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Synchronous Ecological Regime Shifts in the Central Baltic and the North Sea in late 1980s

Synchronous Ecological Regime Shifts in the Central Baltic and the North Sea in late 1980s Jürgen Alheit, Christian Möllmann, Jörg Dutz 1 , Georgs Kornilovs 2 , Peter Loewe, Volker Mohrholz 1 and Norbert Wasmund 1. ICES J. mar. Sci. (in press). Ecological Regime Shift – Definition

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Synchronous Ecological Regime Shifts in the Central Baltic and the North Sea in late 1980s

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  1. Synchronous Ecological Regime Shifts in the Central Baltic and the North Sea in late 1980s Jürgen Alheit, Christian Möllmann, Jörg Dutz1, Georgs Kornilovs2, Peter Loewe, Volker Mohrholz1 and Norbert Wasmund1 ICES J. mar. Sci. (in press)

  2. Ecological Regime Shift – Definition Changes in marine system function that are relatively abrupt, persistent, occurring at a large spatial scale, observed at different trophic levels and related to climate forcing deYoung, Harris, Alheit, Beaugrand, Mantua, Shannon. 2004. Progr. Oceanogr. 60

  3. North Sea Regime Shift after 1987 Reid, Holliday, Smyth. MEPS. 2001 Reid, Edwards. Senckenbergiana marit. 2001 Kröncke, Zeiss, Rensing. Senckenbergiana marit. 2001 Reid, Borges, Svendsen. Fish. Res. 2001 Edwards, Beaugrand, Reid, Rowden, Jones. MEPS. 2002 Beaugrand, Reid. Glob. Change Biol. 2003 Beaugrand. Progr. Oceanogr. 2004

  4. Monthly mean contour plots Edwards, Reid, Planque. 2001 Annual means Edwards, Reid, Planque. 2001 Summer, winter and annual Means, central North Sea Reid, Holliday, Smyth 2001 Phytoplankton Colour

  5. SST central North Sea Reid, Borges, Svendsen 2001 Rel. ratios C. helgolandicus and C. finmarchicus in black, reverse in grey Reid et al. 2003 Decapod + fish larvae Reid, Borges, Svendsen 2001 Abundance zooplankton Reid, Borges, Svendsen 2001

  6. Zooplankton 30 taxa NAO Horse mackerel catches, NE Atl. SST Modelled inflow Phytoplankton Colour Benthic biomass Norderney Annual means Reid and Edwards 2001

  7. Gadoid recruitment Calanoid copepods SST Northern hemisphere temperature anomalies Long-term changes, North Sea Beaugrand 2004

  8. Beaugrand. 2004. Progr. Oceanogr. 60 North Sea regime shift: 1982 –1988  2 periods: 1982 – 1985 SST increase, change in wind intensity and direction, change in biogeographical boundary 1987 – 1988 large-scale hydroclimatic forcing Hypotheses • displacement of oceanic biogeographical boundary (prior to 1987) • change in hydro-meteorological forcing (after 1987)  NAO • increase in oceanic inflow (after 1987) Some indicators showed evidence of a regime shift, while some did not.  current debate about existence of regime shift Compare to Baltic Sea processes

  9. NAO winter index, annnual temperature minimum in the Intermediate Winter Water (IWW) of the Bornholm Basin, Station K2, (solid line) and annual SST anomalies at Helgoland Roads (dashed line)

  10. Fig. 1: Trend in diatom biomass (in mg m-3, given as log10-data, means March-May) in Gotland Sea Fig. 2: Trend in dinoflagellate biomass (in mg m-3, given as log10-data, means March-May) in Gotland Sea WASMUND and UHLIG: ICES J. Mar. Sci. 60 (2003), 177-186,

  11. Silicate consumption  proxy for diatom biomass

  12. Hatching of Acartia spp. nauplii from sediments of Bornholm Basin Dutz, Mohrholz, Peters, Renz, Alheit. 2004. GLOBEC Newsletter.

  13. Comparison of Regime Shifts North SeaBaltic Sea Phytoplankton + + Zooplankton + + Fish + + Benthos + ?

  14. Conclusions • teleconnection between regime shifts in both systems • timing in Baltic Sea: initiated after 1987 suggests that North Sea shift also initiated after 1987 • cause in Baltic Sea: drastic change in NAO suggests that North Sea shift also caused primarily by NAO less importance of biogeographical shift and oceanic inflow

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