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Marine Life in the Antarctic

Julian Gutt1, Graham Hosie2, Michael Stoddart3

1Alfred Wegener Institute, Bremerhaven, Germany
2Department of the Environment, Water, Heritage and the Arts, Australian Antarctic Division, Hobart, Australia
3Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Australia

 

11.1. Introduction

The Southern Ocean covers 35 million km 2 and comprises about 10% of the Earth's oceans. Of the 4.6 million km 2 of continental shelf, one-third is covered by floating ice shelves (Clarke & Johnston 2003). The sea ice oscillates between a coverage of 60% in winter and 20% in summer and is, together with the sea beneath, the main driver of the Antarctic ecosystem and the Earth's ocean circulation. These conditions have caused a partial isolation of the ecosystem in the past 30 million years, and the unique environment has allowed an evolutionary dispersal of Antarctic species into the adjacent ocean's deep sea and vice versa. Recent ecological conditions in Antarctic waters not only attract the charismatic great whales, but also birds and deep-sea invertebrates from the entire world's ocean. The Census of Marine Life recognized that the Southern Ocean is home of a key component of the Earth's biosphere and launched the Census of Antarctic Marine Life (CAML) in 2005, considered the major marine biodiversity contribution to the International Polar Year 2007–8. It followed international initiatives such as the SCAR projects “BIOMASS” (see BIOMASS Scientific Series), “Ecology in the Antarctic Sea-Ice Zone (EASIZ, Arntz & Clarke 2002; Clarke et al. 2006), “Evolution in the Antarctic” (EVOLANTA, Eastman et al. 2004), and “Evolution and Biodiversity in the Antarctic” (EBA, results of the 10th SCAR-Biology Symposium to be published as a special volume of Polar Science) as well as the projects “European Polarstern Study” (EPOS, Hempel 1993), “Investigación Biológica Marina en Magallanes relacionada con la Antártida” (IBMANT, Arntz & Ríos 1999; Arntz et al. 2005), “ANtarctic benthic DEEP-sea biodiversity (ANDEEP, Brandt & Ebbe 2007), and “Latitudinal Gradient Project” (LGP, Balks et al. 2006). Consequently, CAML was based on a very active international scientific community and covered a broad spectrum of organisms ranging from microbes to mammals. It cooperated closely with other Census projects, especially the Ocean Biogeographic Information System (OBIS), Census of Marine Zooplankton (CMarZ), Biogeography of Deep-Water Chemosynthetic Ecosystems (ChEss), Arctic Ocean Diversity (ArcOD), and Census of Diversity of Abyssal Marine Life (CeDAMar), because of two aspects. First, by combining all three other oceans by the Antarctic Circumpolar Current (ACC), the Southern Ocean provides a link for most large marine ecosystems. Second, a considerable part of the rich Antarctic fauna is unique and thus contributes significantly to the world's total marine biodiversity.

The scientific aim of CAML was to provide essential knowledge to answer the most challenging question of the future of the Antarctic ecosystem in a changing world. The strategic objective was to create a network of knowledge within the research community and to provide a forum for communication, including the most intensive outreach activities that ever concerned the work of Antarctic marine biologists. Thanks to the CAML two overarching initiatives, the biogeographic data portal SCAR-MarBIN and the barcoding initiative, intensified their efficiency, providing essential tools for scientists to share data. CAML was one of the leading Antarctic projects of the International Polar Year 2007–8 and was part of the biology program of the Scientific Committee on Antarctic Research (SCAR). Although the Census/CAML was able to support scientific coordination, the field work was funded by the national Antarctic research programs.

This review is compiled at an early stage of CAML's synthesis phase. It provides a preliminary overview and concentrates mainly on results from core projects presented in the Genoa workshop in May 2009, to be published in Deep-Sea Research II in 2010 and edited by S. Schiaparelli et al. All references cited herein as “submitted” refer to this special CAML volume.

 

11.2. The Background

 

11.2.1. Environmental Settings

The extreme seasonality in the Antarctic results in a permanently dark winter and a summer with 24 hours sunshine south of 66° 33¢ S. The low temperature, and consequently the formation of the sea ice, is due to the low angle of irradiation of the sun, the high albedo of ice, and the zonal atmospheric and oceanographic circulation. The marine habitat is geographically limited to the south by a glaciated coast. The ACC combines all three other ocean basins and in the north it adjoins warmer waters at the Antarctic Convergence (Fig. 11.1). Over evolutionary time the Antarctic ecosystem experienced a permanent advance and retreat of continental glaciation which started with the formation of the ACC 25 million to 30 million years ago and has continued with obvious glacial–interglacial cycles in the past 900,000 years.

 Figure Figure 11.1 Temperature of the Southern Ocean; at the sea surface (A), where the Antarctic Convergence is clearly indicated by the sharp gradient between warm (red) to cold (blue) temperatures, white areas within Antarctic waters indicate no data due to sea-ice cover; at the sea floor (B). For details of the occurrence of relatively warm water west of the Antarctic Peninsula, see Clarke et al. (2009). Graph by H. Griffiths and A. Fleming, British Antarctic Survey; data: NASA.
 

11.2.2. History of Antarctic Research and Exploitation

The era of early naturalists was related to both the discovery of the unknown region and the exploitation of natural resources. One example is the German naturalist Georg Forster, who participated with his father Johann Reinhold in James Cook's second trip around the world (1772–75, Fig. 11.2). Another example is the Weddell seal, which was named after the Scottish sealer James Weddell who in 1823 reached 74°34¢ S, the most southerly position ever reached at that time. The famous Adélie penguin was named after the wife of the French explorer Jules Dumont d'Urville, who traveled twice to Antarctica between 1838 and 1840. Milestones of taxonomic surveys (Dater 1975) started with the famous Challenger expedition (1872–76) which resulted in 38 volumes of scientific results: 4,714 new species were discovered of which several were from the Antarctic. The Belgica undertook the first truly scientific expedition to high-latitude Antarctic waters, during which she advanced farther south than any ship before and overwintered in 1898–99 west of the Antarctic Peninsula. The Valdivia expedition of 1898–99 contributed substantially to the understanding of global oceanography and included biological deep-sea sampling in the sub-Antarctic. Highly efficient were also the German Antarctic expedition with the Gauss (1901–03), the Swedish South Polar Expedition with the Antarctica (1901–04), and the British Scotia expedition (1902–04) which conducted trawling and dredging studies of pelagic and benthic organisms. The period 1925–39 was dominated by the Discovery expeditions from which publications, including those of recent surveys, are still ongoing.

 Figure Figure 11.2 Original drawing of the chinstrap penguin, Pygocelis antarctica (J.R. Forster, 1781) by Georg Forster, Handschriftenabteilung der Thüringischen Universitäts- und Landesbibliothek Jena, Germany, MsProv.f 185 (1).

The exploitation of natural resources started at the beginning of nineteenth century. Populations of Antarctic fur and elephant seals crashed close to extinction by the 1820s. Whaling started at the beginning of the twentieth century. The biomass of the largest species – blue, fin, humpback, southern right, and sei whales – were reduced to between 50% and 0.5% of their original worldwide stock whereas the smallest, the Antarctic minke, became most abundant (Laws 1977). Thus, the natural dominance pattern of whale species was turned upside-down. Interesting calculations have been made about the negative impact of the whaling to deep-sea animals since whale carcasses have no longer been important food sources for marine organisms (Jelmert & Oppen-Berntsen 1995). Bottom trawling in the 1960s reduced the stocks of the marbled rock cod (Notothenia rossii) and mackerel ice fish (Champsocephalus gunnari) west of the Antarctic Peninsula (Kock 1992) within very short periods, and devastated slow-growing benthic communities. The exploitation of natural resources was the most effective anthropogenic impact that Southern Ocean biodiversity ever experienced. However, the hitherto inviolacy of most high-latitude Antarctic marine habitats is almost unique on Earth, but the ecosystem is increasingly threatened by the new longline fishing and by the impact of climate change.

