Tales from prehistory

Stonehenge_Aug19

Microscopes and Monsters has been quiet for a couple of weeks, as I have been on holiday, part of which was spent “off grid” at the Green Man Festival in Wales.  From there, we headed to London for a Proms concert (two music festivals in a week!) via the Cotswolds and the ancient landscapes of Salisbury Plain.

My first visit to Stonehenge was 50 years ago, at which time you could pull off the A303 and wander amongst the columns unconstrained by fences and barriers.   Now the visitors are guided to a visitor centre two kilometres from the site, and offered a shuttle bus after being relieved of £20.  Or, if you prefer, you can walk across Salisbury Plain to the monument.  On a sunny afternoon in August this becomes part of the experience as there are ancient burial mounds (some pre-dating Stonehenge) both alongside the path and dotted around the horizon.   Stonehenge itself gradually rose up ahead of us, and we experienced a little of what the ancients must have felt as they approached Stonehenge along the processional way.

The last time that I was here was a stop off between field work on the nearby River Wylye and a meeting in Reading.   At the time I was engaged with two separate projects concerned with the health of chalk streams, which are characteristic of this part of southern England.   The approach we used elsewhere in the country was to compare what we found in samples we collected with what we expected to find if that site was in a pristine condition.

There was, at the time, a vigorous debate about how this “reference condition” should be defined.   This debate had a theoretical component (epitomised by Brian Moss’ paper in the reference list) but also a more pragmatic element (encapsulated by the other paper).  This was necessary because an ultra-strict, but theoretically sound, approach might not yield enough data from which a robust prediction of the “expected” ecology could be derived.   In essence, we searched out remote regions of the UK where population density was low and agriculture was not intensive and used these to derive our understanding of what to expect in the more densely-populated regions of the country.

Avebury_Aug19

Part of Avebury stone circle, Wiltshire, August 2019.  The photograph at the top of the post shows Stonehenge.

This worked quite well (although Brian Moss, predictably, had his own pithy thoughts on the approach).  However,  we simply could not find any sites that fulfilled our criteria of low population density and a low intensity of farming in those parts of lowland Britain where the underlying geology was Jurassic limestone, Cretaceous chalk or another formation that resulted in very hard water.  Our estimates of ecological health in such regions depend, as a result, on extrapolation and judgement rather than evidence.   That is all well and good for an academic journal but, in the case of the River Wylye, Wessex Water were being asked to spend hundreds of thousands of pounds to upgrade sewage works and, rightly, felt that they needed something more in order to explain the consequent price rises to their customers.

The OS maps of the region around my sampling points on the Wylye were dotted with symbols marking ancient monuments (long and round barrows, in particular) and the huge, mysterious religious sites of Stonehenge and Avebury lie just to the east.  Together, they point to continuous occupation of the area for over four thousand years, which means that it is hardly a surprise that we found no sites that met our criteria for a “pristine” stream.   The chalk streams of southern England are famous and rightly regarded as a threatened habitat, but they are not natural.  It is better to think of them as aquatic equivalents to hay meadows or hedgerows: ecologically-rich habitats that have been created by human activity, rather than as a result of “natural” ecological processes.

That means that it we need to diverge from a strict definition of “reference conditions” in order to set a baseline for ecological expectations in such circumstances.  For macrophytes – the larger aquatic plants – there is an expectation that the flora in this baseline state will be rich; however,  this assumption does not work for the microscopic algae in chalk streams.  We also found that river stretches where the macrophytes are thriving and, apparently, healthy, often have diatoms that suggest nutrient enrichment.  That is a puzzle for which we think we may have a solution, and which I will write about in a future post.

Silbury_Hill_Aug19

Silbury Hill, part of the Avebury World Heritage Site.  It is a Neolithic site whose original purpose is unknown though, to a visitor from north-east England, it looks remarkably like a slag heap.

We use low population density and absence of intensive agriculture as a proxy for “natural” in the uplands but need to treat this assumption with care too.  There might be fewer grand Neolithic monuments in the north of England or Scotland but signs of ancient habitation are there if you care to look (see “More reflections from the dawn of time”).   The moorland where these streams rise is, itself, an artificial habitat, created when early agriculturalists removed the natural tree cover.  Modern streams in these areas are, therefore, exposed to more light than in their primeval states and that will have important consequences for the plant life that lives within them.  They may be the best we have, but are hardly “natural”.

