ONE TREE REEF LAGOON, A RELIC OF THE PRE-COLONIAL GREAT BARRIER REEF

Coral reefs are in decline worldwide and benthic Foraminifera are valuable proxies for monitoring coral reef health through time. I examine Foraminifera preserved in a ²¹⁰Pb dated sediment core from the One Tree Reef (OTR) lagoon on the southern Great Barrier Reef (GBR) to quantify palaeoecological changes associated with European colonisation and the subsequent industrialisation of Australia. The GBR is a large and diverse environment with inter-reef zones (between reef and other non-reefal areas) accounting for 95% of the area. Previous work has focused on foraminiferal assemblages from near shore reefs, but OTR is located some 100 km from the mainland, removed from most local and regional stressors likely to drive changes in the foraminiferal assemblages. Foraminifera were picked from nine layers across three time periods, Modern (post 1945), Colonial (1945 – 1788) and Pre-colonial (pre 1788). Over 3,100 specimens were allocated to 65 genera (105 species) with 50 genera representing less than 1% of total specimens (“rare”). Foraminifera assemblages were dominated by Quinqueloculina spp. (50% of all taxa) and rare taxa. Richness, diversity and assemblage composition, measured using standard ecological indices and foraminifera specific metrics such as the Foram Index and the Foram Stress Index, indicate that there has been no discernible trend or significant shift in OTR lagoon Foraminifera assemblages over the last four centuries. Assemblage composition highlighted the importance of the less studied small benthic Foraminifera in the inter-reef zones of the GBR and the need for further work in this area. These results suggest that the OTR lagoon may contain a living example of a pre-colonial GBR lagoon ecosystem that has remained reasonably stable over time.