Subaquatic landscapes in Pangong Tso

My own private counterweight to inclination of fellow diatomists to base their science on the study of empty shells of dead organisms is to reconstruct images of what those diatoms might have looked like when they were still in their natural habitat.   The latest of these thought experiments is based on the samples I’ve described from Pangong Tso (see “Diatoms from the roof of the world” and “Diatoms from Pangong Tso”).   It comes with a number of caveats, not least of which is that the only preservative available (local vodka) would not have been kind to the non-diatom algae in the sample, so I may have over-estimated the contribution of diatoms to the total community.

Pangong_Tso_140928

A visualisation of the subaquatic flora of Pangong Tso, September 2014, including the diatoms Gomphonema (on long stalks), Diatoma (zig-zag chains), Berkeleya rutilans (in mucilage tube, bottom left corner), Achnanthidium minutissimum (epiphytic on Gomphonema stalks) and motile Nitzschia inconspicua.  The Gomphonema cells are approximately 25 micrometres (1/40th of a millimetre) long.

The diatoms that I saw as I looked done the microscope is one that suggests a fairly mature community with only limited grazing. This may reflect the harsh environment endured in this high altitude desert or the brackish nature of the lake, or it may just be a temporary situation. It is impossible to say with so little data.   The organisms that I did see suggest several different ecological strategies.   The giants in my underwater landscape were the Gomphonema cells, which lived on the end of long branched polysaccharide stalks.   As the film of microscopic algae on any surface grows thicker, so the amount of light that penetrates through is reduced and there is a benefit to any organism that can reach up above the hoi polloi to gain access to the limited light.   Entangled amongst these are zig-zag chains of Diatoma cf moniliformis which, like the lianas of tropical forests, are entangled around these stalks.   I also saw cells belonging to the Achnanthidium minutissimum complex and I know, from other samples I’ve looked at, that these are capable of growing as epiphytes on the stalks of Gomphonema species.   Berkeleya rutilans is a species that I have not previously encountered in my studies of the microscopic world but I have followed descriptions in the literature and included a couple of cells in a mucilage tube towards the bottom left corner of the picture.   Finally, the most numerically abundant species in the sample was one that I do know very well: Nitzschia inconspicua. This is a motile diatom which is able to move through the tangle of Gomphonema stalks and Diatoma filaments in search for light.   I was co-author of a paper on the ecology of N. inconspicua published earlier this year and was pleased to see that the habitat of Pangong Tso matches our prescription almost exactly (based on the limited published data). The assumption that most diatoms are cosmopolitan has rightly been challenged in recent years but there are species that do appear to be very broadly distributed.   Even when the species is not familiar (as for the Gomphonema), the genus is identifiable from my experience in Europe. This is in stark contrast to many other groups of organisms encountered in the tropics and sub-tropics.   It does make life easier for the travelling phycologist though, fortunately, there are still plenty of surprises waiting for us out there.

If you want to see Pangong Tso for yourself, Indus Experiences are organising a two-week geology and ecology excursion to Ladakh next year.   See you there.

Reference

Kelly, M.G., Trobajo, R., Rovira, L, & Mann, D.G. (2014). Characterizing the niches of two very similar Nitzschia species and implications for ecological assessment. Diatom Research DOI:10.1080/0269249X.2014.951398

 

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Food for thought in the River Ehen

Last week’s trip to the River Ehen involved close scrutiny of the hydrographs and weather forecast in the days preceding the trip, followed by some crude extrapolations that predicted that the river would be low enough for us to enter. Nevertheless, there were some anxious moments when we first arrived and gazed into the fast-flowing water.   It was an occasion when I was glad of my veterinary gloves which afford some protection as I have to plunge my arms into river almost to my shoulder in order to pluck stones from the bottom.

The top surface of many of the stones had conspicuous chocolaty-brown patches which are a sign that the diatoms are growing vigorously.   We had been surprised that the amount of algae in the river had been quite low compared to our previous measurements in the autumn and had wondered whether the mild weather had allowed the natural grazers in the river to persist for longer than was the case last year.   Now, with a distinctly autumnal chill in the air, the diatoms no longer seem to be held in check which lends credence to this theory.   If true, it is a good demonstration of just how important “top down” processes are in controlling the quantities of algae that we see in our streams and rivers.

Ehen_Mill_biofilms_141106

Chocolate-brown patches of diatoms on the upper surfaces of cobbles on the bed of the River Ehen (Mill) in November 2014.