Two factors, both highly pragmatic, brought this debate to a close.   The first was realisation that, whatever the rights and wrongs of purist versus practical standpoints, most of our rivers are very degraded and alterations in the approach used to define the “expected” condition would be unlikely to change this broad scale picture.   About sixty-five per cent of our rivers fail to achieve good ecological status despite the flaws in the reference concept.  The second factor was simply that, since the financial crisis in the 2008-2010, the UK environment agencies have had too few resources to improve the reference concept.   As any such “improvement” will almost certainly make the true state of UK rivers look even worse than it does at the moment, a more cynical argument is that few of the bureaucrats involved in the process have any great enthusiasm for the task anyway.

References

Moss, B. (2008).  The Water Framework Directive: total environment or political compromise.  Science of the Total Environment400: 32-41.

Pardo, I., Gómez-Rodríguez, C., Wasson, J.G., Owen, R., van de Bund, W., Kelly, M., Bennett, C., Birk, S., Buffagni, A., Erba, S., Mengin, N., Murray-Bligh, J. & Ofenböeck, G. (2012).  The European reference condition concept: A scientific and technical approach to identify minimally-impacted river ecosystems.  Science of the Total Environment420: 33-42.

 

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When is an icon not an icon?

Florence_from_Fiasole_May19

Yet another change in location, this time to Florence for a wedding, but with some time set aside to gorge myself on early Renaissance painting.   That means traipsing around a lot of churches (because much of the best Italian art remains in situ) and a long queue to get into the Ufizzi gallery (because some of it doesn’t), emerging at the end footsore and with more questions than answers.

Having immersed myself in Eastern Orthodox imagery earlier this year (see “Secular icons?”) my first response on looking at the earliest works by Giotto and Cimabue was “those are icons”.  Stylistically and in subject matter, there is nothing to distinguish them from contemporary Eastern Orthodox icons: the flat, gilded backgrounds, the poses of the Madonna and child, and the saints, are all identical.  That made me wonder if the Medieval believers had approached these images in the same way that an Orthodox Christian would have done, in which case we need to think of the Renaissance not just in the conventional art-historical terms (epitomised by Kenneth Clark’s Civilisation) but also in terms of a change in belief.    This is important because, in most cases the artists would have been working to strict instructions from their clerical paymasters and would not have had much latitude to experiment with new designs.

A case in point is Giotto’s Madonna and Child with four saints, which looks very much like a row of icons on an Orthodox iconostasis. Except that this was originally altarpiece and that, itself, tells a story.   The Orthodox iconostasis stands between the priest who conducts the eucharist and the congregation whereas a Catholic altarpiece sits behind the altar, so that the congregation (that part beyond the rood screen at least) can see the ceremony and, in particular, the part when the priest elevates the host.   Theological developments in the 13thcentury, therefore, drove changes in the arrangement of church furniture and, in turn, led to some of the changes that we see in art during this period.

Giotto_Madonna_&_Child_Ufizzi

Giotto: Madonna and Child with St Nicholas, St John the Evangelist, St Peter and St Benedict the Redeemer.  Tempera on wood, 1337.   Ufizzi Gallery, Florence.

It is not just the position of the image that changed in Catholic churches during Medieval times: subject matter also changes from schematic images painted to prescribed formulae to styles that demanded more mental engagement by the viewer.  Look at Gentile da Fabriano’s altarpiece depicting the Adoration of the Magi, painted about a century after Giotto’s Madonna and Child.   The Madonna and child are still present but are now set in a context that would allow the viewers to imagine that they were participants at the original event.   Note, too, how the subjects in the picture are dressed in contemporary attire and original audiences might also have recognised the patron and members of his family painted into the front of the crowd.   At one level, these altarpieces function as a “poor man’s bible”, bringing elements of the Gospel to the largely illiterate congregations but, at the same time, they are also drawing the viewers into the story, ensuring that they are not just passive observers and, in turn, demanding a response.

