Use of stable isotope ratios to delineate coastal benthic food web structure in Adélie Land (East Antarctica)

Context, objectives & methods

Results & discussion

Authors would like to thank the French Polar Institute for welcoming us at Dumont-d’Urville Station in the framework of the REVOLTA program. GL and PD are F.R.S-FNRS research associate and director, respectively. This work is part of the vERSO project, funded by the Belgian Science Policy Office (BELSPO).

 _{Important sea ice cover is linked with high reliance of benthic invertebrates on sympagic algae.}

 _{Important spatial and/or temporal discrepancies in feeding habits and benthic community response to}

sea ice: high trophic plasticity?

 _{Interpretation of data is complicated by the lack of background data ("normal" conditions) and by}

physiological features of studied organisms.

Use of stable isotope ratios to delineate coastal benthic

food web structure in Adélie Land (East Antarctica)

Loïc N. MICHEL

_{, Philippe DUBOIS}

_{, Marc ELEAUME}

_{, Jérôme FOURNIER}

_{, Cyril GALLUT}

_,

Philip JANE

_{& Gilles LEPOINT}

1_{University of Liège, Belgium.} 2_{Université Libre de Bruxelles, Belgium.} 3_{National Museum of Natural History, France.} 4_{Concarneau Biological Station, National Museum of Natural History, France.} 5_{Pierre and Marie Curie University, France.} 6_{Aquarium de Paris – Cinéaqua, France. *E-mail: [email protected], publications available at http://goo.gl/xdxaHM}

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 _{Climate change has contrasted effects on Antarctica. West Antarctic}

Peninsula: T°  and sea ice ; East Antarctica: T°   and sea ice cover .

 _{Dumont-d’Urville station (Adélie Land, East Antarctica) recently}

underwent an event of high spatial and temporal sea ice coverage (no

seasonal breakup during austral summers 2013-2014 and 2014-2015)

Conclusions & perspectives

Acknowledgements

 _{Main organic matter source of most consumers =}

sympagic algae (1, 2).

 _{Important differences in resource use by consumers of}

Adélie Land and from other locations of coastal Antarctica, including sea ice influenced sites (3).

 _{Trophic importance of benthic biofilm comparatively}

limited despite high abundance (2).

 _{Norkko et al. 07: benthic invertebrates consume more}

detrital matter in sea ice influenced locations. Our results

disagree with this hypothesis (2,3).

 _{However, no data about dynamics of biofilm accumulation}

+ long-lived consumers with low metabolic rates: low

isotopic turnover? Is isotopic equilibrium reached?

Sympagic algae Suspended Particulate Organic Matter (SPOM) Benthic algae + Biofilm

OV: O. validus; SN: S. neumayeri; DB: D. brucei; HA: Harmothoe sp.; FM: F. mundata; PO: Polycirrus sp.; OP: Ophiura sp.; PE: Perkinsiana sp.; TL: T. longstaffi; MA: Marsienopsis sp.; HE: Heterocucumis sp.; LE: Laternula elliptica; AC: Adamussium colbecki; ST: Staurocucumis sp.

C ont ribut ion to consum er di et Species DDU 1 2 3 4 5 6 Laternula elliptica Adamussium colbecki Sterechinus neumayeri Odontaster validus Staurocucumis sp. Harmothoe sp.

Main food items Sea ice

   1000 km 1-3 4 5 6 DDU

References: 1-3: Norkko et al. 2007 Ecology 88: 2810-2820; 4: Gillies et al.

2012 Estuar Coast Shelf S 97: 44-57; 5: Dunton 2001 Amer Zool 41: 99-112; 6: Corbisier et al. 2004 Polar Biol 27: 75-82

Sympagic algae / Ice POM Benthic algae / Biofilm

Plankton / SPOM Sediment POM Animal-based diet No data

1) Isotopic biplot of consumers and food sources 2) Main food items according to SIAR mixing model

-2 5 -2 0 -1 5 -1 0 2 4 6 8 1 0 δ1 3C (‰ ) δ 1 5 N (‰ ) H a rm o th o e s p . F la b e llig e ra m u n d a ta P o ly c irru s s p . P e rk in s ia n a s p . T ro p h o n lo n g s ta ffi M a rs e n io p s is s p . L a te rn u la e llip tic a A d a m u s s iu m c o lb e c k i O p h iu ra s p . S t e r e c h in u s n e u m a y e r i D ip la s te ria s b ru c e i O d o n ta s te r v a lid u s H e te ro c u c u m is s p . S ta u ro c u c u m is s p . S P O M B io film H im a n to th a llu s b la d e s S y m p a g ic a lg a e F o o d ite m s P o ly c h a e te s M o llu s c s E c h in o d e r m s

3) Comparison with literature data



 _{How will Antarctic communities respond to such environmental changes? How could increased sea ice cover impact benthic}

food webs?

 _{Use of stable isotope ratios of C and N (integrative trophic markers, "you are what you eat") to identify resources supporting} dominant benthic invertebrates (here: focus on primary consumers and omnivores)

 _{Use of a mixing model to quantify relative importance of 4 producers / organic matter pools: sympagic algae, suspended}

particulate organic matter, benthic macroalgae (Himantothallus grandifolius) and benthic biofilm (unusually abundant,

heterogeneous mix of microalgae, amorphous material and detrital items)

 _{Accumulations of benthic biofilm on coastal rocky bottoms near}