Diatoms from the Valley of Flowers

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My visit to the Valley of Flowers in India (see “Into the Valley of Flowers …”) is a fast fading memory but I have finally managed to get the diatom samples that I smuggled into my suitcase properly mounted and spent some time last weekend peering down my microscope and trying to match what I could see with the habitat that I remembered.

The sample I collected came from a first order stream which appeared from the mouth of a glacier a couple of hundred metres above us on the [north] side of the valley.  About 500 metres downstream it joined the Pushpanati River, a tributary of the Aleknanda, itself a tributary of the mighty Ganges.   It was just over a metre wide and a few centimetres deep and had a mixture of pebbles and gravel as its substratum.  Some of the larger stones were encrusted with what looked like growths of Chamaesiphon  (see “A bigger splash …“).  There were also a few flocs of green algae which turned out to be Zygnema, a relative of Mougeotia and Spirogyra ( see “Fifty shades of green …”) with two distinctive star-shaped chloroplasts.  They are not at their best in the photograph below because they made the journey from India to the UK soused in local vodka (a cheap and effective preservative for algae: your liver will not begrudge you this particular experience …).

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Vinood, our guide, looking at the stream that I sampled in the Valley of Flowers, August 2016.

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Vodka-soused Zygnema sp from a glacier-fed tributary stream of the Pushpanati River (Valley of Flowers),  August 2016.  Scale bar: 20 micrometres (= 1/50th of a millimetre).

The diatoms were a surprise as almost all belonged to a single species, Diatoma mesodon, a species familiar to me from very high quality streams in Europe.  Ninety-five percent of all the diatoms I looked at belonged to this species, an unusually high proportion compared with other samples that I have examined, especially as there are no human pressures in the area that might influence diversity.   The Diatoma cells formed zig-zag chains, though these fell apart during the preparation process and the images just show individual valves.   Other diatoms present in small numbers included Meridion circulare var. constrictum (syn: Meridion constrictum) and two species of Eunotia, all of which suggest relatively soft water.

The low diversity intrigued me.   I have seen very low diversity with headwater streams, possibly because there is low potential for organisms from upstream to “seed” the location.   As small tributaries merge, so incocula from the sparse assemblages of these headwater streams will combine to create more diverse communities downstream.  Curiously, a recent paper argues the opposite: that headwaters are, in fact, hotspots of microbial diversity, and that this declines with increasing distance downstream.   However, this study takes a much broader view than just algae.  The authors suggest that it the close connection between headwater streams and the surrounding catchment leads to soil bacteria being washed into the stream.   So this result does not really contradict my observation; rather it highlights the limited insight that one may glean through looking at a single group of organisms.

Had I had more time (and more samples containers), it would have been interesting to follow the valley as far upstream as possible, to see if the other streams flowing down from the hillside had similar assemblages of algae, or if their algae were different.   My guess is that the patchwork of habitats would mean that the total diversity for the valley (“beta diversity”) would be considerably greater than the diversity at any particular site (“alpha diversity”).   If anyone wants to test this hypothesis, then all they need to do is make a three day journey from Delhi, with an extra day set aside for acclimatisation, followed by a two day hike up to a height of 3500 m.  And don’t forget to pack that bottle of vodka …

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Diatoma mesodon from a glacier-fed tributary stream of the Pushpanati River (Valley of Flowers), August 2016.   a. – e.: valve views; f. – g.: girdle views.  Scale bar: 10 micrometres (= 1/100th of a millimetre.

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Other diatoms from a glacier-fed tributary stream of the Pushpanati River (Valley of Flowers),  August 2016,  a. – b.: valve and girdle views of Meridion circulare var. constrictum; c. Eunotia islandica; d. E. paratridentula; e. Cymbella cf naviculiformis.  Scale bar: 10 micrometres (= 1/100th of a millimetre).

Reference

Besemer, K., Singer, G., Quince, C., Bertuzzo, E., Sloan, W. & Battin, T.J. (2016).  Headwaters are critical reservoirs of microbial diversity for fluvial networks.  Proceedings of the Royal Society of London Series B 280: DOI: 10.1098/rspb.2013.1760

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Into the Valley of Flowers …

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I can safely say that our hotel in Ghangharia was one of the worst in which I have ever stayed.  The rooms were draughty, dirty and damp, there was no hot water and the cheerful Nepali kitchen staff had a very limited grasp of health and safety.  This is one of the downsides of being a Guinea pig for a tour party: we stayed in two excellent hotels and three perfectly adequate ones but, occasionally, we have to suffer so that next year’s paying guests don’t have to.   The tented camp, just outside the village, looks like a much better bet for next year.

