The Southern Bay received an “F” in the 2009 Report Card indicating that there was a considerable decline in ecosystem health from the previous year (“C”).  The primary reasons for the reduction in grade were major increases in the sewage nitrogen signal (δ¹⁵N) and increases in phytoplankton abundance (Chl-a).  It is likely that high rainfall and increased stream flows during the reporting period led to the increased spatial distribution of sewage nitrogen signals in the Southern Bay.  All EHI indicators declined for this zone except for Lyngbya (the latter was not detected during the reporting period).  Nutrient concentrations were mostly compliant with QWQ guidelines (TN, 73%) with the highest TN and TP concentrations found between the mouths of the Logan River and Behm Creek.  A small reduction in seagrass distribution (BHR indicator) was also detected in 2008/2009 for the Southern bay zone.

Abbreviations glossary | Indicators and methods

ECOSYSTEM HEALTH INDEX (EHI)

The EHI is a measure of the proportion of a reporting zone that complied with the water quality objectives for key indicators monitored as part of the Ecosystem Health Monitoring Program. The water quality objectives are defined in the South East Queensland Regional Water Quality Management Strategy (2001).

• EHI 1 = 100% of area complies with the environmental objectives.
• EHI 0 = 0% of the area complies with the environmental objectives.

BIOLOGICAL HEALTH RATING (BHR)

The BHR forms 20% of the the Report Card Grade. The values in this sheets are calculated using the original method used since 2002-03 and is presented for comparison.