Unusually High Sea Ice Cover Influences Resource Use by Benthic Invertebrates in Coastal Antarctica

Unusually high sea ice cover influences resource use by benthic invertebrates in coastal Antarctica

Loïc N. MICHEL, Philippe DUBOIS, Marc ELEAUME, Jérôme FOURNIER, Cyril GALLUT, Philip JANE & Gilles LEPOINT Contact: [email protected]

BASIS 2017 Annual Meeting – 03-04/05/2017 – Utrecht, The Netherlands Context: sea ice in Antarctica

Antarctic littoral is circled by a fringe of sea ice (up to 20 millions km2)

Sea ice is a major environmental driver in Antarctica, influences ▪ Air/Sea interactions ▪ Water column mixing ▪ Light penetration ▪ Organic matter fluxes ▪ …

Sea ice is highly dynamic

Sea ice hosts sympagic organisms

Image: NASA Context: sea ice in Antarctica

Sympagic algae: Mostly diatoms Form thick mats Filaments up to several cm

Source: Australian Antarctic Division Seasonal patterns of sea ice cover

Source: NOAA

Austral winter Austral summer Normal cycle: Thick sea ice cover Thinning and breakup of sea ice Release of sympagic material High productivity events Climate change and sea ice cover

West Antarctic T°  Peninsula Ice cover 

T°  East Antarctica Ice cover 

Turner et al. 2005 Int J Climatol 25: 279-294 (Data 1971-2000) Parkinson & Cavalieri 2012 Cryosphere 6: 871-880 Study site: Dumont d’Urville station Austral summer 2007-08

East Antarctica, Adélie Land Petrels Island Study site: Dumont d’Urville station Austral summer 2007-08

Austral summer 2013-14 East Antarctica, Adélie Land Petrels Island

2013-2015: Event of high spatial and temporal sea ice coverage

No seasonal breakup during austral summers 2013-14 and 2014-15 Study site: Dumont d’Urville station Time of sampling : Austral summer 2014-15

This is the sea (Please trust me) Objectives How will Antarctic communities respond to such environmental changes?

How could increased sea ice cover impact benthic food webs? Objectives How will Antarctic communities respond to such environmental changes?

How could increased sea ice cover impact benthic food webs? 

Use of stable isotope ratios to identify resources supporting dominant benthic invertebrates (primary consumers & omnivores)

Quantification of relative importance of 4 producers / organic matter pools Objectives How will Antarctic communities respond to such environmental changes?

How could increased sea ice cover impact benthic food webs?  1. Sympagic algae

Use of stable isotope ratios to identify resources supporting dominant benthic invertebrates (primary consumers & omnivores)

Quantification of relative importance of 4 producers / organic matter pools:

1) Suspended particulate organic matter (SPOM)

2. Suspended particulate organic matter (SPOM) Objectives How will Antarctic communities respond to such environmental changes?

How could increased sea ice cover impact benthic food webs?

3. Benthic brown algae Himantothallus grandifolius Objectives How will Antarctic communities respond to such environmental changes?

How could increased sea ice cover impact benthic food webs?

4. Benthic biofilm (heterogeneous mix of microalgae, amorphous material and detrital items) Material & methods: sampling

Hand collection

SCUBA diving under fast ice Material & methods: analysis

University of Liège’s setup: Vario MICRO cube EA coupled to an Isoprime 100 IRMS Results: isotopic biplot

1 0 F o o d ite m s S P O M B io film H im a n to th a llu s b la d es S y m p a g ic a lg a e

)

‰

(

N 6

1 

2 -2 5 -2 0 -1 5 -1 0 1 3  C (‰ ) Results: isotopic biplot

1 0 Perkinsiana sp. F o o d ite m s S P O M B io film H im a n to th a llu s b la d es S y m p a g ic a lg a e

8 P o lych a e te s H a rm o th o e sp . F la b e llig e ra m u n d a ta Harmothoe sp. P o lyc irru s sp .

P e rk in sia n a sp .

)

‰

(

N 6

1 

Flabelligera mundata

2 -2 5 -2 0 -1 5 -1 0 1 3  C (‰ ) Results: isotopic biplot

1 0 Trophon longstaffi F o o d ite m s S P O M B io film H im a n to th a llu s b la d es S y m p a g ic a lg a e

8 P o lych a e te s H a rm o th o e sp . F la b e llig e ra m u n d a ta P o lyc irru s sp . P e rk in sia n a sp .

) M o llu scs

‰ ( T ro p h o n lo n g s ta ffi

N 6 5

1 M a rsen io p sis sp .  L a te rn u la e llip tic a A d a m u ssiu m c o lb e c k i

Marseniopsis sp.

2 Adamussium colbecki -2 5 -2 0 -1 5 -1 0 1 3  C (‰ ) Results: isotopic biplot

1 0 HeterocucumisF o o d ite msps . S P O M B io film H im a n to th a llu s b la d es S y m p a g ic a lg a e

P o lych a e te s 8 seastar Odontaster validus H a rm o th o e sp .

