Fouling assemblages associated with estuarine artificial reefs in new South Wales, Australia

Abstract

Previous studies examining the dynamics of succession on artificial reefs have predominantly focussed on fish communities and largely ignored the role of fouling assemblages in explaining the patterns of community structure associated with artificial reefs. The objective of this study was to record the development of epibiotic assemblages on three "design specific" (Reef Ball ®) estuarine artificial reefs systems located in Lake Macquarie, Botany Bay and St Georges Basin in New South Wales, Australia. Recruitment to the artificial reefs was relatively rapid with the majority of taxa identified over the two-year study period observed within the first year post-deployment. The artificial reefs in Lake Macquarie and St Georges Basin were characterised by low diversity with four and nine taxa recorded respectively in contrast to the sixteen taxa observed on the Botany Bay reefs. Results indicated no significant differences in percentage cover of taxa among reefs in either St Georges Basin or Lake Macquarie. In contrast, comparisons between individual Botany Bay reefs identified significant differences in the percentage cover of species between artificial reefs. Analysis of assemblage structure with reef age indicated discrete patterns among estuaries with an overall reduction in the percentage cover of filamentous turfing algae (FTA) identified for all reef systems with an increase in reef age. Variations in environmental and physical conditions (turbidity, water flow, wave action and proximity to naturally occurring reef) may have contributed to the observed differences in fouling assemblages between estuaries and between artificial reefs within Botany Bay.

Fish Assemblages on Estuarine Artificial Reefs: Natural Rocky-Reef Mimics or Discrete Assemblages?

“…The artificial reefs were constructed as part of a larger study to investigate the use of artificial reef in three coastal estuaries along Australia's south east coast in the State of New South Wales [21]–[24]. Lake Macquarie (33°09' S 151°66' E), Botany Bay (33°00' S 151°23' E) and St Georges Basin (35°18' S 150°59 E) have a total area of 114 km2, 38 km2 and 42 km2 respectively (Fig.…”

“…The combined summer/autumn season (approximately 6 months in each estuary) provided a comparable time period, limiting temporal bias associated with seasonal variation. It should be noted that the time period was selected as it was the oldest comparable data available, representing an artificial reef age of >1 year; which based on fish and benthic assemblage development studies of the artificial reefs [22], [24], represented an assemblage that had progressed through the initial rapid development stage and was approaching early stages of assemblage stability.…”

A deep dive into the ecology of Gamay (Botany Bay, Australia): current knowledge and future priorities for this highly modified coastal waterway

“…In contrast to other assemblage parameters, diversity was found to be similar between human-made rock walls and natural reefs in both studies that investigated it (Fowler and Booth 2013;Porter et al 2018). Only two papers have studied the fouling assemblages on artificial habitats in Gamay (Knott et al 2004;Mckenzie et al 2011), which is a small number compared with the neighbouring estuary, Sydney Harbour, which has >20 studies on artificial habitats. Knott et al (2004) found that many fouling invertebrate taxa showed clear differences regarding their cover between natural rocky reefs and concrete breakwalls in Gamay.…”

“…This contrasts with Lake Macquarie where reef ball-associated fish biomass is more evenly distributed among plankton, macrophytes and detritus. Epibenthic assemblages have been assessed on Mini Bay Reef Balls in Gamay, with a total of 16 taxa found, higher than on reef balls deployed in both Lake Macquarie and Georges Basin (Mckenzie et al 2011).…”