Abele, D.

Braeckman, U.

De Troch, M.

Giovannelli, D.

Manini, E.

Monien, D.

Pasotti, F.

Sahade, R.

Saravia, L.A.

Tarantelli, M.S.

Vanreusel, A.

Verleyen, E.

Wölfl, A.-C.

Open Marine Archive

367 
 
S12: Linking ecosystem structure and functioning with bio geochemical cycles 
Unravelling the responses of shallow soft sediment assemblages to 
rapid glacier retreat in an Antarctic fjord: assemblage structure and 
trophic interactions 
Pasotti Francesca1, Ulrike Braeckman1, Doris Abele2, Marleen De Troch1, Donato Giovannelli3, Elena 
Manini3, Donata Monien4, Ricardo Sahade5, Leonardo Ariel Saravia6, Maria Soledad Tarantelli5, Elie 
Verleyen7, Anne-Cathrin Wölfl8 and Ann Vanreusel1 
1  Marine Biology Research Group, Ghent University, Krijgslaan 281/S8, 9000 Ghent, Belgium 
E-mail: francesca.pasotti@ugent.be 
2  Alfred Wegener Institute Helmholtz Center for Polar and Marine Research, Dept. Functional 
Ecology, Bremerhaven, Germany 
3  Institute for Marine Science (ISMAR-CNR), Ancona, Italy 
4  Leibniz Center for Tropical Marine Research (ZMT), Bremen, Germany 
5  Institute of Animal Diversity and Ecology, CONICET, Fac.Cs. E.F. y Nat. National University of 
Cordoba, Córdoba, Argentina 
6  Institute of Sciences, National University of General Sarmiento, Buenos Aires, Argentina 
7  Protistology and Aquatic Ecology Group, Ghent University, Ghent, Belgium 
8  Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Wadden Sea Research 
Station, List, Germany 
 
The West Antarctic Peninsula (WAP) is one of the fastest warming regions on Earth and it is 
characterized by the presence of a high number of fjords, known to be hotspots of marine 
biodiversity. Recent observations on the WAP have documented the rapid retreat of many tidewater 
glaciers whose related calving events lead to more frequent iceberg scouring in the shallow waters, 
coupled to increased fresh water input and higher sediment loads. All these disturbances are known 
to affect the marine assemblages in the shallow coastal regions. At the same time, ice retreat may 
free areas of the marine realm which can in time see the establishment of new local benthic 
assemblages via colonization and successional processes. We investigated three size classes of the 
soft sediment benthos (microbenthos, meiofauna and macrofauna) at three sites within Potter Cove 
(King George Island, WAP) which differed in the glacier retreat-related disturbance regimes and had 
different ice-free age status. We carried a two-fold investigation integrating assemblage structure 
observations (e.g. standing stocks) to the more functional aspects of the biota such as the trophic 
relationships within the assemblages. Our results revealed the presence of a patchy distribution of 
highly divergent benthic assemblages within a relatively small area (about 1 km2). The three benthic 
size classes appeared to respond in different ways to the disturbances, suggesting that the capacity 
to adapt and colonize habitats is dependent on both body size and specific life traits. In a similar 
fashion, the isotopic niches (an extrapolation of the ecological niche into the isotopic biplot space 
formed by the δ13C and δ 15N natural signatures of the organisms) of the assemblages were locally 
shaped by the different degrees of glacier retreat-related disturbance. Wider isotopic niche widths 
were found at the site that had an intermediate ice-free age, whereas they were comparable for the 
older and the newly ice-free sites. In general ice scour and glacial impact appeared to play a two-
fold role within the Cove: i) either stimulating trophic diversity by allowing continuous re-
colonization of meiofaunal species or, ii) over time driving the benthic assemblages into a more 
compact trophic structure with increased connectedness and resource recycling. Finally, we predict 
that, under continued deglaciation, more diverse, but less patchy, benthic assemblages will become 
established in areas free from glacier-related disturbance, with a general trend leading to the 
homogenization of the diversity/trophic pool to be found at these shallow depths. 
  


Unravelling the responses of shallow soft sediment assemblages to rapid glacier retreat in an Antarctic fjord: assemblage structure and trophic interactions

Unravelling the responses of shallow soft sediment assemblages to rapid glacier retreat in an Antarctic fjord: assemblage structure and trophic interactions

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