 

11.2.3. Modern Pre-CAML Biodiversity Studies

In the 1980s, ecological analyses using bulk parameters (see, for example, http://ijgofs.whoi.edu) tried to solve so-called “process orientated” questions without spending much time determining species diversity. Among the few studies with high taxonomic resolution, outstanding progress was made by the work on the evolutionary radiation of fish (Eastman & Grande 1989). In this phase the macrobenthos became known to be regionally dominated by sessile suspension feeders (Bullivant 1967); their communities later turned out to be more dynamic than previously expected (Dayton 1990; Arntz & Gallardo 1994; Gutt 2000, 2006; Gutt & Piepenburg 2003; Potthoff et al. 2006; Barnes & Conlan 2007; Seiler & Gutt 2007; Smale et al. 2008). Plankton studies added substantial information to the traditional view of the simple Antarctic pelagic system consisting only of algae, krill (Euphausia superba), and few apex predators. Small organisms became known to contribute to the microbial loop by being relevant for the re-mineralization in a partly iron-limited “high nutrient – low chlorophyll” system. Improved sea-ice research elucidated the diversity not only of unicellular algae but also of metazoans living in and associated with this unique habitat (Thomas & Dieckmann 2009), including the trophic key species of the Antarctic food web, the Antarctic krill (Thomas et al. 2008).

 

11.3. CAML Projects: Advancing Knowledge

 

11.3.1. The Scientific Strategy

At first the term “census” had to been interpreted literally: species and specimens were identified and counted. Secondly, CAML researchers raised the question why some of these species co-exist in specific communities whereas others do not, the answers demanding both evolutionary and ecologically approaches at various spatial scales.

 

11.3.2. What Were the Major Gaps?

The scientific effort during the pre-CAML phase reflected the good accessibility of the area around the Antarctic Peninsula and historical developments in poorly accessible areas – for example the inner Weddell and Ross Seas – with large gaps in between. The Antarctic deep sea was only known from studies with selective samples with a reduced taxonomic scope. Life in some typical Antarctic habitats was very poorly known, especially from under the ice shelves and the permanent pack ice. The biodiversity not only of microorganisms, but also of rare charismatic species, for example toothed whales, had almost been overlooked and some historic data were hardly accessible. The identification of many invertebrate eggs and larvae to the species level was impossible, and only hypotheses existed in relation to cryptic species. The question about the relation between ecosystem functioning and biodiversity has a long tradition but it is still – at least for the Antarctic – difficult to address. Finally, the pre-CAML era was characterized by the knowledge that climate change would not stop at the Antarctic Circle, but background information and observations on its impact to the ecosystem were scarce.

 

11.3.3. Approaches to Closing Gaps

Core strands of CAML were scientific expeditions and the data management allowing overarching analyses. Success has also been reached through the standardization of field methods, for example by using the standard nets, continuous plankton recorders, video-equipped remotely operated vehicles (ROVs), or sleds. The major tool for ensuring information management is the “Marine Biodiversity Information Network of SCAR” (SCAR-MarBIN, www.scarmarbin.be), being the local node of the Census of Marine Life/UNESCO OBIS network. It was initiated by the Royal Belgian Institute of Natural Sciences and CAML became its major research partner. So far, over 1 million geo-referenced records from 156 datasets are available. The Register of Antarctic Marine Species (RAMS) comprises 6,551 primarily benthic and 702 pelagic species (as at May 2010) and is constantly updated by over 70 editors and contributing scientists (De Broyer & Danis submitted). Datasets range from historic information going back to 1781 to recent and genetic data. A barcode manager supported CAML scientists in analyzing over 11,000 sequences (Grant & Linse 2009). Thus, CAML contributes to the Barcode of Life project (BOLD; www.barcodinglife.org) and the “Fish Barcode of Life Initiative” (FISH-BOL, www.fishbol.org). Spatially explicit ecological models were developed, for example to predict potential fish habitats and to simulate the succession of biodiversity after disturbance (Potthoff et al. 2006). A new tool, “GeoPhyloBuilder” (www.nescent.org/wg_EvoViz/GeoPhyloBuilder), and network analyses (Raymond & Hosie 2009) are being used to visualize phylogeographic data.

 

11.3.4. Evolutionary Large-Scale Patterns and Non-Circumpolar Cryptic Species

The question of bipolar species experienced a renaissance under CAML. No doubt exists about the annual pole-to-pole migrations of the blue, humpback and fin whales as well as seabirds such as the Arctic tern. In addition, a bipolar occurrence of a few benthic and pelagic invertebrate species had been controversially discussed. A recent comparison between the Register of Antarctic Marine Species and the ArcOD database revealed approximately 230 species names to which occurrences from both polar regions were attributed. Recent attempts to provide evidence for their existence with genetic methods were successful, for example for the amphipod Eurythenes gryllus occurring at the upper slopes of the Canadian Arctic, around Antarctica, and in the deep sea in between (France & Kocher 1996;s De Broyer et al. 2007). Such evidence failed for the pteropod Limacina helicina, being so far considered as one species but having 32% divergence between both polar regions (J.M. Strugnell, unpublished observations). Another weak example is the sponge Stylocordyla borealis, which has two sympatric distinct growth forms even within the Antarctic, one with a thick stalk, the other like a lollipop. For the widespread and well-known deep-sea holothurian Elpidia glacialis, which has strong polar emergence, six subspecies are known and, using traditional methods, it is only a matter of interpretation not to consider these as six true species. A morphologic and genetic documentation of the existence of bipolar species among deep-sea komokiaceans and other foraminiferan-like protists was highlighted by Brandt et al. ( 2007a). A high genetic and morphologic similarity was found for the planktonic anthomedusa genus Pandea between the north Pacific near Japan and East Antarctica (D. Lindsay et al., unpublished observations). In conclusion, it remains open whether genetic methods will continue to confirm the bipolar occurrence of species and, consequently, gene-flow over extremely long distances or whether true bipolar species will remain rare exceptions.

Before we can understand the role of the Southern Ocean within global biodiversity patterns and underlying evolutionary processes, our knowledge of geographic coverage has to be completed, especially for the deep sea of the Southern Ocean covering 27.9 million km 2. Recent investigations, especially those of the ANDEEP expeditions, revealed an extraordinarily high species richness at abyssal depths. More than 1,400 species of invertebrates were identified (from only the taxa investigated) and more than 700 of these were assumed to be new to science (Brandt et al. 2007a). For example, within protists, the formaminiferan-like komokiaceans were not known from the Southern Ocean deep sea. Now 50 species are reported from that area of which 35 are undescribed (Godday et al. 2007). Within the macrofauna, the isopods were the most diverse taxon with 674 species, of which 87% are putative new species. If we compare these numbers with the more than 4,400 known marine isopod species from the world oceans, the recent Southern Ocean deep-sea expeditions will add approximately 15% to our knowledge on the worldwide zoogeography of that taxon. For the megafauna, the occurrence of new Hexactinellida (glass sponges) and carnivorous demosponges and the first report of Southern Ocean calcareous sponges (Calcarea) were among the most surprising results (Janussen & Reiswig 2009; Rapp et al. in press).

Despite the incomplete faunal knowledge, several studies show linkages between the Antarctic fauna and that of the adjacent deep sea. These studies benefited from a new biologically orientated view on Antarctic seawater temperature. Satellite images show that the well-known Southern Ocean hydrodynamic isolation separating warm surface water in the north from cold water in the south along the Antarctic Convergence is superimposed by horizontal gyres (Fig. 11.1). These allow floating material, for example larvae, other pelagic organisms, pieces of algae, or material serving as substratum for benthic species to penetrate this boundary in both directions (Clarke et al. 2005; Barnes et al. 2006). Thus, it is mainly the temperature difference that allows only very few species to survive at both sides of the Antarctic Convergence, rather than the front acting as a hydrodynamic barrier. The comparison between the surface and near-seabed temperature shows more obviously than ever before how less isolated are the Antarctic bottom-dwelling fauna – including those on the Antarctic shelf – from those in the adjacent deep sea (Fig. 11.1). This has relevance not only for future scenarios under climate change but also major implications for the dispersal of animals at evolutionary and ecological timescales.

