From Pole to Pole Adaptation and Evolution in Marine Environments, Volume 1 Volume 1: The Impacts of Global Change on Biodiversity Bearbeitet von Cinzia Verde, Guido di Prisco 1. Auflage 2012. Buch. xxiv, 224 S. Hardcover ISBN 978 3 642 27351 3 Format (B x L): 15,5 x 23,5 cm Gewicht: 537 g Weitere Fachgebiete > Geologie, Geographie, Klima, Umwelt > Umweltwissenschaften > Biodiversität Zu Inhaltsverzeichnis schnell und portofrei erhältlich bei Die Online-Fachbuchhandlung beck-shop.de ist spezialisiert auf Fachbücher, insbesondere Recht, Steuern und Wirtschaft. Im Sortiment finden Sie alle Medien (Bücher, Zeitschriften, CDs, eBooks, etc.) aller Verlage. Ergänzt wird das Programm durch Services wie Neuerscheinungsdienst oder Zusammenstellungen von Büchern zu Sonderpreisen. Der Shop führt mehr als 8 Millionen Produkte. Chapter 2 Southern Ocean Deep-Sea Isopod Biodiversity Research: From Census to Ecosystem Functioning Angelika Brandt 2.1 Introduction The isolation of Antarctica makes this continent a perfect evolutionary laboratory for studies of marine biodiversity and biogeography. Attempts to describe and explain patterns of species diversity have become a major goal in biological research since the pioneering deep-sea investigations in the early 60s of the last century (Sanders et al. 1965; Sanders and Hessler 1969). Analyses of large-scale (global) patterns of deep-sea biodiversity include latitudinal gradients, apparent decreases in species richness among a number of taxa from the equator towards the poles (Poore and Wilson 1993; Rex et al. 1993, 1997). The Atlantic sector of the Southern Ocean (SO) does not seem to follow this pattern (Brandt et al. 2007b) although the deep seafloor of the SO remains the least studied even though it is the largest single benthic habitat (Clarke and Johnston 2003). The Southern Ocean benthic marine shelf flora and fauna has been impacted over millions of years by plate tectonics and the resulting changes in the global climate. Tertiary palaeogeologic and -oceanographic changes (e.g. Brown et al. 2006; Zachos et al. 2008) successively generated the psychrosphere and the cold Antarctic Deep Water which is linked to the surface water in polar areas. These key events of cooling and glaciation followed by warmer periods shaped the evolution of many SO marine species. Following evolutionary extinctions some benthic marine invertebrate taxa radiated, others are remnants from the progressive retraction of cosmopolitan taxa established during the Jurassic and Cretaceous when Antarctica was still under greenhouse conditions, some disjunct distribution patterns resulted from vicariance events following the disintegration of A. Brandt (&) Zoological Museum, Martin-Luther-King-Platz 3, 20146 Hamburg, Germany e-mail: [email protected] G. di Prisco and C. Verde (eds.), Adaptation and Evolution in Marine Environments, 21 Volume 1, From Pole to Pole, DOI: 10.1007/978-3-642-27352-0_2, Ó Springer-Verlag Berlin Heidelberg 2012 22 A. Brandt Fig. 2.1 Bathymetry of the southern ocean, showing shelf, slope, abyssal and hadal regions (Kaiser and Barnes 2008) the supercontinent Gondwana. Thus, the present Southern Ocean fauna has changed in biodiversity and composition over geological time scales and species have actively migrated in and out of the SO (depending on dispersal capabilities) during glacial and interglacial periods. Today the Southern Ocean is characterized by unique environmental features, including a very deep and partly narrow continental shelf, a weakly stratified almost isothermal water column and formation of abyssal waters flowing to other basins. Most of the SO seafloor (27.9 million km2, Clarke and Johnston 2003)is deep sea (Fig. 2.1). Characteristic for Antarctica is that the shelves are much deeper than the average, 450–500 m, and can exceed 1,000 m in places; the Antarctic shelf comprises 17% of the world’s total shelf area. The SO deep-sea faunas are related both to adjacent shelf communities and to those in other deep oceans, and both submergence and emergence processes can occur. Nowadays, natural and anthropogenically driven climate change processes shape the Southern Ocean marine fauna and despite our knowledge of the evolutionary historic developments, it is difficult to anticipate how these processes will drive speciation, extinction or the SO food web in future. 