Lakeland panoramas

I spend most of my time focussed in on the smallest inhabitants of lakes and streams, so I thought I would indulge myself in this post by looking at some grand panoramas in the region of the Lake District where I do most of my fieldwork.  I have often looked up at the hills that surround the lakes and rivers of the western Lake District as I worked but my schedule was usually such that there was not time to climb them, even when the weather smiled upon us.   A combination of fine weather and limitations on travel to more distant places gave us an opportunity to rectify this omission and we’ve climbed a few of the peaks surrounding Crummock Water and Ennerdale Water this summer.   The views that these provide offer a great opportunity to set our fine-scale activities into context.

This involved following the old drove road between Ennerdale and Crummock up as far as Floutern Gap, then following the boundary fence up the side of Great Borne (616 metres) which overlooks Ennerdale Water.  From here, we followed the ridge down and up to Starling Dodd (636 metres) then Red Pike (756 metres) and finally High Stile (806 metres).   The latter two peaks are on the watershed between Ennerdale and the Buttermere/Crummock valleys, affording spectacular views of five lakes (Derwent Water was just visible through a gap in the fells).   Further away, we could see the Solway Firth and the coast of Galloway to the north and, just on the eastern horizon, Cross Fell, the highest point on the Pennines, some 65 kilometres away.  

To the south we could see the River Liza flowing along the flat valley floor of Ennerdale, with Pillar and Scoat Fell rising up on the opposite side and, towards the eastern end, the imposing face of Great Gable, with Scafell Pike just behind.  Looking west, along Ennerdale Water, the high sides of the glacial valley give way abruptly (roughly between Angler’s Crag and Bowness Knott) to a softer landscape of improved pasture criss-crossed with dry stone walls.   This reflects a transition from hard volcanic rocks of the Borrowdale group which form the high fells to softer sandstones and mudstones.   

Buttermere, seen from Red Pike, September 2020.   The photograph at the top of the post shows Ennerdale Water from the same vantage point.

The scenery to the north was equally spectacular and its glacial origins even more obvious.   From the south-east end of Buttermere, the Honister Pass climbing up through a classic U-shaped valley.   There is almost no room for improved pasture on the floor of Buttermere, with the land rising even more steeply on the south side than it does on the north.  At the north-west end, however, there is an area of flat land where Mill Beck has deposited silt over the millenia, dividing the original glacial lake into two.  I remember that from O-level Geography as it was one of the examples we were expected to cite in an essay entitled “Lakes are temporary features of the landscape.  Discuss.”

The entire outline of Crummock Water was also visible, with Grasmoor rising up on the north-eastern flank and Mellbreak on the south-western side.   Grasmoor is the higher of the two peaks (## metres) but Mellbreak is the more imposing, rising straight up from the lake almost as starkly as the Screes arise from Wastwater.   Wainwright lets his usually measured prose run away when describing Melbreak: “Melbreak is isolated, independent of other high ground, aloof.  Its one allegiance is to Crummock Water”.   I’ve seen it from all four sides over the past month or so, as well as climbing to the summit last week and, though it is not a particularly high peak (511 metres), it punches above its weight.  Forgive me for sharing a few of my photographs to underline Wainwright’s comments… 

Crummock Water from Red Pike, September 2020, guarded by Grasmoor on the right and Melbreak on the right.  Loweswater is just visible to the left of Melbreak.  
Melbreak from Grasmoor, on the other side of Crummock Water, August 2020.
Whiteside, Grasmoor and Melbreak, seen from the shore of Loweswater. 

Beyond Crummock Water we could see the outline of Loweswater, which is unique amongst Lake District lakes because its outflow flows towards, rather than away from, the centre of the Lake District.   Most of the Lake District’s lakes are deep, elongated affairs, formed in the valleys scoured out by glaciatian.  Loweswater, by contrast, is relatively shallow (maximum depth: 16 metres) and set amongst gentler terrain.  “Improved grassland” – enclosed fields where cattle and sheep graze – form almost a quarter of the catchment of Loweswater, compared to just 3 per cent of the catchment of Ennerdale, 2.3% of the catchment of Buttermere and 7.5% of the catchment of Crummock Water. Esthwaite Water, the most productive lake in the Lake District, by contrast, has improved grassland on about a third of its catchment area.   Not surprisingly, Loweswater has had some issues with eutrophication in the past.

