Transcript 04. Projected changes to food webs for tuna latest

Projected changes to tuna food
webs in the tropical Pacific
Based on……..
Outline
• Nature of food webs for tuna
• Differences in food webs among provinces of
the tropical Pacific Ocean
• Effects of CC on provinces and their food webs
• Uncertainties
Photo: Marc Taquet
Tuna food web
Food webs are complex
Tuna food web
Oceanic provinces
Oceanic provinces
• Warm pool
Normal
El Niño
Oceanic provinces
• Equatorial divergence
Oceanic provinces
• Northern and southern gyres
Impact of climate change
present
future
Increased
stratification
• Decrease in nutrients reaching surface where
photosynthesis occurs
Impact of climate change
• Changes in
surface area
of provinces
Impact of climate change
• Effect on phytoplankton and zooplankton
Present
present
2035
2050
2100
Impact of climate change
Warm pool
Equatorial upwelling
W
Northern gyre
Southern gyre
A = area
P = phytoplankton
Impact of climate change
• Effect on micronekton
Midwater
Dee
micronekton
Deep
micronekton
Image: Valerie Allain, SPC
Shallow
micronekton
Uncertainties
• Need to establish long-term observations for
biological processes
06-13-2008 NZ-Aust start lat-40.4641 end lat -40.6744
0
-60
Photo: Peter Sharples
200
600
800
1000
Image: Rudy Kloser, CSIRO
1200
150
152
154
156
158
160
Longitude d.dm
162
164
micronekton
zooplankton
phytoplankton predators
Photo: Valerie Allain
-70
-75
Image: Valerie Allain, SPC
Depth m
400
-65
166
168
170
-80
Conclusions
•
•
•
•
Food webs are complex, based on phytoplankton
5 provinces have different food webs
Production expected to decrease
Long-term monitoring needed to reduce
uncertainty