Under the microscope, these brown films resolved into a mass of diatoms, along with a few filaments of Bulbochaete (see “The River Ehen in August”). There were two species of Gomphonema species which live at the end of long stalks: G. acuminatum (see “The River Ehen in February”) and G. truncatum, plus other, smaller Gomphonema species.   There were also a lot of long, needle-like cells of Fragilaria tenera, many of which were joined at their bases to form hedgehog-like bundles of cells. My guess is that these start life attached to either the rocks or other algae but that they easily detach, especially when manhandled onto a microscope slide, and appear to be free-living.

Mill_diatoms.141106

Common diatoms from the River Ehen (Mill), November 2014: a. Gomphonema truncatum valve view; b. G. truncatum girdle view; c. Gomphonema acuminatum valve view; d. G. acuminatum girdle view; e. Fragilaria tenera valve view; f. F. cf. tenera girdle view.   Scale bar: 10 micrometres (1/100th of a millimetre).

Ten or fifteen years ago I would not have referred to this diatom as “Fragilaria” but, instead, would probably have called it Synedra tenera.   Older identification guides (such as West and Fritsch’s British Freshwater Algae, from 1927) differentiate between Synedra and Fragilaria based on whether or not the cells form ribbon-like colonies (Fragilaria) or are solitary or form radiating clusters (Synedra). From the 1980s onwards this simple dichotomy was unpicked just enough to demonstrate that it was too simplistic, but not enough to enable our esteemed taxonomists to put all the pieces back into a coherent whole (a story for another day …).   However, the evidence at present leans to the narrow needle-like species that once belonged to Synedra actually sharing more characteristics with true Fragilaria.   I call this species Fragilaria tenera with mild trepidation, knowing that there is at least one other needle-like Fragilaria present in the upper Ehen and, moreover, that a paper has recently been published (though I have not yet read it) in a rather obscure German taxonomic journal that dissects this complex into yet more fragments. Research on Fragilaria has, alas, generated rather more heat than light over the past couple of decades.

Frag_tenera_stack_Ehen_#1

A colony of Fragilaria tenera from the River Ehen, image produced using Helicon Focus stacking software. Individual cells are approximately 50-60 micrometres long.

Reference

Lange-Bertalot, H. & Ulrich, S. (2014). Contributions to the taxonomy of needle-shaped Fragilaria and Ulnaria species 1. Lauterbornia 78:

 

Dipping a toe into the River Jordan

I came across an intriguing short paper recently which got me thinking again about a topic that I wrote about a year ago. I was intrigued, at the time, by how ecosystem services dovetailed with the ideas of ecosystem health that preoccupy my working day and suggested, provocatively, that there may be some instances where stakeholders might not thank ecologists for the high quality ecosystems that we want to achieve (see “More about ecosystem services” and “Ecosystem services … again”).    There is a class of ecosystem services called “cultural services”, which includes uses such as education, amenity and, intriguingly, spirituality.   I have been searching, subsequently, for good examples of rivers and lakes providing “spiritual” ecosystem services and here, at last, is one hiding right under my nose.

The paper describes use of the Jordan River for baptism, and the problems caused by the ongoing regional conflicts along with environmental degradation.   The river is the de facto border between Israel and Jordan and has been heavily militarised since 1967, with access to the river limited to just three locations, one each in Israel, the Occupied Territories (West Bank) and Jordan. Problems are compounded by the extensive use of the Jordan and tributaries as a source of water for this semi-arid region, and by discharges of semi-treated sewage into the river from Israel.   This has reduced the flow to a muddy trickle, about one tenth of its natural quantity. This, combined with the pollution, hardly makes the river a desirable place in which to be totally immersed.   Whether the river was ever crystal clear is open to debate: in 2 Kings chapter 5 we read of Naaman, a general from the eighth century BC, objecting to being told to bathe in the Jordan to cure himself of leprosy.

Jordan_at_Bethany

The River Jordan at Bethany, Jordan (the church of John the Baptist on the left hand side) with, on the right, the baptism site at Qasr al Yehud in the Occupied Territories (West Bank), seen from the Al Maghtas baptism site in Jordan (photos: Heather Kelly)

Reading this article reminded me of one of the stranger instances in my professional life when a local clergyman asked for my advice on a location for an outdoor baptism in the Durham area.   I suggested a couple of locations where the river was accessible from the bank and not too deep, whilst being deep enough for a kneeling person to be dunked.   I also suggested, from my knowledge of the river, a careful search of the river bed in advance in case there was broken glass, and recommended that the initiate kept his or her mouth closed to ensure that they did not swallow too many bacteria.   I was not being consulted on the theology of baptism, else I might have queried whether a purely symbolic act needed all this fuss and bother. And, indeed, we might ask what a baptism candidate gains from being dunked in the Jordan that would not have been achieved using a font full of chlorinated water.   Such issues are for another blogger on another day.

