Twisted tales …

Spirulina_ChrisCarter-

As opportunities for field work are still limited, I have returned to the banks of Lough Down for this post.   Lough Down, as some of you will have worked out for yourselves, is not somewhere that can be defined in terms of exact geographic co-ordinates, rather it is a state of mind.  However, that means that, in ecological terms, it is as diverse as I want it to be and, as such, it offers plenty of opportunities for writing about algae that I would not otherwise come across.   Thankfully, Chris Carter is another habitué of Lough Down and its environs, so I can use his pictures to illustrate these posts.

I used a Pasteur pipette to suck up a likely-looking patch of algae growing over some fine sediments in the littoral zone of Lough Down and brought this back to examine under my microscope.  When magnified, I was presented with the view of blue-green coloured helices twisting and turning across my field of view which means that this is almost instantly identifiable as the Cyanobacterium genus Spirulina.   It is, in effect, a helical cousin of genera such as Phormidium and Oscillatoria which we have encountered many times in this blog.   If you look closely, you’ll see that there are no heterocysts – the specialised cells responsible for nitrogen-fixation – whilst this particular population also has no gas vacuoles.  These are structures inside the cell which make the cells buoyant.  Many of the Spirulinaspecies found in warmer parts of the world have these, enabling them to live suspended in the water, whereas the temperate species tend to live at the bottom of lakes and ponds.  Whilst a few species definitely prefer freshwaters, most are associated with brackish and marine habitats, including saline lakes in Africa such as Lake Chad.

Spirulina is not a particularly common alga in UK and Irish freshwaters, but there is one habitat where it can be conspicuous: the shelves of health food stores.   All sorts of claims have been made for its health-giving properties – some supported by evidence, others not – earning it the epithet “superfood”.   There is, for example, evidence that women from communities around Lake Chad who regularly ate Spirulina (“Dihé”) had higher levels of Vitamin A than those who did not.   However, vitamin A deficiency is common in the region and the effects would not be pronounced in regions where there was a greater range of sources of vitamin A in the everyday diet.   On the other hand, Spirulina comes from the same sub-class as a number of Cyanobacteria known to produce neurotoxins, and there is some evidence (admittedly much less than for other genera) for it also producing toxins.   The aggressive marketing of Spirulina is enough to make me wary: there is no such thing as a “superfood”, except as one small part of a balanced diet.   Buy it and use it, by all means, but do not expect miracles.

I should mention, in closing that “Spirulina”, as commonly understood, is actually two genera: Spirulina and Arthrospira.  Much of the material sold as health food actually belonging to the genus Arthospira, which is broader than Spirulina and has more distinct cross-walls.   Looking at the Freshwater Algal Flora of the British Isles, I see a record for Arthrospira jenneri from a pond just a short cycle ride from my house from 1938.  Maybe I should make a trip one day soon to see if it is still there …

References

McCarron, P., Logan, A. C., Giddings, S. D., & Quilliam, M. A. (2014). Analysis of β-N-methylamino-L-alanine (BMAA) in Spirulina-containing supplements by liquid chromatography-tandem mass spectrometry. Aquatic Biosystems. https://doi.org/10.1186/2046-9063-10-5

Roy-Lachapelle, A., Solliec, M., Bouchard, M. F., & Sauvé, S. (2017). Detection of cyanotoxins in algae dietary supplements. Toxins. https://doi.org/10.3390/toxins9030076

Soudy, I. D., Minet-Quinard, R., Mahamat, A. D., Ngoua, H., Izzedine, A. A., Tidjani, A., … Sapin, V. (2018). Vitamin A status in healthy women eating traditionally prepared Spirulina (Dihé) in the Chad Lake area. PLoS ONE. https://doi.org/10.1371/journal.pone.0191887

Wrote this whilst listening to: Bob Dylan’s Live at Budokan, Slow Train Coming and Saved.  Also, Big Thief’s new single Love in Mine.  Still not sure how I missed their set at Green Man 2019.

Cultural highlights:  Enjoyed the film Peanut Butter Falcon, an indie hit last year which we missed first time around.   Also discovered a podcast on Spotify called Winds of Change by American journalist Patrick Radden Keefe.  It might be about American soft power and psy-ops at the end of the Cold War or it might just be a loopy conspiracy theory.  Not sure I know myself yet.

Currently reading:   Just about to start Sarah Walter’s The Paying Guest.

Culinary highlight:   Either a Yotam Ottolenghi recipe for tamarind and tomato braised chickpeas from the Guardian [https://www.theguardian.com/food/2020/may/09/tamarind-tomato-braised-chickpeas-savoury-porridge-browned-butter-lime-rice-pudding-yotam-ottolenghi-thrifty-recipes] or an improvised East-meets-West better-than-it-sounds risotto topped with steamed sea bass with ginger and spring onions.

