This study examined the effects of warming and nutrient enrichment on plankton production in coastal waters. Outdoor microcosms were used to test the effects of increased temperature and nutrients on phytoplankton and zooplankton biomass over 4 days. Results showed that nutrient addition had a stronger effect on biomass than temperature alone. However, sufficient nutrient levels were needed for temperature to impact biomass. Higher temperatures and nutrients together had the greatest effect, but warming did not significantly affect zooplankton biomass. The findings suggest that resource availability, not just temperature, controls plankton productivity in coastal ecosystems.

1. Effects of warming and nutrient
enrichment on trophic production in
coastal waters
Laura Dobroski
July 24, 2014

2. Aquatic Trophic Levels
http://www.teachoceanscience.net/teaching_resources/education_modules/aquat
ic_food_webs/learn/

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?

4. Trophic Production with Warming
O’Connor et al. 2009

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

10. Temperature
0
5
10
15
20
25
30
35
40
6/2/2014 0:006/3/2014 0:006/4/2014 0:006/5/2014 0:006/6/2014 0:006/7/2014 0:00
Temp(C)
Time
Avg same-temp tank temps
Ambiant
plus 3
plus 5

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?

18. Optimal Temperature
Experiment Ambient Upper
Temperature
O’Connor 20 OC 26 OC
Single
Nutrient
27 OC 32 OC
Double
Nutrient
30 OC 34 OC
Heinle 1969

19. Improvements
• Measurement (biomass vs. counting)
• Productivity

20. Acknowledgements
Suzanne Thompson
Scott Ensign
Nathan Hall
Mike Piehler

21. Questions?
http://blog.nature.org/science/2013/02/01/oceans-and-climate-change-protecting-the-invisible/