Odontaster validus is found throughout Antarctica and the F la b e llig e ra m u n d a ta Antarctic Peninsula, South Shetland Islands, South Orkney Sterechinus neumayeri Islands, South Sandwich Islands , South Georgia Island, Shag Rocks, Marion and Prince Edward Islands, and Bouvet Island at P o lyc irru s sp . depths from 0 to 914 meters [7,10,11,12,14]. O. validus is the most abundant seastar in the shallow shelf waters of Antarctica and is P e rk in sia n a sp . most abundant from 15 to 200 meters [9]. O. validus has a broad disc and short arms tapering to blunt tips [7]. O. validus has been

) collected at sizes up to seven centimeters in radius from its center to the tip of an arm [7,11]. O. validus varies in color includingM darko llu scs

‰ brown, purple, purple-red, orange, red-orange, red, brick red, dark

( [7,11,14]

carmine, and pink; it may have light colored arm tips . O. validus has a characteristic position with its arm tips slightly raised T ro p h o n lo n g s ta ffi

N 6

[7]. 5

1 M a rsen io p sis sp .

 O. validus is usually bright to dull red on the dorsal (abactinal) surface and yellowish white to pale pink on the ventral (actinal) L a te rn u la e llip tic a surface [16]. O. meridionalis is generally pale brown or yellowish white on the dorsal : surface and lighter on the ventral surface [16]. Color in both species can be highly variable and is not always reliable as a field character; the only sure way is to check the number of spines on the actinal plates [16]. A d a m u ssiu m c o lb e c k i

Here's a juvenile and adult of OdontasterE c h in o d e rm s validus. Size-frequency distribution of O. validus can vary with location and is a reflection of the general level of O p h iu ra sp . productivity of a habitat: at McMurdo Station, their size and number decrease S te re c h in u s n e u m a ye ri 4 with depth; at Cape Evans, they are more numerous and generally smaller; and, at East Cape Armitage, they are less D ip la steria s b ru c ei numerous and very small [3]. O. validus is slow growing; well-fed individuals need O d o n ta ste r v a lid u s about nine years to reach thirty grams wet weight which is near the mean size of shallow-water individuals at McMurdo H e te ro c u c u m is sp . Station [3]. Based on its growth rate, collected sizes, and knowledge from other S ta u ro c u c u m is sp . seastars, O. validus may live beyond one hundred years of age, with very low turnover in a population [17].

Odontaster validus

-2 5 -2 0 -1 5 -1 0 27 1 3  C (‰ ) Results: isotopic biplot

1 0 F o o d ite m s S P O M B io film H im a n to th a llu s b la d es S y m p a g ic a lg a e

8 P o lych a e te s H a rm o th o e sp . F la b e llig e ra m u n d a ta P o lyc irru s sp . P e rk in sia n a sp .

) M o llu scs

‰ ( T ro p h o n lo n g s ta ffi

N 6 5

1 M a rsen io p sis sp .  L a te rn u la e llip tic a A d a m u ssiu m c o lb e c k i

E ch in o d e rm s O p h iu ra sp .

4 S te re c h in u s n e u m a ye ri D ip la steria s b ru c ei O d o n ta ste r v a lid u s H e te ro c u c u m is sp . S ta u ro c u c u m is sp .

2 -2 5 -2 0 -1 5 -1 0 1 3  C (‰ ) Results - SIAR modelling Sympagic

algae diet Suspended Particulate Organic Matter (SPOM)

Contribution Contribution consumer to 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. Results - SIAR modelling Sympagic

algae diet Suspended Particulate Organic Matter (SPOM)

Contribution Contribution consumer to Benthic algae + Biofilm

algae diet Suspended Particulate Organic Matter (SPOM)

Contribution Contribution consumer to Benthic algae + Biofilm

algae diet Suspended Particulate Organic Matter (SPOM)

Contribution Contribution consumer to Benthic algae + Biofilm

Main food items SympagicSympagicalgaealgae BenthicBenthicalgaealgae// Biofilm Biofilm Discrepancies in resource use Species DDU 1 2 3 4 5 6 Laternula elliptica Adamussium colbecki Sterechinus neumayeri Odontaster validus Staurocucumis sp. Harmothoe sp.

Main food items Sympagic algae / Ice POM Benthic algae / Biofilm Plankton / SPOM Sediment POM Animal-based diet No data 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 Discrepancies in resource use Species DDU 1 2 3 4 5 6 Laternula elliptica Adamussium colbecki Sterechinus neumayeri Odontaster validus Staurocucumis sp.

Harmothoe sp.   

Sea ice Main food items Sympagic algae / Ice POM Benthic algae / Biofilm Plankton / SPOM Sediment POM Animal-based diet No data 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 Discrepancies in resource use Species DDU 1 2 3 4 5 6 Laternula elliptica Adamussium colbecki Sterechinus neumayeri Odontaster validus Staurocucumis sp.

Harmothoe sp.   

