Concentrations and compositions of metallic elements in commercially important marine species RC Uren orcid.org 0000-0002-8940-9755 Dissertation accepted in fulfilment of the requirements for the degree Master of Science in Environmental Sciences at the North-West University Supervisor: Prof H Bouwman Graduation May 2020 24072044 i Concentrations and compositions of metallic elements in commercially important marine species Preface My dissertation concerns the metal compositions and concentrations of 5 commercially important marine species. This dissertation is presented in an article format. I have already submitted two articles for review; Regional Studies in Marine Science, and African Zoology. Outline of dissertation: This dissertation is presented in four chapters; a short description of each follows: Chapter 1: A general introduction to my study, concluded by the problem statement, aims, objectives, and hypotheses. Chapter 2: Concentrations and relative compositions of metallic elements differ between predatory squid and filter-feeding sardine from the Indian and South Atlantic oceans This is the first article in this dissertation and has been submitted to Regional Studies in Marine Science for review in November 2018. The article was accepted for publication January 2020. This article focuses on the patterns of metal concentrations and compositions in sardine and chokka from the South Atlantic and Indian oceans. This is the first study to compare metal concentrations and compositions in muscle tissue of these species between the Indian and South Atlantic oceans. Chapter 3: Differences in metal compositions and concentrations of sympatric predatory fish and squid from the South Atlantic Ocean This is the second article and has been submitted to African Zoology for review in November 2019. This article focuses on the metal concentrations and compositions of four commercial marine predators; chokka, hake, kingklip, and monkfish in the South Atlantic Ocean. This was the first study to compare the metal concentrations and compositions of these species off the coast of Southern Africa Chapter 4: Discussion and conclusions In this chapter, the results of Chapter 2 and 3 are combined, evaluated, discussed, and synthesized. I contributed towards this dissertation and articles with literature studies, collecting data, sourcing materials, preparation of samples for analyses, data analyses and interpretation, constructing the tables and graphs, drafting and managing the manuscripts, and drafting the introduction and conclusion of the dissertation. The co-authors for the chapters contributed only at the latter stages with corrections and changes. I have been provided with permission to submit these articles for my dissertation by all co-authors of the articles ii Concentrations and compositions of metallic elements in commercially important marine species Table of contents Preface ........................................................................................................................................... ii Acknowledgements ........................................................................................................................ vi Abstract ......................................................................................................................................... vii Chapter 1: Introduction ................................................................................................................... 1 1.1 What are metals? .................................................................................................................. 1 1.2 Sources of metals in the environment .................................................................................... 2 1.3 Essential and non-essential metals ....................................................................................... 2 1.4 Metal toxicity .......................................................................................................................... 3 1.5 Effects of metals on organisms .............................................................................................. 5 1.6 Molluscs as bioindicators ....................................................................................................... 6 1.7 Fish as bioindicators .............................................................................................................. 7 1.7 Conclusions ........................................................................................................................... 8 1.8 Aims, objectives, and hypotheses .......................................................................................... 9 References ................................................................................................................................ 11 Chapter 2: ..................................................................................................................................... 17 Concentrations and relative compositions of metallic elements differ between predatory squid and filter-feeding sardine from the Indian and South Atlantic oceans 1. Introduction ........................................................................................................................... 18 2. Methods and Materials .......................................................................................................... 19 2.1. Sardine and chokka collection sites ................................................................................ 19 2.2. Dissection of sardine and chokka .................................................................................... 20 2.3. Analyses of sardine and chokka ...................................................................................... 20 2.4. Statistical analysis ........................................................................................................... 21 3. Results .................................................................................................................................. 21 3.1 Concentrations ................................................................................................................. 21 3.2. Concentration differences between sardines from different oceans ................................. 22 3.3. Concentration differences between chokka from different oceans ................................... 23 3.4. Concentration differences between sardines and chokka per ocean ............................... 23 4. Discussion ............................................................................................................................. 27 4.1. Concentration differences between sardines from different oceans ................................. 27 4.2. Concentration differences between chokka from different oceans ................................... 27 4.3. Possible sources ............................................................................................................. 28 4.3.1. Geological background ............................................................................................. 28 4.3.2. Anthropogenic sources ............................................................................................. 28 4.4. Differences in concentrations between sardine and chokka ............................................ 29 iii 4.5. Multivariate analyses of relative elemental compositions of sardine and chokka per collection site ......................................................................................................................... 30 4.6. Comparisons with similar studies .................................................................................... 32 4.7. Seafood safety ................................................................................................................ 32 5. Conclusions ........................................................................................................................... 33 Acknowledgements ................................................................................................................... 34 References ................................................................................................................................ 35 Appendix A. ............................................................................................................................... 42 Chapter 3: ..................................................................................................................................... 44 Differences in metal compositions and concentrations of sympatric predatory fish and squid from the South Atlantic Ocean 1. Introduction ........................................................................................................................... 46 2. Materials and methods .......................................................................................................... 46 2.1. Species sampled ............................................................................................................. 46 2.3 Dissection and sample preparation .................................................................................. 49 2.4 Chemical analyses ........................................................................................................... 49 2.5 Statistical analyses .......................................................................................................... 49 3. Results .................................................................................................................................