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Parks Victoria Technical Series No. 79 Flinders and Twofold Shelf Bioregions Marine Natural Values Study silver trevally Pseudocaranx dentex, prickly toadfish Contusus brevicaudus and several leatherjackets are common (Plummer et al. 2003). Depth and sediment affect the distribution of benthic invertebrates along the Victorian coast. Coleman et al. (2007), and Heislers and Parry (2007) found that species richness was greater at 40 metres compared to 10 or 20 metres depth. Their coastal survey of benthic fauna included the benthos of Wilsons Promontory MNP. One transect off Oberon Bay on the west coast and one off Waterloo Bay on the east sampled the soft sediment with two 0.1 m 2 grab samples in 10, 20 and 40 m of water depth. The grab samples contained between 39 to 734 individuals and 16 to 71 species consisting mainly of crustaceans including amphipods, cumaceans, isopods and ostracods and polychaetes (Coleman et al. 2007; Heislers and Parry 2007). The sediment was generally fine sand with some medium sand (Heislers and Parry 2007). Reef Subtidal reefs and the assemblages associated with them are strongly influenced by the position of the reef, its orientation, slope, depth, exposure and topography (Connell 2007). 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, whip corals, soft corals and colonial ascidians. Biotic assemblages can form habitat and food sources for invertebrates and fish. Flora Diversity and species composition varies with location within the Wilson Promontory MNP. Central Waterloo Bay on the east coast and other areas to the north-east of the MNP are identified as having high macrophyte species diversity and richness (Edmunds et al. 2000). The macrophyte population in the southern part of the MNP is of low diversity, predominantly because a dense canopy is comprised of only one to three species with a sparse understorey (Edmunds et al. 2000). These three species (Phyllospora comosa, Ecklonia radiata and Seirococcus axillaris; Figures 7 and 9) form distinct algal assemblages: a Phyllospora dominated, an Ecklonia-Seirococcus dominated (Figure 9); and mixed brown algae (Edmunds et al. 2003; Edmunds et al. 2007). The species richness and diversity of the macroalgal communities is lowest at the exposed western and south-western sites, where the canopy is predominantly Phyllospora with a reduced cover of understorey species (Edmunds et al. 2007). Relatively large variations in community structure were observed between surveys at Oberon Point, Roaring Meg Bight and Fenwick Point (Edmunds et al. 2007). The Phyllospora dominated assemblage is the most common, present at all MNP sites (Edmunds et al. 2007). This assemblage consists of a canopy of predominantly Phyllospora comosa (> 30% cover) and a lesser proportion of Ecklonia radiata. The associated understorey has a sparse cover of thallose red algae, with much of the underlying rock covered by encrusting corallines. Common understorey species included Phacelocarpus peperocarpus, Plocamium angustum, P. dilatatum, Pterocladia lucida, Ballia callitricha, Haliptilon roseum and Melanthalia obtusata. At sites in the south-west of the MNP, South Norman Point, Oberon Point and Sea Eagle Bay, Phyllospora cover has increased since the inception of the monitoring program. Phyllospora has higher abundances, and Ecklonia proportionately less so, at the most exposed sites, particularly Sea Eagle Bay and West Landing. At slightly less exposed sites, Ecklonia has a greater proportion of cover in the canopy, particularly Oberon Point, East Landing and Fenwick Point (Edmunds et al. 2007). 17
Parks Victoria Technical Series No. 79 Flinders and Twofold Shelf Bioregions Marine Natural Values Study Figure 9. Seirococcus axillarus (centre of frame) with Ecklonia radiata in Wilsons Promontory Marine National Park. In the Ecklonia-Seirococcus dominated assemblage Ecklonia radiata and Seirococcus axillaris comprised the dominant proportion of the canopy cover at moderately sheltered Waterloo Bay (Edmunds et al. 2007). Phyllospora comosa was also present at this site, but contributed less than 20 % of the canopy cover. Thallose understorey algae were a greater component of the assemblage, with 50 – 70 % cover compared with less than 30 % cover for the Phyllospora assemblage. The understorey composition is similar to the Phyllospora assemblage but with reduced abundance of Ballia callitricha and the erect coralline Haliptilon roseum, with smaller brown species more prevalent. These brown species included Sargassum verruculosum, Sargassum sonderi, Perithalia cordata and Acrocarpia paniculata (Edmunds et al. 2007). At some sites, i.e. North Anser Island, East Landing, Fenwick Point and North Waterloo, both Ecklonia and Phyllospora are abundant (Edmunds et al. 2007). At Oberon Point and East Landing, there has been a gradual decrease in abundance of Ecklonia radiata since monitoring began in 1999. Seirococcus axillaris was generally most abundant at Oberon Point. An increase in the percent cover of Plocamium angustum has been observed at North Anser Island and Roaring Meg during recent surveys (Edmunds et al. 2007). The sessile flora and fauna of five sites on deep subtidal reefs within Wilsons Promontory MNP have been video surveyed by remote operated vehicle (ROV, Edmunds et al. 2009). Wilsons Promontory MNP deep reefs (up to 50 m) are smooth granite of varying steepness (Edmunds et al. 2009). Eight taxa of algae and 47 taxa of sessile invertebrates were identified (Appendix 1). The most abundant taxa, sponges, could not be identified beyond morphotype from the survey method used, but less than half of Victoria’s sponges have been formally described. The deep reefs in Wilsons Promontory MNP were characterized by the presence of gorgonian corals Pteronisis sp and Acabaria sp and the seawhip Primnoella australasia. The abundance of the sessile flora and fauna is variable (Edmunds et al. 2009; Figure 10). Particularly the deep turf cover, seawhip Primnoella australasia, encrusting 18
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Figure 30. Location map of Cape How
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Figure 33. Biota mapping of Cape Ho
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4 Appendix 1 Compilation of species
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Biotic group Family Species Common
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