2.2 Programmes and Expeditions to the SO Deep Sea Since the early exploratory phase of Antarctic research, and in the course of modern programs such as EPOS, EASIZ, ANDEEP, CAML, EBA, LGP (e.g. Dayton 1990; Arntz et al. 1997; Brandt 1991; Arntz and Clarke 2002; De Broyer et al. 2003; 2 Southern Ocean Deep-Sea Isopod Biodiversity Research 23 Clarke and Johnston 2003; Clarke et al. 2006; Brandt et al. 2007a, b, c), benthic life of the SO has been a subject of great interest. However, none of the deep-sea biology studies in the Southern Ocean was devoted exclusively to the deep sea. Between 1950 and 1960, during Russian and U.S. expeditions of the RVs Eltanin, Glacier, Akademik Kurchatov, and Akademik D. Mendeleiev, deep-sea samples had been taken occasionally. The first deep-sea expedition with HMS Challenger sampled the Beagle Channel and several deep-sea stations. Later, in 1994, the Magellan area was sampled again during the IBMANT programme (Interactions between the Magellan Region and the Antarctic, RV Polarstern) (Arntz and Rios 1999). During EPOS (European Polarstern Studies) and EASIZ (Ecology of the Antarctic Sea Ice Zone), some deep-sea data were obtained from the slope but rarely from abyssal sites. However, both programmes have been biologically outstanding and have provided a wealth of benthic data on species of all taxonomic groups and functional guilds of the high Antarctic Weddell Sea and the Antarctic Peninsula (Arntz and Gutt 1997; Arntz and Clarke 2002; Arntz and Brey 2003). Most information on the ecology of benthic deep-sea fauna in the Weddell Sea comes from a few stations sampled during EASIZ II in 1998 (Arntz and Clarke 2002). The ANDEEP (ANtarctic benthic DEEP-sea biodiversity: colonisation history and recent community patterns) expeditions took place in 2002–2005 in order to investigate this little known realm of the SO and provide first insights into the biodiversity and biogeography of the SO deep sea. ANDEEP con- tributed to the CoML (Census of Marine Life) projects CeDAMar (CEnsus of the Diversity of Abyssal Marine Life) and CAML (Census of the Antarctic Marine Life) and aimed to conduct the first comprehensive survey of megafaunal, macrofaunal and meiofaunal deep-water communities in the Scotia and Weddell Seas. 2.3 Patterns of Biodiversity in the Deep Sea 2.3.1 High Levels of Novel Biodiversity in the Southern Ocean SO benthic shelf communities display high levels of endemism, gigantism, slow growth, longevity and late maturity. In the deep sea it still remains virtually impossible to obtain animals alive and undamaged from abyssal depths and thus knowledge of the deep-sea faunal composition, particularly in the SO, is still scarce in comparison with that from shelf and upper slope environments and we know almost nothing about the physiology, autecology or life histories of the SO deep-sea organisms. During the ANDEEP project the Scotia and Weddell seas were sampled (Brandt et al. 2004, 2007) and the geological and sedimentological backgrounds of this region were reviewed by Thomson (2004) and Howe et al. (2004). A novel approach of this project was sampling across a broad range of taxonomic groups. This was crucial because large-scale biodiversity and bioge- ography patterns largely depend on size, biology (feeding mode and reproductive patterns) and mobility of the taxa, their gene flow (compare also Rex et al. 2005), 24 A. Brandt as well as geological history, productivity, predation and the relationship between regional and local species diversity (Witman et al. 2004). The SO deep-sea communities are unique and highly diverse. The high per- centage (often [90%) of new species in most taxa (Brandt et al. 2007a, b, c) and the high degree of endemism of many groups may reflect undersampling of the area. The high benthic diversity can probably be attributed to the constant, cold environment since about the last 34 m.y. The true deep-sea benthic fauna occurred at depths between 1,500 and 2,500 m depending on the taxon (Brandt et al. 2007c). There is a deep-sea affinity with the Antarctic shelf (Lipps and Hickman 1982; Brandt 1991; Brandt et al. 2007b), but some of the species can also be found in adjacent abyssal deep-sea basins (Brandt et al. 2004; Brandt et al. 2007a, b, c). This can be explained by repeated submergence and emergence processes during the evolution of invertebrate taxa and also by the eurybathy of the slope and deep- sea inhabitants (Brey et al. 1996). For example, Foraminifera, revealed close biogeographic links at the species level between deep Weddell Sea localities and those from similar depths in the North Atlantic and Arctic. The interesting bio- geography of Arctic and Southern Ocean foraminiferan species might be due to their occurrence in the Weddell Sea, a major source of the world’s deep water production, which could enhance the deposition of organic matter to the SO deep- ocean floor (Thomas and Gooday 1996; Brandt et al. 2007b). Isopod and poly- chaete slope assemblages included species that have invaded from the shelf. In sponges and molluscs the shelf and slope assemblages were more distinct. Abyssal faunas showed stronger links to other oceans, particularly the Atlantic, but mainly within good dispersers such as foraminiferans and polychaetes (Brandt et al. 2007b, c). Poor dispersers, like isopods, ostracods and nematodes are SO species rich and include many ‘‘apparently endemic’’ species. In summary, the ANDEEP data provide a valuable basis for exploring the evolutionary significance of the varied biogeographic patterns observed in this remote environment (Brandt and Hilbig 2004; Brandt et al.