Climate Change and Invasibility of the Antarctic Benthos

Abstract

Benthic communities living in shallow-shelf habitats in Antarctica (<100-m depth) are archaic in structure and function compared to shallow-water communities elsewhere. Modern predators, including fast-moving, durophagous (skeleton-crushing) bony fish, sharks, and crabs, are rare or absent; slow-moving invertebrates are generally the top predators; and epifaunal suspension feeders dominate many soft-substratum communities. Cooling temperatures beginning in the late Eocene excluded durophagous predators, ultimately resulting in the endemic living fauna and its unique food-web structure. Although the Southern Ocean is oceanographically isolated, the barriers to biological invasion are primarily physiological rather than geographic. Cold temperatures impose limits to performance that exclude modern predators. Global warming is now removing those physiological barriers, and crabs are reinvading Antarctica. As sea temperatures continue to rise, the invasion of durophagous predators will modernize the shelf benthos and erode the indigenous character of marine life in Antarctica.

Fossil proxies of near-shore sea surface temperatures and seasonality from the late Neogene Antarctic shelf

“…There are currently over 4100 benthic species known in the Southern Ocean (Clarke and Johnston 2003), though this diversity may have increased in recent years because of species invasions (for example king crabs in Palmer Deep; Smith et al 2012). The total macrofaunal diversity on the continental shelf likely exceeds 15,000 species (Gutt et al 2004;Aronson et al 2007); this is under evaluation by the Census of Antarctic Marine Life (CAML: www.caml.aq/). The benthic communities that inhabit the shallow-shelf (<100 m depth) surrounding the vast continent are structurally and functionally archaic when compared to similar communities in other parts of the globe (Aronson et al 2007).…”

“…The total macrofaunal diversity on the continental shelf likely exceeds 15,000 species (Gutt et al 2004;Aronson et al 2007); this is under evaluation by the Census of Antarctic Marine Life (CAML: www.caml.aq/). The benthic communities that inhabit the shallow-shelf (<100 m depth) surrounding the vast continent are structurally and functionally archaic when compared to similar communities in other parts of the globe (Aronson et al 2007). Dense populations of epifaunal suspension feeders such as crinoids, bryozoans and brachiopods are dominant in benthic communities (Aronson et al 2007) and are associated with coarse glacial sand and gravel glacial substrates (Clarke et al 2004).…”

The Early Miocene Cape Melville Formation fossil assemblage and the evolution of modern Antarctic marine communities

“…This resulted in changes in faunal composition and a decrease in taxonomic diversity, 80 which included the disappearance of durophagous predators such as most reptant decapods, 81 sharks, and teleost fish (Aronson and Blake 2001;Eastman 2005;Aronson et al 1997;82 2009;2011). The reasons for the absence of these groups are complex, but have been linked 83 to historical biogeography, physiology, and phylogenetic constraint (Aronson et al 2007;84 2011). For example, the absence of certain reptant decapod crustaceans (benthic, walking 85 decapods, including brachyuran crabs and astacid lobsters) from Antarctic waters today has 86 been cited as a direct result of their physiological intolerance of cold sea temperatures 87 (Frederich et al 2001;Wittmann et al 2010;Aronson et al 2011).…”

“…There may have been reversals in the trend towards a retrograde community structure 421 in periods that were warmer than at the time of deposition of the La Meseta Formation in the 422 Eocene (Aronson et al 2007). This would have led to incursions of reptant decapods along 423 the Scotia arc and via the porous Antarctic Circumpolar Current (Aronson et al 2007).…”

“…This would have led to incursions of reptant decapods along 423 the Scotia arc and via the porous Antarctic Circumpolar Current (Aronson et al 2007). Formation, which does not preserve any evidence for a glacial depositional environment.…”