Hypotheses have always existed about such large-scale dispersal processes. The colonization of the deep sea by Antarctic organisms seemed to be most likely and most common, after the post-Gondwana breakup and establishment of the ACC. Using genetic techniques, phylogenetic trees can be better linked to plate tectonics, especially the opening of deep-water basins between Antarctica and adjacent continents and the resulting global water mass circulation. Recently, evidence has been provided for an evolutionary dispersal of deep-sea octopods that evolved from common Antarctic ancestors around 30 million years ago into the northerly adjacent deep sea, called tropic submergence (Strugnell et al. 2008). Similar development can be reconstructed for isopods (Asellota, Antarcturidae, Acanthaspidiidae, Serolidae, Munnidae, and Paramunnidae; Raupach et al. 2004, 2009; Brandt et al. 2007b), the amphipod Liljeborgia, of which the Antarctic representatives still have eyes whereas their deep-sea relatives are blind (d'Udekem d'Acoz & Vader 2009), and the mollusk Limopsis (K. Linse, unpublished observations). In the opposite direction, multiple evolutionary invasions from the deep sea to the Antarctic shelf, called polar emergence, are very likely for some other isopods, for example Munnopsidae, Desmosomatidae, and Macrostylidae because of their lack of eyes (Raupach et al. 2004, 2009). Similar interpretations are made for representatives of the deep-sea octopod Benthoctopus (Strugnell et al. in press). Such examples of long-term evolutionary dispersal have also been described for other taxa such as hexactinellid sponges, pennatularians, stalked crinoids, and elasipod holothurians but have never been studied in detail. Using techniques to decipher the molecular clock, the echinoid Sterechinus and the ophiuroid Astrotoma agassizii (Hunter & Halanych 2008; Díaz et al. in press) were found to be examples of a split between shallow Antarctic and subantarctic species, which occurred not more than 5 million years ago when glacial–interglacial cycles started. This was long after Antarctica disconnected from South America and the Antarctic Convergence formed. Similar results are available for the limpet Nacella (González Wevar et al. in press) and the bivalve Limatula (Page & Linse 2002). Perhaps the most extreme example for cryptic speciation is the sea slug Doris kerguelensis, from which approximately 29 lineages are derived (Wilson et al. 2009). This puts the development of the Antarctic Convergence 25 million years ago as a main agent of vicariance in question. Surprisingly, this relatively recent split of species within a broad geographical range happened independently of their dispersal potential, because these taxa clearly differ from each other in their early life history traits.

If, despite these few faunistic teleconnections, Antarctica's fauna differs considerably from that of the adjacent slope and the deep sea, for example in the Weddell Sea (Kaiser et al. in press) and from that north of the Antarctic Convergence as for deep-sea gastropods (Schwabe et al. 2007; Schrödl et al. ), the reasons must be searched for in polar-, slope-, or deep-sea-specific environmental parameters. At the level of evolution one major mechanism to generate such biogeographical heterogeneity on the Antarctic shelf is the climate diversity pump, being a modified vicariance concept (Clarke & Crame 1989). Until a few years ago this concept was used to explain a relatively high richness of species with a predominantly circumpolar distribution. It was assumed that during glacial periods populations were spatially separated by grounded ice shelves and as a consequence a radiation of species occurred. At the end of a glacial period when the ice retreated, these new species supposedly mixed around the continent but were obviously not able to interbreed anymore. This has resulted in sibling species, for example ten sympatric octopods of the genus Pareledone (Allcock 2005; Allcock et al. 2007, in press), analogous to approximately eight cryptic species of the isopod Ceratoserolis (Raupach & Wägele 2006) and six allopatric species of Glyptonotus (Held 2003; Held & Wägele 2005; Leese & Held 2008; C. Held, unpublished observations). Mostly allopatric cryptic species also occur among the dendrochirote and aspidochirote holothurians, for example among Laetmogone wyvillethomsoni and Psolus charcoti (Oapos;Loughlin et al. in press) and the amphipod Orchomene sensu lato (Havermans et al. submitted). Significant genetic differences have also been found among the pantopod Nymphon in the East Antarctic Peninsula and Weddell Sea (Arango et al. in press) and the comatulid crinoid Promachocrinus west of the Peninsula and in the Weddell Sea (Wilson et al. 2007) as well as off East Antarctica (L. Hemery & M. Eléaume, unpublished observations). The narcomedusa Solmundella bitentaculata was previously thought to be a single ubiquitous species but molecular studies suggest that it contains at least two cryptic species (D. Lindsay et al., unpublished observations).

Resulting from this, a milestone in evolutionary biodiversity research of the past years might be the paradigm shift from an assumed circumpolar macrobenthos to an obviously long-term patchy occurrence of closely related sibling or cryptic species in many taxa.

If, however, the large-scale pattern of the shelf-inhabiting Antarctic macrobenthos is analyzed, using the current best available dataset (Fig. 11.3), only one single bioregion is found (Griffiths et al. 2009). The exception is gastropods following the pattern of a split into the Scotian subregion mainly comprising the Antarctic Peninsula and the High Antarctic Province, as proposed by Hedgpeth (1969), which was already questioned a few years later (Hedgpeth 1977). The difference between the interpretations is that the one-bioregion result is based on fully reproducible presence/absence datasets with an incomplete systematic coverage. Hedgpeth's conclusion of two provinces included impressions of abundances and consequently of dominance patterns referring mainly to higher taxa and life forms. Additional bias can be caused by the fact that traditional results from the Peninsula were mainly from shallow waters whereas the rest of the Antarctic shelf was sampled at greater depth.

 Figure Figure 11.3 Species richness represented by color-coded residuals. Red implies higher than expected numbers of species (for the number of samples) and green lower than expected. Numbers of species ranged from 1 to 400 benthic (A) and from 1 to 52 pelagic (B). The benthic group covers a broad range of invertebrates. Pelagic includes all zooplankton, fish, sea birds, seals, penguins, and whales. Neither group includes plants and microbes as the available data are insufficient. Residuals are calculated from the regression of observed species number on sample number per 3° × 3° grid cell in benthic and pelagic data from the 122 datasets available in SCAR-MarBIN as of May 2009 (www.scarmarbin.be/scarproviders.php; De Broyer & Danis). Sampling effort is eliminated statistically, but intensive sampling by the Continuous Plankton Recorder off East Antarctica remains visible (see also Griffiths et al. submitted). Graph and data processing: H. Griffiths and Danis.

The Southern Ocean Continuous Plankton Recorder (CPR) Survey (Hosie et al. 2003) was the major contribution of the CAML to the research on the Antarctic pelagic system and provided a close link to the Convention on the Conservation of Antarctic Marine Living Resources (CCAMLR). Use of the CPR has significantly increased our knowledge of Antarctic plankton communities by extending the time series and increasing the geographic coverage of the Southern Ocean CPR Survey to approximately 70% of the region, with the highest resolution off East Antarctica. In the 2007/2008 CAML-campaign alone, 15 nations were involved using eight ships conducting 88 successful tows and over 23 transects at 10 m water depth. Since 1991, 25,791 samples have been taken with a resolution of 5 nautical miles, covering a total of 128,955 nautical miles (Southern Ocean CPR Data Set; http://data.aad.gov.au/aadc/cpr). In terms of large-scale patterns, previous analyses of the Southern Ocean CPR data have shown latitudinal zonation of zooplankton across the ACC, the Sub-Antarctic Front (SAF) acting as a geographic barrier with different species found north and south of it (Hunt & Hosie 2003, 2005). The copepod Oithona similis is not only an example for the large-scale pattern (Fig. 11.4) but also for temporal changes (see below).

