The importance of physical structure: outcropping reef ledges drive patterns of epibenthic assemblage diversity on cross-shelf habitats  

Authors / CoAuthors

Barrett, N. | Hill, N. | Lucieer, V. | Siwabessy, J. | Nichol, S.

Abstract

Continental shelf margin habitats are increasingly being recognized worldwide for conservation and protection from human activities due to their biodiversity value. Yet, quantitative data on the biodiversity of the epibenthic taxa found on these continental shelf margins are scant. Consequently, this paper quantified the diversity of epibenthic taxa on an exposed- and sediment-inundated reef system located on the continental shelf margin off southeastern Australia as part of a program developing deep reef monitoring protocols. The reef system harbored a rich epibenthic taxa, with a total of 55 taxa identified from the images captured by an autonomous underwater vehicle. A Cnidaria/Bryzoa/Hydroid matix dominated the assemblages recorded. Taxa richness, diversity and evenness declined with distance from exposed reef ledge features, a characteristic geomorphic feature of this region. Patterns of the epibenthic assemblages were characterized by (1) taxonomic turnover at scales of 5 to 10's m from exposed reef ledges, (2) 30 % of epibenthic taxa were recorded only once (i.e. singletons), and (3) generally low levels of abundance of the component epibenthic taxa. This suggests that the assemblages in this region contain a considerable number of locally rare taxa, and potentially represent a high level of endemism. This study also highlights the importance of exposed reef ledge features in this region as they provide a refuge against sediment scouring and inundation in sediment-dominated ecosystems. Consequently, from a perspective of conservation planning for continental shelf habitats, protecting a single, or just a few, areas of reef are unlikely to accurately represent the geomorphic diversity of cross-shelf habitats and the epibenthic diversity that responds to this. Likewise, sampling needs to be adaptive, and stratified to incorporate known or suspected patterns relating to such variability. In this context, the data collected here provides a regional baseline dataset on the epibenthic taxa that shape the overall community structure for the Flinders Commonwealth Marine Reserve, and a guideline for sand-inundated cross-shelf reefs in general. Similar studies are now required for other known categories of cross-shelf reefs, including relict coastlines and complex block features more typical of igneous rock types.

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nonGeographicDataset

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83078

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• External PublicationScientific Journal Paper

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• marine

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• NERP

Australian and New Zealand Standard Research Classification (ANZSRC)

• Earth Sciences

• Published_Internal

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2015-01-01T00:00:00

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