Diversity and distribution of Tanaidacea (Crustacea) along the Victoria Land Transect (Ross Sea, Southern Ocean)

The Victoria Land Transect Project was established for the assessment of a possible latitudinal environmental gradient. During the expedition on the board of the RV Italica carried out in February 2004, four areas of the eastern Ross Sea sublittoral were investigated. The diversity and distribution of 2,678 individuals of Tanaidacea found in 18 samples from a depth range of 84-515 m using a Rauschert dredge were analyzed. Fourty species of tanaidaceans almost exclusively of the suborder Tanaidomorpha were identified; 14 of them were apparently new for science; only five species had been found in the Ross Sea before. Two main groups of the samples, with two distinct tanaidacean assemblages associated with the different bottom sediments (sand vs. mosaic bottom deposits), were revealed by cluster analysis and non-metric multidimensional scaling. The sample arrangement in the cluster and ordination analyses did not correlate with the depth or the latitudinal gradient, but it indicated a relationship with the quality of bottom deposits. It is also assumed that the structure of the assemblages might be determined by local habitat conditions. At two stations at Coulman Island, a distinct value of tanaidacean diversity is attributed to the destructive effect of passing icebergs on the benthic groups documented in earlier studies. A similar pattern of distribution and diversity had been observed for cumacean distribution. Analysis of the distribution confirms the previously observed preferences of Nototanais dimorphus and Paratyphlotanais armatus for sandy sediments, and Nototanais antarcticus and Akanthophoreus cf. multiserratoides for muddy bottoms.