Abstract: Surface zooplankton samples were collected between 21°S and 38°S during the Dayang-1 scientific cruise in Southwest Indian Ocean in summer of 2013. By using zooplankton community structure analysis and clustering method, the distribution pattern of community structure and biodiversity of this region were explored. The results showed that the zooplankton species belonged to 69 species of 50 genus, including copepods, euphausiids, amphipods, decapods, ostracods, chaetognaths, tunicates, heteropods, pteropods, cnidarians, polychaetes and etc. In terms of abundance, copepods and euphausiids accounted for the largest percentages (69% and 27%, respectively). The variation of H′, D, J biodiversity indices with the latitude accorded a linear trend, i.e. most biodiversity indices decreased with the increase of latitude. In contrast, a binomial relationship was found between the biodiversity indices and longitude. Most biodiversity indices increased with the longitude. The clustering results showed that northern and southern zones could be distinguished by the latitude boundary around 36°S, with the predominant species of copepods (small particle) in northern zone and euphausiids (large particle) in southern zone respectively. Moreover, the similarity of species composition indicated that the spatial connectivity of zooplankton communities was week between the southern zone and Crocker Strait or Great Wall Bay in Antarctica, as well as between the northern zone and Northwest Indian Ocean.

Key words: Southwest Indian Ocean, zooplankton, community structure, spatial pattern, similarity