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Title: Marine ecosystems and climate change


1
Marine ecosystems and climate change
Geir Huse
CLIMECO, Brest 20-24 April
2
Outline
  • Overview of climate effects on marine ecosystems
  • Climate variability and ecosystem response on
    different time scales
  • Ecological processes and effects of climate
    variability
  • Concluding remarks

3
Sea birds and marine mammals
Larger fish
SALINITY TEMPERATURE LIGHT TURBULENCE
ADVECTION SPREADING VERTICAL MIXING
OCEAN
CLIMATE
Planktivore fish, juv. and fish larvae
Zooplankton
Microbial loop
Phytoplankton
Populations
Individuals
CARBON and NUTRIENTS
4
Ecosystem responses to climate variability and
change
The experience from 20th. century
The scenario for 21th century ?
Linear response
Non-linear respons 1
Non-linear respons 2
Ottersen et al. (2004)
5
A short history of the world
http//pubs.usgs.gov/gip/geotime/time.html USGS
Graham, Newman Stacy
6
Source Wikipedia
7
What happened in the ocean?
Temperature reconstructions from plankton and
sediment (CLIMAP, 1976)
Present day Last glacial maximum
Very little known about effects on fish or other
large marine species
?
8
Interannual climate variations
  • Spatial scale
  • North Sea or Barents Sea
  • Typical climate variable
  • Variations in current strenghts
    Heat
    exchange across the oceans surface
  • Ecosystem responses
  • Phytoplankton production
    Growth
    and changes in advection of zooplankton
    Year-class
    strenghts in fish species

9
Hjort and year-class variation
Age of herring (years)
from Hjort (1914)
Percent of population
The extraordinary favourable environmental
conditions for fish recruitment during one single
year
10
Impacts of interannual climate variations on
different cod stocks
Planque and Fredou (1999)
11
Impacts of interannual climate variations on
Barents Sea cod recruitment
Abundance of cod as 5 months old
Abundance of cod as 3 years old
Annual mean temperature
Ottersen and Loeng (2000)
12
Decadal-scale climate variations
  • Spatial scale
  • Northeastern North Atlantic
  • Typical climate variable
  • Variations in current strenghts
  • Water mass heat content
    Heat
    exchange across the oceans surface
  • Ecosystem responses
  • Phytoplankton production
    Changes
    in advection of zooplankton
    Year-class strenghts in
    fish species
  • Fish population growth
  • Growth and abundance of the top predators

13
The North Atlantic Oscillation (NAO) Index The
difference of the normalized sea level pressure
between the Azores/Lisbon/Gibraltar and Iceland.
Hurrell and Dickson (2004)
14
NAO index
Year
15
Effects of NAO
  • Trees (Darrigo et al. 1993)
  • Marine fish (Wainright et al. 1993)
  • Marine zooplankton (Fromentin and Planque 1996)
  • Marine phytoplankton (Lindahl et al. 1998)
  • Aquatic zooplankton (Straile and Geller 1998)
  • Terrestrial mammals (Post et al. 1999)
  • Aquatic phytoplankton (Straile and Adrian 2000)
  • Marine birds (Thompson and Ollason 2001)
  • Birds (Moller 2002)
  • Marine mammals (Ferguson et al. 2005)

Physics
Biology and ecosystems
16
Strong decadal-scale signals makes the NAO and
Barents Sea ocean climate turn together
Kola temperature
Temperature
NAO Index
17
Multidecadal-scale climate variations
  • Spatial scale
  • northern hemisphere
  • Typical climate variable
  • Change in the atmosphere-ocean thermal regime
  • Ecosystem responses
  • General change in ecosystem productivity on all
    levels in the food chain
  • Latitudinal changes in habitat extents

18
The Atlantic Multi decadal Oscillation (AMO)
1873-2000
Sutton and Hodson (2005)
19
The cod spread northwards during the warm period
of the 1920s and 1930s
Hansen (1940)
20
Vedel Tåning (1953) Long Term Changes in
Hydrography and Fluctuations in Fish Stocks
21
Spawning stock biomass (SSB) of Norwegian
spring-spawning herring and the longterm-averaged
temperature (the AMO signal) (Toresen og
Østvedt 2000)
Long-term averaged temperature
Stock collapse caused by overfishing under a
cooling climate
Start of the new herring period after 17 years of
fishing moratorium and the formation of the
outstanding 1983 year class
22
Ecological processes and climate effects
  • Changes in spatial distribution and productivity
  • Trophic cascades
  • Mortality
  • Climate induced mortality
  • Predation
  • Diseases
  • Reproduction
  • Growth