Whatever doesn’t kill you …

Potamogeton_epiphytes_April20

The previous post focussed mostly on the higher plants that I found in the short stream that connects White’s Level with Middlehope Burn.  I mentioned the mass growths of algae that I found growing immediately below the entrance to the adit, but I did not talk about them in any detail, instead spinning off on a tangent while I mused on why the water cress had a purplish tinge.

When I did find time to examine the algal floc, I found it to consist of a mix of three different algae, the most abundant of which was Tribonema viride, but there were also populations of a thin Microspora (not illustrated) and Klebsormidium subtile.   I talked about Tribonema in the drainage from the Hadjipavlou chromite mine in Cyprus last year (see “Survival of the fittest (1)”) and both Microspora and Klebsormidium are also genera that are known to frequent these habitats.  Indeed, there is evidence that the populations that grow in these extreme habitats have physiological adaptations that help them to cope with the conditions.  Brian Whitton, my PhD mentor, led several studies on these adaptations in the streams of the northern Pennines in the 1970s, and Patricia Foster did similar studies in Cornwall at about the same time.   There is probably a mixture of physiological strategies involved, including the production of low-molecular weight proteins, which bind the toxic metals, and the production of extracellular mucilage.  Most of the populations I find in such habitats have a distinctly slimy feel due to the production of extracellular polysaccharides, and it is possible that these play a role in trapping the metal ions before they can get into the cell and cause damage.

Tribonema_viride_WhitesLevel_Apr20

Filamentous algae from the drainage channel below White’s Level, upper Weardale, April 2020.  a., b. & c.: Tribonema cf. viride, showing the characteristic H-shaped cell ends.   d.  Klebsormidium cf. subtile.  Scale bar: 10 micrometres (= 100th of a millimetre).   The picture at the top of the post shows an artist’s impression of Chamaesiphon cf. confervicolus on the upper surface of a Potamogeton polygonifolius leaf. 

I also had a look at the algae growing on the submerged leaves of Potamogeton pergonifolius in the channel between the adit and Middlehope Burn.   One easy way of examining them is to add a small amount of stream water then shake the leaves vigorously in a plastic bag.  The result is a brownish suspension of algae that can be sucked up with a Pasteur pipette and placed on a microscope slide.  When I did this, I found a community that was dominated by a short cyanobacterium, closest in form to Chamaesiphon cf. confervicolus.  The other abundant alga in the sample was Achnanthidium minutissimum, which is often common in minewaters, along with smaller numbers of a few other species.  The total number of species in the sample was just 12, which is low by the standards of streams without metal pollution, but such suppression of all but the hardiest species is another characteristic effect of heavy metal pollution.

I’ve added a “cf” (from the Latin conferre, meaning “compare to”) to my identification of Chamaesiphon confervicolus because this is the closest name, based on a comparison with images in the Freshwater Algal Flora of Britain and Ireland.  However, it is not an exact match.  Whether this is because the metals have strange effects on Chamaesiphon (as we saw for diatoms in “A twist in the tale …”) or whether our knowledge of the species within this genus is imperfect is not clear.  But discretion is the better part of valour in this instance.  Chamaesiphon species fall into two groups: those that live on stone surfaces (see “Survival of the fittest (2)”) and those that live on algae and plants, such as the one we see today (another is illustrated in “More from the River Ehen”).   They consist of a single, elongate but gently tapering cell, attached at one end to the plant and enclosed in a sheath.   The upper end of the filament forms small spherical buds (technically “exospores”).  One reason that I am wary of calling this population C. confervicolus is that most illustrations of this species show a stack of exospores in the sheath, whereas the White’s Level population all had just a single exospore.

Chamaesiphon_confervicolus

Chamaesiphon confervicolus, growing on Potamogeton polygonifolius in White’s Level outflow, April 2020.   Note the exospores at the end of the cell.  f. and g. show the sheath very clearly.  Scale bar: 10 micrometres (= 100th of a millimetre). 

