Spatial and temporal dynamics of Antarctic shallow soft-bottom benthic communities: ecological drivers under climate change
Background: Marine soft sediments are some of the most widespread habitats in the ocean, playing a vital role in
global carbon cycling, but are amongst the least studied with regard to species composition and ecosystem functioning. This is particularly true of the Polar Regions, which are currently undergoing rapid climate change, the impacts
of which are poorly understood. Compared to other latitudes, Polar sediment habitats also experience additional
environmental drivers of strong seasonality and intense disturbance from iceberg scouring, which are major structural
forces for hard substratum communities. This study compared sediment assemblages from two coves, near Rothera
Point, Antarctic Peninsula, 67°S in order to understand the principal drivers of community structure, for the frst time,
evaluating composition across all size classes from mega- to micro-fauna.
Results: Morpho-taxonomy identifed 77 macrofaunal species with densities of 464–16,084 individuals m−2
metabarcoding of microfauna, in summer only, identifed a higher diversity, 189 metazoan amplicon sequence variants (ASVs) using the 18S ribosomal RNA and 249 metazoan ASVs using the mitochondrial COI gene. Both techniques
recorded a greater taxonomic diversity in South Cove than Hangar Cove, with diferences in communities between
the coves, although the main taxonomic drivers varied between techniques. Morphotaxonomy identifed the main
diferences between coves as the mollusc, Altenaeum charcoti, the cnidarian Edwardsia sp. and the polychaetes from
the family cirratulidae. Metabarcoding identifed greater numbers of species of nematodes, crustaceans and Platyhelminthes in South Cove, but more bivalve species in Hangar Cove. There were no detectable diferences in community
composition, measured through morphotaxonomy, between seasons, years or due to iceberg disturbance.
Conclusions: This study found that unlike hard substratum communities the diversity of Antarctic soft sediment
communities is correlated with the same factors as other latitudes. Diversity was signifcantly correlated with grain
size and organic content, not iceberg scour. The increase in glacial sediment input as glaciers melt, may therefore be
more important than increased iceberg disturbance.
Authors: Vause, Belinda J., Morley, Simon A. ORCID record for Simon A. Morley, Fonseca, Vera, Jażdżewska, Anna, Ashton, Gail V., Barnes, David K.A. ORCID record for David K.A. Barnes, Giebner, Hendrik, Clark, Melody S. ORCID record for Melody S. Clark, Peck, Lloyd S.
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