23
Shift in the dominance of two copepods in the
northern North Sea often referred to as
characteristic of a regime shift induced by
climate change
SAHFOS (2007)
24
All zooplankton species in the northeastern North
Atlantic have moved northwards with the
increasing temperature since the 1970s
Extended spawning throughout the year
e.g. C.
helgolandicus
e.g. C. finmarchicus
Spring spawners
e.g. C.hyperboreus
Based on Beaugrand et al. (2002)
25
Polar Ocean
Calanus hyperboreus
Arctic
Polar cod
Polar bear
Capelin
Ringed seal
Barents Sea
Spring bloom ecosystem
Atlantic cod
Haddock
Calanus finmarchicus
Herring
Saithe
Boreal
Other seals
Blue whiting
North Sea
Extended bloom throughout the year
Atlantic mackerel
Sprat
Calanus helgolandicus
Sandeel
Sardine
Temperate
Anchovy
1
2
3
4
5
Food web level
26
Polar Ocean
Calanus hyperboreus
Arctic
Polar cod
Polar bear
0 oC
Capelin
Ringed seal
Barents Sea
Spring bloom ecosystem
Atlantic cod
Haddock
Calanus finmarchicus
Herring
Saithe
Boreal
Other seals
Blue whiting
North Sea
10 oC
Extended bloom throughout the year
Atlantic mackerel
Sprat
Calanus helgolandicus
Sandeel
Sardine
Temperate
Anchovy
1
2
3
4
5
Food web level
27
Calanus hyperboreus
Polar cod
Polar bear
0 oC
Polar Ocean
Capelin
Ringed seal
Atlantic cod
Arctic
Haddock
Calanus finmarchicus
Herring
Barents Sea
Saithe
Spring bloom ecosystem
Other seals
Blue whiting
10 oC
Boreal
Atlantic mackerel
Sprat
North Sea
Calanus helgolandicus
Sandeel
Sardine
Extended bloom throughout the year
Anchovy
Temperate
1
2
3
4
5
Food web level
28
Northwards migration of North Sea fish stocks
From Perry al 2005
29
Herring migrations - cold climate
30
Herring migrations warm climate
31
Cascade Climate-herring-capelin-cod-seal
32
(No Transcript)
33
Temperature in the Kola section
34
Biomass of fish in the Barents Sea
Gjøsæter al submitted
35
Prey consumption by cod
Gjøsæter al submitted
36
Seal invasions in 1987-88
Number of harp seals caught as by-catch
37
Biomass of fish in the Barents Sea
Gjøsæter al submitted
38
Direct climate induced mortality
39
Coral bleaching
  • Process where the coral expel symbiont algae,
    mainly as a consequence of high temperature
  • Can be reversible or not

Source wikipedia
40
Coral bleaching
  • Major bleaching events took place in 1998 and
    2002 at the Great Barrier Reef
  • -Some bleaching 42 and 54
  • -Strong bleaching 18
  • Occurs with short periods (3 days) of high
    temperature
  • Temperature induced bleaching represents a great
    threat to coral reefs and to marine biodiversity

Berkelmans al 2004
41
Episodic kills of sugar kelp due to high
temperature in 2006
42
  • Dead kelp forest has not been reestablished
  • Cascading community effects

43
Concluding remarks
  • Climate variability affects marine ecosystems in
    many different ways and on a range of different
    time scales
  • Most ecological processes and trophic levels are
    strongly affected by climate variability
  • The changes to come may well exceed the magnitude
    of observed changes in the 20th Century
  • How can we predict ecosystem responses to climate
    change?

44
Acknowledgements
  • I thank my colleagues Svein Sundby, Ken
    Drinkwater and Geir Ottersen for sharing their
    slides with me
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