 Figure Figure 11.4 Predictions for the spatial patterns of relative abundance of the cyclopoid copepod Oithona similis in January using boosted regression tree modeling. Data from the Southern Ocean Continuous Plankton Recorder survey were combined with environmental variables such as chlorophyll a, bathymetry, ice cover, sea surface temperature, and nutrients, to predict the circum-Antarctic distribution of O. similis for bioregionalization. Gray indicates areas with insufficient combined data. From Pinkerton et al. ( 2010); oceanographic fronts according to Orsi et al. ( 1995).

South of the SAF and moving toward the continent, distinct assemblages could be identified which were associated with zones within the ACC. Differences between the assemblages were subtle and based primarily on variation in abundances of species relative to each rather than differences in species composition itself. The CAML provided the opportunity to assess circum-Antarctic patterns. Only night data from the period between December and February were used, rare taxa were excluded, adults and juveniles were merged, and unidentified groups removed. The results on the fauna sampled by the CPR showed no clear longitudinal differences between sectors. In other words, the species composition and abundances of zooplankton within any band of the ACC are effectively the same: it is one community. Tows in January 2008 across Drake Passage did show lower abundances and diversity, but no substantial differences from other transects were observed later in February. The Bellingshausen Sea did show very low abundances and fewer plankton species. The large concentrations of krill, especially in the West Atlantic sector (see Atkinson et al. 2008), were not sufficiently covered by this survey. Probably because of the method used, a neritic community only became obvious among the semipelagic, cryopelagic (ice preferring), and pelagic fish (Koubbi et al. ), which is dominated west of the Antarctic Peninsula by Antarctic rock cod Notothenia and at high Antarctic latitudes by Trematomus, Channichthyidae (icefish) (Fig. 11.5A), and the pelagic Pleuragramma antarcticum (O'Driscoll et al. in press). Other planktonic studies embedded in CMarZ (see Chapter 13) used nets with smaller mesh sizes and sampled at greater depth than before. As a consequence, not only were the planktonic fauna more diverse than previously thought, but also many new species were discovered, including the ice-associated fauna.

