How did Antarctic seafloor communities change over three years?

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Researchers used community DNA metabarcoding to study molecular eukaryotic biodiversity patterns in shallow, hard-bottom Antarctic benthic communities. Polar ecosystems are highly exposed to climate change, and benthic macroinvertebrate communities have responded rapidly to a range of natural and human pressures. Yet these rich ecosystems are poorly studied, and little is known about the biodiversity associated with Antarctic hard-bottom habitats.

The study covered the West Antarctic Peninsula and South Shetland Islands. Using data from seven localities along the western Antarctic Peninsula, the researchers calculated spatial patterns of alpha and beta diversity. They also examined changes in benthic composition at Deception Island over three years, calculating temporal alpha and beta diversity to reveal changes over time.

The final list contained 2,057 molecular operational taxonomic units. Benthic community composition differed significantly between localities and among years. The samples contained 10 kingdom-level lineages and 34 phyla. Arthropoda was the most diverse phylum, followed by Bacillariophyta and Annelida; the highest relative read abundances belonged to Annelida, Porifera and Echinodermata. At Deception Island, community composition changed between 2016 and 2018, and decreasing species richness was the main component of temporal beta diversity.

The researchers concluded that direct sampling methods are required to monitor these complex communities. Informative biodiversity patterns can nevertheless be retrieved, even though most Antarctic benthic biodiversity remains to be taxonomically described and barcoded. Hard-bottom assemblages showed high spatial variability and heterogeneity unrelated to depth, posing a major challenge for large-scale Southern Ocean studies. The researchers suggested that local patchiness and community structure probably result from a combination of biotic and abiotic factors, including ice disturbance, food supply and competition.