Adoraton_of_Magi_Fabriani_Ufizzi

Gentile da Fabriano’s Adoration of the Magi.  Tempera on wood, 1420. Ufizzi Gallery, Florence.

As the fifteenth century progresses, we see the influence of the Renaissance in the images growing. In particular, a better understanding of linear perspective allowed artists to place the characters in their paintings in more plausible settings, drawing the viewer into the pictorial space.   Fra. Angelico’s Annunciation is painted onto a wall at the top of a staircase leading to monk’s cells in the Convent of San Marco, so the engagement with the viewer would be brief: no more than a short pause and a prayer before moving on.   The quiet scene depicted here is, perhaps, better suited to a monastery’s cloisters than the busy-ness that we saw in the Adoration of the Magi but, by focussing on just two people, pictures of the Annunciation create spaces that need to be filled if the illusion of pictorial depth is to be maintained.   And so we see, in the background of both Fra. Angelico’s and Leonardo’s Annunciations, the first tentative steps at depicting landscapes.

Annunciation_Fra_Angelico

Fra. Angelico’s Annunciation at the Convent of San Marco, Florence.  Fresco, 1437-1446.

Annunciation_Leonardo

Leonardo da Vinci’s Annunciation. Oil and tempera on wood, 1472-1474.  Ufizzi Gallery, Florence.

The painting style may have developed through the early Renaissance but one feature that all these pictures still share with their Gothic predecessors, and with Byzantine icons, is that they are still “applied art”: each was painted with a particular purpose in mind, whether for a church or a monastery, and 21stcentury notions of aesthetics have to bear this in mind.   On our trip to Florence this aspect was exemplified by Ghirlandaio’s The Last Supper, also at the Convent of San Marco.  This is in rather better condition than Leonardo’s depiction of the same scene in Milan (which is about a decade younger) but is similar in other ways (some think that Leonardo may have been inspired by Ghirlandaio’s treatment of the subject) and, significantly, was also painted life-size onto the wall of a refectory.   Once again, we can see clever use of linear perspective to create an illusion of depth and, in the background, trees that suggest that, instead of looking at a flat wall we are, in fact, looking into an extension of the room that we are in which, in turn, has windows that look out onto a garden.   That gives us an important clue to unlocking the meaning of the image.

The Refectory where we find The Last Supper is now the gift shop for the San Marco museum, but there are wooden benches along two of the walls where you can sit down and try and put yourself into the place of the monks and their visitors who would have eaten their meals here.   The painting creates the illusion that they were eating in a room that seemed bigger than it really is, and where there were a dozen or so extra guests whose presence was a constant reminder of one of the most important events in the Gospels.  This is the acme of Renaissance thinking: scientific and mathematical principles being utilised to create a work of art that, in turn, synergised man’s relationship with God.   C.P. Snow described what he saw as a profound gulf between arts and sciences in the Two Cultures, written in 1959.  Even then he could conceivably have extended this observation to three cultures by including religion too.  That would have been an anathema in the fifteenth century, when the boundaries between art, science and spirituality were much more fluid.  We’ve learned a lot in the intervening five hundred years but, at the same time, there is much that we have forgotten to remember.

Last_Supper_Angelico

Domenico Ghirlandaio’s The Last Supper in the Small Refectory at the Convent of San Marco, Florence.  Fresco, 1486.

Santa_Croce_from_Palazzo_Vecchio_May19

The church of Santa Croce rising above the rooftops of central Florence in May 2019.    The photograph at the top of the post shows a view of Florence from Fiesole.

Hyperepiphytes in the Shetland Islands

Gossa_Water_May19

I was lucky enough to spend a couple of days in the Shetland Islands during last week’s spell of warm weather and spent one of my mornings there hiking in shirtsleeves across moorland to a remote loch.   Good infrastructure is a legacy of the Shetland Islands’ association with the oil industry, and this includes a strong mobile network, meaning that I managed to find this particular loch using the Ordnance Survey maps on my smartphone. I would not normally rely upon a mobile signal to navigate across such remote terrain but in Shetland it is often possible.  I would, nonetheless, recommend keeping a paper map and a GPS in your kit just in case, as I did lose the signal on a few occasions during my stay.

