Ecosystem implications of projected climate change on the Baltic Sea

Transcription

1 Ecosystem implications of projected climate change on the Baltic Sea Markku Viitasalo & coauthors of the BACC II Marine Ecosystems chapter HELCOM Climate Change Workshop, Warnemünde MPI-MET,

2 The authors Markku Viitasalo SYKE Marine Research Centre Pelagic ecology, cyanobacteria, zooplankton, fish Thorsten Blenckner Baltic Nest Institute Regime shifts, social-ecological systems Anna Gårdmark Swedish Fisheries Board Food web modelling, fish ecology Markku Thorsten Lena Lena Kautsky Stockholm University Biodiversity of shallow water ecosystems, macroalgae Hermanni Kaartokallio SYKE Marine Research Centre Microbial loop, winter ecology Harri Kuosa SYKE Marine Research Centre Pelagic ecology, microbial loop Anna Hermanni Harri Martin Lindegren Technical University of Denmark Modelling, effects of climate change on fish and fisheries Alf Norkko University of Helsinki Biodiversity and biogeochemistry of benthic ecosystems Martin Alf Kalle Olli University of Tarto Biodiversity, pelagic ecology, phytoplankton Kalle Johan Johan Wikner Umeå University Bacterioplankton, climate related O 2 consumption

3 1) Biodiversity 2) Food webs 3) Eutrophication Main Issues Key Questions 1) What is quite certain? 2) Where are the uncertainties? 3) What are the more stringent and supplementary actions?

4 Examples 1) Geographical distribution of species 2) Benthos diversity 3) Plankton diversity 4) Sea ice 5) Cod-herring-sprat-plankton 6) Eutrophication (incl. uncertainties)

5 1. Biodiversity

6 Baltic Sea surface salinity and biogeography Ljungberg et al., in prep. MARISPLAN project Original data: ECOSUPPORT, courtesy of Markus Meier, SMHI, Sweden

7 Baltic Sea surface salinity and biogeography Ljungberg et al., in prep. MARISPLAN project Original data: ECOSUPPORT, courtesy of Markus Meier, SMHI, Sweden

8 The diversity of benthos will go down with salinity Villnäs A, Norkko A (2011) Benthic diversity gradients and shifting baselines: implications for assessing environmental status. Ecological Applications, 21:

9 What will happen to plankton? Protozoans: diversity may decline Telesh et al. 2011: Revisiting Remane s concept Freshw. species Brackishw. species Marine species

10 What will happen to plankton? Protozoans: diversity may decline Telesh et al. 2011: Revisiting Remane s concept Future salinity? Present salinity in the central Baltic This was disputed by Ptacnik et al 2011: evidence from Phytoplankton: Gain of freshwater species will exceed the loss of marine species Ptacnik et al., unpublished Species diversity Artenminimum Salinity

11 2. Food webs

12 Baltic Sea ice ecosystem Hermanni Kaartokallio/SYKE 12

13 Baltic Sea ice ecosystem 13 Hermanni Kaartokallio/SYKE

14 Cascading effects in the pelagic ecosystem Casini et al Multi-level trophic cascades in a heavily exploited open marine ecosystem. -Proc Royal Soc. B 275:

15 POPULATION IMPACTS More nutrients Less O 2 Pelagic ecosystem The case of cod, sprat, herring & copepods in the central Baltic Sea Poorer reproduction of cod Fewer cod More sprat More herring Less zooplankton More phytoplankton Confidence Sprat & herring competition = high = medium = low More freshwater discharge Less frequent saline pulses Lower salinity Less marine zooplankton Less energy ingested per herring Slower herring growth INDIVIDUAL-LEVEL PROCESSES

16 3. Eutrophication

17 Modelling evidence: CC does worsen eutrophication Without climate change With climate change Meier et al. (2012): Modeling the combined impact of changing climate and changing nutrient loads on the Baltic Sea environment Clim. Dyn.

18 Uncertainties regarding eutrophication: stratification and deep water mixing Processes worsening deep water O2 1. SST => Stratification => mixing 2. SSS => Stratification => mixing 3. Freshwater discharge => saline pulses 4. Winter T => reduced convective mixing Processes improving deep water O2 1. Winter T => sea ice => mixing 2. Freshwater discharge => dilution and deepening of halocline => mixing of mid depths Viitasalo (2012). In: Haapala (ed.): From the Earth s Core to Outer Space

19 Uncertainties: What will happen to terrestrial nutrient processes? MARISPLAN project Bertel Vehviläinen & Markus Huttunen et al. Finnish Environment Institute, Freshwater Research Centre

20 tonnes Phosphorus (P-tot) load into the GoF Cumulative sum for the whole year Predicted change: A SLIGHT DECREASE! Huttunen et al. (ICECREAM-model) month

21 Further uncertainties: There are differences between basins in their response to CNP loading

22 Gulf of Bothnia: During years with high freshwater discharge, the ratio of bacterial vs. primary production increases. Wikner & Andersson 2012: Increased freshwater discharge shifts the trophic balance Global Change Biol. 18: Why? Because organic carbon is good food for bacteria!

23 Eutrophication More freshwater discharge into the sea More nutrients from land More phytoplankton & Cyanobacteria Less light More DOC from land More bacteria growth More sedimentation More anoxic sediments More competition for nutrients between bacteria & phytoplankton More phosphorus release from sediments Lower phytoplankton production More freshwater discharge => more phytoplankton More freshwater discharge => less phytoplankton

24 4. Conclusions

25 Main Results 1. Salinity decline will change geographical limits of species as well as biodiversity 2. Response of the pelagic and benthic systems to changes in CNP loading vary from basin to basin 3. Changes in physical-biological interactions and trophic processes may override the effects of increased nutrients

26 The Main Conclusion There is evidence that CC will induce both eutrophication and a decline of biodiversity. Uncertainties do exist, especially regarding food web responses. The existing knowledge calls for a precautionary principle and thus more stringent action - when designing measures to mitigate eutrophication and reducing biodiversity loss.

27 Note: There are 5 full (6-yr) MSFD cycles before 2040 We can still choose between: a) b) Thank You!