| Taxa | Size* | Description/Summary of role in ecosystem** | Key groups/species | Example photograph | Example References |
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Porifera (sponges) | macro/mega | Highly diverse and often a dominant group by biomass with eurybathic distributions. Sponges are sessile, reef building species providing structural heterogeneity for colonizing epiboints. Significant nutrient source to predators. | Hexactinellidae Demospongiae (Image Australian Antarctic Division) | | McClintock et al. 2005 |
Ascidians (sea squirts) | macro/mega | ~250 species recorded between the below the sub-tropical front from the intertidal zone to abyssal depths. Sessile species often dominate numbers and biomass within benthic communities. Important role in structuring suspension-feeding communities. | Molgula pedunculata (Herdman, 1881)(image Martin Rauschert, 1981) | | Primo and Vasquez, 2009; 2014 |
| Bryozoa | macro/mega | Almost exclusively colonial and generally sessile animal, can be encrusting (on rocks, algae or other animals) or form their own structures. Often resemble (and mistaken for) other taxa such as algae, corals and hydroids. The cheilostome order may be one of the most successful taxa on the Antarctic continental shelf often showing eurybathic distributions. Important carbon regulators. | Cheilostomes Cyclostomes (Image Images Top = bryozoan assemblage at 450 m Ross Sea shelf, NIWA. Bottom = Antarctic cyclostome bryozoa Fasciculipora ramosa, Blanca Figuerola)
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 Image Added
| Parker and Bowden, 2010 (and refs there in), Barnes and Downey, 2014, Barnes, 2015, Figuerola et al. 2012, |
| Nematodes | meio | ~524 valid species within Antarctic sediments the most abundant metazoan organism in marine sediments. Important role in decomposition processes and nutrient cycling. | Desmodora campbelli (Allgén, 1932)(image F. Hauquier) | | Ingels et al. 2006, 2010, 2014, |
Polychaetes
(bristle worms) | macro/mega | Highly diverse both taxonomically and functionally from mobile predators, symbionts or sessile tube dwelling filter feeders. Can represent 70% of the macrofauna, ~403 valid species within Antarctic sediments but recent analysis has uncovered high levels of cryptic diversity. | Laetmonice producta Grube, 1877 Polynoidae Spionidae e.g. Laonice weddellia Hartman, 1978 (image, WoRMs). | | Schuller and Ebbe, 2014, Brasier et al. 2016. |
| Foraminifera | meio and mega | Heterotrophic protists, includes calcareous (meio), aggluntinated and organic-walled species (mega). Found at all depths, originally thought to contain many cosmopolitan species but genetic analysis suggests higher levels of endemism. | Septuma ocotillo Tendal & Hessler, 1977 (Image Andrew Gooday) | | Pawlowski et al. 2002, Gooday et al. 2014. |
Hydrozoa Including: Hydroids and Stylasteridae (hydrocorals) | mega | Hydroids: Highly diverse but most diverse is concentrated within a few genera. Sessile filter feeders, highly edemic (90% of species) within Antarctic and sub-Antarctic waters. Eurybathic distributions. Stylasteridae: Calcified, colourful, colonial hydroids. 33 species recorded south of the polar front. Eurybathic within Antarctica and structure forming species. | Hydroids: Staurotheca Stylasteridae: Errina spp. (Image coral field of Errina (orange coral) > 450 m Durmont d'Urville Sea, Australian Antarctic Division) | | Parker et al. 2009, Parker and Bowden, 2010 (and refs there in), Cantero 2004, Bax and Cairns, 2014, Cantero et al. 2014 |
Hexacorals Including: Scleractina (stony corals), Antipatharia (black corals), Zoantharia (zoanthids), Actiniaria (aneomones)
| mega | Scleractina: Solitary cups, not reef forming but may form matrices. Uncommon at depths greater than 1000 m. Most species grow on other biogenic structures, often small (<10 cm), slow growing (0.5-2 cm year-1) and long lived (over 200 years). Antipatharia: Large (can be over 3 m) can be fan or whip shaped, eurybathic from shallow water to ~5000 m. Can be very long lived (1000s years) in the deep sea. Zoantharia: Erect "coral like" colonies, may reach 3m in hieght generally found at 400-600m. Often grow on or colonise other corals. Actiniaria: Sessile filter feeders important in suspension feeding communities. High levels of endemism, some species circumpolar others show differentiation between east and west Antarctica. Eurybathic from littoral to 5000 m. | Scleractina: Caryophyllia antarctica Marenzeller, 1904, Gardineria antarctica Gardiner, 1929, Flabellum inpensum? Antipatharia: Bathypathes Zoantharia: Gerardia Actiniaria: Stomphia selaginella (Stephenson, 1918), Capnea georgiana (Carlgren, 1927), Hormathia lacunifera (Stephenson, 1918) an image by Julian Gutt. | | Parker et al. 2009, Parker and Bowden, 2010 (and refs there in), Rodriguez and Fautin, 2014. |
Octocorals Including: Alcyonacea (soft corals), Gorgonacea (sea whips), Pennatulacea (sea pens) | mega | Alcyonacea: soft corals, abundant on the shelf and slope, less abundant in deep water. Can form dense aggregations of encrusting corals. Gorgonacea: Structure forming coral with diverse morphology. Can be 3 m tall with complex branching morphology. Depth range from very shallow to over 3500 m. Pennatulacea: Live in softer sediments from littoral to abyssal depths and may be more vulnerable to fishing activities. Generally tall with a thin stalk and branched polyps or a head of polyps. | Alcyonacea: Anthomastus Gorgonacea: Thourella spp. Pennatulacea: Umbellula spp. (Image assemblage dominated by Thourella spp. and soft corals at 550 m Ross Sea, NIWA) | | Parker et al. 2009, Parker and Bowden, 2010 (and refs there in), |