Most of the lochs in the northern part of mainland Shetland are shallow, peaty water bodies, with soft water and relatively sparse assemblages of aquatic plants.   Parts of the littoral zone of this particular loch, however, had extensive growths of submerged mosses.  It is a long time since I was proficient at identifying aquatic mosses but these clumps look likeWarnstofia fluitans to me, though I am willing to be proved wrong.  I did try to remove some leaves and have a proper look but that task was complicated by tufts of attached filamentous algae.   In their submerged state, these formed distinct clusters at intervals along the straggly stems of the moss but, once removed, the filaments collapsed to smother the leaves and confound my attempts to run a scalpel blade along the stem.

Warnstofia_Gossa_Water_May19

Submerged colonies ofWarnstorfia fluitans(?) smothered byOedogoniumfilaments in Gossa Water, north Mainland, Shetland (HU 4354 6047). Gossa Water (one of five that share this name in the Shetland Islands!) is illustrated in the photograph at the top of this post.

The filamentous alga proved easier to unmask: the unbranched filaments, reticulate (net-like) chloroplasts and distinctive ‘cap cells’ all identifying it as the green alga Oedogonium.  As is often the case, however, the populations lacked any sexual organs so it was impossible to know which species (see “The perplexing case of the celibate alga“ and, for a rare case of a sexually-mature filament, “Love and sex in a tufa-forming stream”).   Abundant epiphytes can be another feature of Oedogonium: unlike several other filamentous green algae it produces little mucilage which makes it easier for diatoms, in particular, to colonise.  As well as colonies of needle-shaped cells of Fragilaria gracilis there were also several Achnanthidium cells and, entangled around the filaments and the moss, chains of Tabellaria flocculosa.   Given that the Oedogonium was, itself, an epiphyte, these diatoms are ‘hyperepiphytes’, a term that attracts remarkably few Google hits, almost all associated with lower plants.

The ‘cap cells’ are one of the most distinctive features of Oedogonium and results from a distinctive mode of cell division that leaves rings of scar tissue at the point where the two cells split.   That we see four or more of these scars on a few cells whilst the great majority have none suggests that we are looking at a primitive form of specialisation, with a few cells in a filament being responsible for all the cell division.  What is more, these cap cells are also often the ones that form oogonia (see “Love and sex in a tufa-forming stream” for an illustration of this) and asexual zoospores, so there must be something slightly different in the biochemistry within these cells that drives these processes.   However, at this point the formal scientific literature goes strangely silent apart from a single paper published in 1962.  Curiously, the evolution of multicellularity is one of those big questions that attract a lot of top academics (see the reference to a recent paper in Nature Scientific Reports below)  whilst a genus of algae that seem to show some faltering first steps towards specialisation of some cells are largely ignored.  Another case of the “trailing edge” of science?

Gossa_Oedogonium

Oedogonium filaments growing on Warnstofia fluitans in the littoral zone of Gossa Water, north Mainland, Shetland, May 2019.   The arrow on the top image shows the “cap cells”.   Note also the cluster of Fragilaria gracilis(plus a few cells of Achnanthidium) on the lowermost filament and, in the middle image, two of the many cells of Tabellaria flocculosa that were entangled with the Oedogonium filaments and moss stems.  Scale bar: 20 micrometres (= 1/50thof a millimetre). 

Oedogonium_zoospores

A zoospore being released from a filament of Oedogonium.  This series of photographs was taken by me in about 1993 and I have no details of the location from which it came.  The filament is about 40 micrometres (= 1/25thof a millimetre) in diameter.

Reference

Herron, M.D., Borin, J.M., Boswell, J.C., Walker, J., Chen, I-C. K., Knows, C.A., Boyd, M., Rosenzweig, F. & Ratcliff, W.C. (2019).  De novo origins of multicellularity in response to predation.  Nature Scientific Reports 9, Article number: 2328

Rawitscher-Kunkel, E. & Machlis, L. (1962).  The hormonal integration of sexual reproduction in Oedogonium.   American Journal of Botany 49: 177-183.

St_Ninians_tombola_Shetland_May19

Sightseeing in Shetland: the tombolo (sandy isthmus) linking St Ninian’s Isle with Mainland in the Shetland Islands, May 2019.