On the plus side, the low cloud disappeared overnight and we awoke to blue skies with just a few puffy cumulus clouds and gulped lungfuls of cool mountain air in order to banish the fetid atmosphere of the hotel.   The track out of Ghangharia was quiet: the Sikh pilgrims have to walk further and climb higher than those of us heading to the Valley of Flowers, so had made earlier starts.   We paid our 600 rupee entrance fees at a hut beside the path just after our route diverged from the path that the Sikhs took, and followed the track through a fir forest overhung by enormous vertical cliffs of much-folded ancient rocks.

The Valley of Flowers is a hanging valley – a glacial valley which ends in an abrupt drop as it joins with the valleys below.  This meant another stiff climb along a path that zig-zagged up a hillside and across the site of recent landslides.  We were now walking at about 3500 metres, and I was reminded of the limitations of my acclimatisation programme with every step.  But we had reached the tree line and the valley had broadened out to give us our first views of the valley that Smythe had first seen in 1931.   From where we stood at the western end, the valley extended for about five km due west before reaching the foot of the Tipra glacier. Behind these, peaks (several climbed for the first time by Smythe and his associates) rose to 6600 metres although, during our visit, most were hidden by clouds.  On either side of the valley there were lateral moraines deposited by the glacier in colder times whilst the Pushpawti river, carrying the glacier’s meltwater, has gouged out a V-shaped notch along the mid-line of the valley.

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Looking west up the Valley of Flowers towards Tipra glacier with stands of balsam in the foreground.  The photograph at the top of the post shows our first view of the Valley on arrival from Ghanghria.

There was a profusion of flowers but, to our mutual surprise, the most abundant by far, especially close to the mouth of the valley, was Himalayan balsam, scourge of British river banks (see “The politics of pests”).  After a while, however, we started seeing more diversity, especially in areas where the balsam was less prevalent and as we pushed further into the valley.  Everyone has to leave the valley by nightfall, which limits the distance that visitors can penetrate to a couple of kilometres, so there were many areas that Smythe described but which we could not visit.  Nonetheless, Heather, the real botanist in the family, photographed about 100 different species (her own accounts will follow) at a time of year when important groups such as Primula and the orchids are long past their best.

The prevalence of balsam was intriguing.  This is its native habitat, and we don’t have enough knowledge of the plant communities in this part of the world to know how typical these extensive stands of balsam are at these altitudes.  Smythe reported its presence but also commented that it was ruining pastures in the area.  However, he only made a couple of visits so his opinion, too, may not be definitive.  We did learn from a park ranger that the cover of balsam had increased in recent years.  When the valley was declared as a World Heritage Site grazing was banned and though this was at a very low level (a single family), we did wonder whether this had a role in maintaining habitat.   On the other hand, the balsam here is much more varied than the monocultures of Impatiens glandulifera that we are used to seeing in the UK, where it was introduced and perhaps we are approaching it with minds pre-conditioned by negative attitudes at home?   I. glandulifera is found in the valley, but I. sulcata, the Giant Himalayan balsam, is more common here.   There is no doubt that the splashes of pink-purple flowers across the floor of the valley were a dramatic fulfilment of many peoples’ expectations as they first entered the valley.

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Valley of Flowers, looking west at about 1.5 km from the foot of Tilpri glacier.   The plants in the foreground are (probably) Campanula latifolia (bellflower) and Selinum wallichianum (milk parsley), one of several umbellifers that are found in the valley.

By now, the sun was sinking and we needed to start retracing our steps back down to Ghanghria.   Our personal odyssey was over; we had seen the Valley of Flowers. For Heather, at least, it is probably “au revoir” rather than “goodbye” as there is a strong chance that she will bring a tour party back here next year or the year after.   For me, who knows?

And, yes, I did collect some diatoms from a stream whilst I was in the Valley of Flowers.  I’ll write more about those at some point.  Somehow, too, I must have communicated my interest in the diversity of the microbial world to the kitchen staff of our hotel, as they kindly sent me back down the track to civilisation with a payload of grumbly enteric bacteria.  But you don’t want me to write too much about that …

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The Valley of Flowers, showing abundant stands of Persicaria polystachya, a very common plant along river banks (i.e. in the habitat where we would expect to find Himalayan balsam, Impatiens glandulifera, in the UK).