Synchronous Ecological Regime Shifts in the Central Baltic and the North Sea in late 1980s
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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)
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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 - PowerPoint PPT Presentation
Transcript of 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 Dutz1, Georgs Kornilovs2,
Peter Loewe, Volker Mohrholz1 and Norbert Wasmund1
ICES J. mar. Sci. (in press)
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
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
Monthly mean contour plotsEdwards, Reid, Planque. 2001
Annual meansEdwards, Reid, Planque. 2001
Summer, winter and annualMeans, central North SeaReid, Holliday, Smyth 2001
Phytoplankton Colour
Abundance zooplankton
Reid, Borges, Svendsen 2001
SST central North Sea
Reid, Borges, Svendsen 2001
Decapod + fish larvae
Reid, Borges, Svendsen 2001
Rel. ratios C. helgolandicus and C. finmarchicus in black, reverse in grey Reid et al. 2003
NAO
SST
Zooplankton 30 taxa
Horse mackerel catches, NE Atl.
Modelled inflow
PhytoplanktonColour
Benthic biomassNorderney
Annual meansReid and Edwards 2001
Long-term changes, North SeaBeaugrand 2004
Gadoid recruitment
Calanoid copepods
SST
Northern hemisphere temperature anomalies
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
1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005
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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)
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M onth
M onth ly m ean tem perature difference [°C ] in the centra l Bornholm Basin betw een the periods 1970-1987 and 1988 - 2003
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Smoother & confidence interval
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Smoother & confidence interval
Smoother Upper limit Low er limit
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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,
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Year
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Bornholm Sea(c)
Silicate consumption proxy for diatom biomass
Acartia
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Temora
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Pseudocalanus
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Sprat
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Sprat
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north-west, mud, 83 m
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k-1 4 °C 10 °C
Hatching of Acartia spp. nauplii from sediments of Bornholm BasinDutz, Mohrholz, Peters, Renz, Alheit. 2004. GLOBEC Newsletter.
Comparison of Regime Shifts
North Sea Baltic Sea
Phytoplankton + +
Zooplankton + +
Fish + +
Benthos + ?
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
