Ecology of the snow alga Chlainomonas kolii (Chlamydomonadales, Chlorophyta) in New Zealand

Abstract

Chlainomonas kotii, a very rarely reported snow alga, formed red blooms in the surface snow of an alpine tarn on Mt Philistine, Arthur's Pass National Park, New Zealand, in the Austral summers of 1998 and 1999. Morphological characteristics corresponded closely to the descriptions of this organism from North America, and the two were indistinguishable by traditional means. Chlainomonas kolii was found in high numbers (≤ 1175 cells ml−1) only in snow covering the tarn surface (tarn snow), and reached lower abundance (≤ 101 cells ml−1) in snow adjacent to the tarn (shore snow). Levels of NH4-N, NO3-N, and dissolved reactive phosphorus in the Mt Philistine snow were lower (usually < 50 μg l−1) than those found in the Northern Hemisphere snowpacks (≤ 7100 μg l−1). NH4-N was the most abundant inorganic-N species. It was also the only nutrient that was detectably influenced by the growth of the algal population, dropping to 1.1 μg l−1 in tarn snow during an increase in cell abundance from 250 to 1175 cells ml−1. NH4-N remained at 5.8 μg l−1 in shore snow, in which algal abundance did not increase. Because of strong diurnal freeze-thaw cycles in the alpine zone, water stress and cellular disruption may be more severe than those in the well-studied forested snowpacks of North America. Very high total irradiance during fine weather (>5000 μmol photons m−2 s−1) may inhibit growth. Snow-algal abundances were low compared with those in the Northern Hemisphere studies (106 cells ml−1), reflecting the comparatively harsh conditions on Mt Philistine. Growth of C. kolii occurs during major rainstorms when snow melt may reach lip to 15.1 cm day−1, liquid water content of the tarn snow increases (to 28.4%), temperatures remain above freezing, and irradiance decreases to noninhibitory levels (< 200 μmol m−2 s−1).