Varanasi_puja

Performing puja in the River Ganges from the ghats at Varanasi, October 1984.

Indeed making catty comments about other people’s attitudes to sacraments whilst writing about the Israel-Jordan border has a deep irony of its own.   Would that people historically had shown a little more tolerance to other people’s spirituality, the world would be a far more peaceful place.   My intention, when I started writing this piece, was to highlight how rivers can play a role in people’s spiritual life. We don’t need to understand or accept the beliefs of those people, just to recognise that some places – rivers, sometimes – can hold great spiritual significance and that we, as guardians of those rivers, need to respect this.

I was also reminded of my own visit to the holy city of Varanasi in India, thirty years ago, when I watched Hindus using a different (but equally polluted) river as part of their observances.   It was difficult for me, as a westerner, to understand the significance of the river to Hindus yet all around me there were people who clearly saw this river as integral to their worship. The problem, as with so much in this modern world, lies in not understanding what others regard as important.   Some questions, it seems, cannot be answered by scientific rationalism alone.

Reference

de Châtel, F. (2014). Baptism in the Jordan River: immersing in a contested transboundary watercourse.   WIREs Water 1: 219-227.

Diatoms from Pangong Tso

I took the opportunity of the British Diatom Meeting (see “In the footsteps of Sherlock Holmes …”) to wave some images of the diatoms I found in the sample from Pangong Tso (see “Diatoms from the roof of the world”) under the noses of some colleagues in the hope of confirming their names.

The most obvious species in the sample was a Gomphonema which grew on long, branching stalks.   Cleaned valves of this had a broad rostrate head pole and a rostrate to sub-capitate foot pole, strongly radiate striae, and a single stigma (pore) in the central area.   The specimens in this sample ranged from 14 to 29 micrometres in length and 6 to 7 micrometres in breadth.   My colleague, Ingrid Jüttner from the National Museum of Wales, who has considerable experience of Himalayan diatoms, said that she had seen this species once before in a sample from Pakistan but it was, to the best of her knowledge, not yet formally described.

The other species that was very conspicuous when I made my initial scans of the sample belongs to the genus Diatoma. Were I to use a European Flora to identify this, I would call it Diatoma moniliformis.  The length and breadth of the Pangong Tso specimens fell within the range reported for D. moniliformis, as did the density of costae (horizontal ribs) and the outline.   However, as Ingrid is presently writing a paper on Himalayan Diatoma spp. I will wait a little longer before confirming that this is definitely D. moniliformis.

Pangong_Gomphonema_clean

Gomphonema sp – possibly new to science – from the littoral zone of Pangong Tso, north India, September 2014.   The right-hand specimen, which is narrower than the others, may represent a different species.   Scale bar: 10 micrometres (= 100th of a millimetre).

Pangong_Diatoma.clean

Diatoma cf moniliformis from the littoral zone of Pangong Tso, north India, September 2014. Scale bar: 10 micrometres (= 100th of a millimetre).

Two other species in the sample look more familiar to me from my European samples.   The first of these is a small species of Nitzschia, N. inconspicua.   This species was, actually, the most abundant species in the sample, accounting for almost sixty per cent of all the diatoms though, as it is relatively small, it probably accounts for a much lower proportion of the total biomass or biovolume.   I have, coincidentally, just published a paper on the ecology of this species and the habitat of Pangong Tso, as far as we know from the limited data available, matches these criteria very closely: slightly brackish with elevated phosphorus concentrations.

There were also a number of individuals of Achnanthidium minutissimum, a diatom that is very widely distributed in freshwaters around the world.   Our understanding of A. minutissimum has changed a lot over the past twenty years and we now know that there is a complex of species with similar characteristics and, often, overlapping ecological characteristics. The Pangong Tso sample consisted mostly of individuals that belonged to “true” A. minutissimum, but there were also a few individuals that may belong to another species within the complex.

Pangong_Nit_inconspicua

Nitzschia inconspicua from the littoral zone of Pangong Tso, north India, September 2014. Scale bar: 10 micrometres (= 100th of a millimetre).

