as the marine
environment is not as easily visualised as the terrestrial environment (Parks Victoria 2003).
For management purposes, knowledge of the distribution and extent of habitats is required
to more effectively target management activities, including emergency response, monitoring
and research. Mapping of marine habitats provides a baseline inventory, allows the
identification of suitable monitoring sites and possible tracking of environmental change, as
well as identifying areas vulnerable to particular threats or suitable for recreational activities.
Aerial photography (Figure 31) and satellite imagery from 2004 was used to map the
intertidal and shallow (< 10 m) subtidal habitats of Cape Howe MNP (Ball and Blake 2007).
The subtidal area was ground truthed in 2007 with underwater video (Ball and Blake 2007).
The intertidal area could not be ground truthed due to the inaccessibility of the shore (Ball
and Blake 2007). In 2004/2005 the deep (> 10 m) subtidal substrate and biota of Cape Howe
MNP was surveyed and mapped acoustically (Figure 32 and Figure 33) by Holmes et al.
(2007b). Underwater video transects allowed the substrate and biota to be predictively
modelled for the areas not surveyed.
The habitats present in Cape Howe MNP include intertidal soft sediment and some reef,
extensive subtidal soft sediment and some subtidal reef, and open ocean (Figure 32 and
Figure 33). Intertidally a band of rocky shore extends from the east side of Iron Prince to the
NSW border, with the rest of the intertidal area being sand beach fronting an extensive dune
system (Ball and Blake 2007). The majority of the shallow subtidal habitat is bare rippled
sandy sediment. The shallow subtidal reef habitat is restricted to an area running parallel to
the shore for a distance of approximately 700 m from the north-eastern MNP boundary
extending down to depths of approximately 16 m (Ball and Blake 2007). The reef is primarily
a mixture of high profile broken reef and more solid low profile reef. The inshore reef is
generally broken and patchy (Ball and Blake 2007). The reef changes from low relief in the
west to larger bombies, steep ledges and drop-offs in the east (Williams et al. 2007). This
reef has been extensively described and sampled as part of the SRMP (Williams et al. 2007;
Edmunds et al. 2010b).
Based on predictive modelling, deep (> 10 m) subtidal soft sediment covers 33 sq. km of the
MNP, while deep subtidal reef was mapped over 8 sq. km and located mainly in the nearshore
centre of the MNP offshore of Iron Prince (Holmes et al. 2007b). An equal amount of
reef is covered with sediment. The sediment is primarily sand in water < 50 m deep, while
mixed sand and shell fragments in deeper water (Holmes et al. 2007b). The reef generally is
flat or with a gentle slope with some drop offs. The reef structure is a mixture of solid reef
and boulders (Holmes et al. 2007b). Extensive macroalgae beds, predominately of Caluerpa
occur in 30 to 40 m across the MNP (Holmes et al. 2007b).
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