The picture at the top of this post shows an artist’s impression of the Chamaesiphon cf confervicolus on the upper surface of the Potamogeton leaf.   I wanted to get some idea of the size, shape and arrangement of the epidermal and stomatal cells on the Potamogeton leaves and resorted to the tried and tested technique of painting a layer of clear nail varnish onto the leaf surface, then peeling this off when it had dried.  This had the added (and unexpected) benefit of also pulling of the epiphytes, giving some idea of their arrangement on the leaf surface at the same time.   One extra observation that this yielded was that upper surface was dominated by Chamaesiphon, growing in clusters, whilst the lower surface had greater representation of diatoms.   I’ve also tried to portray the chloroplasts in the stomata guard cells.  Plant epidermal cells generally do not contain chloroplasts, as their purpose is to protect the mesophyll cells that are the main centres of photosynthesis.  Guard cells of stomata, however, need energy to open and close the stomata so these are the exception to this rule.  I had not even been sure that I would see stomata on the upper surface of the cell, as these are mostly found on the underside of leaves; however, Potamogeton appears to have stomata on both surfaces.  As ever, there is a certain amount of evidence along with a dose of extrapolation.   Imagined, but not imaginary …

You can find a description of the terrestrial plant life of Slitt Mine and its environs in this post on Heather’s blog.

References

Foster, P.L. (1982).  Metal resistances of Chlorophyta from rivers polluted by heavy metals. Freshwater Biology 12: 41-61.

Harding, J.P.C. & Whitton, B.A. (1976).  Resistance to zinc of Stigeoclonium tenue in the field and the laboratory. British Phycological Journal 11: 417-426.

Robinson, N.J. (1989).  Algal metallothioneins: secondary metabolites and proteins.  Journal of Applied Phycology 1: 5-18.

Say, P.J., Diaz, B.M. & Whiton, B.A. (1977).  Influence of zinc on lotic plants. I. tolerance of Hormidium species to zinc.  Freshwater Biology 7: 357-376.

Sorentino, C. (1985).  Copper resistance in Hormidium fluitans (Gay) Heering (Ulotrichaceae, Chlorophyceae).  Phycologia 24: 366-368.

(Note that Hormidium is the old name for the genus Klebsormidium.  There is an orchid genus called Hormdium and, as this was described first, it takes priority.)

 

Some other highlights from this week:

Wrote this whilst listening to: Bob Dylan’s New Morning and Pat Garrett and Billy the Kid.   Also, Samuel Barber’s Prayers of Kirkegaard.

Cultural highlights:  The Netflix series Unorthodox, about a young woman fleeing a Hassidic community in New York.

Currently reading:  Agatha Christie’s A.B.C. Murders.

Culinary highlight:   Arroz con leche (Spanish rice pudding) served with peaches poached in madeira.

Shuffling the pack

Microcystis-Ladybower_CCarter

The next group of algae I’m going to consider in my review of higher taxonomy and systematics, the Cyanobacteria, or “blue-green algae”, present some significant challenges.  Not least of these is a shift over the past forty years from being classified according to the rules of botanical nomenclature to being classified according to the International Code of Nomenclature of Bacteria.  The former assumed species could be defined from field material on the basis of morphology, with “type specimens” preserved in herbaria; the latter uses axenic (i.e. pure) cultures as the basic taxonomic unit, and allows a wider range of attributes than just morphology.   In recent years, as those who follow this blog will know, properties such as gene sequences have also been used to define species although the Code of Botanical (now Biological) Nomenclature still requires a description of the any new species that are described, with an expectation that the morphology will take a prominent role in that description.  As this post will show, morphology is no longer such a reliable indication of how Cyanobacteria are organised as it was in the past.

For practical purposes, many Cyanobacteria fall into the same size range as other algae, live in communities that include many protist groups and can be identified using similar techniques as would be employed to identify other algae.  They also have a form of photosynthesis that produces oxygen as an exhaust gas, in contrast to other bacteria which are capable of photosynthesis. This means that a default view of the Cyanobacteria as “algae” is a reasonable starting point for a field ecologist.   However, at an intercellular scale, the Cyanobacteria are very different to other algae, and we should never lose sight of the fact that they actually belong to a different Domain to other algae.

The problems are clear when I compare the morphology-based classification that I used when I first taught classes on algae in 1990 with the classifications that are accepted now.  Then, Cyanobacteria were divided into three or four orders, typically:

  • Chroococcales – single cells or cells loosely-bound into irregular gelatinous colonies
  • Oscillatoriales – filamentous forms lacking heterocysts
  • Nostocales – filamentous forms with heterocysts

The high-level classification, in other words, was based solely on whether or not the organism formed filaments and, if so, whether or not it possessed heterocysts (specialised cells responsible for nitrogen fixation).  This made logical sense when your primary source of insight is morphology.  Unfortunately, more recent studies have shown that it bears little relationship to the genetic relationships amongst the organisms that have been revealed over the past thirty years or so.   A more recent organisation is given in the diagram below.

