Despite how barren it can be many species do live in the deep Antarctic ocean beneath the ice sheets. In clades where species can be asexual or sexual many taxa are asexual. Why is this not surprising for this habitat

The organism to produce offspring can undergo either sexual or asexual mode of reproduction. The sexual model has many advantages like it can introduce variation which could allow the organism to live in different habitats but asexual reproduction allows the organism to produce offspring in large number in a short period.

The asexual reproduction also allows the organism to produce the offspring in harsh condition as sexual reproduction does not prove beneficial like in Antarctica.

In the deep oceans of Antarctica, the conditions are very harsh due to very low temperature but the organism survives there with the asexual mode of reproduction as the conditions are not favourable for the gamete production, gamete viability and embryo growth and development. So, asexual reproduction escapes these stages and undergo asexual mode like fission.