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Identifying sources of surface water turbidity in the Elizabeth River Estuary



Identifying sources of surface water turbidity in the Elizabeth River Estuary


Streten, Claire; Logan, Murray; Spagnol, Simon; Brinkman, Richard


E-Publications; E-Books; PublicationNT; 32/2020




Darwin Harbour


The Elizabeth River is one of the major tributaries of Darwin Harbour and freshwater outflows from this river influences the water quality in Inner Darwin Harbour. During flood events the turbid plumes from the Elizabeth River have the potential to cause increased turbidity levels in Inner Darwin Harbour. Reduced light availability, because of elevated turbidity, may reduce the growth and reproduction of photosynthetic organisms such as seagrass and coral symbionts. In addition, high turbidity levels have the potential to cause stress to marine life due to smothering. Thus, elevated turbidity levels can have a negative impact on the health of Darwin Harbour. Without knowledge of what variables drive elevated turbidity levels in the Elizabeth River, it is not possible to assert the effect freshwater flows have on turbidity in the Inner Harbour. This study used two approaches to develop a clearer picture of the drivers of variability of turbidity within the Elizabeth River estuary: 1. Gradient boosted regression tree models were used to unravel the relationship between surface turbidity and potential sources 2. Water column bacteria communities were characterised to assess if they are potential indicator of sediment provenance.


Made available by via Publications (Legal Deposit) Act 2004 (NT).

Table of contents

Summary 1 Background 2 Methods 2.1 Data for statistical model analysis 2.2 Statistical model runs 2.2.1 Gradient boosted model 2.2.2 Extreme gradient boosted 2.3 Sampling sites for bacteria community analysis 2.4 Water and sediment collection 2.5 Water column nutrient analysis 2.6 DNA extraction, sequencing and analysis 3 Results and Discussion 3.1 Gradient boosted tree model 3.2 Bacteria as indicators of source of turbidity 4 Conclusions 5 References Appendix A: Extreme gradient boosting Appendix B: Genera significantly different in water between sampling points Appendix C: Genera significantly different in water with < 10 and > 10 turbidity




Darwin Harbour turbidity

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Northern Territory Government

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Attribution International 4.0 (CC BY 4.0)

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Northern Territory Government



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