Disturbance, colonization and development of Antarctic benthic communities

Abstract

A decade has yielded much progress in understanding polar disturbance and community recovery-mainly through quantifying ice scour rates, other disturbance levels, larval abundance and diversity, colonization rates and response of benthos to predicted climate change. The continental shelf around Antarctica is clearly subject to massive disturbance, but remarkably across so many scales. In summer, millions of icebergs from sizes smaller than cars to larger than countries ground out and gouge the sea floor and crush the benthic communities there, while the highest wind speeds create the highest waves to pound the coast. In winter, the calm associated with the sea surface freezing creates the clearest marine water in the world. But in winter, an ice foot encases coastal life and anchor ice rips benthos from the sea floor. Over tens and hundreds of thousands of years, glaciations have done the same on continental scales-ice sheets have bulldozed the seabed and the zoobenthos to edge of shelves. We detail and rank modern disturbance levels (from most to least): ice; asteroid impacts; sediment instability; wind/wave action; pollution; UV irradiation; volcanism; trawling; non-indigenous species; freshwater inundation; and temperature stress. Benthic organisms have had to recolonize local scourings and continental shelves repeatedly, yet a decade of studies have demonstrated that they have (compared with lower latitudes) slow tempos of reproduction, colonization and growth. Despite massive disturbance levels and slow recolonization potential, the Antarctic shelf has a much richer fauna than would be expected for its area. Now, West Antarctica is among the fastest warming regions and its organisms face new rapid changes. In the next century, temperature stress and non-indigenous species will drastically rise to become dominant disturbances to the Antarctic life. Here, we describe the potential for benthic organisms to respond to disturbance, focusing particularly on what we know now that we did not a decade ago.

Age-dependent expression of stress and antimicrobial genes in the hemocytes and siphon tissue of the Antarctic bivalve, Laternula elliptica, exposed to injury and starvation

“…The calving of glacial fronts and ice shelves produces increased amounts of floating brash ice and icebergs and hence more ice scouring in shallow coastal areas (Turner et al 2009;Barnes and Souster 2011;Brown et al 2004). Such changes will have marked consequences for benthic animals colonizing coastal areas around the WAP (Barnes and Conlan 2007;Barnes and Kaiser 2007).…”

Antarctic Benthic Fauna in the Global Climate Change

“…A large ice mass covered Antarctic continent. It was very dynamic and in the last 2 Myr it has cyclically advanced and retreated (Barnes, Conlan 2007). In glacial maxima ice edge advanced across the continental shelf erasing benthic fauna.…”

“…In glacial maxima ice edge advanced across the continental shelf erasing benthic fauna. In consequence, the shelf habitats have to be repeatedly colonized during ice retreat, resulting in repeated shifts in the distribution of species (Rogers 2009;Barnes, Conlan 2007). Survival of the benthic fauna was possible in the deep sea (hence the eurybathy - Brey et al 1996) or in refugia on the continental shelf resulting from the diachronism in maximum ice extant (Thatje et al 2005).…”

“…With increasing acidity many organisms will face a greater energetic cost to build and maintain their shells or skeletons. Thinning of shells makes them more susceptible to predators or mechanical damage typical for shallow waters (Barnes, Conlan 2007), which may result in depletion of thin-shelled sessile species (Barnes, Peck 2008).…”

Species pool structure explains patterns of Antarctic rock-encrusting organism recruitment

“…The intensity of disturbance typically increases towards the poles due to summer ice scour (the grounding of icebergs, scraping the sea bed), intense wind-driven wave action coupled with freezing temperatures and the occurrence of ice feet (walls or belts of ice frozen to the shore) during winter (see Gutt et al 1996;Barnes 1999;Barnes and Conlan 2007). Some studies suggest that assemblages that experience frequent physical extremes (e.g.…”