The crustacean amphipod genus Jassa is revised to encompass the type species J. falcata (Montagu, 1808), the previously recognized species J. ingens (Pfeffer, 1888), J. herdmani (Walker, 1893), J. pusilla (G. O. Sars, 1894), and J. marmorata Holmes, 1903, and the new species J. alonsoae, J. borowskyae, J. carltoni, J. fenwicki, J. gruneri, J. hartmannae, J. justi, J. morinoi, J. myersi, J. oclairi, J. shawi, J. slatteryi, J. staudei, and J. thurstoni. Jassa odontonyx (G. O. Sars, 1894) is synonymized with J. pusilla, and J. pulchella Leach, 1814 is confirmed as synonymous with J. falcata. Jassa wandeli Chevreux, 1906, J. multidentata Schellenberg, 1931, J. goniamera Walker, 1903, J. barnardi Stephensen, 1949, J. lilipuna J. L. Barnard, 1970, and J. ocia (Bate, 1862) will be assigned to other genera. The nomenclatural disposition of other species that were at one time assigned to the genus Jassa is also given. The genus Jassa can be distinguished from its closest relatives by the following key characters: the outer rami of the third uropods are tipped by a pair of cusps and a basally immersed, dorsally recurved spine; the palms of the first and second gnathopods are defined by a cluster of three spines; at the last molt the male produces a thumb-like protuberance on the propodus of the second gnathopods by incision of the palm anterior to the palm-defining spines; and thumbed males have dimorphic second gnathopods.

A decade has yielded much progress in understanding polar disturbance and community recovery-mainly through quantifying ice scour rates, other disturbance levels, larval abundance and diversity, colonization rates and response of benthos to predicted climate change. The continental shelf around Antarctica is clearly subject to massive disturbance, but remarkably across so many scales. In summer, millions of icebergs from sizes smaller than cars to larger than countries ground out and gouge the sea floor and crush the benthic communities there, while the highest wind speeds create the highest waves to pound the coast. In winter, the calm associated with the sea surface freezing creates the clearest marine water in the world. But in winter, an ice foot encases coastal life and anchor ice rips benthos from the sea floor. Over tens and hundreds of thousands of years, glaciations have done the same on continental scales-ice sheets have bulldozed the seabed and the zoobenthos to edge of shelves. We detail and rank modern disturbance levels (from most to least): ice; asteroid impacts; sediment instability; wind/wave action; pollution; UV irradiation; volcanism; trawling; non-indigenous species; freshwater inundation; and temperature stress. Benthic organisms have had to recolonize local scourings and continental shelves repeatedly, yet a decade of studies have demonstrated that they have (compared with lower latitudes) slow tempos of reproduction, colonization and growth. Despite massive disturbance levels and slow recolonization potential, the Antarctic shelf has a much richer fauna than would be expected for its area. Now, West Antarctica is among the fastest warming regions and its organisms face new rapid changes. In the next century, temperature stress and non-indigenous species will drastically rise to become dominant disturbances to the Antarctic life. Here, we describe the potential for benthic organisms to respond to disturbance, focusing particularly on what we know now that we did not a decade ago.

22Although knowledge of Arctic seas has increased tremendously in the past decade, benthic 23 diversity was investigated at regional scales only, and no attempt had been made to examine it 24 across the entire Arctic. We present a first pan-Arctic account of the species diversity of the