3. Metabolic Theory of Ecology
• Temperature, body size affect individual
metabolic rate
• Individuals’ metabolism can be scaled up to
ecosystem level (Brown et al. 2004)
Climate change?
5. Previous Work
O’Connor et al. 2009
• Outdoor microcosms, altered
temperature and nutrients
• Measured effects on primary
and secondary consumers’
biomass
• Conclusion: temperature
alone can shift food web
structure IF sufficient
nutrients
Marañón et al. 2014
• Analyzed phytoplankton
biomass/C fixation data in
polar, temperate, tropical
regions
• Conclusion: resources >
temperature, which are not
independent
6. Seasonal Variation
• Summer temperature
increase equal to spring
• Will spring results hold
true in summer?
• Modify O’Connor
experiment:
– Season
– Fewer nutrients
– Duration
http://oconnorlab.weebly.com/temperature-
and-food-webs.html
7. Ambient +2 OC
+4 OC
Control Control
Control
+ Nutrients + Nutrients
+ Nutrients
20 μm N
1 μm P
8. Ambient +3 OC
+5 OC
Control Control
Control
+ Nutrients + Nutrients
+ Nutrients
40 μm N
2 μm P
11. Sampling Methods
Phytoplankton
• Fluorometric determination
of [Chl a]
• Sampled on days 1, 2 and 4
Macrozooplankton
• Filtered 2 L each in 63 μm
mesh
• Copepods, rotifers, and
cladocera
• 2 10-mL replicate subsamples
in Ward counting wheel,
averaged
12. Results – Lower Nutrient Addition
0.00
5.00
10.00
15.00
20.00
25.00
[Chla](ug/L)
Time (Days)
1 2 4
Figure 1 Average chlorophyll a concentrations in water samples on days 1, 2, and 4 with standard error, with nutrient
addition of 20 μm N and 1 μm P.
Relationship with nutrients is significant (p<0.05)
13. Results – Lower Nutrient Addition
Figure 3 Average macrozooplankton concentrations
in same-temperature water samples on day 4 with
standard error, with nutrient addition of 20 μm N
and 1 μm P.
Avg [Macro], Day 4
Figure 2 Average chlorophyll a concentrations in same-
temperature water samples on day 1 with standard
error, with nutrient addition of 20 μm N and 1 μm P.
Relationships with nutrients are significant (p<0.05)
0.00
50.00
100.00
150.00
200.00
250.00
Zooplankton/L
Temperature
Ambient +2 OC +4 OC
0.00
5.00
10.00
15.00
20.00
25.00
[Chla](ug/L)
Temperature
Avg [Chl a], Day 1
Ambient +2 OC +4 OC
14. Results – Higher Nutrient Addition
0.00
5.00
10.00
15.00
20.00
25.00
[Chla](ug/L)
Time (Days)
1 2 4
Figure 4 Average chlorophyll a concentrations in water samples on days 1, 2, and 4 with standard error, with nutrient
addition of 40 μm N and 2 μm P.
Relationship with nutrients is significant (p<0.05)
15. Results – Higher Nutrient Addition
Avg [Macro], Day 4
Figure 5 Average chlorophyll a concentrations in same-
temperature water samples on day 1 with standard
error, with nutrient addition of 40 μm N and 2 μm P.
Figure 6 Average macrozooplankton concentrations
in same-temperature water samples on day 4 with
standard error, with nutrient addition of 40 μm N
and 2 μm P.
Relationship with nutrients is significant
(p<0.05)
0.00
20.00
40.00
60.00
80.00
100.00
120.00
Zooplankton/L
Temperature
Ambient +2 OC +4 OC
0.00
5.00
10.00
15.00
20.00
25.00
[Chla](ug/L)
Temperature
Avg [Chl a], Day 1
Ambient +2 OC +4 OC
16. Strength of Nutrients’ Enhancement
with Temperature
0
2
4
6
8
10
12
14
ProportionofControl
Temperature
Chl a, Day 1
Lower
Higher
Ambient +2-3 OC +4-5 OC
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
ProportionofControl
Temperature
Macrozooplankton, Day 4
Lower
Higher
Ambient +2-3 OC +4-5 OC
17. Discussion
• Nutrients affect biomass
more than temperature does
• Sufficient resources needed
for temperature to affect
biomass
– Possibly only found at
unnatural nutrient levels
(sewage, runoff, etc.)
• Control switch from bottom-
up to top-down
• Warming did not affect
zooplankton biomass
– Optimal temperature?
– Methods?
Results that led to conclusion:
O’Connor et al.
**Nutrient-replete temperature strengthened consumer control
**Nutrient-limited constrained production at all temperatures
Maranon et al.
**More nutrients higher biomass turnover
**No (significant) relationship with temperature (with nutrients)
**Water from Bogue Sound
**20:1 nutrients: typical of stormwater
**Screen: light levels ~0.5m deep, avg irradiance that plankton receive
**Flow: ~0.5L/min to regulate water temp. in tubs (i.e. prevent overheating)
**4 days for zooplankton generation time
**Water from Bogue Sound
**20:1 nutrients: typical of stormwater
**Screen: light levels ~0.5m deep, avg irradiance that plankton receive
**Flow: ~0.5L/min to regulate water temp. in tubs (i.e. prevent overheating)
**4 days for zooplankton generation time
Diurnal cycles (temperatures were not constant)
*Axes
*Legend
*Trends (w/in each day)
*Control switched from bottom-up to top-down
Again, control switch from nut.s to zoops.
*Go back one slide to illustrate the division
*The enhancement is similar at summer ambient temps
*Lower, about same effect at all temps for chl/increases with temp in zoops
*Higher, increases and then decreases.
Biomass significantly increased with nutrients in almost all cases, but never significant trends with temperature
No effect even when we doubled highest natural levels. O’Connor added nutrients every other day
