keith brander imber-godae 12 june 2007 variability and shifts in marine ecosytems keith brander...

Keith Brander IMBER-GODAE 12 June 2007

Variability and shifts in marine ecosytems

Keith BranderICES/GLOBEC Coordinator


People are interested in climate change and in changes in

marine ecosystems.


Rapid spread of tropical species along the continental slope

Is the rate of biological shift commensurate with the rate of ocean climate shift?

Should we say:“the ecosystem is changing”

or“the ecosystem is moving”?

What about the conservation of ecosystem functions? Is that allowed to move too?

Is fish production affected?

Should we be managing differently?


1 Biogeographic shifts of ~ 50km y-1 in NE Atlantic

2 Increases in number of warm water species

Attributed to (i) advection and (ii) change in local properties i.e transport of both biota and heat, salt etc.

(Issue of Eulerian vs Lagrangian observation)


Southern shelf edge species Psuedo-oceanic temperate species

Changes in range of copepod species - Beaugrand et al. 2002 Science Based on 176,778 CPR samples.

Euchaeta gracilis, Euchaeta hebes, Ctenocalanus vanus, Calanoides carinatus

Rhincalanus nasutus, Eucalanus crassus, Centropages typicus, Candacia armata, C. helgolandicus

Other taxa have also shifted at similar rates


Northward spread of cod at West Greenland from 1917-1939

0.5

1

1.5

2

2.5

3

1910 1915 1920 1925 1930 1935 1940

Sea

Surf

ace

Tem

per

ature

Other areas have shown similar rates


The cod stock at Greenland is recovering as

conditions there get warmer.

A positive effect which poses some management

questions:• How should it be managed?

• What about the shrimp fishery?

• What about sharing with Iceland?

• Could Greenland help recovery of Canadian stocks?

• IPCC predicts slow warming at Greenland


Cod recruitment at Greenland

Years 1971-97From ICES CM 2001/ACFM:20

0

50

100

150

200

250

300

0 2 4 6 8 10 12

0 group abundance Dohrn Bank and E Greenland

Gre

enla

nd R

84

73

85


Decline of the Baltic cod stock will this continue?

• Less inflow of Atlantic water

• Falling salinity


Recovery of Gulf of St Lawrence cod stock – has begun now the environment has improved

• 2004 year class is biggest since 1980

• Survival is higher

• Seal predation is lower

Recent rise in temperature


Mois - Month

Pro

fond

eur

–D

epth

(m)

Figure 2: Monthly temperatures by depth for the Northern Gulf with recaptures of tagged cod (yellow box-plots).


Regime shifts in N Pacific – are the (physical and biological) processes non-linear?

Note use of regional synoptic indices


Data sources, current trends, attribution of causes

Sources•Time series of commercial fish species for many areas

•Time series (near-surface mesozooplankton) from CPR for some areas

Trends•Northward distribution shifts (fish, plankton) in NE Atlantic

•Decline in abundance of many fish species

Attribution•Physical forcing is both local and via large scale advection

•Biological forcing could be top-down or bottom-up

•Very strong direct human impact through fishing


Data and analyses needed

• Improved availability and presentation of trends and changes in ocean properties (at many scales)

• Climate scenarios which include ocean properties (temperature, salinity, advection, upwelling, stratification)

• Compilation and interpretation of comparative regional data to test the attribution of change


Gaps

• Few time series of marine biota are suitable for detecting and attributing effects of climate change (whether in distribution, abundance or phenology)

• (mention Perkinsus – oyster parasite, as a good example which combines observation and modelling to determine causes)

• The geographic and biotic coverage of this presentation is itself limited


Sensitivity/vulnerability

• Some marine ecosystems are topographically bounded, but others (e.g. planktonic systems) are not, therefore they can shift distributions quickly.

• Shallow areas are more vulnerable to changes in temperature and salinity (the communities there are also more adapted to extremes)

• Coastal areas are vulnerable (and relatively well studied), but are usually impacted by many anthropogenic factors other than climate change

keith brander imber-godae 12 june 2007 variability and shifts in marine ecosytems keith brander...

Documents