Loweswater from the top of Melbreak, photographed a few days before the other pictures in this post, when conditions were more hazy.

And finally, Derwent Water was just visible through a gap in the hills and we could also make out the summits of Skiddaw, Blencathra and Catbells from our vantage points on High Stile and Red Pike.   We got a closer view of Derwent Water a couple of days later when we canoed from Portinscale near Keswick to St Herbert’s Island and back.   A few years back I found my way to the lake impeded by a film set and spent an enjoyable few minutes watching a scene from Swallows and Amazons being filmed.  Apparently, St Herbert’s Island appeared as Wild Cat Island in the film too and was also the fictional Owl Island in Beartrix Potter’s The Tale of Squirrel Nutkin.   Oh yes, and someone called William Wordsworth wrote a poem about it.   I wonder what became of him?

Skiddaw rising above the south end of Derwent Water, September 2020.
On location: filming Swallows and Amazons in Keswick, July 2015.

Some other highlights from this week:

Wrote this whilst listening to:  Shores, the new album by Fleet Foxes

Cultural highlights:  The Farewell, a 2019 film directed by Lulu Wang about a family trying to keep their grandmother from learning about her terminal cancer.  A very warm and humorous film despite the subject matter.   

Currently reading:  Where I Was From, a collection of essays about the history of California by Joan Didion.

Culinary highlight:  Homemade Battenburg cake, inspired by the efforts on the first week of Great British Bake Off.   

Blind to the obvious

I’ve moved just a few kilometres from the River Liza to the location for this post: Croasdale Beck, a stream which joins the River Ehen at Ennerdale Bridge.   Croasdale Beck has featured in a number of posts in the past (see, for example, “That’s funny …” and “Croasdale Beck in February”) partly because it continues to surprise me.   Maybe that reflects a level of complacency on my part: regular visits mean that I know what to expect which, in turn, means that I am alert to things that I do not expect.   Seeing something new in a stream I have never previously visited is evidence of life’s rich pattern; noticing something that was probably there on previous occasions but which I overlooked is a more profound and, somehow, humbling experience.  This post is about one of each of these sensations.

There are, for example, a number of turquoise-coloured boulders in the beck that were certainly not there when I first started visiting in about 2015.   Most of the stones in the beck are cobbles rather than boulders, so these stand out both for their size and colour.   The colour is, if you look closely, due to a thin surface film – a Cyanobacteria which I will call Lyngbya vandenberghenii although, because it is difficult to scrape off (the filaments live in amongst the rock crystals), and lacks any really eye-catching features, it is hard to be totally certain about this.   Presumably it likes the stability that boulders confer in this very flashy little stream.    I also see it in the River Ehen nearby but there its presence is easier to explain as it is confined to chunks of limestone washed in from the foundations of a section of the Coast-to-Coast walk.

Simulium argyreatum growing on a cyanobacteria-covered boulder from Croasdale Beck, Cumbria (shown in the photo at the top of the post).  The stone is about 30 cm across.   

Today, however, I’m interested in what is growing on top of the Lyngbya rather than in the Lyngbya itself: dense patches of what looks, with the naked eye, like small tan-coloured seeds.   These are the tiny larvae of Simulidae, whose adult phases are the annoying blackflies that swarm around streams on summer evenings.   They spin a web of silk on the substrate to which they anchor themselves using a ring of hooks at their posterior.   Their mouthparts include a pair of fans (one of which can be seen in the image below) and, by extending themselves above the stone, they can trap tiny particles (including algae) drifting in the current. They produce a secretion which makes the fans sticky and also have mandibles adapted to brush the trapped particles from the fans into their mouths.   Most descriptions of the Simulidae refer to this filter-feeding life-style but I’ve also seen them bent double so that their fans can brush up the algae which grow on the stone surfaces. 