Beyond the Tower of Babel …

Danube_at_Vienna_May19

A week after I return from China, I was off on my travels again; this time to Vienna for a workshop between molecular ecology specialists and ECOSTAT, the committee of Member State representatives who oversee ecological aspects of Water Framework Directive implementation.   As ever, I found some time to visit some art galleries around the meeting and, as Vienna has one of the most impressive collections of paintings by Pieter Brueghel, I could not resist spending some time in front of his “Tower of Babel”.  A few years ago I cheerfully included this picture in a talk on EU ecological assessment methods, as we tried to make sense of the myriad national approaches.   Three years after the Brexit vote, however, it seems to better reflect UK domestic politics where, ironically, language is one of the few things that all protagonists do have in common.

The River Danube seems to encapsulate the reasons why Europe needs collaborative thinking on the state of the environment.  It is the second longest river in Europe, after the Volga, and flows through ten countries, with tributaries extending into nine more.   Eight of the nine countries through which the river flows are members of the EU (the ninth, Serbia, is in the process of joining) so the river represents a case study, of sorts, on whether EU environmental policies actually work.   This is not just an academic question: ecologists are generally in favour of integrated management of entire catchments whilst the EU operates on a principle of “subsidiarity”, which means that decision-making is devolved to the lowest competent authority (individual Member States in the case of the environment).   Finding the right balance between these principles takes a lot of patient discussion and is one reason why EU decision-making can appear to be agonisingly slow.

Breughel_Tower_of_Babel

Pieter Bruegel’s “Tower of Babel” in the Kunsthistorisches Museum in Vienna.

And there are more problems: the Water Framework Directive evaluates the sustainability of water bodies by their naturalness yet very large rivers such as the Danube have been very heavily modified by human use for centuries.   The river has been broadened, deepened and impounded, and its banks have been straightened and strengthened in order to make it navigable, and there is a huge human population, with associated industry, living on its banks.  The stretch of the Danube along which I walked on my last morning in Vienna was also lined with embankments to protect the surrounding land from flooding but these, at the same time, cut the river off from the ecological benefits of the floodplain.

What hope for a large river such as the Danube in the face of all these challenges?   First of all, when dealing with rivers such as these we need to adjust our expectations, recognising that they are so central to the economic life of the regions through which they flow that there are limits to their capacity to ever resemble truly natural rivers.   Once we have done this, we can start to unpick the challenges that can be addressed by individual Member States.  In the case of water quality, in particular, the story for the Danube is encouraging and European environmental legislation has played its role in this process.  By the time the Danube reaches the borders with Romania, for example, nutrient concentrations are low enough for many of the benthic algal-communities to meet criteria for “good ecological status”.

You can see this in the graph below, from a paper that we’ve published recently.   The Romanian sites are largely clustered at the top left hand side of the graph, relative to data from other countries – indicating low phosphorus concentrations and good ecology (expressed as “ecological quality ratios”, EQRs).   Thanks to an extensive exercise that took place a few years before I started grappling with the Romanian data, we already had a consensus view of the EQR boundaries for high and good status, and most of the Romanian data fits into the band representing “good status”.  That’s encouraging and whilst these communities are just one element of a much more complex ecosystem, but it is a clear step in the right direction.

RO_VLR_intercalibration

The relationship between dissolved phosphorus and ecological status of the phytobenthos (expressed as the Ecological Quality Ratio, EQR, based on the intercalibration common metric (which gives a harmonised view of status between Member States).   Horizontal lines show the average position of “high” (blue) and “good” (green) status boundaries.   RO = Romanian data; XGIG = data from other Member States.   See Kelly et al. (2018) for more details.  

Romania is, of course, a long way downstream from where I was standing in Vienna.  Before the Danube gets there it has to cross Slovakia, Hungary and Serbia.  The river also forms the boundary between Romania and Bulgaria for about 300 kilometres, so it is important that there is joined-up thinking between those responsible for water quality on the two opposite banks.  That’s why the EU is so important for the environment on a pan-European scale.  It is easy for those of us crammed onto our insignificant archipelago in the north-west corner of the continent to overlook this, but the Danube is really a great success stories for European environmental collaboration and, indeed, a reason for staying with this ambitious project into the future.   Too late, I know, but it needs to be said.

