Approaching the tipping point?

Erhai_hu_panorama_Apr19

From Kunming we travelled by train 200 km to the east, to Dàlī, which sits between Ērhāi Hú (literally ‘ear-shaped lake’), another of Yúnnán’s plateau lakes, and the Cāng Shān mountains.  These rise to about 4000 metres and still, even at this time of year, have patches of snow near their summits.   Dàlī’s old city has escaped the ravages of modernisation that have blighted many Chinese cities and we spent hours wandering the narrow streets lined with the traditional Bai architecture, along with a very large number of Chinese tourists.

On one day we hired bicycles and cycled along quiet roads lined with market gardens to reach the lake, then turned north and followed the lake shore for about five kilometres.  There were many areas of semi-natural shoreline along this stretch, with a fringe of wetland, but the filamentous algae (mostly Cladophora) coating the rocks that had been piled up along the settled parts of the shoreline told their own story.  This lake is clearly in better health than Diān Chí but it, too, is nutrient-rich.

Erhai_Hu_algae

A fringe of filamentous algae, along with floating leaves of Trapas natans(Eurasian water chestnut) growing on a jetty beside Ērhāi Hú.

Just after midday we pulled into a small family-run restaurant at the edge of a village.   A short conversation between the waitress and Ed (our only Mandarin-speaker) revealed that they specialised in serving fish from the lake so that seemed to be the obvious choice for our lunch.  The waitress disappeared, then reappeared with a net which she dunked into a tank behind our table and, with a couple of deft flicks, pulled it up with two carp wriggling inside.   These she quickly dispatched, cleaned and took into the kitchen.   About twenty minutes later she reappeared with a delicious stew comprising the whole fish cut into chunks, a generous seasoning of dried red chilli and tongue-numbing Sichuan pepper, lightly-pickled vegetables (white radish, celery and turnip) and some green leaves.   This, along with rice and endless green tea, and with Ērhāi Hú as a backdrop, created a perfect lunch for appetites whetted by our exercise.

Erhai_hu_fish_soup

From tank to table in twenty minutes: our fish stew made from carp from Ērhāi Hú.

We had seen some locals fishing with poles, and there is also some commercial fishing using cormorants in the area. However, the abundance of fish on the menu confirmed my hunch that the many booms we could see across bays along the lakeshore were fish farms (maybe ‘fish ranches’ is a more appropriate term when the fish have, relatively speaking, plenty of space in which to roam and forage).   The nutrients pouring into the lake here are, at least, able to support a economically-viable industry rather than undermine the supply of resources, as is the case for Diān Chí.

Of course, the story is not that simple.   In the past, Ērhāi Hú, like Diān Chí, had some endemic species, found nowhere else, but these have not been recorded for about 20 years.   Pollution from surrounding cities is the most likely explanation and, if Ērhāi Hú is in a better state than Diān Chí, then this is partly because the lake is larger and deeper, the catchment area is bigger and the scale of urban development is smaller (Dàlī is about a twentieth of the size of Kunming).  That said, local scientists have identified a significant declining trend in water quality, particularly over the past 25 years.   Importantly, however, they also note that it is not too late to do something about the situation.

Erhai_Hu_fishermen

Fishermen cleaning their nets beside Ērhāi Hú.  

In brief, nutrient concentrations in Ērhāi Hú are increasing. That leads to a more productive ecosystem which is, up to a point, good for commercial fishing but also means that oxygen concentrations drop, which is bad for the fish.   High nutrient concentrations also mean more algae but, at the present, these are not so high that cyanobacterial blooms develop as they have done in Diān Chí.  That means that the water in the lake can still be used as a drinking water supply for Dàlī and its environs.   However, if nutrient concentrations rise further then oxygen concentrations may pass a tipping point when it becomes almost impossible to manage lake phosphorus concentrations.

This is because phosphorus and other nutrients accumulate over time in lake sediments.  Phosphorus is not very soluble in the presence of oxygen, but becomes more soluble as conditions in the sediment and overlying water turn anoxic.   That means that when dissolved oxygen concentrations fall to the point where there is none at the sediment surface, the sediments are no longer a ‘sink’ for excess phosphorus, but become a ‘source’, releasing the stored nutrients back into the water.   From this point forwards, eutrophication in the lake becomes self-perpetuating and no amount of regulation alone will reverse this.

Better regulation now, on the other hand, might prevent the lake reaching this stage.  That, in turn, will protect the drinking water supply for the region, the economic benefits from the fishery and other ecosystem services. A survey of the local community revealed a willingness to pay an extra 27 Yuan a month for five years continuously in order to achieve this.  This is a small sum in absolute terms (27 Yuan is just over £3), but represents, on average, 1.7% of household income.   The economics of water quality improvement must look even more attractive to the regional government: if Ērhāi Hú crosses this tipping point then the investment in alternative water supplies, as was required in Kunming, will be equally expensive.  Looking at it from this perspective, applying a sensible ‘polluter pays’ policy now should be no more painful for the average resident than having to pay for new reservoirs to replace the resource on their doorstep.

