Abstract:

The composition, abundance and vertical distribution of planktonic Siphonophores, collected in Chukchi Sea and adjacent southern edge waters of Canada Basin, Arctic Ocean during the summer 1999 by first Chinese National Arctic Scientific Expedition, have been analysed. Totally, only two species of Siphonophores were identified in southern edge waters of Canada Basin, and they are absent in the Chukchi Sea. The principal morphological characteristics of the polygastric (asexual) and eudoxid (sexual) stages of Muggiaea bargmannae Totton and Dimophyes arctica Chun are fully described and illustrated. Besides, their morphological forms and ecological habits are discussed. The abundance of Dimophyes arctica , with a mean value of 42×10 -3 ind/m 3, is higher than that of Muggiaea bargmannae (24×10 -3 ind/m 3) in southern edge waters of Canada Basin. These two species of Siphonophoras were found in water layers of 100-800m and were the most abundant in 300-200m, in and above which a sharp halocline occurred .