Newly identified nematodes from the Great Salt Lake are associated with microbialites and specially adapted to hypersaline conditions

Extreme environments enable the study of simplified food-webs and serve as
models for evolutionary bottlenecks and early Earth ecology. We
investigated the biodiversity of invertebrate meiofauna in the benthic
zone of the Great Salt Lake (GSL), UT, one of the most hypersaline lake
systems in the world. The hypersaline bays within the GSL are currently
thought to support only two multicellular animals: brine fly larvae and
brine shrimp. Here, we report the presence, habitat, and microbial
interactions of novel free-living nematodes. Nematode diversity drops
dramatically along a salinity gradient from a freshwater river into the
south arm of the lake. In Gilbert Bay, nematodes primarily inhabit
reef-like organosedimentary structures built by bacteria called
microbialites. These structures likely provide a protective barrier to UV
and aridity, and bacterial associations within them may support life in
hypersaline environments. Notably, sampling from Owens Lake, another
terminal lake in the Great Basin that lacks microbialites, did not recover
nematodes from similar salinities. Phylogenetic divergence suggests that
GSL nematodes represent previously undescribed members of the family
Monhysteridae – one of the dominant fauna of the abyssal zone and deep-sea
hydrothermal vents. These findings update our understanding of halophile
ecosystems and the habitable limit of animals.