First, note that this shows subclasses, rather than orders, within the class “Cyanophyceae” (the only class in the division Cyanophyta).   There is rarely unanimity amongst experts on the appropriate organisation of high-level classifications so just bear with me on this one.   Of the four sub-classes, one, Nostocophycidae, contains a single order (Nostocales) which includes all the heterocyst-bearing forms.  No change there.   However, the other two classes diverge very much from the older classifications in that they both contain a mixture of filamentous and non-filamentous forms.

Cyanobacteria_subclasses

The organisation of the Cyanobacteria (blue-green algae) division into four sub-classes.  Filled boxes indicates the classes that are represented in UK and Irish freshwaters.   Organisation follows Algaebase.   The image at the top of this post shows a Microcystis bloom at Ladybower Reservoir (photo: Chris Carter)

The Oscillatoriophycidae is a good example, with five sub-classes, four of which are represented in the UK and Ireland.  Two of these have featured in several posts (see Appendix) so you can see for yourself just how different they are in appearance.  The Oscillatoriales includes filamentous forms without heterocysts whilst the Chrococcales has taxa that either exist as single cells or in masses loosely-bound within gelatinous colonies.    A similar situation exists within the Synechococcophycidae; indeed, some genera that would formerly have been considered to be relatives of taxa within Oscillatoriales (e.g. Schizothrix and Heteroleibiana) are now included in families in this group.   There is, however, still more work to be done to unravel all the relationships within this sub-class.   The current understanding is that there is a single order (“Synechococcales”) but a great number of families.  Similarly, all the heterocystous forms are grouped into a single order, the Nostocales, within the Nostocophycidae, also divided into a large number of families.

Oscillatoriophycidae_orders

Organisation of the Oscillatoriophycidae showing the orders that include genera found in UK and Irish freshwaters.  

I always stress that taxonomy and identification are two distinct crafts: the taxonomist calls on a wide range of tools to find natural groupings of species at different levels whilst an ecologist only needs a parsimonious route to an unambiguous identification.  For the purposes of identification, recognising whether an organism is filamentous or not is a logical early step, even though both options will contain representatives of both Oscillatoriophycidae and Synecchococcophycidae.   We need to recognise that some of the characteristics that contribute to our taxonomic understanding (gene sequences, arrangement of thylakoids) are useless from the point of view of someone trying to name an organism encountered in a field sample but, at the same time, the taxonomist’s standpoint will not necessarily capture all of the features that explain how an organism contributes to energy and nutrient flow within ecosystems.

Calothrix-stagnalis_CCarter

Calothrix stagnalis: a member of the Nostocales.  Note the heterocysts at the base of the filaments (photo: Chris Carter)

References

Mai, T., Johansen, J.R., Pietrasiak, N., Bohunciká, M. & Martin, M.P. (2018).  Revision of the Synechococcales (Cyanobacteria) through recognition of four families including Oculatellaceae fam. nov. and Trichocoleraceae fam. nov. and six new genera containing 14 species.  Phytotaxa 365: 1-59.

Palinska, K.A. & Surosz, W. (2014).  Taxonomy of cyanobacteria: a contribution to consensus approach.  Hydrobiologia 740: 1-11.

Appendix

Links to posts describing representatives of the major groups of Cyanobacteria found in freshwaters.  Only the most recent posts are included, but these should contain links to older posts (you can also use the WordPress search engine to find older posts).

Group Link
Synechococcophycidae
Synechococcales Chamaesiphon: A bigger splash

Heteroleibleinia: River Ehen … again

Oscillatoriophycidae
Chrococcales Aphanothece: No excuse for not swimming …

Gloeocapsa: The mysteries of Clapham Junction …

Oscillatoriales Microcoleus: How to make an ecosystem

Oscillatoria: Transitory phenomena …

Phormidium: In which the spirit of Jeremy Clarkson is evoked …

Pleurocapsales Watch this space …
Spirulinales Spirulina/Arthospira: Twisted tales …
Nostocophycidae
Nostocales Nostoc: How to make an ecosystem (2)

Rivularia: Both sides now

Scytonema, Stigonema, Tolypothrix: Tales from the splash zone

Some other highlights from this week:

Wrote this whilst listening to: Leonard Cohen’s posthumous album Thanks for the Dance.   And, as I used it to name a post, Joni Mitchell’s Both Sides Now.

Cultural highlights:  David Hockney: Drawing from Life at the National Portrait Gallery.   Great examination of the importance of drawing and observation to artistic practice.   By coincidence, another post I’ve cited is named after one of Hockney’s paintings

Currently reading: Robin Wall Kimmerer: Gathering Moss (Oregon State University Press).  A collection of essays on the natural and cultural history of mosses.