Reference

Kelly, M.G., Chiriac, G., Soare-Minea, A., Hamchevici, C. & Birk, S. (2018).  Defining ecological status of phytobenthos in very large rivers: a case study of practical implementation of the Water Framework Directive in Romania.  Hydrobiologia 828: 353-367.

Vienna_sights_May19

Sightseeing in Vienna: Stefansdom, the historic cathedral in the city centre and the Ferris wheel at the Prater amusement park, which played a starring role in Graham Greene’s The Third Man.

The limits of science …

Daci_temple_Chengdu_Apr19

Back in a rather smoggy Chengdu I find it easier to describe the environmental problems that China faces than it is to propose solutions but perhaps that is the nature of my calling. Coming from a scientific background, I tend to think primarily in terms of technological ‘fixes’.  I help to define ecological and chemical targets in order that a motley band of regulators and engineers can restore a lake or river to good ecological status.  But these targets, as is the case with most legislation, really define the lower limits of acceptable behaviour, setting a threshold for the point at which the state should intervene to limit bad behaviour.  Achieving ecological targets does not, necessarily, equate to morally good behaviour.

This brings to mind a quotation from the US environmental lawyer Gus Speth: ‘I used to think the top environmental problems were biodiversity loss, ecosystem collapse and climate change. I thought that with 30 years of good science we could address those problems.  But I was wrong.  The top environmental problems are selfishness, greed and apathy … to deal with these we need a spiritual and cultural transformation – and we scientists don’t know how to do that.’

The only part of that statement with which I disagree is the need for 30 years of good science. In the case of aquatic ecosystem health, I think we already know what needs to be done in broad terms.  Reconciling the investment required with the ‘willingness to pay’ is as big a challenge in China just as much as in Europe.   Willingness to pay recognises that environmental improvements come with an ‘opportunity cost’ – a pleasure that has to be foregone.   And by focussing attention on selfishness, greed and apathy, Gus Speth is spot on, for China just as for the West.

The irony of the situation in China is that two of its most prominent religions – Buddhism and Daoism – have a philosophy that should, in theory, provide a justification for a less materialistic lifestyle but which, somehow, exist in an uneasy equilibrium with modern China’s capitalism.  This is amply summed up by the photograph at the top of this post: showing the Daci Bhuddhist temple close to the centre of Chengdu overlooked by the gleaming skyscrapers that encapsulate modern Chinese capitalism.   The monks and continue their devotions just a few metres from an upmarket shopping mall that has been built around this temple complex, complete with Western brands such as Gucci, Dior, Louis Vuitton and Cartier (see “Reflections from the banks of the Yangtze” for another of these paradoxes).

Yuantong_temple_Kunming

The shrine to Guanyin, goddess of mercy and compassion, at the Yuántōng Temple in Kūnmíng. 

It maybe that we in the West see Buddhism, in particular, through rose-tinted spectacles.  The reality is that most Chinese are only nominally Buddhist (often with a seasoning of Daoism and Confucianism too) rather than strict in their adherence.   Somehow, these eastern religions co-exist with materialism, just as Christianity does in the West.   The infrastructure of all religions depends upon individuals producing more than they need for basic sustenance and being prepared to donate part of the surplus as ‘alms’ or ‘tithes’ in return for the benefits that the religion confers.  This is exemplified by the prominent shrines to Guanyin, the goddess of compassion and mercy (roughly equivalent to the Virgin Mary in Catholicism) and a mediator between worshippers and the divine.   The temple becomes a focus for transactions, rather than for reflection and transformation.  In this way, Buddhism can be one more part of a system that indirectly encourages wants and desires even if the religion, in theory, is about transcending these.

I would encourage you to read Kate Raworth’s Doughnut Economics, for an inspirational look at how modern economic theory has resulted in an unsustainable situation.  She also proposes solutions yet, for these to work, each of us will have to accept that creating a sustainable world will carry a considerable opportunity cost.  That will mean an adjustment in expectations, and a need to find a source of contentment that is independent of materialism.   The environment, to be blunt, cannot be considered without also thinking about economics.  At the same time, radical thinking about economics will need to be accompanied by a deeper shift in behaviour and attitudes if it is to succeed.  That pushes us to the very edges of rationalism, and into the realms of mysticism.

