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Regional estuary monitoring programme: sediment monitoring April 2001 to April 2003

Report: TR05/27
Authors: Bronwen Gibberd, Nick Carter


In April 2001 Environment Waikato initiated the Regional Estuary Monitoring Programme (REMP) at permanent monitoring sites in the southern Firth of Thames and Whaingaroa (Raglan) Harbour. The programme focuses on intertidal sediments and their benthic macrofauna communities as "indicators" of the health of the Region's estuaries. The objective is to determine the current status of, and monitor the temporal changes in benthic macrofauna communities that may occur as a direct or indirect consequence of catchment activity and/or estuary development. Details of the rationale and design of the programme are provided in full in Turner (2000 and 2001).

This report presents the results for the sediment-monitoring component of the REMP between the commencement in April 2001 and April 2003. Detailed results for the ecological component are available in Turner & Carter (2004).

Regional Estuary Monitoring Programme: Sediment Monitoring April 2001 to April 2003
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Table of Contents

Acknowledgements i
1 Introduction 5
2 Methods 6
2.1 Field sites 6
2.2 Sample collection and processing 8
2.2.1 Surficial sediment grain-size 8
2.2.2 Sediment organic matter content 8
2.2.3 Rates of sediment deposition and erosion 8
2.2.4 Sediment level: Buried plate measurements 9
3 Results and discussion 11
3.1 Surficial sediment grain-size 11
3.1.1 Southern Firth of Thames 12
3.1.2 Whaingaroa Harbour 16
3.2 Sediment total organic carbon and total nitrogen 19
3.2.1 Southern Firth of Thames 19
3.2.2 Whaingaroa Harbour 20
3.3 Sediment level: buried plate measurements 23
4 Recommendations 23
Literature cited 25
Appendix 1 - NZMG GPS Positions 27
Appendix 2 - Total organic carbon and total nitrogen content results 28
Appendix 3 - Cross-shore surveys 33
Appendix 4 - Changes in sediment elevation 34