 Figure Figure 11.5 (A) Antarctic ice fish (Pagothenia macropterus) exhibit the most developed adaptation to low temperatures. Thus they are traditionally a target of evolutionary, physiological, genetic, and ecological studies. Repository reference DOI: 120.1594/PANGAEA.702107, also for Fig. 5F. (Photograph: J. Gutt and W. Dimmler; © AWI/Marum, University of Bremen.) (B) Hexactinellid sponges (Rossella nuda, Scolymastra joubini) are common on the Antarctic shelf, where they grow to a size of up to 2 m. They indicate areas free of disturbance for long periods owing to their slow growth when they are adult. Eastern Weddell Sea, 233 m water depth. (Photograph: J. Gutt and W. Dimmler; © AWI/Marum, University of Bremen.) (C) Concentrations of bryozoans can form together with hydroids and demosponges a microhabitat for other animals (for example holothurians) as seen here north of D'Urville Island, West of the Antarctic Peninsula, at ca. 230 m water depth. Owing to their life traits, they can serve as indicator species for Vulnerable Marine Ecosystems for CCAMLR. (Courtesy of S. Lockhart and D. Jones; © US-AMLR program.) (D) The concentrations of hydrocorals of the genus Errina and other sessile organisms such as sponges (background) at the George V Shelf, 65.7° S 140.5° E, 680 m depth, were the reason for designating this area as a “Vulnerable Marine Ecosystem”. (Courtesy of A. Post and M. Riddle; © Australian Antarctic Division.) (E) Stalked crinoids (Hyocrinidae) dominate the macro-epibenthos on parts of Admirality Seamount (67° S 171° E) at 550–600 m depth. They are unknown from elsewhere on the Antarctic shelf. (Courtesy of D. Bowden, National Institute of Water and Atmospheric Research; © Land Information New Zealand.) (F) Ascidians (Molgula pedunculata) can form almost monospecific assemblages in highly dynamic areas owing to iceberg scouring or disintegrating ice shelves. The Larsen B area, east of the Antarctic Peninsula, was covered by ice shelf five years before the photograph was taken, 188 m water depth. (Photograph: J. Gutt and W. Dimmler; © AWI/Marum, University of Bremen.)
 Figure Figure 11.5(continued) (A) Antarctic ice fish (Pagothenia macropterus) exhibit the most developed adaptation to low temperatures. Thus they are traditionally a target of evolutionary, physiological, genetic, and ecological studies. Repository reference DOI: 120.1594/PANGAEA.702107, also for Fig. 5F. (Photograph: J. Gutt and W. Dimmler; © AWI/Marum, University of Bremen.) (B) Hexactinellid sponges (Rossella nuda, Scolymastra joubini) are common on the Antarctic shelf, where they grow to a size of up to 2 m. They indicate areas free of disturbance for long periods owing to their slow growth when they are adult. Eastern Weddell Sea, 233 m water depth. (Photograph: J. Gutt and W. Dimmler; © AWI/Marum, University of Bremen.) (C) Concentrations of bryozoans can form together with hydroids and demosponges a microhabitat for other animals (for example holothurians) as seen here north of D'Urville Island, West of the Antarctic Peninsula, at ca. 230 m water depth. Owing to their life traits, they can serve as indicator species for Vulnerable Marine Ecosystems for CCAMLR. (Courtesy of S. Lockhart and D. Jones; © US-AMLR program.) (D) The concentrations of hydrocorals of the genus Errina and other sessile organisms such as sponges (background) at the George V Shelf, 65.7° S 140.5° E, 680 m depth, were the reason for designating this area as a “Vulnerable Marine Ecosystem”. (Courtesy of A. Post and M. Riddle; © Australian Antarctic Division.) (E) Stalked crinoids (Hyocrinidae) dominate the macro-epibenthos on parts of Admirality Seamount (67° S 171° E) at 550–600 m depth. They are unknown from elsewhere on the Antarctic shelf. (Courtesy of D. Bowden, National Institute of Water and Atmospheric Research; © Land Information New Zealand.) (F) Ascidians (Molgula pedunculata) can form almost monospecific assemblages in highly dynamic areas owing to iceberg scouring or disintegrating ice shelves. The Larsen B area, east of the Antarctic Peninsula, was covered by ice shelf five years before the photograph was taken, 188 m water depth. (Photograph: J. Gutt and W. Dimmler; © AWI/Marum, University of Bremen.)
 Figure Figure 11.5(continued) (A) Antarctic ice fish (Pagothenia macropterus) exhibit the most developed adaptation to low temperatures. Thus they are traditionally a target of evolutionary, physiological, genetic, and ecological studies. Repository reference DOI: 120.1594/PANGAEA.702107, also for Fig. 5F. (Photograph: J. Gutt and W. Dimmler; © AWI/Marum, University of Bremen.) (B) Hexactinellid sponges (Rossella nuda, Scolymastra joubini) are common on the Antarctic shelf, where they grow to a size of up to 2 m. They indicate areas free of disturbance for long periods owing to their slow growth when they are adult. Eastern Weddell Sea, 233 m water depth. (Photograph: J. Gutt and W. Dimmler; © AWI/Marum, University of Bremen.) (C) Concentrations of bryozoans can form together with hydroids and demosponges a microhabitat for other animals (for example holothurians) as seen here north of D'Urville Island, West of the Antarctic Peninsula, at ca. 230 m water depth. Owing to their life traits, they can serve as indicator species for Vulnerable Marine Ecosystems for CCAMLR. (Courtesy of S. Lockhart and D. Jones; © US-AMLR program.) (D) The concentrations of hydrocorals of the genus Errina and other sessile organisms such as sponges (background) at the George V Shelf, 65.7° S 140.5° E, 680 m depth, were the reason for designating this area as a “Vulnerable Marine Ecosystem”. (Courtesy of A. Post and M. Riddle; © Australian Antarctic Division.) (E) Stalked crinoids (Hyocrinidae) dominate the macro-epibenthos on parts of Admirality Seamount (67° S 171° E) at 550–600 m depth. They are unknown from elsewhere on the Antarctic shelf. (Courtesy of D. Bowden, National Institute of Water and Atmospheric Research; © Land Information New Zealand.) (F) Ascidians (Molgula pedunculata) can form almost monospecific assemblages in highly dynamic areas owing to iceberg scouring or disintegrating ice shelves. The Larsen B area, east of the Antarctic Peninsula, was covered by ice shelf five years before the photograph was taken, 188 m water depth. (Photograph: J. Gutt and W. Dimmler; © AWI/Marum, University of Bremen.)
 Figure Figure 11.5(continued) (A) Antarctic ice fish (Pagothenia macropterus) exhibit the most developed adaptation to low temperatures. Thus they are traditionally a target of evolutionary, physiological, genetic, and ecological studies. Repository reference DOI: 120.1594/PANGAEA.702107, also for Fig. 5F. (Photograph: J. Gutt and W. Dimmler; © AWI/Marum, University of Bremen.) (B) Hexactinellid sponges (Rossella nuda, Scolymastra joubini) are common on the Antarctic shelf, where they grow to a size of up to 2 m. They indicate areas free of disturbance for long periods owing to their slow growth when they are adult. Eastern Weddell Sea, 233 m water depth. (Photograph: J. Gutt and W. Dimmler; © AWI/Marum, University of Bremen.) (C) Concentrations of bryozoans can form together with hydroids and demosponges a microhabitat for other animals (for example holothurians) as seen here north of D'Urville Island, West of the Antarctic Peninsula, at ca. 230 m water depth. Owing to their life traits, they can serve as indicator species for Vulnerable Marine Ecosystems for CCAMLR. (Courtesy of S. Lockhart and D. Jones; © US-AMLR program.) (D) The concentrations of hydrocorals of the genus Errina and other sessile organisms such as sponges (background) at the George V Shelf, 65.7° S 140.5° E, 680 m depth, were the reason for designating this area as a “Vulnerable Marine Ecosystem”. (Courtesy of A. Post and M. Riddle; © Australian Antarctic Division.) (E) Stalked crinoids (Hyocrinidae) dominate the macro-epibenthos on parts of Admirality Seamount (67° S 171° E) at 550–600 m depth. They are unknown from elsewhere on the Antarctic shelf. (Courtesy of D. Bowden, National Institute of Water and Atmospheric Research; © Land Information New Zealand.) (F) Ascidians (Molgula pedunculata) can form almost monospecific assemblages in highly dynamic areas owing to iceberg scouring or disintegrating ice shelves. The Larsen B area, east of the Antarctic Peninsula, was covered by ice shelf five years before the photograph was taken, 188 m water depth. (Photograph: J. Gutt and W. Dimmler; © AWI/Marum, University of Bremen.)
 Figure Figure 11.5(continued) (A) Antarctic ice fish (Pagothenia macropterus) exhibit the most developed adaptation to low temperatures. Thus they are traditionally a target of evolutionary, physiological, genetic, and ecological studies. Repository reference DOI: 120.1594/PANGAEA.702107, also for Fig. 5F. (Photograph: J. Gutt and W. Dimmler; © AWI/Marum, University of Bremen.) (B) Hexactinellid sponges (Rossella nuda, Scolymastra joubini) are common on the Antarctic shelf, where they grow to a size of up to 2 m. They indicate areas free of disturbance for long periods owing to their slow growth when they are adult. Eastern Weddell Sea, 233 m water depth. (Photograph: J. Gutt and W. Dimmler; © AWI/Marum, University of Bremen.) (C) Concentrations of bryozoans can form together with hydroids and demosponges a microhabitat for other animals (for example holothurians) as seen here north of D'Urville Island, West of the Antarctic Peninsula, at ca. 230 m water depth. Owing to their life traits, they can serve as indicator species for Vulnerable Marine Ecosystems for CCAMLR. (Courtesy of S. Lockhart and D. Jones; © US-AMLR program.) (D) The concentrations of hydrocorals of the genus Errina and other sessile organisms such as sponges (background) at the George V Shelf, 65.7° S 140.5° E, 680 m depth, were the reason for designating this area as a “Vulnerable Marine Ecosystem”. (Courtesy of A. Post and M. Riddle; © Australian Antarctic Division.) (E) Stalked crinoids (Hyocrinidae) dominate the macro-epibenthos on parts of Admirality Seamount (67° S 171° E) at 550–600 m depth. They are unknown from elsewhere on the Antarctic shelf. (Courtesy of D. Bowden, National Institute of Water and Atmospheric Research; © Land Information New Zealand.) (F) Ascidians (Molgula pedunculata) can form almost monospecific assemblages in highly dynamic areas owing to iceberg scouring or disintegrating ice shelves. The Larsen B area, east of the Antarctic Peninsula, was covered by ice shelf five years before the photograph was taken, 188 m water depth. (Photograph: J. Gutt and W. Dimmler; © AWI/Marum, University of Bremen.)
 Figure Figure 11.5(continued) (A) Antarctic ice fish (Pagothenia macropterus) exhibit the most developed adaptation to low temperatures. Thus they are traditionally a target of evolutionary, physiological, genetic, and ecological studies. Repository reference DOI: 120.1594/PANGAEA.702107, also for Fig. 5F. (Photograph: J. Gutt and W. Dimmler; © AWI/Marum, University of Bremen.) (B) Hexactinellid sponges (Rossella nuda, Scolymastra joubini) are common on the Antarctic shelf, where they grow to a size of up to 2 m. They indicate areas free of disturbance for long periods owing to their slow growth when they are adult. Eastern Weddell Sea, 233 m water depth. (Photograph: J. Gutt and W. Dimmler; © AWI/Marum, University of Bremen.) (C) Concentrations of bryozoans can form together with hydroids and demosponges a microhabitat for other animals (for example holothurians) as seen here north of D'Urville Island, West of the Antarctic Peninsula, at ca. 230 m water depth. Owing to their life traits, they can serve as indicator species for Vulnerable Marine Ecosystems for CCAMLR. (Courtesy of S. Lockhart and D. Jones; © US-AMLR program.) (D) The concentrations of hydrocorals of the genus Errina and other sessile organisms such as sponges (background) at the George V Shelf, 65.7° S 140.5° E, 680 m depth, were the reason for designating this area as a “Vulnerable Marine Ecosystem”. (Courtesy of A. Post and M. Riddle; © Australian Antarctic Division.) (E) Stalked crinoids (Hyocrinidae) dominate the macro-epibenthos on parts of Admirality Seamount (67° S 171° E) at 550–600 m depth. They are unknown from elsewhere on the Antarctic shelf. (Courtesy of D. Bowden, National Institute of Water and Atmospheric Research; © Land Information New Zealand.) (F) Ascidians (Molgula pedunculata) can form almost monospecific assemblages in highly dynamic areas owing to iceberg scouring or disintegrating ice shelves. The Larsen B area, east of the Antarctic Peninsula, was covered by ice shelf five years before the photograph was taken, 188 m water depth. (Photograph: J. Gutt and W. Dimmler; © AWI/Marum, University of Bremen.)