Larvae of Simulum argyreatum on boulders in Croasdale Beck.  The upper photograph was taken in situ with the macro facility on my Olympus Tough camera (each is ~0.3 – 0.5 millimetres long) from a stone without the crust of Lyngbya whilst the lower photograph shows a magnified view of the feeding fan of one larva.

At some point, the larvae cease feeding and spin slipper-shaped cocoons with the closed end facing upstream and the open end downstream.   Six white ribbon-like gills protrude from the open end, ensuring a ready supply of oxygen to the pupa inside.   The adult develops inside this cocoon, eventually emerging with a duel raison d’être of having sex and irritating humans.  “Adult” hardly seems like the appropriate word: “perpetual teenager” seems more apt. 

Whilst the adult males feed on nectar, the females need a blood meal before mating, adding a dark Gothic twist to their natural history.  This difference arises from the roles each plays in reproduction: the male only needs the spurt of energy that the sugary nectar confers whilst the female needs the proteins and minerals from the blood in order to nourish the eggs.  In the south of England, bites from the Blandford Fly, a relative of the Simulium I watched in Croasdale Beck, can cause nasty rashes whilst in large parts of Africa the bites from other species of Simulium can inject the parasite responsible for Onchocerciasis, or river blindness.   This was a common disease in the region of Nigeria where we lived in the early 1990s so I’ve seen the damage that these flies can cause.   Much as we find black flies and midges to be a nuisance in this country, at least they are not vectors for potentially deadly diseases. 

At a deeper level, knowing about the life cycle of Simulium reminds us that we are not just observers of aquatic ecosystems, we are, indirectly, part of these ecosystems too.  We may like to think of ourselves as the ultimate predator (remembering that this power brings with it great responsibility) but sometimes, as here, we can be the prey too. 

Clusters of Simulium argyreatum pupae on the Lyngbya-covered surface of a boulder in Croasdale Beck.   Each is about 3-5 millimetres long. 


And thanks to Richard Chadd for identifying the Simulium from my photographs.

Some other highlights from this week:

Wrote this whilst listening to:  The late great Toots Hibbert, remembering, in particular, Toots and the Maytals’ set on the West Holt Stage on a glorious summer evening at Glastonbury 2010

Cultural highlights:  We’re in the Lake District this week and, having recently watched part of Simon Scharma’s BBC series on the Romantic Movement, I’m reflecting on the role that the landscapes around me played in catalysing the work of Wordsworth, Turner and others. 

Currently reading:  English Pastoral by James Rebanks, a thoughtful analysis of the state of British agriculture that does not shy away from criticism either of farmers or naïve ecologists.

Culinary highlight:  James Rebank’s thesis hangs on the necessity of animal husbandry to maintain healthy soils.  With that in mind, I ate a Lakeland lamb steak at the Shepherd’s Arms hotel in Ennerdale Bridge with a clear conscience. 

Distant relatives …


The easing of lockdown means that fieldwork can resume (real fieldwork, that is, rather than virtual perambulations around the margins of Lough Down) and I was in the Lake District last week collecting samples for an ongoing project.  The New Normal means a rethink of logistics to account for social distancing which, in my case, meant Heather taking the place of Ben as BenthoTorch wielder so that we could safely share a single car.

Our travels took us to the River Calder, a short river that rises on the western fells of the Lake District, just south of Ennerdale Water, and flows about 12 kilometres to join the Irish Sea at Sellafield (it actually flows through the BNFL site and those with a long memory may remember that the first incarnation of the nuclear reprocessing site was known as “Calder Hall”).   This is one of a number of rivers of this name in the UK, with an ancient Celtic root referring either to the violence of the flow or the stony nature of the bed.   The two roots are linked: a harsh hydrology will flush away all but the largest and roughest stones and, as the photograph above shows, the bed of the Calder has plenty of these.

