An Ecological Health Assessment of the Karuah River Brendan Haine, Peter Scanes & Adam McSorley Office of Environment and Heritage Contents List of Tables .................................................................................................................iii List of Figures ................................................................................................................ iv Acknowledgements...................................................................................................... vii Executive Summary..................................................................................................... viii 1. Introduction ...........................................................................................................1 1.1. Background ....................................................................................................1 1.2. Scope..............................................................................................................2 2. Methods.................................................................................................................4 2.1. System Structure............................................................................................5 2.1.1. Saltmarsh, Mangrove and Seagrass Habitats ........................................5 2.1.2. Condition of Riparian Zones in the Karuah River Catchment................5 2.2. Biological Structure........................................................................................7 2.2.1. Mudflat Invertebrate Assemblages .......................................................7 2.2.2. Estuarine Fish Assemblages...................................................................9 2.2.3. Shorebird Assemblages..........................................................................9 2.2.4. Freshwater Macroinvertebrates..........................................................10 2.3. Energy Flow..................................................................................................10 2.3.1. Phytoplankton......................................................................................10 2.3.2. Benthic Microalgae ..............................................................................12 2.3.3. Algal Recruitment on Pneumatophores and Seagrass ........................12 2.3.4. Micro-Carnivore Scavenging................................................................12 2.3.5. Macro-Carnivore Scavenging...............................................................12 2.4. Biological Stress ...........................................................................................13 2.4.1. Fish Ulcers............................................................................................13 2.4.2. Mangrove Leaf Damage.......................................................................13 2.5. Pressures......................................................................................................13 2.5.1. Water Column Turbidity ......................................................................13 2.5.2. Water Column Nutrients......................................................................13 2.5.3. Nutrients and Turbidity in Surface Runoff...........................................14 2.5.4. Catchment Landuses............................................................................16 2.6. Data Analysis................................................................................................16 3. Results and Discussion.........................................................................................24 3.1. System Structure..........................................................................................24 3.1.1. Saltmarsh, Mangrove and Seagrass Habitats ......................................24 Condition of Riparian Zones in the Karuah River Catchment..............................29 Biological Structure..................................................................................................35 3.1.2. Mudflat Invertebrate Assemblages .....................................................35 3.1.3. Estuarine Fish Assemblages.................................................................38 3.1.4. Shorebird Assemblages........................................................................42 3.1.5. Freshwater Macroinvertebrates..........................................................44 3.2. Energy Flow..................................................................................................46 3.2.1. Phytoplankton......................................................................................46 3.2.2. Benthic microalgae ..............................................................................47 3.2.3. Algal Recruitment on Pneumatophores and Seagrass ........................48 3.2.4. Micro-Carnivore Scavenging................................................................51 3.2.5. Macro-Carnivore Scavenging...............................................................52 i | Ecological Condition of the Karuah River 3.3. Biological Stress ...........................................................................................53 3.3.1. Fish Ulcers............................................................................................53 3.3.2. Mangrove Leaf Damage.......................................................................53 3.4. Pressures......................................................................................................55 3.4.1. Water Column Turbidity ......................................................................55 3.4.2. Water Column Nutrient Concentrations .............................................56 3.4.3. Nutrients and Turbidity in Surface Runoff...........................................63 3.4.4. Catchment Landuses............................................................................69 3.5. Estuarine Site Grades...................................................................................71 4. Conclusion............................................................................................................73 5. References ...........................................................................................................76 6. Appendix ..............................................................................................................82 6.1. Fish Species Lists ..........................................................................................82 6.2. Estuarine Fish Assemblages: A Comparison with the lower Myall River Ecological Condition Assessment.............................................................................85 6.3. Existing Water Quality Data for the Karuah River Estuary ..........................85 6.4. Relationships among Water Quality Variables in the Karuah River Estuary90 6.5. Relationships among Water Quality Variables in Surface Runoff in the Karuah River Catchment ..........................................................................................93 6.6. Prawns and Shrimp ......................................................................................95 ii | Ecological Condition of the Karuah River List of Tables Table 1. Ecological health measures utilised.................................................................5 Table 2. Habitat characteristics and pass criteria used in riparian assessments. .........7 Table 3. Summary of sampling methods. ....................................................................18 Table 4. Extent of macrophyte habitats in the Karuah River.......................................25 Table 5. Proportion of sites that passed the riparian assessment. .............................29 Table 6. Mean OE50 ratios, mean OE50 SIGNAL scores and typical AUSRIVAS band of macroinvertebrate samples from sites in the Karuah River catchment......................45 Table 7. Median water column chlorophyll a concentrations in the Karuah River estuary. ........................................................................................................................46 Table 8. Median water column turbidities in the Karuah River estuary. ....................55 Table 9. Median nutrient concentrations in the Karuah River estuary.......................57 Table 10. Proportion of samples from sites in the Karuah River estuary that were below upper limit and above lower limit triggers. ......................................................58 Table 11. Median nutrient concentrations and turbidity levels for runoff in the Karuah River catchment...............................................................................................64 Table 12. Proportion of samples from sites in the Karuah River catchment that were below triggers. .............................................................................................................64 Table 13. Total nitrogen (TN), total phosphorus (TP) and total suspended sediment (TSS) loads for the Karuah River catchment. ...............................................................67 Table 14. Explanation of site grading system. .............................................................71 Table 15. Site sample pass rates, scores and grades in relation to turbidity and chlorophyll a trigger values. ........................................................................................72 Table 16. Summary of the ecological condition of the Karuah River estuary and catchment. ...................................................................................................................74