Microorganisms and the gelatinous plankton likely belonged to the most under-represented groups of organisms in Antarctic surveys. During the CAML phase, the understanding of both the extent and ecological variability of Antarctic marine bacterioplankton diversity was greatly enhanced. In just one study approximately 400,000 sequence tags spanning a short hypervariable region of the SSU rRNA gene were determined for 16 samples collected from four regions (Kerguelen Islands, Antarctic Peninsula, Ross Sea, and Weddell Sea) (Ghiglione & Murray, unpublished observations). This effort revealed over 25,000 different sequence tags, of which 13,000 represented equivalents to new species (at a distance greater than 0.03 from the nearest known sequence in public databases). Samples at a low-activity cold seep in the Larsen B area, west of the Antarctic Peninsula, revealed 29 seep-related operational taxonomic units of bacteria and 10 of Archaea, of which 20–30% have no closely cultivated relatives (Niemann et al. 2009). The numbers of gelatinous plankton species increased by a factor of 2–3, especially among hydromedusae, siphonophores, and scyphomedusae, particularly within the neritic assemblage (Lindsay et al., unpublished observations).

Apex predators were also included in the CAML studies. An extensive census in the Atlantic sector of the Southern Ocean, mainly west and east of the Antarctic Peninsula (Scheidat et al. 2007a), showed that whale diversity was higher than expected. Four rare toothed whales from the family of the beaked whales (Ziphiidae) were registered: Arnoux's beaked whale (Berardius arnuxii), Gray's beaked whale (Mesoplodon grayi), strap-toothed whale (M. layardii), and southern bottlenose whale (Hyperoodon planifrons), the last with occurrences only in waters deeper than 500 m. Some of the sightings were southernmost records (Scheidat et al. 2007b).

 

11.3.5. Ecologically Driven Community Heterogeneity between Extremes

One milestone to which CAML researchers contributed is a paradigm shift from a supposed Antarctic circumpolar benthos being rich in species, life forms, and biomass (Figs. 11.5B, C and D) to the general understanding that there is a full range of benthic assemblages from extremely diverse to extremely meager (Fig. 11.6).

 Figure Figure 11.6 Scheme of Antarctic macro-benthic assemblages. From Turner et al. ( 2009), modified after Gutt ( 2007).

Within such a heterogeneous patchwork, poor assemblages were already known decades ago; however, during the CAML phase these were more intensively studied, for example on seamounts (Fig. 11.5E) (Bowden et al. submitted) and in areas formerly covered by the ice shelf (Fig. 11.5F) (Gutt et al. in press). This extreme variability can also be attributed to the pelagic system, where on the one hand krill swarms are extremely rich in biomass, but on the other hand extremely low biomass and production are known from the winter season, with a deepest-ever recorded Secchi depth of 80 m, measured on October 13, 1986 in the Weddell Sea (Gieskes et al. 1987). At the seafloor, extremely low abundances can be found in different habitats; at shallow depths with permanent disturbance, in fresh iceberg scours (Gutt & Piepenburg 2003), and under the ice shelf (Gutt 2007). The question of how extremely low abundances can be explained is especially challenging. Unfavorable environmental conditions can lead to the total absence of specific life forms or ecological guilds, such as filter feeders. If food supply is poor then perhaps no more than a few individuals the size of a tennis ball in an area of a tennis court could exist. However, abundances in the formerly ice shelf covered Larsen B area east of the Antarctic Peninsula remained at obviously even lower levels, observed in situ during a Polarstern expedition in 2007, five years after the ice shelf disintegrated (Gutt et al. in press). Because reduced long-term dispersal capacity, at least of species with a circumpolar distribution, can hardly explain this alone, a hypothesis was developed that a poor temporal predictability of food supply during the early life phase could explain extremely rare abundance of adults (Gutt 2007).

Very low biodiversity is also known from different seamounts. At the Admiralty Seamount (East Antarctic), high local densities of stalked crinoids (Hyocrinidae, Fig. 11.5E), brachiopods, and suspension-feeding ophiuroids (Ophiocamax) may reflect ecological conditions such as low predation pressure and low food supply or evolutionary factors (Bowden et al. submitted). The sediment here was dominated by crinoid ossicles, indicating a long persistence of these populations. In contrast, the benthos of the Scott Seamount less than 400 km away at the same latitude was characterized by a higher abundance of predators, including lithodid crabs, regular sea urchins, and sea stars. A very similar pattern had previously been found on the Spiess Seamount, with large specimens of sea urchins (Dermechinus horridus) as well as lithodid crabs (Paralomis elongata) being the most conspicuous species and, like the Admiralty Seamount, the seafloor was almost completely covered by spine debris ( J. Gutt, unpublished observations).

These differences of dominant species might not only represent temporal parallel ecological processes leading to different results: they could also represent differently advanced stages of long-term developments because stalked crinoids resemble ancient Palaeozoic assemblages and predators indicate a more modern benthos. Generally, in situ images of crinoids could even be used to sample wide-range information on near-bottom current, which is important in explaining benthic community structures (Eléaume et al. in press). Also, early recolonization stages of iceberg scours or areas after ice-shelf disintegration can, but do not necessarily always, consist of almost monospecific assemblages such as bryozoans, cnidarians, or ascidians (Fig. 11.5E). A dominance of one single species due to an assumed competitive displacement seems to be rare on the Antarctic shelf, but was observed, for example for the sponge Cinachyra barbata in the Weddell Sea. Favorable environmental conditions can cause a clear dominance on shallow hard and soft substrata, for example of the scallop Adamussium colbecki, the limpet Nacella concinna (Barnes & Clarke 1995a; Chiantore et al. 2001), or the infaunal clam Laternula elliptica and the deep-sea holothurian Elpidia glacialis (Gruzov 1977; Gutt & Piepenburg 1991). The richness of species of the Southern Ocean deep sea has already been discussed and does not support the hypothesis of a gradient of decreasing richness toward the south (Brandt et al. 2007a). Even the opposite was found for gastropods (Schrödl et al. ), which is in contrast to shallow habitats. Communities on the shelf can reach extremely high values for wet weight biomass, up to 12 kg m –2 (Gerdes et al. 2003), with relatively high biodiversity compared with the Arctic shallow water. And they are not always defined by the well-known sponge concentrations: recently an assemblage shaped by the elsewhere rare hydrocoral Errina has been discovered (CCAMLR 2008) (Fig. 11.5D).

A high geographical turnover of macrobenthic assemblages within larger regions can generally be explained mainly by sea-ice conditions and proxies for food supply such as current and pigments in the sediment (Gutt 2007; V. Cummings, unpublished observations). Such a regional co-existence of different communities is found almost everywhere, at the Antarctic Peninsula (Lockhart & Jones 2008), at smaller places such as the well-investigated Admiralty Bay including macroalgae (Siciski et al. submitted), in the Weddell and the Ross Seas (Gutt 2007; V. Cummings, unpublished observations), or off East Antarctica (Gutt et al. 2007). For selected deep-sea polychaetes, the challenging question of how allied species can co-exist without out-competing each other was answered by their different food preferences, analyzed by biochemical analyses (Würzberg et al. ).

Use of the CPR to study plankton patterns has shown that the large-scale zonation around Antarctica (subantarctic, sea ice, neritic) is consistent with latitudinal oceanographic zones as defined by Orsi et al ( 1995) or Sokolov and Rintoul ( 2002); see also Takahashi et al. ( 2002), Umeda et al. ( 2002), Hunt & Hosie ( 2003, 2005, 2006a, 2006b), and Takahashi et al. ( 2010). These patterns are superimposed by the sea-ice margin and related melting processes, which directly affect the success of some species and consequently the entire community (Raymond & Hosie 2009). The Bellingshausen Sea, for example, exhibited low diversity and abundances. Temporal changes during the past decade have been observed with a decrease in the dominance of krill in the sea-ice zone of eastern Antarctic and an increase in dominance by smaller zooplankton more typical of the permanent open ocean zone, notably the cyclopoid copepod Oithona similis, small calanoid copepods Calanus simillimus and Ctenocalanus citer, foraminiferans, and larvaceans. Zooplankton abundances in general increased by about 50 times but probably with a lower effect on the total biomass because generally the shift was to small species. Besides the above-described coarse and well-known circumpolar pattern, no latitudinal zonation became obvious within a broad band of the ACC ranging from approximately 52° to 64° S covering a temperature range between a sea surface temperature of 2 and 6 °C. However, within the single surveys differences between predominantly north–south-orientated transects became visible. It is too early to speculate whether the temporal and spatial turnover in community structure is a result of global change, or a shift between two natural events.

