Salt tolerance and survival thresholds for two species of Antarctic soil nematodes

We evaluated the response of the Antarctic soil nematodes Scottnema lindsayae and Plectus antarcticus to various salts (NaCl, MgSO4, KNO3 and NaCl + MgSO4) and salt concentrations in prepared salt solutions ranging from 0.1 to 3 M, and in saturation paste extracts of soils collected from multiple locations where nematode abundance varied from zero to numerous, and where electrical conductivity ranged from 108 to > 12,000 mu S/cm. Nematode salt tolerance was salt specific; both nematode species survived in low-experimental concentrations of NaCl and MgSO4, and neither species survived in KNO3 solutions of any concentration. There was no survival of nematodes in the saturation paste extracts of highly saline soils (4,100 mu S/cm), while survival was over 80-97% in less saline soils (1,945 mu S/cm). A 1:1 dilution of these highly saline saturation paste extracts increased S. lindsayae survival to 80%, while survival of P. antarcticus was not observed until dilutions of greater than 200%. The results complement previous studies demonstrating niche partitioning of S. lindsayae and P. antarcticus across salinity gradients and strengthen interpretations of the physiological mechanisms underlying previously reported spatial correlation between soil salinity and nematodes abundance in the Antarctic Dry Valleys.