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Emma Versteegh, Cindy Van Dover, Max Coleman NASA Jet Propulsion Laboratory, California Ins9tute of Technology
Copyright 2014 California Ins9tute of Technology. U.S. Government sponsorship acknowledged.
Life without sunlight
NASA/JPL/Ted Stryk
NASA/JPL
Photosynthesis: 6 CO2 + 12 H2O + sunlight → C6H12O6 + 6 H2O + 6 O2 Chemosynthesis: 6 CO2 + 6 H2O + 3 O2 + 3 H2S → C6H12O6 + 3 H2SO4
Would work on Europa too Quan9fy biomass expected? → look on Earth How much new biomass/9me? → food web
• Piccard vent field, world’s deepest: 4985m, basal9c
• Von Damm vent field: 2309m, ultramafic
Mid-‐Cayman Rise (MCR)
Jack Cook, WHOI NOAA Okeanos Explorer
Von Damm Vent Field
A shrimp world
Rimicaris hybisae
• Abundant at MCR • Spa9al variability in popula9on structure: dense ~ sparse
• Bac9vorous (un9l now) • Unexplained varia9ons in δ13C values
• δ13C not a good food web tracer?
Previous work
Bennee et al. (under review)
~10‰
What is the structure of the food web around MCR vent fields? Who eats whom (or what)?
Ques9ons 1. What causes the wide range
of δ13C values? 2. Are δ13C values related to
dense and sparse assemblages?
3. Do dense and sparse have different diets?
4. Do dense and sparse differ in δ15N and δ34S values?
5. How do δ15N and δ34S relate to diet?
Hypotheses
1. Dense and sparse Rimicaris have different diets
2. They are metabolically different
You are what you eat:
• +1 (δ13C ‰ vs. VPDB) • +3 (δ15N ‰ vs. AIR) • +? (δ34S ‰ vs. VCDT)
Methods E/V Nau9lus Expedi9on August 26, 2013 • Von Damm vent field • Remotely operated vehicle
Hercules • Dense and sparse, separated by
~1m • R. hybisae dissected, frozen on
board
In lab: • Freeze dried & homogenized • Stable isotope analyses: Costech
ECS 4010 & MAT 253 IRMS www.nau9luslive.org
Shrimp tail δ13C, δ15N & δ34S values
® Rimicaris hybisae tail (sparse)¯ R. hybisae tail (dense)� Lebbeus virentova wholep R. hybisae gut (crustacea)p R. hybisae gut (bacteria & crustacea)r R. hybisae gut (bacteria)£ R. hybisae gill covers (dense)
~3‰
<<3‰ ~6‰
~7‰
~15‰
Gut contents
• Dense: – bacteria
• Sparse: – crustacea (5 out of 13) – bacteria and crustacea (3 out of 13)
– bacteria only (5 out of 13)
® R. hybisae (crustacea)® R. hybisae (bacteria & crustacea)¯ R. hybisae (bacteria)
Tails & gut contents
® R. hybisae (crustacea)® R. hybisae (bacteria & crustacea)¯ R. hybisae (bacteria)
Results
• Sparse / crustacea-‐ea9ng shrimp: – Lower δ13C values (-‐2.4 ‰) – Elevated δ15N values (+0.3 ‰) – Lower δ34S values (-‐2.2 ‰)
• Lebbeus virentova δ13C and δ15N overlap with R. hybisae, differ from sparse in δ34S only
• Exoskeleton of R. hybisae same δ15N and δ34S as guts, but different δ13C
Results
• Tail δ13C and δ34S reflect gut content, no enrichment
• Tail δ15N enriched by +3.4‰ vs. gut • Bacteria in gut: higher tail δ13C and δ34S • Crustacea in gut: lower tail δ34S
Conclusions
• Dense and sparse R. hybisae use different food sources.
• Dense Rimicaris eat / absorb episymbio9c bacteria only.
• Sparse shrimp eat bacteria, crustacea, and possibly gastropods.
• They might have different episymbio9c bacterial communi9es.
• Diet switch possibly related to mol9ng cycle.
Implica9ons / future work
• DNA analysis on dense / sparse R. hybisae • Gut contents vs. stage in mol9ng cycle
• Analogous dense and sparse assemblages in Rimicaris exoculata and Rimicaris kairei – do they differ in diet?
Thank you! Ques9ons?
Acknowledgements • NASA ASTEP Oases for life • E/V Nau9lus &
ROV Hercules team • Kenneth Williford &
Michael Tuite (JPL) • JPL ISOLAB team:
Bethany Theiling, Kathrin Streit, Emma Gar