The stretch of lakefront along which we cycled also had a steady trade in photographs, with photographers ready with diaphanous dresses for prospective models, and a number of ways for them to pose.  The girls in the photograph below posed, informally, on stones whilst friends photographed them using smartphones, but some photographers placed their models on the tops of jeeps or in hanging chairs, with an uninterrupted view of the lake behind. In their own way, they were valuing the broad scale panorama that the lake offered, just as we had enjoyed more local offerings during our lunch.  The challenge for the next decade, then, is to make the links between these valuations and the ecology of the lake, so that any price increases are recognised as sound investments in the future of Dàlī rather than as yet another form of negative taxation.

Erhai_hu_posers

Women posing for photographs with Ērhāi Hú as a backdrop

References

Wang, H., Shi, Y., Kim, Y. & Kamata, T. (2015).  Economic value of water quality improvement by one grade level in Erhai Lake: a willingness-to-pay survey and a benefit-transfer study.   Frontiers of Economics in China 10: 168-199.

Wang, S., Zhang, L., Ni, L., Zhao, H., Jiao, L., Yang, S., Guo, L. & Shen, J. (2015). Ecological degeneration of Erhai Lake and prevention measures.  Environmental Earth Sciences74: 3839-3847.

Zhang, K., Dong, X., Yang, X., Kattel, G., Zhao, Y. & Wang, R. (2018).  Ecological shift and resilience in China’s lake systems during the last two centuries.  Global and Planetary Change165: 147-159.

 

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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.

 

Reflections from a Green Lake

Green_lake_panorama_#1

Our guest house in Kunming is a few hundred metres from the Green Lake, which sounds like an obvious magnet to someone with an interest in algae.   The name itself seems to embody the well-publicised problems of water pollution in this huge country and I walked down to the edge fully expecting to gather material for a post about extreme eutrophication.

This is not a post about extreme eutrophication.  That’s partly because it is not easy to get close enough to the water itself in order to look closely at the algae.  I did see some floating cyanobacterial scums amidst the duck weed and lotus plants, but I’m also not equipped with a high-power microscope whilst on my travels, so would not have been able to make a detailed diagnosis, even if I could have got a sample.   However, my feelings about the lake have changed over the four days that I have been here, and as I believe that travellers should prepared to be changed by what they encounter, I thought I should explain my change of heart.

Green lake is a small lake with a perimeter of about two kilometres and an area of about 15 hectares set in the middle of Kunming.   According to a book I have been reading, this whole area used to be part of the much larger Dianchi Lake (which will be the subject of a future post). However, during the Ming Dynasty, about 600 years ago, the area that we now know as Kunming was reclaimed, leaving Green Lake as a low-lying remnant.   At this time it was known as “Caihaizi”, the vegetable lake, perhaps because of the lotus plants that grew there.   If you want to apply a very basic measure of ‘naturalness’ to a lake, you could start by measuring the proportion of the perimeter that is artificial. In the case of Green Lake, the perimeter is 100 per cent artificial, unless you add in the islands and the causeways leading to these, in which case the proportion of artificial margins rises to 200 per cent or more.

Green_lake_panorama_#2

A corner of Green Lake, showing duckweed blooms in the foreground and one of the causeways on the right.  The upper picture shows the lake with lotus plants in the foreground and Kunming rising up in the background. 

Yet the lake margins and the islands are thrumming with activity: joggers use the lake margin as a running track, badminton players set up nets between trees and thrash shuttlecocks back and forth whilst elderly men show off wiry torsos on the gym equipment.  Then there are the more quintessentially Chinese activities: groups of people practising Tai’chi and Quigong just a few metres from a dance class practising some moves.   On one of the islands about half a dozen different styles of dance are taking place, each moving to an amplified tune, all of which seem to bleed into one another.  We sat and ate cold noodles (local speciality: better than it sounds) in a café at one side until the noise drove us away.   A little further from here, on a bandstand on one of the causeways, a group of musicians played traditional instruments.   There were also pedalos and motorboats for hire on some of the sections of the lake, plus shops selling Yunnan tea and coffee and other souvenirs.

Green_Lake_panorama_#3

Cultural ecosystem services at Green Lake, Kunming.  The top image shows a group practising tai’chi and the bottom image shows a dance class nearby. 