Culinary highlight: dinner at The Sichuan on City Road in London.

Hockney_drawings

Close to the edge in Wastwater …

Wastwater_190610

I’m back in the Lake District for this post, standing beside Wastwater, the most remote and least disturbed of England’s lakes and, especially obvious on a sunny day in June, the most spectacularly-situated.  I stood on the western shore looking across to the screes and, beyond to the mass of Scafell Pike, England’s highest peak, looming up in the distance.

When I was done admiring the scenery I adjusted my focus to the biology of the lake’s littoral zone and some dark brown – almost black – marks on the boulders in the littoral zone.  In contrast to the grand vista stretching away to the north, these were beyond unprepossessing and my attempts to photograph them yielded nothing worth including in this post. However, I had seen similar looking marks in Ennerdale Water and there is a photograph in “Tales from the splash zone …” that should give you some idea of what I was seeing.

Under the microscope, my expectations were confirmed.  As in Ennerdale Water, these patches were composed of Cyanobacteria – gradually tapering trichomes of Calothrix fusca and more robust trichomes of Scytonema calcareum, both encased in thick, brown sheaths which, when viewed against the granite boulders on which they lived, resulted in the dark appearance of the growths.  To the untrained eye, these barely look like lifeforms, let alone plants yet they offer an important lesson about the health of Wastwater.

Calothrix_fusca_Wastwater_June19

Calothrix cf fusca from the littoral zone of Wastwater, June 2019. Scale bar: 20 micrometres (= 1/50thof a millimetre)

Though hard to see amidst the tangle of filaments in these population, both Calothrix and Scytonema have specialised cells called “heterocysts” that are capable of capturing atmospheric nitrogen (you can see these in the photographs of Nostoc commune in “How to make an ecosystem (2)”.   Nitrogen fixation is a troublesome business for cells as they need a lot of energy to break down the strong bonds that bind the atoms in atmospheric nitrogen together.   That means that plants only invest this energy in nitrogen fixation when absolutely necessary – when the lack of nitrogen is inhibiting an opportunity to grow, for example.   The presence of these Cyanobacteria in Wastwater is, therefore, telling us that nitrogen is scarce in this lake.

The dogma until recently was that phosphorus was the nutrient that was in shortest supply in lakes, so attention has largely focussed on reducing phosphorus concentrations in order to improve lake health.   Over the last ten years, however, evidence has gradually accumulated to show that nitrogen can also be limiting under some conditions.   That, in turn, means that those responsible for the health of our freshwaters should be looking at the nitrogen, as well as the phosphorus, concentration and, I’m pleased to say, UK’s environmental regulators have now proposed nitrogen standards for lakes.   That marks an important shift in attitude as, a few years ago, DEFRA were quite hostile to any suggestion that nitrogen concentrations in freshwaters should be managed.   In this respect, the UK is definitely out step with the rest of Europe, most of whom have nitrogen as well as phosphorus standards for freshwaters.

Scytonema_crustaceum_Wastwater_June16

Scytonema cf calcareum from the littoral zone of Wastwater, June 2019. Note the single and double false branches.   Scale bar: 20 micrometres (= 1/50thof a millimetre)

Wastwater flows into the River Irt and, a few kilometres down from the outflow, I found another nitrogen-fixing Cyanobacterium, Tolypothrix tenuis.  Once again, I could not get a good photograph, but you can see images of this in an earlier post from the River Ehen in “River Ehen … again”.   Nitrogen fixing organisms, in other words, are not confined to the lakes in this region, which raises the question why the UK does not have nitrogen standards for these as well (see “This is not a nitrate standard …”).   In rivers such as the Irt and Ehen that are already in good condition, it might only take a small increase in nitrogen concentration for the ecology to change.   Whether the loss of these nitrogen-fixing organisms will be noticed is another question.

For now, I am just happy to see that nitrogen in lakes has finally made it to the regulatory agenda.  It has taken about 15 years for the science to percolate through the many layers of bureaucracy that are an inevitable part of environmental management.  Give it another decade and maybe we’ll get nitrogen standards for rivers too.

References

Maberly, S. C., King, L., Dent, M. M., Jones, R. I., & Gibson, C. E. (2002). Nutrient limitation of phytoplankton and periphyton growth in upland lakes. Freshwater Biology. https://doi.org/10.1046/j.1365-2427.2002.00962.x

Moss, B., Jeppesen, E., Søndergaard, M., Lauridsen, T. L., & Liu, Z. (2013). Nitrogen, macrophytes, shallow lakes and nutrient limitation: Resolution of a current controversy? Hydrobiologia. https://doi.org/10.1007/s10750-012-1033-0

P.S. any guesses as to which 1970s prog rock group I was listening to over the weekend?  The clue is in the title.