The mesopelagic fish fauna, mainly comprising myctophids, were only recently recognized as a key component in the open ocean system because they prey on mesozooplankton, especially copepods, and in turn are the major prey of top predators. They also contribute to fast vertical energy flux of organic material due to their vertical migrations (Koubbi et al. submitted). Major success has been made in understanding their ecological demands and physical environment, for example in terms of chlorophyll a, sea surface temperature, salinity, and nutrients. Based on that, predictions can be made about suitable habitats for their biodiversity, even for areas from which no such biological data exist.

 

11.3.6. Small-Scale Heterogeneity, a Contribution to Large-Scale Biodiversity

Epibiotic relationships have become more obvious since the first seabed photographs were taken in the late 1950s. However, for a long period, symbiotic associations, which include parasitic relationships, were judged to be rare in Antarctica (AAVV 1977, p. 389). Later, sponges, bryozoans, and cnidarians (Figs. 11.5B, C and D) were recognized as the main substratum for a variety of echinoderms. In total 347 of such interspecific relationships were found using imaging techniques (Gutt & Schickan 1998). More recent and detailed studies revealed that cidaroid sea-urchin spines alone provide the microhabitat for some 156 species, for example bryozoans, sponges, bivalves, and holothurians, of which some even live obligatorily on the spines. So far, 23 especially close associations (encompassing commensalism, associational defense, and parasitism) have been reported for the Antarctic. Hosts are generally echinoderms, whereas the symbionts are mainly mollusks and polychaetes (S. Schiaparelli, unpublished observations). The more such symbioses are searched for, the more that are found, for example between a polynoid polychaete and the holothurian Bathyplotes bongraini (Schiaparelli et al. in press). Many Antarctic symbioses represent relict interactions, already present before the isolation and cooling of the continent. They might play an important role in explaining an ecological coexistence of species. Such specific relationships are also considered to characterize a mature ecosystem. In the area where the Larsen Ice Shelf recently disintegrated, the composition of epibiotic species did not differ from that living on boulders (Hétérier et al. 2008; Linse et al. 2008; Hardy et al. in press), which indicates a transitional stage of ecological development. A possible hypothesis could be that, in general, symbionts not only linearly contribute to biodiversity as all other species do, but also by providing potential living substrata they might instead accelerate the increase in Antarctic macrobenthic biodiversity by attracting other species.

 

11.3.7. Applied Aspects and Biodiversity Change

Antarctic waters might be the best protected marine areas on Earth owing to the “Protocol on Environmental Protection to the Antarctic Treaty” (the “Madrid Protocol”). Science managers and politicians have not given high priority to specific marine nature conservation actions for a long time. Recently, interest in such approaches has increased. In 2008 the CCAMLR adopted a proposal by Australia, based on CAML's CEAMARC expedition Collaborative East Antarctic Census of Marine Life (Hosie et al. 2007), to declare two areas of the Southern Ocean mentioned above as Vulnerable Marine Ecosystems (VMEs) because of their complex and vast coralline assemblages. The purpose of the classification is to protect the sites from longline fishing impact, a major concern after bottom-trawl fishing was banned in the most profitable area west of the Antarctic Peninsula (CCAMLR 2008). In addition to several VMEs, one of the world's largest Marine Protected Areas (MPAs) has recently been designated in an area south of South Georgia.

CCAMLR initiated a bioregionalization project (Grant et al. 2006), which predicts potential habitats for key ecological species and assemblages in order to identify biological hot spots (Koubbi et al. ). The United Nations Environmental Program developed criteria to define Ecologically and Biologically Significant Areas as determined by the Convention on Biological Diversity in 2008, which is independent of any sustainable use of the ecosystem. The Scientific Committee on Antarctic Research recently compiled a comprehensive Report on the “Antarctic Climate Change and the Environment” (Turner et al. 2009), which addresses the necessity for baseline information and long-term observations to monitor the mainly climate-induced affects on the ecosystem. All these initiatives were significantly supported, some even initiated, by leading CAML scientists. The results also provide a valuable basis to keep the Red List of Threatened Species (http://www.iucnredlist.org) updated.

Bioprospection in the Antarctic is still in its infancy. Providing that international law and conventions are respected, CAML can contribute to a further development of this opportunity, and consequently of Antarctic ecosystem services to the benefit of human well-being. Marine biodiversity is protected from large-scale offshore fertilization for CO2 mitigation by the Convention on Biological Diversity and the Madrid Protocol to the Antarctic Treaty. Fish stocks around the Antarctic Peninsula have been protected from bottom trawling since the 1990–91 season. The development of fish stocks was observed around Elephant Island and the lower South Shetland Islands in December 2006 – January 2007 surveys (K.-H. Kock, unpublished observations). One of the most abundant species before exploitation, the mackerel icefish (Champsocephalus gunnari), has not yet recovered. The status of the second target species of the fishery, the marbled notothenia (Notothenia rossii), is unclear as no specific surveys for the species have been conducted. Bycatch species, icefish, and nototheniids, appear to have recovered since the area was closed to commercial fishing. Unexplainable so far is the recruitment failure in the past seven or eight years of the yellow notothenia (Gobionotothen gibberifrons). The stock currently consists to a very large extent only of adult fish.

 

11.4. Blueprint for the Future

 

11.4.1. Hot and Cold Spots of Biodiversity

During the CAML period, knowledge of Antarctic biogeography steadily increased, in some cases exponentially, in others blank spots were filled. We are now able to identify more local biodiversity hot (and cold) spots. However, regionally comparable criteria are still difficult to apply. In this context it is necessary to establish a systematic geographic coverage, as spatially homogenous as possible for as many as possible relevant regions, and not so much to reach detailed results at one single location. Then, the total number of species in the Antarctic must not remain unknown forever (Gutt et al. 2004). It can be mathematically extrapolated (Chao 2005), although most algorithms demand information on rare species. Consequently, not only presences but also information on the absence and abundance of species is strongly needed.

Ecological modeling will become increasingly important to fill gaps in our understanding of biodiversity dynamics. The first objective is to understand the relations between environmental parameters, biological traits, and biodiversity patterns. If robust correlations are found, then in a second step the flora and fauna can be deduced from well-known environmental patterns and perhaps vice versa. When ecological interactions are well understood, then the most difficult challenge of predicting the future becomes possible. Some important steps in this direction have already been made. The community approach tries to classify ecologically complex relationships and to identify key species (Gutt 2007; Post et al. in press). The habitat suitability or potential habitat modeling approach tries to extrapolate from known environmental parameters using information on the ecological demands of key organisms to fill geographical gaps in their distribution and, thus, also contribute to a general understanding of ecosystem functioning (Koubbi et al. ). The bioregionalization/ecoregionalization approach reaches a complete geographic coverage in ecologically relevant parameters that have been classified (Grant et al. 2006; see also Fig. 11.4) and databases provide a comprehensive source for species numbers and their occurrence. A handful of international working groups could reach highly synergistic effects by integrating these approaches, which could result in both a circumpolar mapping of biological processes and structures and, finally, an integrated “Antarctic biodiversity and ecology model”.

