No excuse for not swimming …

Lyons_lake_Hetton-le-Hole

Lyon’s Lake, Hetton-le-Hole, County Durham, May 2015.

After my sojourns in the Lake District and Latvia, I find myself back home in north-east England for a few days.   Whilst I was away, a small packet had arrived in the post, containing a sample of algae collected from a local lake. The bottles contained globules of bright green jelly-like material, with enough integrity to pick up with the fingers and they were intriguing enough for me to drive across one lunchtime to take a closer look at the lake where they came from.

Hetton Lyons Country Park is on the Permian Limestone plateau about 10 kilometres from where I live. It is on the site of a former colliery which closed in 1960 and the surrounding land has been reclaimed and partially converted to a country park.   The lake – probably a hectare or so in size – is used for angling and water sports, and the paths around the edge were busy with cyclists and dog-walkers.   It is on the edge of Hetton-le-Hole, a small town whose odd name refers to its location in one of the more sheltered parts of the plateau.

Aphanothece_stagnina_Hetton

A mucilaginous colony of Aphanothece stagnina (left) with (right) a microscopic view of the individual cyanobacterial cells embedded in mucilage. Scale bar: 25 micrometres (= 1/40th of a millimetre).

There were plenty of green algae around the margins of the shallow lake but, amidst this in a few locations, I could also see the small globules of the alga resting on the bottom which, like the colonies I had been sent, could easily be picked –up.    Under the microscope, these resolved into tiny cyanobacterial cells, mostly oval in outline and about five micrometres in diameter.   These belong to Aphanothece stagnina, a relative of the Gloeocapsa alpina, which we have seen in two other recent posts (see “The mysteries of Clapham Junction” and “Poking around amongst sheep’s droppings …”), albeit in very different habitats.

The word “cyanobacteria” alone is usually enough to make the manager of a recreational lake break out in a sweat.   Many cyanobacteria produce toxins that can affect the nervous system and the liver. This means that no contact water sports (swimming and canoeing, for example) can take place and dog-owners have to be warned not to let their pets drink from the water.   However, as far as I can tell from a brief search on the internet, Aphanothece is not a genus that is often reported in association with toxic blooms.   One less excuse, then, not to go wild swimming in a lake in north-east England on a breezy May afternoon …

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More from Loughrigg Fell

As I do not pretend to great expertise on the desmids, I sent photographs of the specimens I collected during my visit to Loughrigg (see “A visit to Loughrigg Fell”) to Dave John who, in turn, passed them to David Williamson, to confirm their identities.   David Williamson co-authored the most comprehensive work on British desmids currently available, so I’m pleased to have his views on these specimens. To be honest, I was a little disappointed that I found so few desmids at a location from which so many had been recorded in the past. But then I am not a desmid expert, and may not have been looking in the best places.

Lily_Tarn_desmids_May15

Desmids from the margins of Lily Tarn, Loughrigg Fell, Cumbria, May 2015. a. Netrium digitus var. latum; b. Closterium dianae; c. Closterium dianae var. minus; d. Closterium directum (e. shows an entire cell of C. directum, photographed at lower magnification). Scale bar: 25 micrometres (= 1/40th of a millimetre).

I also found several cells of Eremosphaera viridis in squeezings from submerged Sphagnum at the edge of Lily Tarn.   At first, I thought that this was a colony of small cells but it is, in fact, a single large cell containing numerous small chloroplasts around the edge, giving it a very distinctive appearance. Like the desmids, it is a member of the Chlorophyta, or green algae, but it belongs to a different order, the Chlorellales rather than the Zygnemetales. That means that they are as different to one another as a rat is to a human.   By contrast, Euglena mutabilis, which we met in the previous post, is as different from a desmid as a human is from a slug.

