transparent exopolymer particles (tep) under ocean acidification conditions

Transparent exopolymer particles (TEP) under ocean

acidification conditions

Presented by Daneil Newcomb at Friday Harbor Labs for the Ocean Acidification Apprenticeship

What is TEP?• A carbohydrate rich polysaccharide form of organic matter

produced by phytoplankton and some bacteria• Most likely produced as a response to cell stress (too little or too

much of a resource), not seen in actively growing cells • Increased TEP production is correlated with the maintenance

and senescence phases of phytoplankton growth• In previous ocean acidification studies:

– Bulk TEP has been correlated to chlorophyll-a, bacterial production, dissolved organic matter, and particulate organic matter• These correlations appear to be dependent on the presence of a phytoplankton bloom.

• A possible mechanism to increase export of carbon from surface waters to depth

(Wurl et al. 2011)

Phytoplankton exude polysaccharides

(Wurl et al. 2011)

Phytoplankton exude polysaccharides TEP is formed through

aggregation

(Wurl et al. 2011)

TEP is formed through aggregation

Phytoplankton exude polysaccharides

Aggregates are removed from system via export

marine snow

(Wurl et al. 2011)

Factors affecting TEP production and cycling

• Abiotic– Temperature– Turbulence– pH– Nutrients– Sedimentation

• Biotic– Phytoplankton and

bacterial production– Bacterial

remineralization– Viral lysis– Grazing by zoo- and

microzooplankton

Factors affecting TEP production and cycling

• Abiotic– Temperature– Turbulence– pH– Nutrients– Sedimentation

• Biotic– Phytoplankton and

bacterial production– Bacterial

remineralization– Viral lysis– Grazing by zoo- and

microzooplankton

Factors affecting TEP production and cycling

• Abiotic– Temperature– Turbulence– pH– Nutrients– Sedimentation

• Biotic– Phytoplankton and

bacterial production– Bacterial

remineralization– Viral lysis– Grazing by zoo- and

microzooplankton

Factors affecting TEP production and cycling

• Abiotic– Temperature– Turbulence– pH– Nutrients– Sedimentation

• Biotic– Phytoplankton and

bacterial production– Bacterial

remineralization– Viral lysis– Grazing by zoo- and

microzooplankton

Factors affecting TEP production and cycling

• Abiotic– Temperature– Turbulence– pH– Nutrients– Sedimentation

• Biotic– Phytoplankton and

bacterial production– Bacterial

remineralization– Viral lysis– Grazing by zoo- and

microzooplankton

Factors affecting TEP production and cycling

• Abiotic– Temperature– Turbulence– pH– Nutrients– Sedimentation

• Biotic– Phytoplankton and

bacterial production– Bacterial

remineralization– Viral lysis– Grazing by zoo- and

microzooplankton

Experimental Objectives

• Determine how chosen factors affect TEP production within the mesocosm experiment– To examine correlations between bulk TEP

production and phytoplankton, bacteria, and microzooplankton.

– To determine any significant difference in TEP production between in situ water conditions and FHL and the acidified ocean of the future.

Materials and Methods

• Nine mesocosms, three treatments

• Duplicate samples taken with an integrated sampler

• Samples filtered within two hours of collection*

* Except made for fossil hunting

Materials and Methods

• Analyzing TEP– Filters are stained with

Alcian Blue, soaked in 80% sulfuric acid, then analyzed using the colorimetric method.

• Absorbance is related to weights using a calibration curve

0 20 40 60 80 100 120 140 160 180 2000

0.05

0.1

0.15

0.2

0.25

f(x) = 0.00110775654408222 x + 0.0252643556860676R² = 0.920987852328837

f(x) = 0.00073285264969438 x + 0.0201494866773486R² = 0.574697241955753

f(x) = 0.000830184635169479 x + 0.0575097522888025R² = 0.682588050178922

Gum Xanthan (mg)

Abs

orpt

ion

(E78

7 - C

787)

TEP Mesocosm Time Series

0 2 4 6 8 10 12 14 16 18 200

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800

Time (Days)

Med

ian

TE

P (m

g G

um X

anth

an L

-1)

HIGHCONTROLDRIFTDOCK

TEP Mesocosm Time Series

0 2 4 6 8 10 12 14 16 18 200

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Time (Days)

