The Department of the Environment, Tourism, Science and Innovation (DETSI) has monitored the health of South-east Queensland’s (SEQ) waterways as part of the Ecosystem Health Monitoring Program (EHMP) for over 20 years. The overarching aim of the EHMP is to assess the environmental condition of the region’s waterways, with a major strength being its ability to detect spatio-temporal environmental trends. The identification of trends at a regional scale can help evaluate management effectiveness, underpin informed decision making, and capture early signs of environmental degradation.
SEQ is home to numerous ecologically significant ecosystems. Of particular importance is Moreton Bay, a RAMSAR-listed, semi-enclosed embayment located off the southeast coast of Queensland. Moreton Bay and its connected estuaries support vital ecosystems, including seagrass meadows, mangrove forests, and tidal flats. Despite their importance, SEQ’s estuaries and bay zones face increasing anthropogenic pressure.
Since European settlement, the catchments of SEQ have undergone extensive modification, with more than two-thirds of the region’s woody vegetation cleared for agriculture and urban development. SEQ’s aquatic ecosystems are naturally event-driven, often experiencing extreme rainfall and subsequent runoff. This, coupled with widespread vegetation loss, has led to the degradation of ecological health in the region’s waterways. Point source pollution remains a major concern, with numerous wastewater treatment plants discharging directly into rivers that drain into Moreton Bay.
Since 2001, the estuarine-marine component of the EHMP has monitored key water quality parameters, including turbidity, nutrients, and chlorophyll a, at 143 estuarine and bay sites. These sites are sampled monthly, twelve months per year until 2014, and eight months per year thereafter. This extensive dataset has been leveraged to uncover spatio-temporal water quality trends within the estuaries and bay zones of SEQ. Significant trends were identified using non-parametric Seasonal Man-Kendall tests. To capture the potential influence of diffuse and point source pollution as well as population growth, trends were assessed across two time periods, long term (2001-2024) and short term, (2010-2024).
Regional scale results suggest an interplay between long-term reductions in turbidity and short-term increases in nutrients, which may have deleterious consequences for the ecological health of Moreton Bay. Emergent patterns were most pronounced in estuaries subject to significant anthropogenic activities. These findings underscore the potential environmental consequences of interacting trends and highlight the critical importance of long-term regional ecosystem health monitoring.