The document discusses a study on the priming effect in lakes and its impact on carbon cycling. The priming effect occurs when easily decomposable labile carbon causes an increase in the breakdown of recalcitrant carbon. The study aimed to test if this priming effect exists in aquatic environments like lakes. It found that higher amounts of labile carbon (glucose) led to higher rates of recalcitrant carbon breakdown and CO2 emissions, supporting the hypothesis. Certain lakes showed a statistically significant priming effect while others did not. The results provide evidence that the priming effect occurs in lakes and has implications for understanding lake and global carbon cycling.

1. The Priming Effect:
Discovering the future
of lake carbon cycling
Cassie Craig
Mentor: Jake Zwart

2. Lakes
 Lakes have recently been recognized as important
components of the global carbon cycle.
 Leaves can fall into lakes and dissolve into the water
column that contain carbon and can alter the internal
carbon cycle.
 CO2 emission from inland lakes is very similar to the
CO2 uptake in the ocean and therefore has the same
effect on the atmosphere.

3. What is the priming effect?
 When labile organic matter (LOM) such as glucose,
cellouse, or root exudates are in the soil…
 It changes the mineralization rate of recalcitrant organic
matter (ROM) present…
 Therefore altering the amount of CO2 released in the
atmosphere.
 Priming effect can enhance the recalcitrant organic
matter mineralization rate anywhere from 10% to
500%.

4. Priming Effect
 This all meaning that labile carbon (carbon that is easily broken down
from phytoplankton in aquatic systems) increases the rate that
bacteria breaks down recalcitrant carbon (carbon that is hard to break
down and comes from terrestrial sources such as trees.

5. Positive or Negative
 It is found that the priming effect could have negative
and positive effects.
 A negative effect is…
 the labile organic matter decreasing recalcitrant organic
matter mineralization rate
 A positive effect is...
 labile organic matter (LOM) can increase recalcitrant
organic matter (ROM) mineralization rate.
(Guenet et al. 2010).

6. Importance
 Significant findings for understanding current and
predicting future lake carbon cycling.
 Also changing our view of how lakes fit into the global
carbon cycle.
 There has not been much research on the importance
and mechanisms of the priming effect.
 Some scientists do not believe it even exists in aquatic
ecosystems.

7. Hypothesis
 That higher amount of labile carbon (glucose), the
higher the rate will be of recalcitrant carbon being
broke down, increasing the amount of CO2 into the
atmosphere.

8. Methods
 Lake water was collected from five lakes on UNDERC
property in the Upper Peninsula Michigan.
 1. East Long
 2. West Long
 3. Hummingbird
 4. Crampton
 5. Morris

9. Methods Cont..
 The lake water was filtered through 0.2 µm filters to remove
any bacteria from the water.
 Leaving dissolved organic carbon behind with 100 mL of
lake water used in each incubation bottle.

10. Methods Cont..
 Glucose was used as the source of labile organic
matter.
 Four treatment groups per lake: 0.25, 1.0, 2.25, and 4.0
mg of glucose
 One control treatment for each lake. (no glucose)
 One glucose control treatment per lake. (no lake water)
 Three replicates for each treatment.

11. Methods Cont..
 All treatments had 1 mL of unfiltered lake water added
as the source of natural lake bacteria.
 Headspace gas from each sample was extracted five
times during the incubation after every 5 days and
analyzed on a gas chromatograph to see how much
CH4 and CO2 was released.
 Another round of glucose was added in the second
week to stimulate a pulse of fresh labile carbon.
 This reflects what would happen in a lake with a
phytoplankton bloom.

12. Results
0
1000
2000
3000
4000
5000
6000
1 2 3 4 5
Respiration
Week
MO Control Cumulative
MO 0.25 Cumulative
MO 1.0 Cumulative
MO 2.25 Cumulative
MO 4.0 Cumulative

13. ANOVA Test on Slopes
 Morris overall had a p-value of 0.0246
 Within the treatments, only the control and the 4.0 mg
of glucose were statically different in their slopes of
carbon respired.
 p-value of 0.0194313

14. ANOVA Test on Respiration
 Morris overall had a p-value significant at 0.01617.
 The respiration rate that was statically different was
between the treatment groups of the control and 4.0
mg.

