The study was aimed at analyzing patterns of abundance and diversity of macrozoobenthic communities along a depth gradient in the Admiralty Bay, a semi-enclosed basin located in a rapidly changing region of the western Antarctic Peninsula. The study concerns primarily the Polychaeta and Amphipoda, the taxonomic richness and diversity of both groups being analyzed at different taxonomic levels (species, genus and family). Such an analysis, which uses a basic surrogacy measure (low taxonomic resolution) can be very useful in future monitoring programs of the Admiralty Bay. The analysis was based on 35 samples collected in the summer seasons of 1984/85 and 1985/86, with a Tvärminne sampler (within the 7–30 m depth range) and an 0.1 m2 van Veen grab (deeper areas) along a transect with the depth changing from 7 to 502 m. The total macrozoobenthos abundance was found to decrease with depth, from 1581 ± 730 ind./0.1 m2 within the 7–30 m to as few as 384 ± 145 ind./0.1 m2 at 400–500 m. The number of phyla per sample was observed to increase along the depth gradient of 7–30 to 200–300 m but was substantially reduced in the deepest sublittoral (400–500 m). The results showed large differences between amphipods and polychaetes in their respective depth-related biodiversity changes. On the other hand, the diversity metrics used (Pielou’s evenness, Shannon-Wiener index, number of species per sample, number of genera per sample, number of families per sample) at different taxonomic levels within each group produced similar patterns, demonstrating the usefulness of surrogacy in studies of Antarctic fjords.
Zoidbergus , a new genus of Apseudidae, is described for deep−water Tanaidacea classified previously in the genus Apseudes : A. abyssalis , A. lagenirostris , A. paragracilis , A. tenuimanus , A. tenuis and A. vicinus . The new genus differs from Apseudes s. str. by having acute eyelobes without visual elements, elongated second article of mandibular palp, and carpus of pereopods 2–3 longer than or as long as propodus. Zoidbergus gen. n. can also be distinguished from Apseudes s. str. by the lack of large bases of pereopods 5–6 covered by numerous plumose setae as well as the lack of dense plumose setation on lateral margins of pereonites and pleonites. By general body habitus and structure of pereopods Zoidbergus gen. n. resembles the apseudid genus Leviapseudes , although the genera can be distinguished by the presence of leaf−shaped seta and elongated pereonites 3–6 in Leviapseudes . Based on specimens collected during the IceAGE1 Cruise in September 2011, Zoidbergus tenuis is redescribed and morphology of an undescribed species Zoidbergus sp. A is provided. Supplementary description for Zoidbergus vicinus is given based on type material from Statens Naturhistoriske Museum, University of Copenhagen. Additionally comments on the other deep water Apseudes species: A. siegi and A. vitjazi , are given.