REEF FORAMINIFERA AS BIOINDICATORS OF CORAL REEF HEALTH: LOW ISLES REEF, NORTHERN GREAT BARRIER REEF, AUSTRALIA

Declining water quality because of changes in land use over the past century is considered a significant environmental threat to the health of coral platforms of the Great Barrier Reef, Australia, in particular for those situated in nearshore areas of the wet tropics. Of these reefs, the most well-known is Low Isles Reef, which has been studied since 1928. Declines in scleractinian corals and increased abundances of soft-bodied corals and macroalgae since the 1950's have led researchers to speculate that the changes stem from increased nutrient and sediment fluxes from nearby rivers. The Foraminifera in Assessment and Monitoring (FORAM) Index is a statistical method that measures nutrient levels in the water column through the use of foraminiferal assemblages. To assess whether eutrophication is an issue in vicinity of Low Isles Reef, FORAM Index (FI) values were calculated from a suite of 50 samples collected from the reef top. Results were compared to FI values from Heron Reef, a mid-shelf platform in the southern Great Barrier Reef Province known for a lush scleractinian coral population. FI values from both reefs indicate that overall, conditions are suitable for coral growth. Moreover, cluster analyses of FI values indicate no significant differences between the two reefs. Lower FI values, which indicate conditions unsuitable to marginal for coral growth, are restricted to particular locations on Low Isles Reef and can be explained in the context of local processes associated with long-term reef development. Results (1) do not support the notion that agricultural activities in nearby coastal catchments have adversely affected coral populations on Low Isles and (2) demonstrate the applicability of the FI for regions outside of the Caribbean, for which the index was originally created.