More diatoms from the roof of the world

tso_moriri_aug16

I have written about the algae in two samples that I brought back from my Indian travels earlier in the year (see “Diatoms from the Valley of Flowers” and “Diatoms from a holy river”) but I also had one other sample packed in the recesses of my suitcase.   This was collected by Heather, as part of her travels from Kashmir to Shimla via Ladakh and the Zanskar Valley, before we met up for our expedition to the Valley of Flowers.  In 2014 and 2015 she collected samples from the littoral zone of Pangong Tso (see “Return to Pangong Tso”); this year, her expedition with Indus Experiences bypassed this lake and, instead, visited another high altitude lake, Tso Moriri .

Tso Moriri is located in Ladakh, in north west India (32° 54’ N, 78° 18’ E), at an altitude of 5200 metres above sea level. It is about 26 kilometres long by 5-6 kilometres wide (between Windermere and Loch Lomond in size, in other words) and a maximum depth of 106 metres.   It is covered in ice between late October and early May.   Like Pangong Tso, the lake is slightly brackish (conductivity: ~1.6 mS cm-1) though this is not quite high enough for the water to have a salty taste.  The lake is a staging post on migration routes for several birds and this, plus the unique fauna of the region, has led to the lake being placed on the list of Ramsar Wetland Sites.

karzok_tso_moririr_aug16

The village of Karzok, and the flat alluvial plain created by the freshwater tributary stream flowing into Tso Moriri, Ladakh, August 2016.

My sample comes from close to the camp site at the village of Karzok, where Heather’s group stayed.  As the photo shows, one of the two major inflows to the lake flows past this village.   The precise location is at the top right of the alluvial fan and, as the photograph below shows, the substrate at this point is mostly gravel and pebbles with just a few larger stones.  As for my other Indian samples, the diatoms were removed from the top surface by vigorous scrubbing with a toothbrush, after which they were treated to a shot of Indian vodka to dull their senses before the long journey back to the UK.

tso_moririri_diatom_samplin

John Macgillivray collecting stones from the littoral zone of Tso Moriri to sample for diatoms, August 2016. 

The diatoms in this sample were sparse but there were enough present to get some idea of the diversity at this particular location.  As is often the case, most of the forms are sufficiently similar to the diatoms I am used to seeing in European samples that it is tempting to use these names, and to infer the ecology from their preferences.   Prominent in the sample (though not particularly abundant) were large valves that were close to Gomphonema gracile or G. hebridense (a. and b.), and there were also at least two species from the Achnanthidium minutissimum complex (d. – g.) and a few valves of Encyonopsis (j.) and girdle bands of Tabellaria flocculosa (not photographed).  Taken together, these suggest low nutrients but, at the same time, lower levels of salts than the reported figures suggest.   Of the other valves present, some resembled Amphora pediculus and there were also Navicula and Nitzschia species, plus a specimen of Sellaphora pupula and a few fragments of a Halamphora species.  Some of these might suggest slightly elevated salinity, but it is an ambiguous signal at best.  Finally, there is a single small specimen of Gomphonema that shares some features (especially the very radiate striae and isolated stigma) with the Gomphonema that I described from Pangong Tso.

tso_mariri_diatoms

Diatoms from Tso Moriri: a., b.: Gomphonema cf gracile / hebridense; c.: Gomphonema species; d. – f.: Achnanthidium sp. (valve views); g.: Achnanthidium sp. (girdle view); h., i.: Amphora cf pediculus; j. Encyonopsis sp.; k., l.: Navicula sp.; m.: Nitzschia sp.; n.: Sellaphora pupula complex.   Scale bar: 10 micrometres (1/100th of a millimetre).

The moral of this story may be that we should not infer too much from a single sample, collected without supporting environmental data, and with valve morphology as the only criterion by which forms are differentiated.   My working hypothesis is that the areas close to the inflow stream may well have fresher water than the main body of the lake, but a proper study would be needed before I would offer that as anything more than an educated guess.

That study is, unfortunately, not an easy task.  The most straightforward overland route into Ladakh is via Kashmir, a route that also allows plenty of opportunity for acclimatisation.   However, the deteriorating political situation in that region complicates travel (the Foreign and Commonwealth Office advise against all but essential trips, which effectively invalidates most travel insurance policies).    Alternatives are to fly to Leh and then take time to acclimatise on arrival, or to travel from Shimla via Manali, which is  longer than the Kashmir routes.  My grumbles about the intrusion of politics into ecology in a recent post (see “This is not a nitrate standard …”) are put into perspective by the very real dangers of travel in many parts of the world.   Samples from both Pangong Tso and Tso Moriri suggest some intriguing questions about biodiversity of ecosystems that have been barely studied until now.   Unfortunately, their mysteries will have to remain unsolved for some time to come.

Reference

Mishra, P.K., Anoop, A., Jehangir, A., Prasad, S., Menzel, P., Schettler, G., Naumann, R., Weise, S., Anderson, N., Yousuf, A.R. & Gaye, B. (2014).  Limnology and modern sedimentation patterns in high altitude Tso Moriri Lake, NW Himalaya – implications for proxy development.  Fundamental and Applied Limnology 185: 329-348.

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