SPATIAL AND TEMPORAL VARIATIONS IN MACROZOOBENTHIC COMMUNITIES IN KWAZULU-NATAL TEMPORARILY OPEN/CLOSED ESTUARIES by Catherine Anne Stow Submitted in fulfilment of the academic requirements for the degree of Master of Science in the School of Biological and Conservation Sciences, University of KwaZulu Natal, Durban, through the Oceanographic Research Institute Supervisor C. F. Mackay Date Submitted 10 June 2011 “But science is not about establishing certainty. It's about understanding change. Certainty is a vestigial concept from the time when constancy supposedly ruled life and the cosmos. There is no constancy in nature - there is only constant change, and lots of it.” TOM SIEGFRIED Editor of Science News For both universe and life, only constant is change Science News, February 14, 2009 ABSTRACT Estuaries are complex ecosystems, typified by remarkable fluctuations in environmental conditions. In addition to this natural variability, stochastic events and anthropogenic influences effect change at different spatial and temporal scales. Macrozoobenthic invertebrates are preferable biological indicators because of their sensitivity to variations in habitat quality. This thesis describes inherent changes in the macrozoobenthos of temporarily open/closed estuaries (TOCEs) in KwaZulu-Natal, ‘change’ as measured in spatial and temporal community differences using various community metrics, namely species composition, abundance and diversity. Standard and widely published quantitative sampling techniques were employed, with simultaneous measurements of ambient physico-chemical conditions, including sediment characteristics. The thesis is in three parts. Regional distributions and long-term decadal-type changes in macrozoobenthic community structure were determined for 31 TOCEs using historical data (1998/9) compared with more recently collected data (2009/10). Results showed that, although of the same estuary type, the macrozoobenthic communities of these estuaries differed significantly. Furthermore, community composition did not reflect a north to south progression of predominantly tropical species to predominantly warm-temperate species. In the last decade, the macrozoobenthos of these systems had indeed changed (in composition, abundance and/or diversity), the scale of change within each estuary being estuary-dependent. The recolonisation of two urban and non-urban estuaries by macrozoobenthos following a stochastic flood disturbance was investigated, describing the short-term community changes during the recovery process. Differential recolonisation patterns were attributed to inherent differences in community composition and not to the influence of urbanisation. Recolonisation was marked by distinct changes in community structure, with the recovery trajectory being interrupted by localised disturbances (e.g. change of mouth state). Species indicative of the observed spatial and temporal community changes were examined for similarities in habitat association and trophic characteristics. The species that were ii representative of these KwaZulu-Natal TOCEs were identified and included common and highly abundant generalists of varying trophic groups. In conclusion, the present findings illustrated the effectiveness of using macrozoobenthic communities to depict ‘change’ over multiple temporal and spatial scales. This also supports their usefulness as a study group in environmental monitoring and detecting the loss of ecological functioning and biodiversity in estuaries in the long- and short-term. iii FACULTY OF SCIENCE AND AGRICULTURE PREFACE The work described in this thesis was carried out at the Oceanographic Research Institute, an affiliate of the University of KwaZulu-Natal, Durban, under the School of Biological and Conservation Sciences. This work was undertaken from January 2008 to March 2011, under the supervision of Fiona Mackay. DECLARATION - PLAGIARISM I, ……………………………………….………………………., declare that 1. The research reported in this thesis, except where otherwise indicated, is my original research. 2. This thesis has not been submitted for any degree or examination at any other university. 3. This thesis does not contain other persons’ data, pictures, graphs or other information, unless specifically acknowledged as being sourced from other persons. 4. This thesis does not contain other persons' writing, unless specifically acknowledged as being sourced from other researchers. Where other written sources have been quoted, then: a. Their words have been re-written but the general information attributed to them has been referenced, b. Where their exact words have been used, then their writing has been placed in italics and inside quotation marks, and referenced. 5. This thesis does not contain text, graphics or tables copied and pasted from the Internet, unless specifically acknowledged, and the source being detailed in the thesis and in the References sections. Signed ……………………………………………………………………………… Catherine Anne Stow June 2011 iv LIST OF CONTENTS ABSTRACT ....................................................................................................... ii PREFACE ........................................................................................................ iv DECLARATION OF PLAGARISM ....................................................................... iv LIST OF CONTENTS .......................................................................................... v LIST OF FIGURES .............................................................................................. ix LIST OF TABLES .............................................................................................. xiv LIST OF APPENDICES..................................................................................... xvii ACKNOWLEDGEMENTS ............................................................................... xviii CHAPTER 1: GENERAL INTRODUCTION ............................................................ 1 1.1 Types of Estuaries in South Africa .................................................................. 2 1.1.1 Characteristics of Temporarily Open/Closed Estuaries .................................. 3 1.2 Susceptibility of South African Estuaries to Change ........................................ 6 1.3 Estuarine Macrozoobenthos and the Response to Environmental Change ...... 7 1.4. Monitoring Change in South African Macrozoobenthos ................................. 9 1.5. Project Aim and Objectives .......................................................................... 10 1.6. Thesis Outline ............................................................................................. 11 CHAPTER 2: GENERAL MATERIALS AND METHODS ........................................ 12 2.1 Study Area – The KwaZulu-Natal coastline ................................................... 12 2.1.1 Location and Topography ........................................................................... 12 2.1.2 Climate ...................................................................................................... 12 2.1.3 Geology ..................................................................................................... 14 2.1.4 Human Settlement ..................................................................................... 15 2.1.5 Estuaries of KwaZulu-Natal ........................................................................ 16 2.2 Estuary Sampling Procedure ........................................................................ 17 2.2.1 Macrozoobenthos ...................................................................................... 18 v 2.2.2 Physico-Chemical Environment .................................................................. 19 2.3 Laboratory Processing ................................................................................. 19 2.3.1 Macrozoobenthos ..................................................................................... 19 2.3.2 Physico-Chemical Environment .................................................................. 20 2.3.2.1 Sediment Granulometry ..................................................................... 20 2.3.2.2 Organic Content ................................................................................. 21 2.4 Generic Statistical Analyses ......................................................................... 21 2.4.1 Univariate Techniques ............................................................................... 22 2.4.2 Multivariate Techniques ............................................................................ 24 CHAPTER 3: LONG-TERM CHANGE AND INTER-ESTUARINE VARIABILITY ........ 27 3.1 Rationale .................................................................................................... 27 3.2 Introduction ................................................................................................ 27 3.2.1 Assessment of the state of the South African estuarine environment .......... 27 3.2.2 Factors affecting the distribution of macrozoobenthos in KwaZulu-Natal estuaries ................................................................................................... 31 3.2.3 Aim and Hypotheses .................................................................................. 32 3.3 Methods and Materials ............................................................................... 34 3.3.1 Study Area ................................................................................................ 34 3.3.2