The 2002 Oxygen Depletion Event in the Kattegat, Belt Sea and

2,92

MB

Western Baltic

66

stron

3793

ID

Helsinki Commission

2003

rok

Contents

Preface 4

1. Introduction 5

2. Description of the 2002 oxygen depletion 7

Seasonal development at representative stations 7

Seasonal development in area and volume affected 7

Material and methods 7

Results 10

Conclusion 13

3. Nutrient loads from surrounding land and atmosphere 15

Introduction 15

Runoff and nutrient loads 15

Atmospheric deposition 17

Nutrient sources 18

Conclusion 19

4. Nutrients, chlorophyll-a and primary production 21

Nutrient concentrations 21

Chlorophyll-a concentrations 21

Phytoplankton primary production 27

Conclusion 27

5. Atmospheric forcing 29

Introduction 29

Results 29

Conclusions 30

6. Hydrography 33

Introduction 33

Results 33

Discussion 35

Conclusions 37

7. Water exchange and residence times 39

Introduction 39

Results 39

Conclusions 43

8. Assessment 45

9. Conclusions 47

10. References 49

Annex A:

The development and decline of hypoxia in 2001 and 2002 51