WELCOME to OCB 2018 1 The Baltic Sea

WELCOME to OCB 2018 1

The Baltic Sea Ida Carlén Ida. carlen@ccb. se 2

The Baltic Sea • Enclosed sea • Surrounded by nine nations • Environmental issues 1. Bothnian Bay, 2. The Quark 3. Bothnian Sea 4. Åland Sea 5. Archipelago Sea 6. Gulf of Finland 7. Northern Baltic Proper 8. Western Gotland Basin 9. Eastern Gotland Basin 10. Gulf of Riga 11. Southern Baltic Proper 12. Gdansk Basin 13. Mecklenburg Bight 14. Kiel Bight 15. Little Belt 16. Great Belt 17. The Sound 18. Kattegat 3

Covered by ice • The entire Baltic region was covered by ice during the last ice age. • The ice started melting approximately 15 000 years ago • The ice was completely gone 10 000 years ago Ancylus lake ~10 500 yryr. BP The Yoldia Sea ~11 000 BP Littorina yr BP Baltic icesea lake~6500 ~12 000 yr BP 4

Physical conditions • • • Land still rising Series of basins Salinity gradient Limited exchange with Atlantic Anoxic bottom waters 5

Physical conditions • • • Series of basins with shallow underwater sills Kattegat max 124 m Belt Sea max 80 m Inner Baltic Sea max 459 m Sills between 18 -50 m depth 6

Physical conditions Ice and currents 7

Physical conditions • Salinity gradient 8

Physical conditions • Limited exchange with Atlantic • Anoxic bottom waters 9

Physical conditions 10

Physical conditions • Limited exchange with North Sea • Anoxic bottom waters No influx of saline waters Anoxia in deep areas of the Baltic Influx of saline water No mixing of waters Oxygen to bottom waters Stronger density gradient 11

Habitats and species • • • Salt water species Freshwater species Hard bottom habitats Soft bottom habitats Habitat building species - eel grass - blue mussel - bladder wrack 12

Species Brackish water environment Relatively few species ”New” ecosystem Saltwater and freshwater species Sensitive ecosystem 13

Species 14

Species Saltwater species Freshwater species Insert pic of perch, pike, sik etc 15

Species Soft substrate species Hard substrate species 16

Habitat building species Bladder wrack - Structure provides shelter for juvenile fish and other organisms 17

Habitat building species Blue mussel - Food source for many sea birds - Creating hard substrate, almost like reefs 18

Habitat building species Eel grass - Important for juvenile fish - Binds the substrate, hindering erosion 19

Pressures • • • Eutrophication Environmental contaminants Underwater noise Overfishing Invasive species 20

Pressures Eutrophication 21

Pressures Eutrophication Oxygen used in the decomposition of excess growth No influx of saline waters Anoxia in deep areas of the Baltic Influx of saline water No mixing of waters Oxygen to bottom waters Stronger density gradient 22

Pressures Underwater noise Affects marine mammals but also fish species such as cod - Engine noise - Echosounders - Constructions - Piling - Active sonars - Explosions 23

Pressures Invasive species 24

Pressures Environmental contaminants 25

Pressures Overfishing 26

Pressures Overfishing 27

Pressures Environmental contaminants Overfishing Lack of top predators Fundamental changes to the ecosystem Flip from top-down to bottom-up control 28