10ο Πανελλήνιο Συμπόσιο Ωκεανογραφίας & Αλιείας 7-11 Μαΐου 2012, Αθήνα Μεσόγειος Θάλασσα - Μαύρη Θάλασσα: Ένα ωκεανογραφικό «εργαστήριο»

1. BIOGEOCHEMISTRY OF THE ANAXIMENES SEAMOUNT
(E.MEDITERRANEAN): MOLECULAR EVIDENCE FOR A
“SEAMOUNT EFFECT” IN PARTICULATE ORGANIC MATTER
QUALITY?
Kostas Kiriakoulakis1,2 and George Wolff2
1Liverpool John Moores University, School of Natural Sciences and
Psychology, K.Kiriakoulakis@ljmu.ac.uk
2 University of Liverpool, School of Environmental Sciences,, wolff@liverpool.ac.uk

2. Global estimates of seamounts
33452 seamounts (4.7%) and 138412 knolls (16.3%) globally (Yesson et al. 2011)
seamounts
(Yesson et al. 2011)
knolls

3. Observations and theories
• Less than 300 have been studied in some degree
• “Hotspots” of marine life and diversity
– Large pelagic (fish stocks and zooplankton) and
benthic biomass (e.g. cold water corals etc.)
– ‘Island’ theory: Endemism – not much evidence
– ‘Oasis’ theory: productive in an otherwise
nutrient depleted ocean – open question

4. Complex physics
Upwelling ⇒ Closed circulation :Taylor columns
High primary production (e.g. White et al. 2007)
• Particle retention?
• Zooplankton migration blockage?

5. Effect on carbon cycling?
Mather 2009
36°N
CD171
2005
DOC
Downwelling of DOC above topography

6. Is there a “Seamount effect” in the ocean?
• Enhanced local primary/secondary productivity, trapping of
advected particles?
• Temporal variability?
• Primary production is seasonal
• Taylor columns are (thought to be) transient features
• Nutritional status of the ecosystems?
• Quality of organic matter
• Can be assessed by molecular studies (e.g. lipid biomarkers)

7. PUFAs: markers of POM quality
Lipids of known biological origin
Docosahexaenoic acid (DHA) - Dinoflagellates
Eicosapentaenoic acid (EPA) - Diatoms
PUFAs: Poly-Unsaturated Fatty Acids
• Essential fatty acids
• Very labile (1/2 life ~ < 1 week) and energy rich
• Markers of (high) OM quality

8. Quality of POM: link with zooplankton?
POC Data from Kiriakoulakis et al. 2009 PUFAs
µg L-1 North
top % lipids
25 South Far 60
20 50
40
15
30
10 20
5 10
0
0
Zooplankton biomass Spring 2003
day
Seine
seamount
night
Seine
seamount
Martin and Christiansen 2009

9. Anaximenes Seamount
• Within very oligotrophic, warm (even at depth) waters
• Part of Anaximander Mountains complex
• Elongated summit at ~700 m, eastern trough at ~1600 m
• Comparison with a reference site (Northern Rhodes Basin ~4300 m)
• Suspended particles (best sampled with SAPS)
In situ pump (SAPS)
Map is modified from ten Veen et al. (2004).

10. Sampling scheme
Between
Northern
Anaximenes
Rhodes Anaximenes
and
Basin
Anaxagoras
Control (1) Summit (3) Trough (2)
50m euphotic layer
150m below euphotic layer
Close to bottom (10-20mab)

11. Particulate Organic C and N
POC PN
µg L-1 water µg L-1 water
0 5 10 15 20 25 30 0 1 2 3 4 5
10 10
Sampling Depth (m)
Sampling Depth (m)
100 100
1000 1000
control summit 1 summit 2 control summit 1 summit 2
summit 3 trough 1 trouph 2 summit 3 trough 1 trouph 2
10000 10000
• Variable POC and PN concentrations close to surface
• Lowest POC at reference site (one sample only)
• Exponential decrease of POC with depth but not for PN
• Unclear interpretation for PN: relation to atmospheric N input
and P limitation in the region?

12. Particulate Lipids
Modified OM
markers
(zooplankton
+ faecal
pellets)
• Lowest [lipids] at reference site
• Fatty acids (and PUFAs) almost disappear below euphotic layer
• Simultaneously heterotrophic signal increases at depth
• Lower quality suspended POM at depth

13. Particulate Lipids
• Statistically significant compositional differences between
surface (50 m) and deeper waters
• Except surface sample at control site (Northern Rhodes Basin):
similar composition to deeper waters = not good OM quality
Seamount effect?

14. Seamount effect?
• Can’t say with only one sample (although 50 variables!) but intriguing
• Denda and Christiansen 2011 did not find ‘seamount effect’ in
zooplankton (same cruise)
• They suggest that larger-scale structures of cyclones and
anticyclones, dominate circulation in the area
AMC: Asia Minor Current;
MMJ: Mid-Mediterranean Jet
Denda and Christiansen 2011
The jury is still out

15. Thank you for listening!
• Many thanks to:
• The Crew and Master of RV Meteor 71/1
• CENSEAM for funding this research