Nutrient and major ion concentrations were measured in surface water samples from lakes, ponds and streams at sites 30–320 km south of McMurdo Sound: the Darwin Glacier region (79.7–80.0°S), Pyramid Trough in the southern Dry Valleys (78.2°S), and the McMurdo Ice Shelf ablation zone (77.8–78.4°S). These aquatic environments ranged from dilute meltwaters (conductivity <0.05 mS cm−1) to concentrated brines (>50 mS cm−1). The lowest nitrate concentrations were recorded at the sites closest to the seasonally open waters of the Ross Sea. Much higher values (100–142000mg NO3–Nm−3) were recorded at sites further south. These observations support the hypothesis that NO3 precipitation over Antarctica is of stratospheric rather than coastal marine origin. The nitrogen-rich waters contained chloride and nitrate in the ratio 5.45g Cl:1g N (C.V.=8.4%) which is within the range for Antarctic snow, and indicative of nitrate enrichment by freeze concentration processes. Cyanobacterial mats were conspicuous elements of the biota across the full range of salinities, and were usually dominated by oscilatoriacean species. Nitrogen-fixing cyanobacteria and diatoms were also represented in these benthic microbial communities at the more northern sites, but were absent from all samples from the Darwin Glacier region.

Seedlings of Pinus sylvestris L. were grown in Plexiglas® observation chambers in limed (CaCO3, pH5·0 and 5·9) and untreated (pH 4·1) peat. The seedlings were either colonized by the mycorrhizal fungus Paxillus involutus (Batsch: Fr.) Fr. Or were non-mycorrhizal. After 18 wk in the observation chambers, 15N-labelled organic nitrogen, as lyophilized and ground mycelium of Suillus variegatus (Swartz: Fr.) O. Kuntze, or ammonium, was added to the peat. The plants were harvested after an uptake period of 14 d.

Irrespective of the nitrogen form added, liming decreased both the content and concentration of 15N in non-mycorrhizal plants, and, to a lesser extent, those in mycorrhizal plants. In mycorrhizal plants the uptake of 15N was not correlated with area colonized by the mycorrhizal mycelium. The amount of KCl-extractable 15N in peat without plants and mycorrhizal fungi decreased with liming. It is proposed that liming induced chemical or microbial immobilization of the added 15N. This is suggested to be the main reason for the decreased uptake of 15N in lime treatments.