Iron Cycle in Oceans

Stéphane Blain, Professor, Université Pierre et Marie Curie, France. Alessandro Tagliabue, University of Liverpool, UK.

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