And, yes, this whole post was written in China so I have to admit to an element of hypocrisy if I am to write about a more sustainable world whilst still indulging in long-distance air travel.  More about that in a future post.

Pagodas_over_Dali

Pagodas at the Chongsheng temple complex at Dàlī, with Ērhāi Hú in the background.

Chongsheng_temple_Dali

The Chongsheng temple complex at Dàlī, against the backdrop of the Cāng Shān mountains.

Survival of the fittest (2) …

As well as the bright green flocs of Tribonema, the stream draining the Hadjipavlou chromite mine also had bright orange-red growths on some of the pebbles on its bed.  These seemed to be composed primarily of the Cyanobacterium Chamaesiphonthough I am still not sure what species.   Using the limited literature I have, from the UK and Germany, I would opt for either Chamaesiphon polymorphusor C. polonicus.   This particular alga was very easy to remove from stones, compared to other epilithic Chamaesiphon species (see “A bigger splash …”).  This is a feature of C. polymorphus, though the colour is more typical of C. polonicus*.  On the other hand, that bright colour could be the response to high solar radiation, so maybe my north European guides are not that reliable.  It could be something else altogether.

Chamaesiphon_polonicus_Troodos

Chamaesiphon growths on pebbles in the stream draining Hadjipavlou chromite mine in the Troodos mountains, Cyprus, March 2019.

Chamaesiphon_Troodos_Mar19

Colonies of Chamaesiphon from Hadjipavlou chromite mine under the microscope.   Scale bar: 10 micrometres (= 1/100thof a millimetre). 

In addition to the Chamaesiphon, there were a few diatoms, mostly Achnanthidium minutissimumand Meridion circulare.   These are typical species of metal-rich streams, as is the general lack of diversity that was evident.   There were also a few filaments of the cyanobacterium Phormidium, along with quite a few Paramecium and Vorticella.  As these are both heterotrophs that feed on organic matter, their abundance is probably at least partly a reflection of the long time that the sample spent in my suitcase between collection and analysis.  The latter is a fascinating organism to watch: it is a goblet-shaped cell with a fringe of cilia around the lip (or “peristome”).  These beat in unison to create water currents that draw small particles towards the cell.   These particles mostly at least an order of magnitude smaller than the algae)  are then collected in food vacuoles where they are digested.   A few of these vacuoles can be seen in the image of Vorticella below.

Vorticella is attached to its substrate by a stalk which contains contractile filaments, giving it spring-like qualities.  Watching a Vorticella is a beguiling experience, with the undulating rows of cilia drawing food into the vestibule (as the opening is known).  At intervals, the whole cell lurched across the field of view as the “spring” in the stalk suddenly contracted, shortening the stalk.  After this, the stalk would gradually extend again, the cilia not having missed a beat meanwhile.   This process may simply be a device that enables the Vorticellato exploit its locality to the full, as well as creating some additional turbulence to keep a steady flow of particles towards the peristome.  To be honest, I haven’t seen a more convincing explanation but, even if we don’t know why it does what it does, Vorticella is a fascinating organism to watch, whether or not I understand what is going on.

I’ll be coming back to talk more about the diatoms in a future post, and writing these posts has also reminded me that I’ve never written about the interesting mine sites almost on my own doorstep.  I cut my ecological teeth looking at these habitats back in the 1980s and they are striking examples of natural selection in action.   So, plenty of potential for more left-field natural history …

Hadjipavlou_organisims_Mar19

Other organisms present in the Hadjipavlou chromite mine. a. – d.: Meridion circulare; e. Phormidiumsp.; f. Vorticellasp.   Scale bar: 10 micrometres (= 1/100thof a millimetre). 

* Note: after I had written this post Brian Whitton confirmed that it was, most likely, Chamaesiphon polonicus.