Pangong_Achnanthidium_minut

Achnanthidium minutissimum from the littoral zone of Pangong Tso, north India, September 2014. The five specimens on the left are A. minutissimum sensu stricto; the two specimens on the right belong to a linear form closely related to A. minutissimum.   Scale bar: 10 micrometres (= 100th of a millimetre).

Finally, I found a number of individuals of Berkeleya rutilans (synonym: Amphipleura rutilans), a small diatom which Krammer and Lange-Bertalot (1986) describe as living in coastal areas and inland saline waters and which Ralph Lewin describes as a “common littoral diatom of the Atlantic coast [of the USA]”, where it grows in branched mucilage tubes.   This is another diatom m that has recently been shown to be a complex of closely-related but distinct species,

It is an intriguing mixture of species. First of all, the total number of species that I found was very low – less than ten, whereas I usually expect twenty, thirty or more species in a sample. Second, we have an interesting mix of truly freshwater taxa (Gomphonema, Achnanthidium minutissimum), alongside taxa that are found in both freshwater and brackish habitats (Diatoma moniliformis – if I am right – and Nitzschia inconspicua) and, finally, a species mostly associated with brackish and saline habitats (Berkeleya rutilans).   All living together in a slightly saline lake over 4000 metres above sea level.   Of course, we cannot conclude very much from a single sample and scant environmental data but then that just creates an incentive to get back to collect some more samples …

Pangong_Amphipleura_rutilan

Berkeleya rutilans from the littoral zone of Pangong Tso, north India, September 2014. Photographed with phase contrast illumination.   Scale bar: 10 micrometres (= 100th of a millimetre).

References

Hamsher, S.E. & Saunders, G.W. (2014). A floristic survey of marine tube-forming diatoms reveals unexpected diversity and extensive co-habitation among genetic lines of the Berkeleya rutilans complex (Bacillariophyceae). European Journal of Phycology 49: 47-59.

Krammer, K. & Lange-Bertalot, H. (1986)   Süsswasserflora von Mitteleuropa. Bacillariophyceae. 1: Naviculaceae. Gustav Fischer-Verlag, Stuttgart, Germany.

Lewin, R.A. (1958). The mucilage tubes of Ampiphleura rutilans. Limnology and Oceanography 3: 111-113.

 

Fieldwork tales from the tail of a hurricane …

I had more or less decided to cancel my fieldwork when I heard the weather forecast a couple of weeks ago. The last remnants of Hurricane Gonzalo were blowing themselves out over western and northern Britain and the prediction was for heavy rain over the Pennines. I heard the rain during the night and checked the river levels in the morning. They were not outrageously high, but the trend was upwards and common sense dictated that I wait a day and try again.   You can see from the hydrograph below just how quickly the river rose and then fell again over the course of 24 hours.   Even by 09:00 the following day the river was not at its lowest, but at least it was safe to wade in and collect some samples.

river_levels_stanhope_14102

River Levels in the River Wear at the Environment Agency’s monitoring station at Stanhope, 20th – 22nd October 2014 (http://apps.environment-agency.gov.uk/river-and-sea-levels/120695.aspx?stationId=8196). The arrows indicate the approximate time of the rainfall associated with Hurricane Gonzalo.

A sign that the river was still higher than usual was that some cushions of moss that are usually well clear of the water were at or, in a few cases, still below water level.   There are a few species of moss, including members of the genus Cinclidotus and Racomitrium aciculare, that seem to thrive on the upper parts of boulders.   They spend most of their life out of the water, then just a few days each year submerged. Those few days will bring down suspended material which will become entrapped around the dense network of stems in the cushions and, in the process, provide a nice little “compost heap” that will keep the moss supplied with nutrients. The stems also trap water, through capillary action, so that the cushions stay moist for some time after the water levels have dropped again.   Yet such generalisations do not explain why a few genera thrive in this habitat whereas others are never found here.

Much of the magic of rivers is associated with organisms which are rarely, if ever, seen: the fish, of course, but also otters, kingfishers and other vertebrate organisms. I’m also fascinated by the microscopic world of rivers. Mosses have the opposite problem: we always see them on visits to rivers yet almost never notice them, let alone spend time unravelling the stories that they can tell us.   I am reminded of Mungo Park’s words back in 1795 (see “More about mosses…”). Perhaps I should write a little more about the extraordinary diversity of mosses over the next few months?

Cinclidotus_mucronatus_Wols

Cushions of Cinclidotus mucronatus just above water level in the River Wear at Wolsingham, October 2014.