Relicts, remnants or refuges? South Australian jetties as habitat for biogenic reef-forming species

Dr Craig Styan1, Dr Hazel Vandeleur2

1University College London, UniSA Mawson Lakes Campus, Mawson Lakes, Australia, 2Futures Industries Institute, UniSA, Mawson Lakes, Australia

The economic and social value of jetties are well known in South Australia, but jetties’ ecological roles are less understood. Scientifically, jetties have proven convenient places to test theories about subtidal ecology but connections with broader subtidal ecosystems remain unexplored. Addressing this, we are repeating surveys of jetty pilings done by Alan Butler and his group in the 1970’s and 80’s, testing whether patterns in assemblage composition and ecology documented then have persisted. Despite some physical changes to jetties, most assemblages of marine invertebrates seem similar 40 years later and characteristic differences among jetties appear to have continued.  One spectacular example is the large colonies of bryozoans still present at Port Giles, where growths sometimes dislodge to form small (biogenic) reef structures on the adjacent seabed.  In contrast to jetty pilings, habitat mapping work in the early 2000s suggests reef building species including bryozoans and sponges (and habitats created by them) have all but disappeared across the deeper parts of Gulf St. Vincent since the 1970s.  It is unclear now whether assemblages of bryozoans and sponges underneath jetties represent relict, remnant or refuge populations of formerly widespread species, or what role assemblages under jetties currently play in the broader population dynamics of these species. While jetties create unique, artificial habitat, the environmental conditions under them can partially replicate natural reef overhangs and deeper regions of the gulfs – and, by harbouring species formerly found in such areas, jetties could have an important role in restoring gulf ecosystems.


Craig Styan is an Associate Professor at University College London and leads an Engineering group based in South Australia, as part of a partnership between the Faculty of Engineering Sciences at UCL and the University of South Australia. His research aims to better understand and manage the impacts of energy and natural resources development, particularly in the marine environment. Consequently, he works across a range of areas including environmental monitoring and statistical analysis, ecotoxicology and pollution studies, policy and impact assessment, engineering and economics, though to studies of community engagement and ‘Social Licence to Operate’.

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