Sea ice Main food items Sympagic algae / Ice POM Benthic algae / Biofilm ImportantPlankton / SPOMspatial and/or temporal variation in resource use by dominant consumers Sediment POM Animal-basedHighdiet trophic plasticity of Antarctic invertebrates? No data 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 consumption: how and why? Sea ice is a dynamic system: constant melting/freezing

Sympagic algae aggregates sink quickly

Sinking speed is size-dependent and range from 100 to 500 m/day (i.e. 1-5 hours to reach a depth of 20 m) Sympagic algae consumption: how and why? Sea ice is a dynamic system: constant melting/freezing

Sympagic algae aggregates sink quickly

Sinking speed is size-dependent and range from 100 to 500 m/day (i.e. 1-5 hours to reach a depth of 20 m)

Why is it preferred by many consumers over more 8 abundant food items such as biofilm?

a r

Better nutritional value? Unlikely… 

N / C 6 Better palatability? Pure aggregates of microalgae… 5

4 S y m p . a lg a e B io film Role of benthic biofilm in the food web Preliminary microscopic examination: Benthic biofilm = heterogeneous mix of microalgae, amorphous material and detrital items

Here: importance of benthic biofilm in food web comparatively limited despite high abundance Role of benthic biofilm in the food web Preliminary microscopic examination: Benthic biofilm = heterogeneous mix of microalgae, amorphous material and detrital items

Here: importance of benthic biofilm in food web comparatively limited despite high abundance

Ross Sea: Benthic invertebrates consume more detritic matter in sea-ice influenced locations (Norkko et al. 07) Role of benthic biofilm in the food web Preliminary microscopic examination: Benthic biofilm = heterogeneous mix of microalgae, amorphous material and detrital items

Here: importance of benthic biofilm in food web comparatively limited despite high abundance

Ross Sea: Benthic invertebrates consume more detritic matter in sea-ice influenced locations (Norkko et al. 07)

Important variation in benthic ecosystem response to sea ice: sudden changes vs. stable conditions? However: no data about dynamics of biofilm accumulation! Here: long-lived benthic invertebrates with low metabolic rates  low isotopic turnover? Is isotopic equilibrium reached? Our model could underestimate actual biofilm importance for invertebrate feeding Take home message

▪ Important sea ice cover is linked with high reliance of coastal benthic primary consumers / omnivores on sympagic algae Take home message

▪ Important sea ice cover is linked with high reliance of coastal benthic primary consumers / omnivores on sympagic algae

▪ Resource use by consumers of Adélie Land markedly differs from results obtained in other locations. High trophic plasticity of Antarctic invertebrates? Sudden changes vs. stable conditions? Take home message

▪ Important sea ice cover is linked with high reliance of coastal benthic primary consumers / omnivores on sympagic algae

▪ Resource use by consumers of Adélie Land markedly differs from results obtained in other locations. High trophic plasticity of Antarctic invertebrates? Sudden changes vs. stable conditions?

▪ Interpretation of results is complicated by lack of background data ("normal" conditions) and by physiological features of studied organisms Take home message

▪ Important sea ice cover is linked with high reliance of coastal benthic primary consumers / omnivores on sympagic algae

▪ Resource use by consumers of Adélie Land markedly differs from results obtained in other locations. High trophic plasticity of Antarctic invertebrates? Sudden changes vs. stable conditions?

▪ InterpretationDespite being interpretedof results is ascomplicated a positive bysignal lack byof mainstream media, localbackgroundor large- scaledata ("normal"trends of seaconditions) ice increase and in by Antarctica could actually physiological havefeatures strong of studiedimpacts organisms on benthic ecosystems Funding

Belgian Federal Science Policy Office (BELSPO)

vERSO project (Ecosystem Resilience in Southern Ocean)

French Polar Institute (IPEV)

Image: NASA Thanks for your attention

Download this presentation: http://hdl.handle.net/2268/210019 Image: NASA SIAR parameters

SIAR 4.2 in R 3.2.2

No concentration dependencies

TEFs: Δ13C = 0.40 ± 1.20 ‰; Δ15N = 2.30 ± 1.61 ‰ (mean ± SD; TEFs for aquatic consumers from McCutchan et al. 2003 Oikos 102: 378-390)

106 iterations

Burn-in size: 105

Image: NASA Sample numbers

Sample nature N SPOM 12 Biofilm 57 Sympagic algae 20 Himantothallus grandifolius blades 16 Harmotohe sp. 30 Flabelligera mundata 22 Polycirrus sp. 19 Perkinsiana sp. 24 Trophon longstaffi 22 Marseniopsis sp. 21 Laternula elliptica 21 Adamussium colbecki 25 Ophiura sp. 23 Sterechinus neumayeri 21 Diplasterias brucei 21 Odontaster validus 23 Heterocucumis sp. 23 Staurocucumis sp. 19 Image: NASA A glimpse at secondary consumers

1 2

S a lia ste ria s b ra c h ia ta A c o d o n ta ste r s p . Iso te a lia a n ta rc tic a D e c o lo p o d a a u stra lis 1 0 A m m o th e a c a ro lin e n s is P a rb o rla s ia c o rru g a tu s

)

‰

(

1 

2 -2 5 -2 0 -1 5 -1 0 1 3  C (‰ ) Image: NASA Low trophic positions of consumers

Image: NASA Inter-annual change in isotopic compositions

Image: NASA