Pangong Tso, from the Indian shore, looking towards China, July 2015 (photograph: Heathe Kelly).
You may remember that a year ago I wrote some posts about a high altitude lake on the India-China border (see “Subaquatic landscapes in Pangong Tso” and references therein). This year, Heather made a second trip to Pangong Tso (described here) under the auspices of Indus Experiences and brought me back another sample from the littoral zone. There was a beautiful thick biofilm here, an unusual bright yellow-brown colour and a jelly-like consistency, but bubbling away as the algae photosynthesised busily. Once again, local vodka was pressed into service as a preservative and, once again, peering through my microscope a few days later, I could see that the sample was dominated by the same long-stalked Gomphonema species that I recorded a year ago (see “Diatoms from Pangong Tso”). The jelly-like consistency did worry me, as this is not what I would expect of a pure growth of diatoms and I did wonder if there were cyanobacteria growing amongst the diatoms that had not survived the journey home in their marinade of cheap vodka.
Growths of diatoms (predominately a long-stalked Gomphonema sp) on a boulder in the littoral zone of Pangong Tso, India, July 2015. The right hand image is a close up showing oxygen bubbles being produced by the the jelly-like masses. Photographs: Heather Kelly.
Intriguingly, the Gomphonema seems to occur in two forms: a fatter form, with a width around eight micrometres, and a narrower form, about six micrometres wide. I’ve written before about how diatoms tend to get shorter over time (see “Diminishing with age”). What I did not make clear in this post is that cell breadth tends to stay relatively constant during this process. This does not happen with every species but it is interesting to see that the fat and narrow forms have overlapping sizes, so it is not a simple matter of the narrow ones being the far end of the size reduction sequence. More work is definitely needed here although, alas, I don’t think Pangong Tso is on the itinerary for next year’s visit to India.
Gomphonema sp from the littoral zone of Pangong Tso, north India, July 2015. a. – d. represent the “fat” form; e. – h. are the narrower form(s). Scale bar: 10 micrometres (= 1/100th of a millimetre).