I can recommend the desmids to anyone interested in microscopy.   They are, in many ways, much more amenable to amateur study than the diatoms. Desmids are generally about an order of magnitude larger than diatoms, which means that you can study them with a medium-power objective, rather than an expensive oil-immersion objective.   There is, in addition, a good English-language guide available whereas much of the key literature on diatoms is in German.   There are also plenty of sources of information available online. The only drawback with desmids is that their habitats are less widespread. Alternatively, I could put a positive spin onto this and remind you that a fascination with desmids will take you to some of our most spectacular landscapes.

Eremosphaera_viridis_Lily_T

Eremosphaera viridis from submerged Sphagnum at the margin of Lily Tarn, Loughrigg Fell, Cumbria, May 2015. Scale bar: 25 micrometres (= 1/40th of a millimetre).

Reference

Brook, A.J. & Williamson, D.B. (2010): A Monograph on some British Desmids. Ray Society, London.

Poking around amongst sheep’s droppings …

A couple of kilometres away from the stream featured in the previous post is an old quarry that we visit each year as part of this course (see “Nosing around for blue-green algae …”).   In a damp flush at the edge of the quarry floor, we found some patches of what looked, from a distance, like sheep droppings.   A useful strategy, shared by most of the human race, is to assume that anything that looks like a sheep’s dropping probably is a sheep’s dropping, and not to go prodding at this with a finger.   However, a curious soul in the distant past with a sense of adventure ignored this precept and discovered that a few of these were, in fact, growths of Cyanobacteria.   Most natural historians, wisely, focus their attention on more spectacular aspects of life on earth; however, a few of us have retained this childish instinct to poke at anything that looks like sheep’s droppings.

Scytonema_Whitbarrow_May15

Scytonema sp. from a flush at Whitbarrow Quarry, Cumbria, May 2015

A small part of one of these growths, teased out and mounted on a cover slip, reveals itself to have the characteristics of the genus Scytonema although, today and despite a long hunt, I could not find any filaments that presented themselves in a suitable position to photograph. The illustration below, therefore, is of a growth of Scytonema from another calcareous site in Cumbria. The Cyanobacteria is, you may remember, the modern name for the “blue-green algae” which is often confusing as many Cyanobacteria are not blue-green in colour.   What we can see here is a chain of cells (a “trichome”) which are surrounded by a thick sheath (“trichome” plus “sheath” equals “filament”, in Cyanobacteriological lore).   The sheath is a yellow-brown colour, due to a pigment called “scytonemin” which acts as a sunscreen, absorbing ultra-violet radiation and, in the process, obscuring the blue-green colour of the trichome within.

Scytonema_Sunbiggin_Tarn

Scytonema sp. from a calcareous flush at Sunbiggin Tarn, May 2005.   Scale bar: 10 micrometres (= 1/100th of a millimetre).

Two other characteristics of Scytonema are visible in the photograph.   Both the left and right hand pictures shows “false branches”: if the trichome breaks for any reason, either or both of the broken ends keep growing and break out of the filament. The left hand illustration is a single false branch and, just to the left of the branch you can see the distinct “heterocyst”, a cell where nitrogen fixation takes place.   The wall of the heterocyst is thicker than that of other cells, as nitrogen fixation can only occur in the absence of oxygen.

Walking back from the quarry towards the minibus, Allan pointed up at dark patches on the cliffs looming over us.   It was Gloeocapsa alpina, the same species that we met a short while ago in a cave on Malta (see “The mysteries of Clapham Junction …”).   The cliffs at Whitbarrow are, in effect, a vertical “desert” from the point of view of any organism that aspires to live there. These Cyanobacteria, with their ability to “re-boot” on those occasions when conditions are favourable for growth, have an advantage here.   One guesses that the damp climate of north-west England is slightly more forgiving than that of a Mediterranean hillside but it is still a tough habitat in which to survive.

Gloeocapsa_alpina_Whitbarro

Growths of Gloeocapsa alpina (arrowed) on the cliffs at Whitbarrow Quarry, May 2015.