Asteroidea (sea stars) | mega | Successful benthic species in the Antarctic containing about 235 species. Abundant, widely distributed and eurybathic. Diverse feeding strategies including omnivorous, deposit-feeding, suspension-feeding, and often top predators. | Odontaster validus Koehler, 1906 (image, Stefano Schiaparelli) | | Danis et al. 2014. |
Crinoidea (sea lillies and feather stars) | mega | Contains mobile unstalked forms and sessile stalked forms. 43 recognised species, 31 endemic to the Southern Ocean found on the shelf and to > 2000 m. Suspension feeders. | Promachocrinus kerguelensis Carpenter, 1879 (image Martin Rauschert, 1986) | | Hemery et al. 2012, Eleaume et al. 2014. |
Echinoidea (Urchins) | mega | 82 species south of the polar front, widely distributed from shelf to abyssal depths but most abundant at shallower depths. Include epifaunal and endofaunal species with a variety of feeding strategies. Cidariod species (pencil urhcins) provide microhabitats for other species including bivavles | Ctenocidaris spp. Abatus spp. Sterechinus neumayeri (Meissner, 1900)(image Stefano Schiaparelli) | | Linse et al. 2008, Saucede et al. 2014. |
Ophuroidea (brittle stars) | mega | Very common throughout the Southern Ocean, 219 recognised species, 126 are endemic to the Southern Ocean. Omnivore/scavengers within the Antarctic benthos. | Ophionotus victoriae Bell, 1902 (image WoRMs) | | Martin-Ledo and Lopez-Gonzalez, 2014, Galaska et al. 2016. |
| Amphipoda | macro/mega | 801 benthic or bentho-pelagic species south of the sub-tropical polar front. Highly diverse functional traits across habitats, feeding strategies and size. Important food source for other invertebrates, fish, seabirds and marine mammals. | Epimeria (Hoplepimeria) rubrieques (De Broyer & Klages, 1991) on the bryozoan Reteporella sp. (image, naturalsciences.be) | | De Broyer and Jazdzewska, 2014. |
Decapoda: Crabs and lobsters | mega | 22 species recorded from the from the Southern Ocean, 12 of which can be found south of 60o. restricted to areas above 0-0.5oC. Most abundant species are Lithodidae (king crabs) which are predatory. | Lithodidae (king crabs) Paralomis stevensi Ahyong & Dawson, 2006 (image Ahyong and Dawson, 2006). | | Hall and Thatje, 2011, Griffiths et al. 2013, Griffiths et al. 2014, |
| Isopoda | macro/mega | Isopod can be a major component of the Antarctic benthos particularly in the deep sea with over 700 species. Diverse functional traits especially in feeding strategies from detritus and filter feeding to ecto-parasites and active predators. | Glyptonotus antarcticus Eights, 1852 (image Martin Rauschert, 1981). Ceratoserolis trilobitoides (Eights, 1833) | | Brandt, 1992, Kaiser et al. 2009, Kaiser, 2014. |
Shrimp (Decapoda and Mysida) | mega | Play a significant role in the food web as prey and in the recycling of organic material at the sea floor. Variable trophic traits from deposit feeding to carnivory. | Nematocarcinus lanceopes Spence Bate, 1888 Chorismus antarcticus (Pfeffer, 1887)(image Dianne Pitassy) | | Basher and Costello, 2014. |
Pycnogonida (sea spiders) | mega | 264 species recorded in Munilla and Membrives (2009) from Antarctic and sub-Antarctic waters. 108 species are endemic to Antarctica waters and 55 are circumpolar including Nymphon australe, the most abundant species. Mostly carnivorous feeding on other invertebrates. | Nymphon australe Hodgson, 1902 (image Adrian James Testa) | | Gusso and Gravina, 2001, Munilla and Membrives 2009, Arrango et al. 2011. |
Gastropoda (Snails) | macro/mega | ~600 species known within the Southern Ocean at the time of the Biogeographic Atlas accounting for <1% of the global specie of gastropods. Highest abundance and diversity on the shelf, diverse feeding behaviours from grazers to scavenger/predators found in deep-water locations. | Nacella concinna (Strebel, 1908)(image Matrin Rauschert, 1986) | | Linse et al. 2006, Schiaparelli and Linse, 2014 |
Bivalvia (Clams, mussels, scallops etc.) | macro/mega | Functionally diverse within the Antarctica, over 50% of species are <10 mm in size with 90% have a very thin shell. Most are infaunal or epifaunal species either desposit or suspension feeders. The exception is Adamussium colbecki the Antarctic scallop that can swim and attach to substrate using byssus. | Aequiyoldia eightsii (Jay, 1839) Adamussium colbecki (E. A. Smith, 1902)(image Stefano Schiaparelli) | | Bailey et al. 2005, Linse, 2014. |
| Octopoda | mega | Most southern ocean octopus are found within the orders Cirrata (finned) or Incirrata. The number of species is not known. Some species have limited depth ranges which may reflect their reproductive mode. Prey on benthic invertebrates, some species selective feeders. | Pareledone spp. (images Mike Vecchione, Uwe Piatowski and Lousie Allcock). | | Daly, 1996, Allcock, 2014. |
| Macroalgae | mega | ~120 recognised species in Antarctica, this is a lower species richness than temperate and tropical waters. The highest biomass and diversity of macroalgae in Antarctica is found in the shallow sub-tidal zone. Important for carbon drawn down and grazers. | Desmarestia antarctica R.L.Moe & P.C.Silva, 1989, Himantothallus grandifolius (A.Gepp & E.S.Gepp) Zinova, 1959 (Image Martin Rauschert, 1986).
| | Wiencke and Clayton, 2002, Wiencke et al. 2014. |
