Abstract
Habitat heterogeneity is important for maintaining high levels of benthic biodiversity. The Prince Gustav Channel, on the Eastern Antarctic Peninsula, is characterized by an array of habitat types, ranging from flat, mud-dominated sheltered bays to steep and rocky exposed slopes. The channel has undergone dramatic environmental changes in recent decades, with the southern end of the channel permanently covered by the Prince Gustav Ice Shelf until it completely collapsed in 1995. Until now the marine benthic fauna of the Prince Gustav Channel has remained unstudied. A shallow underwater camera system and Agassiz trawl were deployed at different locations across the channel to collect information on habitat type and heterogeneity, benthic community composition and macrofaunal biomass. The texture of the seafloor was found to have a significant influence on the benthos, with hard substrates supporting higher abundances and diversity. Suspension and filter feeding organisms, including porifera, crinoids, and anthozoans, were strongly associated with hard substrates, with the same being true for deposit feeders, such as holothurians, and soft sediments. Habitat heterogeneity was high across the Prince Gustav Channel, particularly on a local scale, and this was significant in determining patterns of benthic composition and abundance. Other physical variables including depth and seafloor gradient played significant, interactive roles in determining composition potentially mediated through other processes. Sites that were once covered by the Prince Gustav Ice Shelf held distinct and unique communities, suggesting that the legacy of the ice shelf collapse may still be reflected in the benthos. Biomass estimations suggest that critical thresholds of vulnerable marine ecosystem indicator taxa, as defined by the Commission for the Conservation of Antarctic Marine Living Resources, have been met at multiple locations within the Prince Gustav Channel, which has implications for the future establishment of no take zones and marine protected areas within the region.
Highlights
The Antarctic continental shelf and slope is characterized by a highly diverse benthos that displays high levels of endemism and spatial variability (Convey et al, 2014)
An increase in hard substrates was observed at the Prince Gustav Channel (PGC) Mid and PGC South sites where mud only covered an average of 13% of the seafloor
PGC South 200 m had the highest occurrence of boulders, which covered an average of 19.3% of the seafloor
Summary
The Antarctic continental shelf and slope is characterized by a highly diverse benthos that displays high levels of endemism and spatial variability (Convey et al, 2014). All main types of macrobenthic communities, in particular suspension and mobile or deposit feeders, can occur all around the Southern Ocean, which suggests that their distribution on a regional and local scale is likely unpredictable and assumed to be shaped by complex biological and physical interactions (Gutt et al, 2013). Constraining interactions between physical and biological variables is vital for understanding drivers of Antarctic biodiversity and enabling development of predictive ecological models (Convey et al, 2014). Physical datasets provide an opportunity to build predictive models of species distributions and diversity if significant relationships can be established. Such models can be significant for guiding Southern Ocean ecosystem management, including the selection and monitoring of Marine Protected Areas (MPAs)
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