Med

ian

TE

P (m

g G

um X

anth

an L

-1)

TEP Mesocosm Time Series

0 2 4 6 8 10 12 14 16 18 200

100

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Time (Days)

Med

ian

TE

P (m

g G

um X

anth

an L

-1)

Drift-High 0.848 p < 0.001Control-High 0.030 p = 0.902Drift-Control 0.879 p = 0.001

TEP Mesocosm Time Series

0 2 4 6 8 10 12 14 16 18 200

100

200

300

400

500

600

700

800

Time (Days)

Med

ian

TE

P (m

g G

um X

anth

an L

-1) Why are the high and control

different from the drift but not each other?

What makes the drift different?

0 2 4 6 8 10 12 14 16 18 200

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Time (Days)

Med

ian

TE

P (m

g G

um X

anth

an L

-1)

– How are the biotic factors, such as phytoplankton and bacteria, responding to the treatments?

– How do the abiotic factor differ between treatments?

– Which of these abiotic factors effect the physiological response of these organisms?

Biotic Factor: Phytoplankton

T0 T2 T4 T6 T8 T10

T12

T14

T16

T18

T20

0

5

10

15

20

25

30

35

40

Time (Days)Med

ian

Chl

orop

hyll

(mg

L-1

)

• Both Chlorophyll a and TEP show the control ending above the high, and increase over time.

• For both the drift treatment is significantly lower than the high treatment.

• Suggest phytoplankton are the main producers of TEP in the system.

0 2 4 6 8 10 12 14 16 18 200

100

200

300

400

500

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700

800

Time (Days)Med

ian

TE

P (m

g G

um X

anth

an L

-1)

r

Control 0.837

High 0.851

Drift 0.794

P < 0.001

Biotic Factor: Bacteria

• The control and high treatments are significantly higher than the drift treatment for both Bacterial Abundance and TEP.

0 2 4 6 8 10 12 14 16 18 200

100

200

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400

500

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800

Time (Days)Med

ian

TE

P (m

g G

um X

anth

an L

-1)

r

Control 0.882

High 0.754

Drift 0.388

P < 0.03

But why is the drift significantly lower?

• All treatments experienced the same temperature and turbulence conditions

• Initial nutrients were highly similar in all treatments

• The only factor which changed between treatments was the pCO2– Drift was allowed to change whereas High and

Control concentrations were maintained

But why is the drift significantly lower?

DRIFT

But why is the drift significantly lower?

But why is the drift significantly lower?

But why is the drift significantly lower?

Photosynthesis: 106CO2 + 16NO3 + PO4 ORGANIC MATTER + 138O2

But why is the drift significantly lower?

HIGH OR CONTROL

But why is the drift significantly lower?

But why is the drift significantly lower?

But why is the drift significantly lower?

Photosynthesis: 106CO2 + 16NO3 + PO4 ORGANIC MATTER + 138O2

But why is the drift significantly lower?

Photosynthesis: 106CO2 + 16NO3 + PO4 ORGANIC MATTER + 138O2

But why is the drift significantly lower?

Conclusions

• TEP production is affected by repetitive enrichment of waters with CO2

• The ways different factors influence TEP concentrations are complex. Further studies should be completed to ensure a better understand of how TEP functions under ocean acidification conditions.

Acknowledgements• OA apprentices, technicians, and advisors!

– Jim Murray, Evelyn Lessard, Mike Foy, Amanda Fay, Barbara Paul, Kelsey, Amy,

Natsuko, Jennifer, Kiely, Phil, Kelly, Andrew.

• Friday Harbor Labs

• Project Funding:– Educational Foundation of America and the National Science Fund for funding the project

– Alice M. Barger and Andrea Reister for funding my education the past two years

– Mary Gates Research Endowment Fund

• Steve Emerson and Kathy Krogsland for use of their lab equipment at the UW

• My family, partner, friends, and current roommate, Collin, for all of the great support

Works Cited

TEP Mesocosm Time Series

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 210.00

100.00

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800.00

Time (Days)

TE

P (m

g G

um X

anth

an L

-1)

Figure 1. Transparent exopolymer particle time series based on median values. Error bars are the median standard deviation Green data represent control mesocosms, red high mesocosms, blue drift mesocosms, and black the dock. Statistically significant differences were found between the drift and high treatment (0.848, p=0.001) and the drift and control treatment (0.879, p=0.000).