Survival of the fittest (1) …

Hadjipavlou_mine_March19

When I signed up to a trip to Cyprus in late March I was anticipating feeling some warm Mediterranean sun on my skin after the ravages of the British winter.  I did not expect snow and sleet.   However, as one of our destinations was the Troodos mountains, the location of Cyprus’ only ski resort, maybe it was a case of unrealistic expectations.   Fortunately, we realised our mistake just in time to pack some warm clothes, and the unseasonable weather did, at least, mean that the spring flowers at lower altitudes were, even by Cypriot standards, particularly impressive.

I was in Cyprus primarily as a camp follower on a reconnaissance trip for a geology and botany excursion next year.   Cyprus is, to put it in layman’s terms, the outcome of a collision between the African and European continental plates.   The Troodos mountains are a geologist’s paradise, having a wide range of features arising from this and from associated volcanic activity.   As the molten rocks cooled, minerals precipitate out and the resulting geological strata reflect differences in the melting points of these minerals.   Some of these minerals, such as chromite, are commercially valuable and have been mined for centuries.   Indeed, the name Cyprus itself is derived from cuprous, the Greek word for copper, which was mined here since 4000 BC.

The Hadjipavlou mine is set amidst pine forests close to the highest point of the Troodos.  It was an active chromite mine from 1950 to 1954 and from 1979 to 1982 but was abandoned when cheaper sources of chromite became available in South Africa.   Over a million tonnes of ore were extracted in the period when the chromite mines in the area were active, but now there are few obvious signs apart from this adit driven into the hillside.   A small stream bearing water that has percolated through the rocks and collected in the mine’s galleries emerges from the mine entrance and tumbles down the hillside to join the stream below.   This, on closer inspection, has some quite interesting microbial growths.

First of all, having been told that this is a chromite mine, you might expect the water to carry toxic concentrations of heavy metals.   So you might also be surprised to see abundant growths of bright green algae thriving in the stream immediately downstream of the mine entrance.   This is, in fact, a common phenomenon in mine waters and happens, we think, because the fast-growing algae evolve metal tolerance whilst the animals that feed on them are slower to adapt.   This is, literally, survival of the fittest and, with nothing to eat them, the algae grow prolifically.

These filaments belong to the genus Tribonemawhich, despite being bright green in colour, actually belongs to the yellow-green algae, the Xanthophyta, rather than to the green algae.  This group is actually more closely related to the diatoms than to the green algae, though it can be hard to understand why simply by peering through a microscope.  One useful test is to add a little iodine  solutionto the slide: this binds to the starch inside green algae cells, staining them a dark brown colour.   The Xanthophyta, by contrast, do not have starch as their storage product so the cells are not stained by iodine.   The only other member of this group that I have discussed in this blog is Vaucheria, a very different alga (see “Who do you think you are?”).

Tribonema_affine_Troodos

Tribonema cf affinein the channel draining the Hadjipavlou chromite mine in the Troodos mountains, Cyprus, March 2019.   a. close-up of the alga in situ; b.  microscopic view of filaments; c. fragments of disintegrated filaments showing the H-shaped cell endings.  Scale bar: 10 micrometres (= 100thof a millimetre).   

Tribonemahas simple, unbranched filaments with two or more plate-like chloroplasts arranged around the cell periphery.   One other feature is the arrangement of the cell wall, which tends to consist of two overlapping halves.  When filaments disintegrate (as they often do) the fragments have an H-shape, with each end forming half the cell wall of a different cell.   The cells are, in fact, cylindrical but this is not apparent with the flattened perspective of a high magnification objective.   This feature is not universal in the Xanthophyta, nor is it unique to this group (a few green filamentous algae show the same characteristic) but it is a useful hint that you may be looking at Tribonema.

Whilst lush growths of algae is a common feature of streams draining mines, the species that form these growths can vary.   In the northern Pennines, I am used to seeing green algae in these habitats, but there are at least three different genera that I find.  Typically there is just one filamentous alga in this location, and they tend to be  constant over time: they are reliable sources for material for undergraduate practical classes as a result.  There is more to this story but I will have to come back to it at some point in the future.  .

There is also more to the algal flora of the Hadjipavlou chromite mine but, again, that will have to wait for another post.  I should also confess that, although I visited the mine briefly last year, these samples were collected by Heather, whilst I was sitting snugly below the snow line.