Structure of bryozoan communities in an Antarctic glacial fjord (Admiralty Bay, South Shetlands)

Abstract

Bryozoans are among the most important groups of the Southern Ocean benthic macrofauna, both in terms of species richness and abundance. However, there is a considerable lack of ecological research focused on their distribution patterns and species richness on smaller scale, especially in the soft bottom habitats of Antarctic glacial fjords. The aim of this study was to describe those patterns in the Admiralty Bay. Forty-nine Van Veen grab samples were collected at the depth range from 15 to 265 m, in the summer season of 1979/1980, at three sites distributed along the main axis of the fjord. Among 53 identified species of bryozoans, 32 were recorded in the Admiralty Bay for the first time. The most common and abundant species were Himantozoum antarcticum, Inversiula nutrix and Nematoflustra flagellata. Genera such as Arachnopusia, Cellarinella and Osthimosia were the most speciose taxa. It was demonstrated that depth was important for the distribution of the bryozoans. More than half of the recorded species were found only below 70 m. An influence of glacial disturbance was reflected in the dominance structure of colony growth-forms. The inner region of the fjord was dominated almost entirely by encrusting species, while the diversity of bryozoan growth-forms in less disturbed areas was much higher. In those sites the highest percentage of branched, tuft like species represented by buguliform and flustriform zoaria was observed.

Low abundance and high species richness: the structure of the soft-bottom isopod fauna of a West Antarctic glacial fjord

“…The Admiralty Bay is one of the most comprehensively studied small-scale marine basins in the whole Southern Ocean, with about 100 studies focused on diverse groups of macroinvertebrates, including the following: polychaetes (Siciński 2004;Petti et al 2006;Pabis and Siciński 2010a, b), echinoderms (Presler and Figielska 1997), bryozoans (Nowak et al 2014;Pabis et al 2014) and some groups of peracarid crustaceans (Ja_ zd_ zewski et al 1991; Ja_ zd_ zewska 2011). The Bay has therefore been suggested as a good choice for a monitoring site .…”

Late Cenozoic Bryozoa from diamictites of Cape Lamb, Vega Island, Antarctic Peninsula

“…Biogeographically, the studied fauna from the Pleistocene of Cape Lamb (Vega Island), which includes Micropora notialis and Microporella stenoporta, is similar to the Pliocene fauna of the Cockburn Island Formation (Hara and Crame 2010), as well as to the Recent assemblage documented from Admiralty Bay, King George Island, South Shetlands (Pabis et al 2014). Neogene microporellids are represented in the studied Vega Island assemblage by M. stenoporta, an endemic species, which is widely distributed around Antarctica.…”

“…Hippothoa flagellum is known from the Ross Sea and other nu− merous localities in West Antarctica (Hayward 1995), and will probably be found to occur throughout Antarctic shelf seas. H. flagellum was recently documented from the Admiralty Bay, King George Island (Pabis et al 2014) Material. -Two complete colonies and six fragments on bivalve shells from level 5 (CPBA 21690.1-8).…”

“…Bryozoans of Antarctic shelf seas constitute one of the most dominant ben− thic groups and include a substantial proportion of new and endemic species (Rogick 1955(Rogick , 1962Hayward 1995;Hayward and Winston 2011;Pabis et al 2014;De Blauwe and Gordon 2014).…”

Assemblages and habitat preferences of soft bottom Antarctic Amphipoda: Admiralty Bay case study

“…Due to relatively small size of these peracarid crustaceans their proportion in the biomass, particularly in the deeper areas, dominated by large ascidians, bryozoans or polychaetes, is small (Jażdżewski et al , 1991b(Jażdżewski et al , 2001Jażdżewska 2011;. Assemblages of various macrobenthic groups of Admiralty Bay, including Polychaeta, Tanaidacea, Cumacea, Isopoda and Bryozoa, were already described Siciński 2010a, b, 2012;Pabis and Błażewicz-Paszkowycz 2011;Siciński et al 2011;Pabis et al 2014;Zemko et al in press and references therein). Also amphipods of this fjord were already the subject of studies, especially in the subtidal and in shallow sublittoral (Jażdżewski et al 1991a(Jażdżewski et al , 2001) as well as in shallow glacial coves .…”