Blooms from above

Dianchi_lake_cyano_bloom

Saturday’s excursion saw us travelling to the southern end of the Kunming metro and joining a procession of locals trekking up the wooded slopes of the Xī Shān hills to the settlement of Lóng Mén (‘Dragon’s Gate’), which gave us some spectacular views over Diān Chí (Dian Lake) stretching away into the distance, After a lunch of fried noodles from one of the many takeaway stalls at Lóng Mén, we travelled back down to lake level by cable car, which gave us our second panoramic view of Cyanobacteria in three days.   The lake, China’s eighth largest, had a very conspicuous Cyanobacterial bloom that serves as the ‘yin’ to the Green Lake’s ‘yang’.

The environmental problems of Diān Chí are well known with an article in Newsweek describing it as the ‘ground zero of China’s toxic algae problem’.  The problems starts with Diān Chí’s location on a high plateau (1886 m above sea level) in Yunnan, which means that it has a relatively small catchment area relative to its size (40 km long, about 300 square kilometres area and with an average depth of 4.4 metres).   The city of Kunming sits at the north end of this lake and now has a population of over six million people.   For a long time, their untreated sewage was pumped directly into the lake, leading to high concentrations of phosphorus which, in turn, fertilised the lake water, allowing blooms of Microcystis aeruginosa to develop.   Many genera of Cyanobacteria, including Microcystis, produce potent toxins that attack the liver or nervous system, and which can cause skin rashes.

Unfortunately, the city of Kunming depended upon Diān Chí for its water supply in its past but now, due to this contamination, it has to rely upon reservoirs upstream of the city.  It has, according to the Newsweek article, invested $660 million dollars to reduce industrial pollutants, building sewage treatment works, intercepting polluted water and banning detergents containing phosphorus but that, as my photograph from the cable car shows, has had little effect.   There are two reasons for this.  The first of these is a reluctance to control fertiliser use in the productive agricultural areas to the west of the lake (China is not unique in this respect; a similar tardiness can be found in the West, where agriculture is a potent political lobby).  The second is that much of the phosphorus that was pumped into the lake in the past is still there, sitting in the sediments and being constantly recycled by the algae.  In small lakes it might be possible, albeit expensive, to dredge out this sediment but on a lake the size of Diān Chí this is an unimaginable prospect.

Another paper that I found online demonstrated a dramatic loss of higher plants and fish from Diān Chí. Since the 1950s, over half of all native higher plant species have been lost, along with 84 per cent of native fish.  Diān Chí also had a number of unique species, which evolved in this remote habitat, but 90 per cent of these, too, have been lost since the 1950s.  That is a catastrophe in biodiversity terms, but the collapse of the lake ecosystem also led to the loss of valuable commercial fisheries.  In the past, some of the fish and shellfish that we ate in local restaurants might have been bought from fishermen who worked the lake; now they have to be imported.

Dianchi_reaeration_equipment

A view from the cable car over Diān Chí, with yellow rafts bearing reaeration apparatus visible on the lake surface.  The picture at the top of the lake shows one edge of the Cyanobacteria bloom, with clearer water along a channel flushed by inflow from a lagoon.

We can see, in other words, another interesting case study in competing ecosystem services emerging. We might imagine a time in the far past when there was a balance between the use of the lake as a supply of resources (drinking water, fish and shellfish, irrigation water) was not compromised by the use of the lake’s natural biogeochemical cycles to break down any waste products that flowed in from the catchment.   More likely, human and animal wastes would have been recycled more directly as manure for local agriculture so, again, some sort of equilibrium would have pertained.   Now, we see the ‘provisioning’ services compromised due to the overuse of the ‘regulating’ services and, at the same time, opportunities for ‘cultural’ services such as recreation are also much reduced.

Thinking more widely, what about the ecosystem services lost due to the construction of the new water supply reservoirs around Kunming?   But then, rather than end on an overly sanctimonious tone, to what extent have we in the West, ‘solved’ some of our own environmental problems in recent decades through the contraction of our own manufacturing industries in the face of competition from countries such as China?  \

view_along_Dian_Chi

A view south along Diān Chí with the far shore, 40 km away, just visible in the distance.

References

Liu, J., Luo, X., Zhang, N. & Wu, Y. (2016).  Phosphorus released from sediment of Dianchi Lake and its effect on growth of Microcystis aeruginosaEnvironmental Science and Pollution Research23: 16321-16328.