Love and sex in a tufa-forming stream …

The reason behind my trip to the Lake District a couple of weeks ago was to teach a short course on identification of freshwater macroalgae with Allan Pentecost (see “Heatwave? What heatwave” and subsequent posts for more about last year’s course).   One of the sites we visit with the students is a small stream flowing off Whitbarrow, a Carboniferous limestone outcrop in southern Cumbria.   The bed of the stream is covered with tufa, formed from calcium carbonate precipitated from the water. We bring the students here because there is usually a good variety of cyanobacteria for them to learn to recognise in the field and to sample for later investigation in the laboratory.   Amongst these cyanobacterial growths, however, we also saw a few patches of green filaments on the stream bed, which we also took back with us.

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Sampling Whitbarrow tufa stream in May 2015.

These filaments turned out to be growths of the green alga Oedogonium. You may remember that I wrote a post last year with the title “The perplexing case of the celibate alga …” in which I commented that Oedogonium, though a common genus in freshwaters, is difficult to identify to species because this requires the reproductive organs which are rarely seen in the wild.

Our population of Oedogonium, however, was fertile, and this enabled us (Allan, to be strictly honest, as he knows the algae of tufa-forming streams extremely well) to name it.   The images below show the distinctive swollen oogonia within filaments of narrow cells (compare these with the much broader cells observed in “A case of mistaken identity?”). These oogonia look as if they have already fused with the male antheridia to form zygotes, which will eventually be released. These zygotes can lie dormant for a long time, which makes sexual reproduction a useful technique for overcoming adverse conditions (see also: “The River Ehen in March”). Not very romantic, I know, but that’s the reality of life at the unprepossessing end of biodiversity.

Oedogonium_calcareum_Whitba

Oedogonium calcareum from Whitbarrow tufa stream, May 2015, showing oogonium. Arrows indicate position of “caps” (scar tissue from intercalary cell division) a. scale bar: 20 micrometres (= 1/50th of a millimetre); b. & c.: scale bar: 10 micrometres (= 1/100th of a millimetre).

Following in Arthur Ransome’s footsteps …

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Town square in old Riga, with St Peter’s church and the ‘House of Blackheads’, once belonging to the ‘Guild of Unmarried Merchants’.

Last week, as I watched sailing dinghies on Windermere from the windows of the Freshwater Biological Association’s laboratory, I was reminded of the novels of Arthur Ransome, which I had read avidly when I was young. This week, by curious serendipity, I find myself in another city with strong associations with Arthur Ransome. In preparation for this trip, I pulled my old copy of Racundra’s First Cruise from my bookshelf and started reading. The first paragraph is one of the most evocative in all travel literature:

“Houses are but badly built boats so firmly grounded that you cannot think of moving them. They are definitely inferior things, belonging to the vegetable not the animal world, rooted and stationary, incapable of gay transition. I admit, doubtfully, as exceptions, snail-shells and caravans. The desire to build a house is the tired wish of a man content thenceforward with a single anchorage. The desire to build a boat is the desire of youth, unwilling yet to accept the idea of a final resting-place.”

That was written in 1923, as Ransome sailed in his small cruiser, Racundra, travelling from Riga to Tallinn (then known by it’s German name, Reval), and then across the Baltic to Helsinki (which Ransome refers to by it’s Swedish name, Helsingfors), and finally back to Riga. Ransome, at the time, was the Guardian correspondent in Russia, and had covered the Russian revolution and the subsequent wars of independence in the Baltic states. The person referred to coyly as ‘The Cook’ was actually his lover (he was already married at this time), Eveginia Petrovna Shelepina, formerly Trotsky’s secretary.

And so here I am in Riga, en route to a scientific meeting and, alas, amongst the ‘badly built boats’ of the terrestrial world rather than afloat. Ransome’s phrasing is harsh on Riga, whose old town centre is a UNESCO World Heritage Site, with architecture betraying its historical links with Germany, as part of the Hanseatic League. Walking through the old town’s narrow cobbled streets, lined with attractive gabled buildings was a delight, though the journey in from the airport contained plenty of reminders of Riga’s recent past as part of the Soviet empire.

