The Priming Effect: Discovering the future of lake

carbon cycling Cassie Craig

Mentor: Jake Zwart

LakesLakes 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.

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%.

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.

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).

ImportanceSignificant 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.

HypothesisThat 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.

MethodsLake water was collected from five lakes on

UNDERC property in the Upper Peninsula Michigan.

1. East Long2. West Long3. Hummingbird4. Crampton5. Morris

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.

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.

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.

Results

1 2 3 4 50

1000

2000

3000

4000

5000

6000

MO Control Cumulative MO 0.25 Cumulative MO 1.0 Cumulative MO 2.25 Cumulative MO 4.0 Cumulative

Week

Res

piration

ANOVA Test on SlopesMorris 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

ANOVA Test on RespirationMorris 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.

1 2 3 4 50

500

1000

1500

2000

2500

3000

EL Control CumulativeEL 0.25 CumulativeEL 1.0 CumulativeEL 2.25 CumulativeEL 4.0 Cumulative

Week

Resp

iratio

n

ANOVA test on SlopesEast 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

ANOVA Test on RespirationEast 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.

1 2 3 4 50

500

1000

1500

2000

2500

3000

3500

4000

4500

WL Control CumulativeWL 0.25 CumulativeWL 1.0 CumulativeWL 2.25 CumulativeWL 4.0 Cumulative

Week

Resp

iratio

n

ANOVA Test on SlopesWest 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.

ANOVA Test on RespirationWest 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

0.0035390The control and 4.0 mg at a p-value 0.0011113.

1 2 3 4 50

500

1000

1500

2000

2500

3000

3500

4000

HB Control CumulativeHB 0.25 CumulativeHB 1.0 CumulativeHB 2.25 CumulativeHB 4.0 Cumulative

Week

Resp

iratio

n

ANOVA Test on SlopesOverall 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.

ANOVA Test on RespirationHummingbird respiration values overall were not

statically significant.p-value of 0.262.

The treatment groups compared to one another showed no significance as well.

1 2 3 4 50

200

400

600

800

1000

1200

1400

1600

1800

2000

CR Control CumulativeCR 0.25 CumulativeCR 1.0 CumulativeCR 2.25 CumulativeCR 4.0 Cumulative

Time

Resp

iratio

n

ANOVA Test on SlopesOverall the slopes of Crampton were not

statistically significantp-value of 0.134.

None one of the treatment groups in that lake were statistically different from one another.

ANOVA Test on RespirationCramptons’ 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.

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.

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

Questions?