Subtidal assemblages associated with a geotextile reef in south-east Queensland, Australia

In marine habitats, the use of geotextile materials as a 'soft-engineering' solution is increasingly being considered as an alternative to hard structures. However, very little is known about biological assemblages that develop on geotextile structures. This study provides the first ecological comparison of subtidal assemblages between Narrowneck Artificial Reef (NAR), a geotextile reef in south-east Queensland, Australia, and three nearby natural reefs. Benthic community structure, fish assemblages and habitat complexity were compared between reef types using an asymmetrical design. Although natural reefs supported distinct biotic assemblages, as a class, these reefs differed significantly from NAR. The artificial reef was dominated by macroalgae and supported fewer benthic categories, whereas the natural reefs were characterized by a diverse range of sessile invertebrates. Benthic and demersal fish assemblages were less diverse on NAR, but pelagic fish assemblages were similar on both reef types. The substratum of NAR was less complex than that of the natural reefs; this physical variable was correlated with some of the differences in benthic communities and benthic and demersal fish assemblages. It is likely that the key determinants of the biotic patterns observed in this study are interactions between the age of NAR and the physical properties of geotextile substratum.