 

11.4.2. Biodiversity and Ecosystem Functioning

Integrated research projects are a fundamental basis to decipher the relation between biodiversity and ecosystem functioning. One complex set of questions centers around the environmental processes generating biodiversity hot and cold spots. What are the main physical and biological drivers of the rich benthic suspension feeder communities? If silicate alone supported the abundant sponges, they would grow everywhere on the high-latitude shelf. Instead, they show complex population patterns. Or is the near-bottom current the main driver providing high amounts of food for the benthos, which is regionally and temporally highly unpredictable (see, for example, Montes-Hugo 2009)? Why are some areas dominated by single species whereas others are highly diverse? We know assemblages shaped by prey–predator relationships (Dayton et al. 1994) but why are they so rare? Is the co-occurrence of vivipary and indirect development an evolutionary adaptation to glacial conditions with isolated habitats and interglacials with large areas for colonization but with interspecific competition (Teixidó et al. 2006)? Are rare species just a quirk of nature, and only algae, nematodes, and krill matter, or does biodiversity contribute to the resilience of the ecosystem through stability and adaptation? Does iron limitation of the pelagic system support high or low diversity among primary and secondary producers? How can the pelagic system lose large amounts of its key prey Antarctic krill through climate-induced changes in the sea-ice dynamics, but allow whales to recover? Answers to these questions will not only contribute to advances in fundamental research but will also contribute to the needs of politicians and other decision-makers.

 

11.4.3. Response of Marine Biodiversity to Global Change and Ecosystem Services

When dealing with the response to climate change of any ecosystem there are two major concerns: (1) the reduction in ecosystem services; (2) the irreversible loss of biodiversity. For the latter, CAML has provided a benchmark of current biodiversity in certain habitats, but also changes have already been observed. Compared with the situation in other continents, most effects of climate change are still poorly understood. We do not know whether this is just the beginning of a rapid development similar to that seen in the Arctic or whether the Antarctic will generally remain relatively isolated from anthropogenic processes. To track such process we need long-term, regular observations as proposed for the Southern Ocean Observation System, supported by repeated CAML-type census activities conducted at regular intervals, station-based surveys, as well as the use of moorings. These must be at (1) sensitive habitats presumed to be affected in the near future, for example along the Antarctic Convergence (Cheung et al. 2009), (2) areas that can act as refuges, and (3) systems that have already experienced a significant change, for example west of the Antarctic Peninsula (Ducklow et al. 2007). Attention should also be paid to the Antarctic deep sea, because virtually nothing is known about its sensitivity to change (Kaiser & Barnes 2008). Several CAML projects have provided valuable information for predictive models on ecosystem developments, which need higher spatial resolution in physical parameters, information on extreme climate events, and more data on life-history traits of representative key ecological species. It might become easy – but currently it is not trivial – to correlate biodiversity information with environmental parameters, for example changes in the ice-loving biota related to changes in sea-ice dynamics. The biggest challenge, however, is to simulate synergistic effects through the trophic system, which amplify or buffer the effects of climate changes. In the case of acidification, future research should consider not only pteropods and the famous coccolithophorid Emiliana huxleyi but a cascade of associations including the planktonic anthomedusa Pandea rubra, pycnogonids, amphipods, and baby cuninid medusae (Lindsay et al. 2008), and benthic calcifying organisms, e.g. the coral Errina. It should examine the effects of increased ultraviolet radiation on the composition of food for benthic and pelagic consumers, and the consequences of increased particulate matter resulting from the retreat of the coastal glaciation, which affects primary producers and filter feeders.

 

11.4.4. New Technology and Gaps

Antarctica's biodiversity has two clear characteristics: there are only a few large and charismatic species such as penguins and whales, but tens of thousands of invertebrates. There are also legions of microbes, almost all of which are unknown. For the last two groups, the quality of next-generation biodiversity studies will depend upon how well we can identify species. Traditional methods of species identification may be supplanted by genetic methods, which may contribute to larger ecological and evolutionary concepts. Barcoding must be as applicable in the future as traditional methods are today (including the accessibility of information about the species described so far). The new genetic technology has a bright future if existing knowledge is not wasted and if it does not remain an elitist tool for geneticists. It must be a complementary method for use by all biologists as they would use computers or microscopes today. Because ecological studies depend on the biological species concept of interbreeding populations, it must also be agreed that genetically defined species serve as good proxies for the biologically defined species bringing the same degree of confidence as morphologically defined species did in the past. In addition, reconstruction of phylogeny demands the application and further development of modern genetic techniques, for example a better understanding of the “molecular clock”. Until these aims are reached, traditional taxonomic work must continue to be supported including the development of new strategies to speed up the publication of hundreds of putative new species.

One of the biggest challenges to discovering Antarctica's life is to survey the large areas underneath the large floating ice shelves, some being up to several hundreds of meters thick. Only ROVs, autonomous underwater vehicles, gliders, and crawlers are suited to operate in this kind of habitat. Let us imagine such vessels are equipped with autonomously working gene sequence analyzers. That would be the “key” to surveying the biodiversity of this extreme habitat and answering major evolutionary and ecological questions. The same could be applied to permanent pack-ice areas and 60% of the Southern Ocean when it is ice-covered in winter. It has recently been discovered that benthic and pelagic life does not necessarily slow down during winter as formerly suggested, for example, by Gruzov (1977). Thus, it is very important for a general understanding of the Antarctic ecosystem to continue with studies on the adaptation of key ecological organisms to the extreme winter conditions (see, for example, Barnes & Clarke 1995b; Schnack-Schiel 2001).

At the ecological level, a promising strategy to discover unknown processes might be studies in well-known hot spots in one ecological subsystem but with poor knowledge of the rest of the ecosystem. These could be pelagic and benthic studies near feeding grounds of vertebrates or benthic deep-sea areas with and without krill concentrations. In addition, areas with intensive downwelling can be of specific scientific interest. They are rare, but such sites have been found at the slope of East Antarctica and are assumed to exist in the western Weddell Sea. It is not only interesting how organic material as food for pelagic and benthic life is rapidly transported from shallow to deeper waters but also what the role is of such a current for the evolutionary and short-term dispersal of shelf animals into the deep sea. The relevance of ecological interfaces for Antarctic biodiversity is frequently discussed in the scientific community. Results for interactions between ice and water column, euphotic zone and underlying water masses, or the pelagic–benthic coupling at all water depths should not remain tantalizingly out of reach.

 

11.5. Conclusions

CAML has demonstrated that life in the coldest marine ecosystem on Earth is rich, unique, and worthy of high-priority study. We have taken a significant step forward toward the long-term aim of a complete documentation of its biodiversity and a comprehensive understanding of its sculpting forces. The major findings at the evolutionary scale are of a large systematic coverage of cryptic species with distinct non-circumpolar occurrence. Extreme ecological heterogeneity exists at various spatial, biological, and temporal scales. The key to convincing decision-makers to finance a progressive continuation of this work is to assess the contribution of Antarctica's biodiversity to human well-being and ecosystem services. This can include sustainable exploitation of genetic information and the recognition of the role of the ecosystem as a natural CO2 sink. Antarctica's life is part of the global biodiversity in which causes of and biological response to anthropogenic impact are spatially separated. It is recognized as “the canary in the coal mine”, able to provide early warning of dire environmental effects of global warming (IPCC 2007). In this respect, future marine biodiversity surveys have an important role to fill.

 

11.6. Acknowledgments

We are very grateful to the Alfred P. Sloan Foundation and the national programs for financial support, and Angelika Brandt, Claude De Broyer, Russell Hopcroft, Alison Murray, Lucia de Siqueira Campos, Victoria Wadley (CAML secretariat), Stefano Schiaparelli, Sigrid Schiel, and Huw Griffiths for integration efforts and ideas. We also thank the CAML research community for allowing us to use preliminary results presented at the CAML Genoa symposium. Thanks are also due to the providers of data from SCAR-MarBIN and which are used in Fig. 11.3.

 
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