C cycling at two Mid-Cayman vent sites: a lipid compound-specific isotope study of Rimicaris hybisae

Kathrin Streit

I am a terrestrial ecologist.What am I doing working in on Oceanography and Planetary Sciences?

Kathrin Streit 2

IntroductionMethodsResults Conclusions

PhD: C cycling in an alpine treelineecosystem in a warmer world

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IntroductionMethodsResults Conclusions

III.

II.

I.

Why is a terrestrial ecologist working in ?

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IntroductionMethodsResults Conclusions

Herndl 2013 Nature

Why is a terrestrial ecologist working in JPL? ?

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IntroductionMethodsResults Conclusions

Bennett et al., submitted

Producers

Primary consumers

Secondary consumers

Tertiary consumers

Why is a terrestrial ecologist working in JPL ?

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IntroductionMethodsResults Conclusions

Chyba and Hand, 2001, Science

C cycling at two Mid-Cayman vent sites: a lipid compound-specific isotope study of Rimicaris hybisae

Objective 1: “To what extent does Rimicarishybisae rely on the photosynthetic C source in diet relative to the chemosynthetic C source?”

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IntroductionMethodsResults Conclusions

C cycling at two Mid-Cayman vent sites: a lipidcompound-specific isotope study of Rimicaris hybisae

1/15/2014 Kathrin Streit 8Connelly et al. 2012 Nature Communications

Piccard, 4987 m, 398°C, basalt hosted, metal, sulfide and hydrogen rich

Von Damm, 2300 m, 232°C, ultramafic hosted, sulfide, hydrogen and methane rich

IntroductionMethodsResults Conclusions

Piccard, 4987 m, 398°C, basalt hosted, metal, sulfide and hydrogen rich

Objective 2: “How does vent chemistry and vent depth affect R. hybisae nutrition?”

Von Damm, 2300 m, 232°C, ultramafichosted, sulfide, hydrogen and methanerich

Lipids– main functions

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Phosphate group

GlycerolStorage

Membrane structure and function

C cycling at two Mid-Cayman vent sites: a lipidcompound-specific isotope study of Rimicaris hybisae

IntroductionMethodsResults Conclusions

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C20:4n6

C20:5n3

C22:6n3

Considered essential for cell membrane structure and function Fatty acids of photosynthetic origin

IntroductionMethodsResults Conclusions

C cycling at two Mid-Cayman vent sites: a lipidcompound-specific isotope study of Rimicaris hybisae

Polyunsaturated long chain fatty acids of n3 and n6 family

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Fatty acids of bacterial origin

IntroductionMethodsResults Conclusions

C cycling at two Mid-Cayman vent sites: a lipidcompound-specific isotope study of Rimicaris hybisae

n7 family n4 familyC16:1n7 C16:2n4

desaturation

C18:1n7elongation elongation

C18:2n4

C cycling at two Mid-Cayman vent sites: a lipidcompound-specific isotope study of Rimicaris hybisae

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δ- notation

Isotopic ratio:

Isotopic fractionation:

1000*)1(tan

13−=

dards

sample

R

RCδ

standard

C

CR

12

13

=

1000*)1(13 −=∆product

substrate

R

RC

IntroductionMethodsResults Conclusions

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Sulfur and hydrogen oxidizing autotrophs Reductive tricarboxylic acid cycle (rTCA) Between -13 to -2‰

Berg, 2010

~-18 to -22‰ particulate organic matter of photosynthetic origin Goericke and Frey, 1994

IntroductionMethodsResults Conclusions

Sulfur and hydrogen oxidizing autotrophs Reductive pentose phosphate cycle (CBB) Between -30 and -20‰

C cycling at two Mid-Cayman vent sites: a lipidcompound-specific isotope study of Rimicaris hybisae

Methanotrophs Reductive acetyl CoA pathway (WL)Below -30‰

C cycling at two Mid-Cayman vent sites: a lipid compound-specific isotope study of Rimicaris hybisae

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Carapace

Zbinden et al. 2004

Ponsard et al. 2013

Ectosymbiotic chemosynthetic bacteria build a biofilm on gill cover and in the mouth: organic matter is taken up by host by permeation across the gill chamber integument

IntroductionMethodsResults Conclusions

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IntroductionMethodsResults Conclusions

C cycling at two Mid-Cayman vent sites: a lipid compound-specific isotope study of Rimicaris hybisae

Densely vs. sparsely distributed R. hybisaeDixon et al. 1998

Cobari et al. 2008

Objective 3: “How is distribution (dense vs. sparse) affecting R. hybisae nutrition?”

Free FAsaponification

derivatizationFAME

Fatty acid (FA) analysis

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PLFATG TGPLFAextraction

Abdominal tissue

R

IntroductionMethodsResults Conclusions

Adult R. hybisaeGill cover membraneGill cover

Fatty acid (FA) analysis

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IntroductionMethodsResults Conclusions

GC-IRMSGC-MS

Proportion of single FA as fraction of total FA - Nonmetric multi dimensional scaling analysis

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All tissues, all sites (n=15)

IntroductionMethodsResults Conclusions

Stress = 8.2%

• FA composition of tail tissue differs from gill cover membrane tissue

• FA composition of sparse shrimp differ from dense shrimp

Proportion of single FA as fraction of total FA

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IntroductionMethodsResults Conclusions

Contain little photosynthetic FA: total 5%

• Sparse shrimp contain less n4 and more photosynthetic FA

• No difference in proportion of photosynthetic FA between Piccard and Von Damm

δ13C values of single FA - Nonmetric multi dimensional scaling analysis

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All tissues, all sites (n=15)

IntroductionMethodsResults Conclusions

Stress = 5.8%

Clear separation in FA δ13C values between shrimp from Piccard and Von Damm vent site

δ13C values of fatty acids - differences between tissues and sites

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Only Von Damm dense

IntroductionMethodsResults Conclusions• Photosynthetic FA are lower in δ13C values• Tissues are similar in FA δ13C values

• Shrimp from Piccard vent site have FA higher in δ13C • Photosynthetic FA are excluded from this rule

Conclusion• Particulate organic matter of photosynthetic origin plays a minor

role in the diet of adult R. hybisae• Vent fluid chemistry influences bacterial community composition

and, therefore, pathways of C fixation used, while vent depth has no influence on amount of particulate organic matter sinking to the ground

• Sparse shrimp show a reduced contribution of C fixed by chemosynthetic symbionts. They use an alternative food source, which is partly photosynthetic.

• While chemosynthetically driven ecosystems are possible on Europa, R. hybisae like organisms could not be part of it (photosynthetic FA dependency). Primary consumers would have a different membrane structure not relying on photosynthetic input.

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IntroductionMethodsResultsConclusions

Outlook: Amino acids δ15N • ∆15N -> strong fractionation between trophic

levels• Amino acids represent most N of organism

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IntroductionMethodsResultsConclusions

TCAFantle et al. 1999

Diet

Essential

Non-Essential

Small ∆15N

Large ∆15N