When not photographing me peering at stream beds through a bathyscope, Heather noticed some bright yellow growths on the floor of the forest surrounding the stream which she recognised as a slime mold with the rather unappetisiing name of dog’s vomit.  For once, the Latin name, Fuligo septica, sounds more appealing.   Under the microscope, all I saw were spherical spores but these will germinate and the cells will aggregate to form an amoeboid-like mass that moves around searching for nutrients.    YouTube has some fascinating videos that shows this happening.


Fuligo septica – dog’s vomit slime mold – photographed in woodland beside the River Calder, Cumbria, June 2020 (photograph: Heather Kelly)

Slime molds interest me for another reason today: they are a group that has bounced around the tree of life in the years since I started my career.  When I was at school, slime molds were dealt with cursorily as one group within the fungi which, in those far-off days, were considered to be part of the plant kingdom.  In the far past, algae and fungi were grouped together as the “Thallophyta”.   This particular slime mold still sits in a class called the Myxomycota (literally “slime fungi”) which alludes to this heritage.  Now, the idea of fungi being relatives of the plants is quite laughable: they differ in so many ways, not least the completely different form of the cell wall and the absence of photosynthesis.   The fungi are treated as a separate kingdom but the slime molds have undergone one further divorce. No longer are they considered to be a group within the fungi, rather they have all been shifted to the Protozoa, itself also a separate kingdom.  The slime molds do, superficially, resemble some fungi in some respects but, in others, they are completely different.  This fragmentation from the straightforward view of biological classification of the past, resembles that which has occurred in the algae: once considered primitive “plants” but now spread between four kingdoms.   The Euglenophyceae, which have appeared in this blog on a couple of occasions (see “A visit to Loughrigg Fell” and “Puzzling puddles on the Pennine Way”), are, in fact, more closely related to dog’s vomit slime mold than they are to any other group of algae.


Microscopic view of cells of Fuligo septica, dog’s vomit slime mold. Scale bar: 10 micrometres (= 100th of a millimetre).

The slime molds are not the only group that used to be classified as fungi but which are now more closely allied to algae.   Potato blight (Phytophora infestans) belongs to the Oomycota (or “egg-fungi”, due to their large oogonia).   This group is now classified in the same kingdom (Chromista) and phylum (Heterokontophyta) as several groups of algae including the diatoms and brown seaweeds.   It is a fairly distant relationship in the grand scheme of things (equivalent to comparing yourself to a sea squirt) but it still means that I make my living from relatives of the organism that drove my ancestors to leave Ireland.


Some other highlights from this week:

Wrote this whilst listening to: old Glastonbury sets on the BBC iPlayer, particularly from 2009 and 2010, when I was there.   Notably Blur’s headline set (watch out for the crowd surfer who disappears from view halfway through Song 2.  I was directly underneath.   Also Dizzee Rascal from 2010 and highlights from Bruce Springsteen’s 2009 set.   And Radiohead from 1997.

Cultural highlights:  The new interpretations of Alan Bennett’s Talking Heads, produced by Nicholas Hytner on BBC2.  ]

Currently reading:   Lethal White by Robert Galbraith (aka J.K. Rowling).

Culinary highlight:  French onion ramen, a French/Japanese fusion from Tim Anderson’s Vegan Japaneasy.

Rhapsody in red


On an overcast winter day with just a sprinkling of snow on the fells the Lake District can appear very monochrome.  Look closely at the bed of some rivers, however, and you are confronted by a much more vibrant palette with browns, greens and reds vying for your attention.  Somehow, paradoxically, the stream algae are at their most prolific and vigorous when the rest of Cumbria’s biological diversity has hunkered down to wait for the onset of Spring.