I’m enjoying the food here, too: hearty meat-rich dishes washed down with local beers. The words ‘sausage’ and ‘dumpling’ crop up frequently on menus, separately and, on occasions, together. This is not a great place to be a vegetarian, I fear. My culinary highlight? Sliced bull’s testicles. Recommended, so long as you are not the one who has to explain to the bull what is about to happen.

Ellerbeck and Ellerbeckia

In the post I wrote just after John Lund’s death had been announced (see: “John Walter Guerrier Lund (1912-2015)”), I mentioned that there was a diatom genus named after his house in Ambleside. As I was in the area, I thought I would pay a quick visit so that I could put a picture of Ellerbeck, the house, alongside images of Ellerbeckia, the genus.   I walked down off Loughrigg Fell, through Ambleside and onto the road that leads out towards Kirkstone Pass. A left turn onto, Sweden Bridge Lane followed by a right onto Ellerigg Road brought me, a couple of minutes later, to Ellerbeck, the last of a row of stone cottages right at the edge of the village.

Set on a hillside and surrounded by garden plants, Ellerbeck was not an easy house to photograph, so forgive the odd perspective in the picture below.   The gardens around Ellerbeck are, I imagine, quite wonderful in the summer, though today was not a day to linger.

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Ellerbeck: the home of John and Hilda Canter-Lund in Ambleside, Cumbria, photographed May 2015.

The next pictures show Ellerbeckia arenaria, the only representative of the genus found in the UK.   First there is a colony of live cells; after this, I have included some views of cleaned valves.   It is, as you can see, a large, heavily silicified valve with a distinctive cross-hatched pattern on the mantle.  The cells are joined together to form long chains, which often stay together even after the cells have been cleaned with oxidising agents.   One interesting feature of Ellerbeckia that is not easy to see with the photographs here is that the two valves that make up the cell wall are different from one another. One has a convex face, whilst the other has a concave face.   The radial markings on the valve face also differ, so that the “ridges” on one knit with the “grooves” on the next.   This may explain why the colonies are so resilient compared to, for example, Melosira varians (see “Fertile speculations”).

Ellerbeckia_arenaria_CFC

Ellerbeckia arenaria, photographed by Chris Carter.

There is an irony to Ellerbeckia, the genus, being named after a house surrounded by the soft waters of the Lake District in northern England. Looking at my database, I noticed that most of my records were from hard waters in the south, including several chalk streams. I have found it in Cassop Pond, near my house, which is at the foot of the Permian limestone escarpment, but I would not expect to find it in the softer waters of the Lake District.   On the other hand, my old copy of West and Fritsch (1927) says it “occurs on wet rocks, sometimes forming crisp mat-like masses on dripping sandstone, and is common on the Brit[ish] Carboniferous sandstone.”   Maybe I’m just not looking in the right places.

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Cleaned valves of Ellerbeckia arenaria, from the Great Stour (Kent), Ripper’s Cross, May 2011.

Reference

Crawford, R.M. (1988) A reconsideration of Melosira arenaria and M. teres, resulting in a proposed new genus. pp. 413-433. In: Algae and the Aquatic Environment, edited by F.E. Round. Biopress, Bristol.

West, G.S. & Fritsch, F.E. (1927). A Treatise on the British Freshwater Algae.   Cambridge University Press, Cambridge.

A visit to Loughrigg Fell

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Looking east across Lily Tarn, Loughrigg Fell, near Ambleside in Cumbria, May 2015.

I was in the Lake District earlier this week, teaching a course at the Freshwater Biological Association (of which, more later). En route, I stopped off at Ambleside, and climbed up onto Loughrigg Fell in search of algae. Why here? Well, this was one of a small number of locations identified as an “Important Plant Area” (IPA) for freshwater algae.   IPAs are an initiative of the charity Plantlife as a way of identifying those areas of the country of greatest botanical importance.   The problem we have with freshwater algae is the strong tradition of recording that is central to understanding distributions of organisms is less well established for freshwater algae than it is for many other groups (see “A “red list” of endangered British diatoms?”).   This, in turn, probably links back to the small number of amateurs interested in the microscopic world. Competent amateurs form the backbone of recording networks for much of the UK’s flora and fauna.

