The Role of Salps for Carbon Export The Role of Salps for Carbon Export
in the Southern Ocean in the Southern Ocean
L. von Harbou
*1, Ilka Peeken
1,2, E. A. Pakhomov
3, C. D. Dubischar
1, U. Bathmann
11Alfred-Wegener-Institute for Polar- and Marine Research, Bremerhaven
2MARUM Center for Marine Environmental Sciences, Bremen
3 Department of Earth and Ocean Sciences, University of British Columbia, Canada
Acknowledgements This project is funded by the DFG project Pe565-6 “The role of salps for carbon export in the Southern Ocean” to Ilka Peeken. Parts of this poster are published at http://nbn-resolving.de/urn:nbn:de:gbv:46-diss000119205(PhD thesis, LvH, Universität Bremen, Germany)
Results
¾Salpa thompsoni shows high variation in gut content concentrations and digestion efficiency is reduced in diatom blooms.
¾Pigments reflect different feeding and/or digestion:
• I. racovitzai→low seasonal variability in Lazarev Sea
• S. thomsponi→high seasonality and geographical differences
¾Fecal pellets of S. thompsoni contain high amounts of undigested chl-a in high food areas
Poster 1886
Conclusions
¾Results suggests different diets of the two salps
¾No clear signal between digestion efficiency and food concentration is evident
¾Food quality strongly affects degradation of ingested material
Further Studies
¾Is the varying local phytoplankton distributions reflected in the gut pigment content of salps ?
¾What do salps feed in winter time at extreme low phytoplankton concentrations ?
¾Are there regio-ecologically relevant differences found in the two salp species ?
Changing Quality of Fecal Pellets
Fig. 5: Box plots (median and 5th/95th percentile) A) Salp gut chlorophyll contents. B) Ratio of degradation product Phaeophytin and Pyro- phaeophytin to chl-a. C) Ratio of fucoxanthin as pigment marker for diatoms to chl-a. D) Average surface chlorophyll (av. sf chl-a) conc. (10, 20 and 50 m) of ambient waters
Pigment Degradation in Salp Guts Salp Gut Contents
D. Summer
Fig. 4: A-C) Southern Ocean salps D-G) SEM examples of salp gut content
of different seasons av
. sf chl-a +s.d. [mg m-3]
0 1 2 3 4 Pigment degradation [Fucoxanthin : chl-a]
0 20 40 60 80 Pigment Digestion [phaeophytins : chl-a]
0 20 40 60 Salp gut content [ng chl-a/ mg C]
0 100 200 300 400
Fig. 6: Chlorophyll content of fecal pellets egested during incubation experiments with S.
thompsoni in fall 2004 (EIFEX)
Questions
¾ Will digestion of salps change with food concentration and food composition?
¾ How will this be reflected in the export quality of salp faeces?
flocculent pellets export ? Diatom bloom
Fig. 1: Potential carbon export by salp fecal pellets
Carbon Export by Fecal Pellets
• Estimates of S. thompsoni pellets based on average salp biomass and defecation rates:
~ up to 0.95 mg C m-² in fall 2004, Lazarev Sea
~ up to 4-20 mg C m-2in summer 2006, Western Peninsula region (Phillips et al. 2009)
Study Sites and Methods
LM Gould 2-2006
Jan-Feb 2006
EIFEX PFZ Salpa
norm al
diatom bloom
depth
LAKRIS Lazarev Sea
Ihlea Salpa
A
su mmer
fall winter
su mmer
fall winter
LM Gould Peninsula Salpa
agg so
l
D C B Ihlea racovitzai
¾small, greenish guts
¾no microscopic evidence of seasonal diet change
E. Winter
G. Winter Salpa thompsoni
¾large redish guts solitary
stage A
F. Fall aggregate
stage
solitary stage
10 mm
B
C
Fig.2: Study areas
Project Hypothesis
¾The pigment gut content of salps varies seasonally
¾Ihlea racovitzai and Salpa thompsoni occupy different food niches
¾Low available food concentrations result in poor quality of egested material
Low food
Daily and seasonal vertical migration of salps
carbon export compact pellets
Medium food Diatom bloom 0.004
0.006 0.008 0.010 0.012 0.014 0.016 0.018 0.020
Fecal pellet chl-a [µg chl-a / µg mg C]
mean mean ±s.e.
mean ±1.96*s.e.
Pakhomov et al. 2002
EIFEX European Iron Fertilization Experiment Jan-March 2004
EIFEX
• Pigment analysis of water masses inside and outside bloom area some down to bottom water by HPLC (High Performance Liquid Chromatography)
• Gut pigment analysis of salps (S. thompsoni) from low and high chlorophyll areas
• Incubation experiments of S. thompsoni for fecal pellet studies
LM Gould
• HPLC pigment data acquisition of salp guts (S. thompsoni) and ambient waters
• Feeding rates of S. thompsoni determined in incubation experiments LAKRIS
• HPLC pigment data acquisition of salp guts (S. thompsoni and I. racovitzai) and ambient waters from all year round LAKRIS cruises
• Gut content analysis by microscopy and POC/PON measurements
LAKRIS Lazarev
Krill Study March-April 2004 Nov-Jan 2005/06 July-Aug 2006 Dec-Feb 2007/08
¾strong seasonality