15. 0
500
1000
1500
2000
2500
3000
1 2 3 4 5
Respiration
Week
EL Control Cumulative
EL 0.25 Cumulative
EL 1.0 Cumulative
EL 2.25 Cumulative
EL 4.0 Cumulative

16. ANOVA test on Slopes
 East Long slopes overall showed were significant at a
p-value of 0.00555.
 The treatments that were statically different from one
another was 2.25 and 0.25 with a p-value of 0.0448610

17. ANOVA Test on Respiration
 East Long overall was significant at 0.125
 The respiration rate that was statically different was
between the treatment groups was the control and 1.0
mg.

18. 0
500
1000
1500
2000
2500
3000
3500
4000
4500
1 2 3 4 5
Respiration
Week
WL Control Cumulative
WL 0.25 Cumulative
WL 1.0 Cumulative
WL 2.25 Cumulative
WL 4.0 Cumulative

19. ANOVA Test on Slopes
 West Long overall had a significant p value at 0.00509.
 Within in West Long, the treatment slopes that were
statistically different from each other were…
 4.0 mg and 0.25 at a p-value of 0.0588166.
 The control and 2.25 with a p-value at 0.02434633.
 The control and 4.0 mg at a p-value of 0.0037442.

20. ANOVA Test on Respiration
 West Long was significant overall at 0.00138.
 The respiration rate that was statically significant was
between…
 The control and 0.25 mg at a p-value of 0.0035390
 The control and 4.0 mg at a p-value 0.0011113.

21. 0
500
1000
1500
2000
2500
3000
3500
4000
1 2 3 4 5
Respiration
Week
HB Control Cumulative
HB 0.25 Cumulative
HB 1.0 Cumulative
HB 2.25 Cumulative
HB 4.0 Cumulative

22. ANOVA Test on Slopes
 Overall the slopes of Hummingbird were not statistically
significant.
 p-value of 0.162
 None of the treatment groups in that lake were
statistically different from one another.

23. ANOVA Test on Respiration
 Hummingbird respiration values overall were not
statically significant.
 p-value of 0.262.
 The treatment groups compared to one another
showed no significance as well.

24. 0
200
400
600
800
1000
1200
1400
1600
1800
2000
1 2 3 4 5
Respiration
Time
CR Control Cumulative
CR 0.25 Cumulative
CR 1.0 Cumulative
CR 2.25 Cumulative
CR 4.0 Cumulative

25. ANOVA Test on Slopes
 Overall the slopes of Crampton were not statistically
significant
 p-value of 0.134.
 None one of the treatment groups in that lake were
statistically different from one another.

26. ANOVA Test on Respiration
 Cramptons’ respiration values overall were not
statically significant.
 p-value of and 0.147.
 The treatment groups compared to one another
showed no significance as well.

27. Conclusion
 The results of this experiment supported the hypothesis
that stated that the higher amount of labile carbon
(glucose), the higher the rate of recalcitrant carbon
being broke down there would be, increasing the
amount of CO2 into the atmosphere.
 The priming effect does exist in aquatic environments.
 Further tested whether the contents of the lakes had an
effect on how much CO2 was released such as the
nutrients present.

28. References
 Attermeyer, K., Hornick, T., Kayler, Z. E., Bahr, A., Zwirnmann, E.,
Grossart, H.-P., and Premke, K. 2014. Enhanced bacterial
decomposition with increasing addition of autochthonous to
allochthonous carbon without any effect on bacterial community
composition, Biogeosciences, 11, 1479-1489, doi:10.5194/bg-11-
1479-2014.
 Guenet B, Michael Danger, Luc Abbadie, and Gérard Lacroix
2010. Priming effect: bridging the gap between terrestrial and
aquatic ecology. Ecology 91:2850–2861. doi.org/10.1890/09-
1968.1
 Tranviket Lars J. et.al. 2009. Lakes and reservoirs as regulators of
carbon cycling and climate. Limnology and Oceanography, 54 part
2, 2298-2314. 10.4319/lo.2009.54.6_part_2.2298

29. Questions?