Likely responses of the Antarctic benthos to climate‐related changes in physical disturbance during the 21st century, based primarily on evidence from the West Antarctic Peninsula region

Abstract

Disturbance has always shaped the evolution and ecology of organisms and nowhere is this more apparent that on the iceberg gouged continental shelves of the Antarctic Peninsula (AP). The vast majority of currently described polar biodiversity occurs on the Southern Ocean shelf but current and projected climate change is rapidly altering disturbance intensities in some regions. The AP is now amongst the fastest warming and changing regions on earth. Seasonal sea ice has decreased in time and extent, most glaciers in the region have retreated, a number of ice shelves have collapsed, and the surface waters of the seas west of the AP have warmed. Here, we review the influences of disturbance from ice, sedimentation, freshening events, wave action and humans on shallow water benthic assemblages, and suggest how disturbance pressures will change during the 21st century in the West Antarctic Peninsula (WAP) and Scotia Arc region. We suggest that the intensity of ice scouring will increase in the region over the next few decades as a result of decreased winter sea ice periods and increased ice loading into coastal waters. Thus, the most frequently disturbed environment on earth will become more so, which will lead to considerable changes in community structure and species distributions. However, as ice fronts retreat past their respective grounding lines, sedimentation and freshening events will become relatively more important. Human presence in the region is increasing, through research, tourism, and resource exploitation, which represents a considerable threat to polar biodiversity over the next century. Adapting to or tolerating multiple, changing environmental stressors will be difficult for a fauna with typically slow generation turnovers that has evolved largely in isolation. We suggest that intensifying acute and chronic disturbances are likely to cause significant changes in ecosystem structure, and probably a considerable loss of polar marine biodiversity, over relatively short timescales.

Major impacts of climate change on deep-sea benthic ecosystems

“…Parts of the Antarctic Peninsula, including the WAP, are already experiencing the greatest increase in mean annual atmospheric temperature on Earth (Chapman and Walsh, 2007;Clarke et al, 2007;Solomon et al, 2007;Smale and Barnes, 2008), and temperatures at the seafloor in the Southern Ocean are predicted to rise by as much as 0.7°C at abyssal depths and 1.7°C at bathyal depths by 2100 ( Table 2). Field and modeling studies have also revealed rapid atmospheric and surface-water warming in the Arctic Ocean during recent decades (Overland et al, 2004;Spielhagen et al, 2011).…”

“…Large icebergs can scour the sediment down to 400 m on the Antarctic shelf. This disturbance leads to scale-dependent recolonization of scoured areas and an increased input of dropstones (Smale and Barnes, 2008). These processes will enhance seafloor heterogeneity and create hard substrates for sessile megafauna (Schulz et al, 2010;Meyer et al 2015Meyer et al , 2016.…”

Macrozoobenthos of two Antarctic glacial coves: a comparison with non-disturbed bottom areas

“…Polar regions are affected by a high level of disturbance associated with iceberg scour and glacial sedimentation (Barnes 1999;Gutt 2001;Smale and Barnes 2008); however, not all aspects of these problems were studied equally in the Arctic and in the Antarctic. While ice scour disturbance was intensively studied in both polar regions (Conlan et al 1998;Gutt and Piepenburg 2003;Brown et al 2004;Conlan and Kvitek 2005;Gerdes et al 2008;Smale 2008a), it was recently emphasized by Smale and Barnes (2008) that studies on benthic communities affected by mineral suspension inflow are still lacking from the Southern Ocean.…”

“…While ice scour disturbance was intensively studied in both polar regions (Conlan et al 1998;Gutt and Piepenburg 2003;Brown et al 2004;Conlan and Kvitek 2005;Gerdes et al 2008;Smale 2008a), it was recently emphasized by Smale and Barnes (2008) that studies on benthic communities affected by mineral suspension inflow are still lacking from the Southern Ocean.…”

“…The ongoing climate warming observed in the West Antarctic Peninsula region (Walsh 2009), which resulted in strong retreat of glaciers during the last 60 years (Cook et al 2005), may change the structure of Antarctic benthic communities (Smale and Barnes 2008). According to predictions for both polar regions, the rate of suspension matter inflow driven by climate change will significantly increase in a short period of time (Syvitski and Andrews 1994;Smale and Barnes 2008) and will be especially pronounced in the Antarctic.…”