ORI Unpublished Report No. 310 Biophysical Assessments of the Zinkwazi & Nonoti Estuaries: High & Low Flow Surveys December 2013 Zinkwazi Beach Ratepayers and Residents Compiled For: Association Lower Tugela Biodiversity Protection Project Critical Ecosystem Partnership Fund Funded By: & through Wildlands Conservation Trust Compiled By: Fiona MacKay Oceanographic Jill Sheppard Research Bronwyn Goble Institute In Collaboration Council for With: Scientific & Steven Weerts Industrial Research ORI Unpublished Report 310 The ORI Unpublished Report Series is intended to document various activities of the Oceanographic Research Institute. This is the research department of the South African Association for Marine Biological Research. Oceanographic Research Institute P.O. Box 10712 Marine Parade, 4056 Durban, KwaZulu-Natal, South Africa Tel: +27 31 3288222 Fax: +27 31 3288188 Web site: www.ori.org.za © 2013 Oceanographic Research Institute Title: Biophysical Assessments of the Zinkwazi & Nonoti Estuaries: High & Low Flow Surveys Document Creator/s: Fiona MacKay, Jill Sheppard, Steven Weerts & Bronwyn Goble Client/Funding Zinkwazi Beach Ratepayers and Residents Association Agencies: Lower Tugela Biodiversity Protection Project Critical Ecosystem Partnership Fund & through Wildlands Conservation Trust Subject and Zinkwazi & Nonoti Estuaries, baseline biophysical surveys, keywords: macrobenthos, ichthyofauna, information for estuarine management plans and environmental flow assessments Description: This study presents data and information gathered during low (winter, July 2012) and high flow (summer, February 2013) surveys conducted in the Zinkwazi and Nonoti Estuaries. An account of the biophysical condition of each system is presented, including additional material on spatial analysis of land use, coastal vulnerability and interpolation of the estuarine physico- chemical habitat as they pertain to input information towards estuarine management plans and estuarine flow assessment studies. ORI Project Codes: 330 & 335 Document Status: Final Year Issued: 2013 Report Type: Unpublished Report ORI Report No.: 310 Latest Version ORI Unpublished Report No. 310.pdf Language: English Coverage: KwaZulu-Natal, South Africa Distribution: ORI Library, authors and clients Cover Photos: by F MacKay Citation: MacKay F., Sheppard J. Weerts S. & Goble B. 2013. Biophysical Assessments of the Zinkwazi & Nonoti Estuaries: High & Low Flow Surveys. Oceanographic Research Institute, Durban: 160pp & Appendices 126pp. (ORI Unpublished Report 310). ORI Unpublished Report 310 COPYRIGHT RESERVED Copyright subsists in the work. This publication or any part thereof may not be reproduced or transmitted in any form or by any means, electronic, mechanical or optical, for any purpose, without the express written permission of the Director of the Oceanographic Research Institute, and the individual authors of the document. The distribution and use of this document is restricted to the parties for which it was produced unless otherwise indicated ORI Unpublished Report 310 Table of Contents Table of Contents ................................................................................................................................. i 1. PREAMBLE ................................................................................................................................. 1.1 1.1 Terms of Reference ................................................................................................................ 1.1 1.2 Layout of Document............................................................................................................... 1.2 2. INTRODUCTION TO ESTUARINE CONCEPTS & LEGAL FRAMEWORKS ......................................... 2.1 2.1 Basic definitions pertaining to estuarine ecology ........................................................................ 2.1 2.2 The legal landscape pertaining to South African estuaries .......................................................... 2.5 3. ESTUARIES .................................................................................................................................. 3.1 3.1 Importance and value ............................................................................................................ 3.1 3.2 Classification .......................................................................................................................... 3.1 3.3 Distribution ............................................................................................................................ 3.3 3.4 Estuarine habitats ........................................................................................................................ 3.4 3.5 Status of KZN estuaries .......................................................................................................... 3.5 3.6 Study systems .............................................................................................................................. 3.8 4. FRAMEWORK FOR MANAGING BIOPHYSICAL FUNCTION OF THE NONOTI & ZINKWAZI ESTUARIES.......................................................................................................................................... 4.1 4.1 RDM Methodologies .............................................................................................................. 4.1 4.2 Estuarine Management Plans ...................................................................................................... 4.6 5. SPATIAL ANALYSIS ...................................................................................................................... 5.1 5.1 Methods ................................................................................................................................. 5.2 5.2 Nonoti Estuary ....................................................................................................................... 5.8 5.3 Zinkwazi Estuary................................................................................................................... 5.11 6. PHYSICO-CHEMICAL HABITATS OF NONOTI & ZINKWAZI ESTUARIES ....................................... 6.1 6.1 Methods ................................................................................................................................. 6.5 6.2 Nonoti Estuary ....................................................................................................................... 6.8 6.3 Zinkwazi Estuary................................................................................................................... 6.17 7. BIOTA OF NONOTI & ZINKWAZI ESTUARIES ............................................................................... 7.1 7.1 Methods ................................................................................................................................. 7.5 7.2 Nonoti Estuary ..................................................................................................................... 7.14 7.3 Zinkwazi Estuary................................................................................................................... 7.31 i 8. COASTAL VULNERABILITY ........................................................................................................... 8.1 8.1Methods ....................................................................................................................................... 8.1 8.2 Assessment of Vulnerability: Coastal area Nonoti to Zinkwazi .................................................... 8.2 9. SUGGESTED PRESSURES AND THREATS EVALUATION ........................................................ 9.1 9.1 Following the Millennium Ecosystem Assessment ............................................................ 9.1 9.2 Risk assessment of pressures on Nonoti & Zinkwazi Estuaries using the DPSIR framework ........................................................................................................................................ 9.2 9.3 Generic pressures and threats to KZN estuarine health and function .......................................................................................................................... 9.7 10. CONCLUSION & RECOMMENDATION .................................................................................. 10.1 11. REFERENCES ......................................................................................................................... 11.1 ii Biophysical Surveys of 2013 Zinkwazi & Nonoti Estuaries 1. PREAMBLE The assessment and monitoring of abiotic parameters and biological communities in the evaluation and management of water resources such as estuaries, is now well recognised and commonplace. National (e.g. DWAF 1999) and international directives (e.g. European Union 2000) indicate that there is increasing recognition that such programmes should be based on monitoring of environmental indicators against a baseline condition. In many cases monitoring programmes are only implemented after anthropogenic activities have impacted upon a water resource and the lack of information on the reference state of the system being monitored is often problematic. In such cases, the reference condition could be determined by comparison with a control area (often difficult to locate), hindcasting (requires good previous data), predictive modelling (requires adequate empirical and stochastic models) or expert judgement (subjective and difficult to quantify) (Whitfield & Elliot 2002). The state of our environment