Why did TEP peak and then drop in all treatments?

What caused the sudden decreased in

TEP?0 2 4 6 8 10 12 14 16 18 20

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100.00

200.00

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400.00

500.00

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TE

P (m

g G

um X

anth

an

L-1

)

• Unlikely due to sampling error, present in all bags

• Both Temperature and pCO2 decrease in days prior to TEP decrease– Source says

temperature affects TEP production?

0 2 4 6 8 10 12 14 16 18 200

2

4

6

8

10

12

pCO

2

0 2 4 6 8 10 12 14 16 18 207.807.908.008.108.208.308.408.508.608.70

Time (days)

Tem

pera

ture

(°C

)

Biotic Factor: Phytoplankton

• TEP production often associated with maintenance and senescence phase of phytoplankton

• Population of Thalassiosira has growth rates constant and close to zero, suggesting this is a source of TEP

0 2 4 6 8 10 12 14 16 18 20

-20

-10

0

10

20

30

40

50

60

70

80

Time (days)

Gro

wth

Rat

e ( c

ells

days

^-1)

Experimental ResultsWere there any significant differences in TEP production between current water conditions and the predicted future conditions?

What biotic factors was TEP correlated to within our mesocosm?

Why was the drift significantly different from the high and the control, but the high and control were not different from each other?

Why were initial TEP concentrations about zero?

There was no significant difference between TEP production in the control treatment and the high treatment, but the drift treatment was different from the control and high.

TEP is significantly correlated to Chlorophyll a, Biogenic Silica, and Bacteria Abundance.

higher production is most likely associated with the repeatative enrichment of CO2 to the control and high treatments but not the drift

Turbulence during filling of the mesocosms

TEP Mesocosm Time Series

0 2 4 6 8 10 12 14 16 18 200

100

200

300

400

500

600

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800

Time (Days)

Med

ian

TE

P (m

g G

um X

anth

an L

-1) Why doesn’t TEP start at zero?

Why were initial concentrations of TEP above zero?

0 2 4 6 8 10 12 14 16 18 200

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900

Time (Days)

Med

ian

TE

P (m

g G

um X

anth

an L

-1)

• Previous mesocosm studies show increased turbulence results in increased TEP formation in water

• Highly turbulent conditions persistent during mesocosm filling

Biotic Factor: Phytoplankton

0 5 10 15 20 250

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300

400

500

600

700

800

f(x) = 22.4317339734945 x + 163.092827072178R² = 0.9136486377523

f(x) = 22.6234216283096 x + 152.069867794619R² = 0.742508647762496

f(x) = 21.1550559666342 x + 134.805217331239R² = 0.755077045524911

Median Chlorophyll a (mg L-1)

Med

ian

TE

P (m

g G

um X

anth

an L

-1)

2 3 4 5 6 7 8 9 10 11 12 13 140

100

200

300

400

500

600

700

800

f(x) = 61.230335973375 x − 13.771970581756R² = 0.905318141834004

f(x) = 43.3406556533693 x + 11.0071400800144R² = 0.836035604876101

f(x) = 47.1711280538585 x + 7.03606472309059R² = 0.700042222877542

Median Biogenic Silica (mmol L-1)

Med

ian

TE

P (m

g G

um X

anth

an L

-1)

p < 0.01p < 0.01

Biotic Factor: Bacteria• Two possible reasons for

this correlation:– Bacteria are producing

TEP• Currently no method for

discerning from a bulk value whether TEP is phytoplankton or bacteria derived

– Bacteria are remineralizing TEP• Further information

necessary 5.00E+05 1.00E+06 1.50E+06 2.00E+06 2.50E+06 3.00E+06 3.50E+060

100

200

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800

f(x) = 0.00017362065764817 x + 28.1966162127956R² = 0.725255960412949f(x) = 0.000306851572870818 x − 89.0666937085923

R² = 0.652842411733566

f(x) = 0.000132378335507074 x + 106.047935049809R² = 0.19061389248151

Median Bacterial Abundance (cell mL-1)

Med

ian

TE

P (m

g G

um X

anth

an L

-1)

p < 0.05