Comparison of the nematode fauna from the Weddell Sea Abyssal Plain with two North Atlantic abyssal sites

This study provides for the first time data on the nematode community composition from the Weddell Sea Abyssal Plain. In addition, new data on the nematode communities from the Cape Verde Abyssal Plain and the Porcupine Abyssal Plain are provided. Three stations along an east-west transect in the Weddell Sea were sampled during the ANDEEP II campaign and compared with two north-east Atlantic abyssal sites, characterized by a contrasting food supply, in terms of densities, community structure and biodiversity. Local total nematode densities on the Weddell Sea Abyssal Plain (station 138) rank among the highest values recorded from abyssal plains worldwide, pointing to a locally high availability of food for meiofauna. Minor differences in the proportion of dominant genera were observed between the Weddell Sea Abyssal Plain and both North Atlantic sites. The nematode communities at the Weddell Sea Abyssal Plain were dominated by Thalassomonhystera and Acantholaimus, which is comparable to the North Atlantic abyssal plains. No endemic genera for the Southern Ocean were found. However, the higher abundance of the genera Microlaimus and Dichromadora seems to be typical for the Southern Ocean deep-sea, and might be related to the availability of fresh food.