Iron Cycle in Oceans

This book presents an up to date view of iron biogeochemistry in the ocean. It encompasses the description of iron speciation, the analytical methods used to measure the different iron forms in seawater and the different iron biogeochemical models.

Preface ix

Chapter 1. Iron Speciation in Seawater 1

1.1. The chemical element 1

1.2. Iron speciation 2

1.2.1. Inorganic speciation 2

1.2.2. Organic speciation 3

1.2.3. Redox speciation 6

1.2.4. Operational definitions of iron speciation 11

1.3. Applying speciation 12

1.3.1. Solubility 12

1.3.2. Photochemistry 15

1.3.3. Cultures in artificial seawater with well-defined iron speciation 17

1.3.4. Iron bioavailability: the chemical perspective 18

1.3.5. Iron speciation on geological timescales 19

Chapter 2. Analytical Methods 23

2.1. Trace-metal clean sampling techniques 23

2.2. Processing of the sample before measurement of concentrations 25

2.3. Particle collection 25

2.4. Iron determination 27

2.4.1. Historical perspective 27

2.4.2. Flow injection analysis 28

2.4.3. Electrochemistry 29

2.4.4. Mass spectrometry 31

2.4.5. Iron reference samples 32

2.4.6. Probing iron bioavailability 32

Chapter 3. Modeling Methods 35

3.1. Overview 35

3.2. Modeling frameworks 36

3.3. Modeling iron cycle processes 36

3.3.1. Modeling iron supply 37

3.3.2. Modeling iron speciation 37

3.3.3. Modeling biological uptake of iron 40

3.3.4. Modeling iron regeneration 42

3.4. Synthesis 43

Chapter 4. Iron Sources 45

4.1. Overview 45

4.2. Dust deposition 45

4.3. River supply 47

4.4. Continental margins 49

4.5. Hydrothermalism 50

4.6. Glaciers, icebergs and sea ice 52

4.7. Submarine groundwater discharge 54

4.8. Synthesis 54

Chapter 5. Iron Cycling in the Ocean 55

5.1. The biological iron demand 55

5.1.1. Phytoplankton iron requirement 55

5.1.2. Iron requirements of heterotrophic organisms 61

5.2. Iron cycling in the surface ocean 62

5.3. Iron export and its cycling below the mixed layer 65

Chapter 6. Dissolved Iron Distributions in the Ocean 69

6.1. Overview 69

6.2. Temporal evolution in the number of observations 69

6.3. The contemporary view of the distribution of iron in the ocean 72

6.4. The vertical profile of iron 74

6.5. Synthesis 77

Chapter 7. The Iron Hypothesis 79

7.1. Introduction 79

7.2. From bottle incubations to mesoscale experiments 81

7.3. Natural iron fertilization 84

7.4. Paleo iron hypothesis 87

7.5. Large-scale iron fertilization: climate engineering 89

Bibliography 91

Index 117

Stéphane Blain, Professor, Université Pierre et Marie Curie, France.

Alessandro Tagliabue, University of Liverpool, UK.