Transcript 04 Vulnerability of tuna food webs

Vulnerability of open ocean food
webs in the tropical Pacific to
climate change
Presented by
Valerie Allain
Authors
This presentation is based on Chapter 4 ‘Vulnerability of
open ocean food webs in the tropical Pacific to climate
change’ in the book Vulnerability of Tropical Pacific
Fisheries and Aquaculture to Climate Change, edited by JD
Bell, JE Johnson and AJ Hobday and published by SPC in
2011.
The authors of Chapter 4 are: Robert Le Borgne, Valerie
Allain, Shane P Griffiths, Richard J Matear, A David
McKinnon, Anthony J Richardson and Jock Young
Photo: Marc Taquet, FADIO, IRD/IFREMER
Photo: Photoshot/Superstock
The tuna food web
Food webs are complex
The tuna food web
Nutrients
Light
Phytoplankton at the base of the food web require
light and nutrients to develop
Photo: Gustaaf Hallegraeff
Phytoplankton
The five oceanic provinces
The five oceanic provinces
• Warm Pool
Normal
El Niño
The five oceanic provinces
• North and South Gyres (Case 3) and equatorial
divergence (Case 4)
Impact of climate change
• Surface
area of the
provinces
Present day
The impact of climate change
• Surface
area of the
provinces
2035
↘ rich equatorial divergence
↗ poorer gyres and warm pool
Impact of climate change
• Surface
area of the
provinces
2050
↘ rich equatorial divergence
↗ poorer gyres and warm pool
Impact of climate change
• Surface
area of the
provinces
2100
↘ rich equatorial divergence
↗ poorer gyres and warm pool
Impact of climate change
present
future
• GYRES
Exchanges
between deep
rich water and
surface poorer
waters
↘ of nutrients reaching the surface where
photosynthesis can occur
Impact of climate change
present
future
• Equatorial
upwelling
Exchanges
between deep
rich water and
surface poorer
waters
↘ nutrients reaching the surface where
photosynthesis can occur
Impact of climate change
• Effect on phytoplankton and zooplankton
present
2050
2035
Today
Impact of climate change
• Effect on phytoplankton and zooplankton
present
2050
2035
2035
↘ of phytoplankton and zooplankton
Impact of climate change
• Effect on phytoplankton and zooplankton
present
2050
2035
2050
↘ of phytoplankton and zooplankton
Impact of climate change
• Effect on phytoplankton and zooplankton
present
2050
2035
2100
↘ of phytoplankton and zooplankton
Impact of climate change
Image: Valerie Allain, SPC
• Effect on micronekton
↘ micronekton
Uncertainties and adaptation
• Need to establish long-term observations for
biological processes
Phytoplankton
Image: Valerie Allain, SPC
Uncertainties and adaptation
• Need to establish long-term observations for
biological processes
Zooplankton
Uncertainties and adaptation
• Need to establish long-term observations for
biological processes
06-13-2008 NZ-Aust start lat-40.4641 end lat -40.6744
0
-60
200
-65
600
-70
800
-75
1000
Image: Rudy Kloser, CSIRO
1200
150
152
154
156
Micronekton
158
160
Longitude d.dm
162
164
Image: Valerie Allain, SPC
Depth m
400
Image: Valerie Allain, SPC
166
168
170
-80
Uncertainties and adaptation
• Need to establish long-term observations for
biological processes
Predators
Photo: Peter Sharples
Uncertainties and adaptation
• Global reduction of greenhouse gas emissions
• Appropriate tuna fisheries management
measures can help maintain healthy food
webs and fisheries giving better chances to
food webs and tuna to adapt to climate
change
Conclusions
•
•
•
•
•
Food webs are complex, based on phytoplankton
5 provinces and food webs in the Pacific
Reduction of the production
Long-term monitoring is needed
Reducing greenhouse gas emissions and
managing tuna fisheries