After a few days here I am growing to love Green Lake.   It is a small ‘green lung’ set in the heart of a large, busy city to which local inhabitants, especially the elderly, seem to gravitate.  I have not written about ecosystem services – the benefits humankind derive from natural systems – for some time.  When I last touched on this subject, it was to consider the conflict between conservationist’s desire for naturalness and ‘cultural ecosystem services’ (see “More about ecosystem services”).   Green Lake seems to encapsulate this conflict very well: it is about as far from a ‘natural’ lake as it is possible to get yet, at the same time, it plays a role in the health and vitality of the local community partly as a result of the many modifications that have occurred over time.

To paraphrase jay-z, China has 99 [environmental] problems but Green Lake ain’t one.   I’ll come back to one of these in the next post but, meanwhile, I’m going to take one more stroll through the elaborately decorated gates at the entrance to the closest causeway and enjoy the pleasures of Green Lake for a final time before we move on.

Green_Lake_panorama_#4

A gateway to one of the Green Lake’s causeways in Kunming.

Reference

The book to which I refer is “Green Lake: Reflections from the Surface of China” by Hardy Wieting Jr (www.chinagreenlake.com), a conservationist who happened to be staying at the Lost Garden Guest House, near Green Lake, at the same time as us.

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

 

 

How to make an ecosystem (2)

Ennerdale_Apr19

My most recent visit to Ennerdale and the River Ehen almost did not happen: unexpected overnight snowfall led to my wheels spinning on the Whinlatter Pass before I retraced my steps to Braithwaite and followed roads at lower altitudes around the outskirts of the fells.   Fieldwork in the morning took place amidst intermittent snow showers but, by the afternoon, it was dry if not quite as balmy as the visit I described in “Croasdale Beck in February”.   “Unseasonable”, I was reminded, is a two-edged term.

There was little incentive to linger with my arm in the agonisingly cold water, so this post is about some algae growing on dry land that caught my eye.   Amidst the gravel in a farmyard in Ennerdale Bridge I saw some dark brown leathery growths that I recognised straight away as the Cyanobacterium Nostoc commune (see “Nosing around for blue-green algae …”).  It looks rather nondescript, even slightly unsavoury, with the naked eye but, under the microscope, the rosary-like structure of the filaments suspended within a jelly-like matrix is revealed.  The slightly larger cells with thicker walls and lighter contents are the heterocysts, responsible for fixing nitrogen from the atmosphere (fulfilling the same function as the nodules on the roots of legumes).

Nostoc_commune_Ennerdale_Apr19_#1

A patch of Nostoc communein a farmyard in Ennerdale Bridge in April 2019.   The picture frame covers about 30 centimetres. 

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Nostoc communefrom Ennerdale Bridge under the microscope.  Scale bar: 10 micrometres (= 100thof a millimetre). 

This type of coarse, well-drained gravel is a good habitat for Nostoc and, once you know what you are looking for, it is a common sight on gravel driveways, usually to the annoyance of the owners.   If there is only a small amount, the best way to control it is simply to pick up the colonies and toss them onto the compost heap.  However, once it is established, this can be a big undertaking and many people are quite happy to tolerate some of this brown gunk on their driveways.   On the other hand, it can sometimes get out of hand and the consequences of not doing anything are well illustrated by the photograph below.  The Nostoc colonies have spread but these, in turn, have created a habitat into which first mosses and later grasses can establish.

This small farmyard on the edge of the Lake District contains, in short, the first stage of an ecological succession.  We could think of a gravel driveway as a mini-desert, as the copious Cumbrian rainfall will not be retained in the surface layers, making it hard for plants to survive.   However, if a tough organism such as Nostoc is able to establish itself, then this, in turn, will trap water and make the driveway more amenable to slightly more fussy organisms such as mosses.   As the moss and Nostoc grow together so, eventually, grasses are able to establish too.  Were there to be no interruption to this process then, eventually, decades later, we might even see trees growing on this driveway.

It is hard to imagine, but just about every type of terrestrial habitat started out, aeons ago, as a bare rock surface.  Various forms of physical weathering start the process of breaking this up allowing, over time, organisms such as Nostocto get a foothold and convert the virgin surface into a mature ecosystem (you can read about another example in “How to make an ecosystem”).   It may take centuries for this to happen in the natural world, so it is particularly fortuitous to see this human-assisted succession so well developed.  At some stage, I suspect, the owner will decide that enough is enough, and rake the gravel.  Meanwhile, however, we have a rare opportunity to reflect on the role that primitive micro-organisms play in shaping even the grandest of our natural habitats.

Nostoc_commune_Ennerdale_Apr19_#2

A lawn of Nostoc, moss and grass growing on a gravel driveway in Ennerdale Bridge, April 2019.  

Reference

Miles, J. & Walton, D.W.H. (1993).  Primary Succession on Land.  Special Publication of the British Ecological Society 12, Blackwell Scientific Publications, Oxford.

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.