One of the most conspicuous groups at this time of the year are the red algae.  The green algae, diatoms and cyanobacteria are there all year round, even if winter is the time when they are most abundant.  The red algae, however, are barely evident – and certainly not to the naked eye – during the summer months.   It is only when autumn is well underway that the first blushes of pinkish red appear on the stones lining the beds of rivers.   This is in contrast to the red seaweeds which can be found on our coasts all year round, and indeed, to the many red algae that inhabit warm tropical seas.  What is so different about red algae in streams that leads them to favour the colder periods of the year?   What is it about streams, too, as I rarely see red algae in lakes (Batrachospermum is the exception: see “More algae from Shetland lochs”)?

This post will not answer those questions, but will give a quick overview of the red algae we find in freshwaters, in the manner of an earlier post about green algae (see “The big pictures …”).   The table below shows the systematics of the red algae, following a molecular phylogeny study by Hwan Su Yoon and colleagues from 2006.   There are two sub-phyla, of which one, Cyanidophytina, has no representatives recorded from the UK or Ireland.   There are just eight species in this group of primitive red algae, associated mostly with extreme environments.

The other subphylum, by contrast, has over 7000 species, divided between six classes, but 94 per cent of these are marine.   There are just thirteen genera of red algae recorded from freshwaters in the UK and Ireland, but spread amongst five of these six classes.   This seems to suggest that an ability to thrive in freshwaters has evolved several times during the evolution of this group.


The organisation of the red algae (Rhodophyta) showing division into two subphyla and seven classes.  Pink fill indicates the classes that are represented in UK and Irish freshwaters.   Organisation follows Algaebase and Yoon et al. (2006).    The photo at the top of this post shows Audouinella hermainii in the River Ehen, Cumbria, in December 2019.

Of the five classes that do have freshwater representatives, well over half of the genera and species recorded from the UK and Ireland are found in the Floridiophyceae.   This class has over 6900 species (95% of all red algae) split between 34 orders, of which five contain genera found in UK and Irish freshwaters.   Of these, the Batrachospermales, one of the few red algal orders that is exclusively freshwater, contains five genera and eleven species, whilst the other four contain just one genus each.

The Batrachospermales contain two morphologically-distinct groups of genera: Batrachospermum, Sheathia and Sirodotia form one of these, whilst Lemanea and Paralemanea form the other (see links below for more details and images).   Whilst we have molecular evidence that suggests that the Batrachospermales are a natural group, it is hard to point to a single characteristic that helps someone more interested in identification than taxonomy.   In fact, it is the life-cycle that is most distinctive (“… diplohaplontic … heteromorphic and contains a reduced tetrasporophyte”) but few of us are as well-schooled in algal life-cycles now as our predecessors were (see “Reflections from the Trailing Edge of Science”).   A hundred years ago, we would have had to rely upon the same limited set of morphological characters for both identification and taxonomy; now the taxonomist’s toolkit has expanded considerably whilst identification is still mostly reliant on features we can see with the naked eye or a light microscope.  For the red algae, this is still mostly enough to answer questions about what species we have found but unravelling the logic behind a classification may need a broader perspective.


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



Entwisle, T.J., Vis, M.L., Chiasson, W.B., Necchi, O. & Sherwood, A.R. (2009).  Systematics of the Batrachospermales (Rhodophyta) – a synthesis.   Journal of Phycology 45: 704-715.

Yoon, H.S., Müller, K.M., Sheath, R.G., Ott, F.D. & Bhattacharya, D. (2006).  Defining the major lineages of red algae (Rhodophyta).  Journal of Phycology 42: 482-492.

van den Hoek, C., Mann, D.G. & Jahns, H.M. (1995).  Algae: an Introduction to Phycology.  Cambridge University Press, Cambridge.


And some other cultural highlights from the week:

Wrote this whilst listening to: Dave’s Psychodrama,

Cultural highlights:  Dave’s performance of Black (from Psychodrama) at the Brits Award Show.  I would not normally have watched this but was stuck in a hotel room with no wifi reception and was totally blown away by the power of his performance.

Currently reading: Bill Bryson’s The Body

Culinary highlight: I’m trying to cook one meal each month using only UK-sourced ingredients, in order to help me focus on seasonal cycles.  My February effort was a beer and cheese fondue: very easy to cook, using beer from about 500 metres from my house (Durham Brewery’s Evensong) and a mixture of Cheddar and Lancashire cheeses from Durham Indoor Market.



