Biogeochemistry of the Anaximenes Seamount (E. Mediterranean): molecular evidence for a "Seamount effect" in particulate organic matter quality? Kiriakoulakis, K.
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,, email@example.com
Global estimates of seamounts33452 seamounts (4.7%) and 138412 knolls (16.3%) globally (Yesson et al. 2011) seamounts (Yesson et al. 2011) knolls
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
Complex physicsUpwelling ⇒ Closed circulation :Taylor columnsHigh primary production (e.g. White et al. 2007) • Particle retention? • Zooplankton migration blockage?
Effect on carbon cycling? Mather 200936°NCD1712005DOC Downwelling of DOC above topography
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)
PUFAs: markers of POM quality Lipids of known biological origin Docosahexaenoic acid (DHA) - Dinoflagellates Eicosapentaenoic acid (EPA) - DiatomsPUFAs: Poly-Unsaturated Fatty Acids • Essential fatty acids • Very labile (1/2 life ~ < 1 week) and energy rich• Markers of (high) OM quality
Quality of POM: link with zooplankton?POC Data from Kiriakoulakis et al. 2009 PUFAsµg 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
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).
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 10Sampling 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?
Particulate LipidsModified OMmarkers(zooplankton+ faecalpellets) • 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
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?
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
Thank you for listening!• Many thanks to:• The Crew and Master of RV Meteor 71/1• CENSEAM for funding this research