Wang, S., Wang, J., Li, M., Du, F., Yang, Y., Lassoie, J.P. & Hassan, M.Z. (2013).  Six decades of changes in vascular hydrophyte and fish species in three plateau lakes in Yunnan, China.  Biodiversity and Conservation222: 3197-3221.

Zhu, L., Wu, Y., Song, L. & Gan, N. (2014).  Ecological dynamics of toxic Microcystis spp. and microcystin-degrading bacteria in Dianchi Lake, China.  Applied and Environmental Microbiology80: 1874-1881.

Notes:many authors, Western and Chinese, refer to ‘Dianchi Lake’.  However, as ‘chí’ means ‘lake’, I have just referred to ‘Diān Chí’ throughout.  See “Lake lakelake lake” for more about this. “La Grande Assiette de Lac Léman”  describes a similar conflict between ecosystem services in Lake Geneva, albeit with more positive outcomes.

 

Algae in a stone forest

Shilin_panorama_#1

A change in location from the previous post: this one is being written on the roof terrace of a guest house in Kunming, in Yunnan Province, China, whilst sipping a cup of the local pu’er tea.   I’m in China with my family visiting my eldest son who works in Chengdu, a sprawling metropolis of 11 million people in Sichuan Province, and have escaped to the warmer climate and more sedate environs of Kunming (only 6 million people) for a few days.  We’ll then move on to Dali (a mere village, by comparison, with less than half a million people) before returning to Chengdu.

From Kunming we travelled about 120 km southeast to Shílín, the site of a strange Karst phenomenon known as the “stone forest”, a collection of upright pillars of limestone often with other limestone blocks perched precariously on top.   In geomorphological terms, we are looking at a limestone pavement on a huge scale, but with substantial erosion of the “grykes” (the gaps between the “clints”).   Geologically, it is a little more complicated than that, with the Permian limestone being later overlain by basalt which was subsequently eroded away to leave a red soil.  However, that is enough to give you some context for what follows.

The photograph at the top of the post gives you some idea of what the stone forest looks like, and also some idea of the crowds to be expected at mainstream tourist attractions in China.  At times, the mass of people and, in particular, the overlapping amplified commentaries from tour guides, dressed in the costumes of the local Sani ethnic minority, made the experience almost unbearable.  But then, as is often the case, you turn a corner, the hubbub dies away, and you are able to enjoy the ethereal landscapes almost undisturbed.  In our case, however, we turned a corner too many, found ourselves outside the officially-sanctioned tourist beat and were unceremoniously ejected by an officious security guard.

Once we had talked our way back into the park through the main entrance, using Ed’s Mandarin skills, the park was noticeably quieter.   Most of the organised tours squeeze the stone forest and a local cave network into the same trip so the morning crowds had been hustled back onto their coaches, and the whole experience in the park was much more pleasant.   Walking through the Major Stone Forest gives you an ants-eye experience of living in a limestone pavement habitat, with the clints towering above you and only occasional glimpses of sunshine.   The park authorities have provided a concrete path and steps to lead you through but it is, at times, an arduous trek with some narrow and low gaps through which to squeeze.   This, in turn, lets you get up close to the limestone and, in my case, gets the phycological antennae twitching …

Shilin_panorama_#2

The Major Stone Forest at Shílín from the inside.   The photo at the top of the post shows the Major Stone Forest from the main public viewing area.

The limestone from which the stone forest is made is largely slate-grey in colour, rather than the creamy beige that I normally associate with this rock.   Only after reading one of the interpretation boards in the park did the penny drop, and I realised that I, and thousands of other tourists, had each spent 130 RNB to stare at algae.   After my brush with officialdom in the morning I was not in the mood to scrape at the rocks to collect a sample but am guessing we are looking at the Cyanobacterium Gloeocapsa alpina or something similar (see “The mysteries of Clapham Junction …”).   We were visiting the park close to the end of the long dry season but for the next few months the climate here will be much damper, creating a more conducive environment for these microorganisms to grow.

A few of the rock faces, particularly those associated with seepages, had multicolour streaks, with the grey supplemented with pinks and greens.  The former may well be other Cyanobacteria (possibly Schizothrix) and the greens could be Apatococcus, Desmococcus or a relative (see “Little round green things …”).  There were also a few orange-red patches of Trentepohlia (see “Fake tans in the Yorkshire Dales”).   All of these are forms are familiar to me from the UK and, whilst it would be rash to assume that the species were identical to those I find back home, the genera are generally cosmopolitan, so some extrapolation can be permitted.

