Biodiversity and community structure of freeliving marine nematodes from the Larsemann Ice Shelf, East Antarctica

Abstract

Subtidal (500-700 m) meiofaunal assemblage of the Larsemann Ice Shelf, East Antarctica, is described with special emphasis on the free-living marine nematodes. The sampling was conducted with a 25 x 25 x 40 cm VSNL Spade Box corer and sub-sampling was performed with an acrylic core (4.5 cm dia.). The meiofauna comprised of eight taxa dominated by nematodes. A total of 75 nematode genera and 4 species were identified. They were randomly distributed and showed a significant difference (P less than 0.05) between the sampling stations. The total density varied from 239 to 639/20 cm sup(2) and maximum density was recorded at a water depth of 722 m. Nematodes constituted more than 82% of the total meiofauna. A total of 1053 nematodes were isolated from the three cores. Vertically, approx. 90% nematodes were in the surface (0-2 cm) sediment, and their abundance decreased with sediment depth. Among the nematodes, selective feeder and non-selective deposit feeder were most abundant at the surface sediment, whereas omnivores and predators were higher at depth. Sabatieria and Paralinhomoeus were the most common genera. The higher nematode abundance at the surface was possibly due to their preferences to the freshly arriving food particles in the sediment-water interface. Availability of predatory omnivores in the deeper layers was perhaps due to their adaptation to the sedimentary conditions and could be their part of survival strategy in the harsh Antarctic environment.