NEW OR POORLY KNOWN DIATOMS FROM HIMALAYAN STREAMS

Abstract

Diatoms were sampled from over 200 first to third order Himalayan streams, at altitudes of 350–4700 m asl, between 1992 and 1996. This paper describes two new species, one new variety and Cymbella stuxbergii, providing extensive water chemistry and habitat data for these taxa. Gomphonema chubichuensis occurred at high altitudes (2300–4320 m) in meltwater channels or other unstable streams. Navicula obtecta was common in base-poor and nutrient-poor streams in undisturbed catchments of Nepal's Middle Hills. These species have the potential to indicate climatic change and catchment disturbance, respectively. The geographical distribution of the species was restricted: Synedra inaequalis var. jumlensis was only found in Western Nepal and north-western India, G. chubichuensis occurred from northwestern India to Central Nepal, and N. obtecta was mainly found in Eastern Nepal. C. stuxbergii has previously been recorded from more northerly latitudes, apart from one other record from the Eastern Himalaya.