Shilin_algae_Apr19

Algal crusts on rocks in the Major Stone Forest at Shílín, April 2019. The left hand image shows a mixture of Cyanobacteria and (possibly) green algae on a vertical surface associated with a seepage; the right hand image shows Heather photographing a growth of Trentepohlia nearby.

Trentepohlia_Shilin_Apr19

Trentepohlia growths inin the Major Stone Forest at Shílín, April 2019.  The picture frame spans about 10 centimetres. Photograph: Heather Kelly.

I did hunt around for some verification for these names but it is not possible to access Google Scholar in China without a VPN.  I am limited to whatever Bing throws up, and have not yet been able to find any papers on the algae of Shílín.  What I did find, during these searches, however, was an article about the world’s largest Haematococus farm, which is very close to here.   I’ve described Haematococcus in earlier posts (see “An encounter with a green alga that is red”) and mentioned that it was the source of the food colouring astaxanthin.   The combination of the limestone geology, warm weather and the huge market for food additives in China makes this possible.  Travelling in China with two vegetarians makes me realise that, even in this enormous, technocratic country, the market for natural products is growing.

Shilin_panorama_#3

 

 

More about measuring biomass …

The previous post showed how the proportions of green algae and diatoms changed as the total quantity of algae in the River Ehen waxed and waned over the course of a year.   The BenthoTorch, however, also measures “blue-green algae” and so let’s look at how this group changes in order to complete the picture.

Before starting, though, we need to consider one of the major flaws of the BenthoTorch: its algorithms purport to evaluate the quantities of three major groups of algae yet, in my posts about the River Ehen I have also talked about a fourth group, the red algae, or Rhodophyta (most recently in “The only way is up …”).  Having pointed a BenthoTorch at numerous stones with thick growths of Audouinella,we can report that Rhodophyta seem to be bundled in with the blue-green alga signal, which is no great surprise given the similarity in their pigments.  It is, however, one of a number of examples of the need to interpret any BenthoTorch results with your brain fully engaged, and not just to treat outputs at face value. Similar questions need to be asked of the Xanthophyta and Chrysophyta, though the latter tend not to be common in UK streams.

cyanos_in_Ehen

Relationship between the proportion of “blue-green algae” (Cyanobacteria and Rhodophyta) and the total quantity of benthic algae (expressed as chlorophyll concentration) in the River Ehen (c.) and Croasdale Beck (d.).  The blue lines show quantile regression fits at p = 0.8, 0.5 and 0.2.  

In contrast to the green algae and diatoms, the Cyanobacteria/Rhodophyta signal shows a strong negative relationship as biomass increases though, again, there is enough scatter in this relationship to make it necessary to approach this graph with caution.  I suspect, for example, that the data points on the upper right side of the data cloud represents samples rich in Audouinella, which tends to occur in winter when biomass, generally, is much greater.   On the other hand, Croasdale Beck, in particular, has a lot of encrusting Chamaesiphon fuscus colonies which are pretty much perennial (see “a bigger splash …”) but whose relative importance in the BenthoTorch output will be greatest when the other two groups of algae are sparse.   I suspect that encrusting members of this genus are favoured by conditions that do not allow a high biomass of other algae to develop, as these will reduce the amount of light that the Chamaesiphonreceives.

Thicker biofilms in the River Ehen often have some narrow Phormidium-type filaments as well as small bundles of nitrogen-fixing Calothrix, but the overall proportion is generally low relative to the mass of diatoms and green algae that predominate.    But that is not really telling us the whole story.  I finished my previous post with a graph showing how the variation in biomass increases as the biomass increases.  The heterogeneity of stream algal communities, however, cannot be captured fully at the spatial scale at which the BenthoTorch works: there is a patchiness that is apparent to the naked eye: one of our sites has distinct mats of Phormidium autumnale towards one margin, and dense Lemaneagrowths in the fastest-flowing sections, largely attached to unmovable boulders, which makes biomass measurement very difficult. I’ve also written about distinct growths of Tolypothrix and its epiphytes (see “River Ehen … again”), another alga which forms discrete colonies at a few locations. I try to collect a random sample of stones from a site but there are constraints, including accessibility, especially when the river rises above base flow.   In the River Ehen we also have to take care not to disturb any mussels whilst removing stones.

Whilst our sampling cannot really be described as “random” I do think that there is sufficient consistency in the patterns we see for the results to be meaningful. We could spend a lot more time finessing the sampling design yet for little extra scientific gain.   I prefer to think of these measurements as one part of a complex jigsaw that is slowly revealing the interactions between the constituents of the dynamic ecosystem of the River Ehen.   The important thing is to not place too much faith in any single strand of evidence, and to have enough awareness of the broader biology of the stream to read beyond the face value indications.