Inventory of rock types, habitats, and biodiversity on rocky seashores in South Australia’s two south-east marine parks: pilot study

Geological, habitat, and biodiversity inventories were conducted across six rocky seashores in South Australia’s (SA) two south-east marine parks during August 2014, prior to the final implementation of zoning and establishment of management plans for each marine park. These inventories revealed that the sampled rocky seashores in SA’s South East Region were comprised of several rock types: a soft calcarenite, Mount Gambier limestone, and/or a harder flint. Furthermore, these inventories identified five major types of habitat across the six sampled rocky seashores, which included: emersed substrate; submerged substrate; boulders; rock pools; and sand deposits. Overall, a total of 12 marine plant species and 46 megainvertebrate species were recorded across the six sampled seashores in the Lower South East and Upper South East Marine Parks. These species richness values are considerably lower than those recorded previously for rocky seashores in other parts of SA. Low species richness may result from the type of rock that constitutes south-east rocky seashores, the interaction between rock type and strong wave action and/or large swells, or may reflect the time of year (winter) during which these inventories were conducted. The species richness and space occupancy of marine plants displayed no significant difference among sampled sites, although a significant difference in the structure of marine plant assemblages was detected among sites (pvalue = 0.0001). Exploration of patterns within the megainvertebrate assemblage revealed very strong canonical correlations (δ1 = 0.98 and δ2 = 0.85) between invertebrate assemblage structure and the type of habitats that were sampled. With a megainvertebrate species richness two standard deviations greater than the regional average, Racecourse Bay West was identified as a potential hotspot for intertidal megainvertebrates. Due to the short timeframe of the current pilot project, the data presented here should be viewed as the first step in creating a baseline of the geology, habitats, and biodiversity for rocky seashores in SA’s two south-east marine parks. Ideally, this report should be supplemented by a replicated sampling regime, that spans multiple seasons, a greater spread of sites, and is balanced across seashores of hard, soft, and mixed rock types, to capture data on the true variability within marine plant and mega invertebrate assemblages present on rocky seashores in SA’s south-east marine parks.