The desmids are one of the few exceptions to this generalisation, and the freshwater algae IPAs are largely based on the careful observations of one expert amateur, David Williamson. Loughrigg Fell was one of a number of sites that fell out of an analysis of his data, as a large number of species of desmid have been recorded from here, including a few that have rarely been recorded elsewhere.

Euglena_mutabilis_Loughrigg

Euglena mutabilis, from a Sphagnum pool on Loughrigg Fell, close to Lily Tarn, May 2015. Scale bar: 10 micrometres (= 1/100th of a millimetre).

However, the most distinctive taxon that I found in the first sample I looked at (from a squeezing of Sphagnum living in a boggy pool near Lily Tarn) was not a symmetrical and sedate desmid (see “Hunting for desmids in Upper Teesdale”) but a wriggly and squirming alga that I recognised as Euglena mutabilis.   When I was teaching at university in Nigeria, I used to set my students an essay “Euglena: plant or animal? Discuss”.   The Euglena that I found in this boggy pool on Loughrigg had distinct green chloroplasts for photosynthesis, but not all species in this group have these. Some, instead, obtain their nutrition from carbon compounds dissolved in the water. What is more, I expect “plants” to have rigid cell walls whereas Euglena has a flexible “pellicle” (made of protein, not cellulose) which enables the organism to constantly change its shape, and to move around.   Most Euglena species have a flagellum; E. mutabilis is an exception and the photographs and video show characteristic euglenoid movement (“metaboly”) as the cell changes shape and the cytoplasm streams in to fill this up.   Of course, modern biologists do not really hold with a rigid distinction between “plants” and “animals” but it was still a useful way to get undergraduates thinking.

Euglena mutabliis is a very characteristic species of acidic environments, found not just in Sphagnum bogs, but also in acid mine drainage, where the pH can be as low as 2.0.   Living in such acid environments creates considerable problems for organisms so E. mutabilis has attracted much attention from people wondering how it copes.   The inside of all cells tends to be more-or-less neutral and most enzymes are optimised to work best under such conditions.   However, cell interiors also naturally have a negative charge, which means that hydrogen ions – the ‘active ingredient’, if you like, of acidity, naturally flow into cells. The evidence that we have shows that the pH inside E. mutabilis cells adjusts as the pH outside changes, though it is never as acid as conditions outside the cell. This must mean that the cells are using a lot of energy pumping the unwanted hydrogen ions out.

There are some great views from Lily Tarn, though the clouds were quite low during my visit.   Windermere spreads out to the south, and I could just make out Wray Castle on the west shore, the original home of the Freshwater Biological Association.   To the north, I could see the flanks of Helvellyn when the clouds parted, and the track that led up to the Fairfield Horseshoe.   The ground falls away steeply to the east of Lily Tarn, and you can look down into Ambleside itself, only a couple of kilometres away.   And that’s where I’m heading for my next post …

Reference

Brodie, J., John, D. M., Tittley, I., Holmes, M.J.,Williamson, D.B. (2007) Important Plant Areas for algae: a provisional review of sites and areas of importance for algae in the United Kingdom. Plantlife International, Salisbury, UK.

Hargreaves, J.W. & Whitton, B.A. (1976). Effect of pH on the growth of acid stream algae. British Phycological Journal 11: 215-223.

Hargreaves, J.W., Lloyd, E.J.H. & Whitton, B.A. (1976). Chemistry and vegetation of highly acidic streams. Freshwater Biology 5: 563-576.

Pentecost, A. (1982). The distribution of Euglena mutabilis in Sphagna, with reference to Malham Tarn North Fen. Field. Studies 5: 591-606.