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

Group Link
Bangiophyceae Watch this space …
Bangiophyceae Watch this space …
Compsopogonophyceae Watch this space …
Achrochaetiales Something else we forgot to remember
Balbianiales The Hilda Canter-Lund prize
Batrachospermales Lemanea: The complicated life of simple plants

Batrachospermum: More algae from Shetland lochs

Hildenbrandiales More about red algae
Thoreales Watch this space
Porphyridiophyceae Watch this space …
Stylonematophyceae More pleasures in my own backyard

Spheres of influence

Back to Moss Dub for this post because Chris Carter has sent me some stunning images of the filamentous desmid Desmidium grevillei that I talked about in my earlier post.   I mentioned that it is surrounded by a mucilaginous sheath, which was just apparent in my brightfield image.   Chris has added Indian ink to the wet mount.  The ink forms a dense suspension in the water but is repelled by the mucilage around the desmid cells, resulting in a much better impression of the extent of the sheath around the cell than is otherwise possible.


Desmidium grevillei from Moss Dub, photographed by Chris Carter using Indian ink to highlight the mucilage sheath around the cells. 

Indian ink is a negative stain, which means that it is the background, rather than the specimen itself, which takes up the colour.   This, in turn, alters the passage of light through the sample and appears to improve the contrast of the final image.   Chris’ images of the apical view show this well, and also illustrates the complicated three-dimensional arrangement of the chloroplasts within each semi-cell.   His photographs also show the pores through which the mucilage is secreted.

The curious thing about this negative stain is that, whilst it appears to emphasis a halo of nothingness around the Desmidium filament, it is actually drawing our attention to something important.   In his presidential address to the British Phycological Society in 1981 A.D. Boney referred to mucilage as “the ubiquitous algal attribute” and goes on to list the many functions that the slimes produced by a wide range of algal groups may perform.  Not all will apply to our Desmidium but Boney does use desmids as examples of some of the roles slime may play: it can be, for example, a buoyancy aid, keeping the desmids in the well-lit regions of a lake or pond and it can protect cells against desiccation if a pond or lake dries out.  It may also play a role in helping desmids adhere to their substrates and there is also evidence that mucilage layers may help to protect algae from toxins.


Apical view (at four different focal planes) of Desmidium grevillei from Moss Dub, photographed by Chris Carter, September 2019.

But that’s only part of the story.   There is two-way traffic across the membranes of algal cells, with essential nutrients moving into the cell but, in some cases, enzymes moving in the opposite direction.  If nutrients are in short supply then these enzymes can help the cell by breaking down organic molecules in order to release nutrients that can then be absorbed. Those enzymes take energy to manufacture, and the sheath of gunk around the filament means that there is a lower chance of them diffusing away before doing their job (see “Life in the colonies …”).   The same principle applies to sexual reproduction too, with mucilage serving, in some cases, as “sperm traps” or simply as the phycological equivalent of KY Jelly.

It is not just the algae that benefit from this mucilage: the outer layers, especially, can be colonised by bacteria which will also be hoovering up any spare organic molecules for their own benefit with, no doubt, some collateral benefits for the organisms around them.  The connection is probably too tenuous to count as a symbiosis with the desmids but we could think in terms of mutual benefits.

So that “nothing” really is a “something”, and that is before we consider the role of these extracellular compounds in the wider ecosystem.  I mentioned the role of similar compounds in consolidating the fine sediments on coastal mudflats in “In the shadow of the Venerable Bede” to give a flavour of this.   The least prepossessing aspect of the least prepossessing plants can, given time, change landscapes.  That should give us all pause for thought.


Close-up of Desmidium grevillei filament with focus on the left-hand cell adjusted to show the apical pores.   Photographed by Chris Carter from material from Moss Dub collected in September 2019.


Boney, A.D. (1981). Mucilage: the ubiquitous algal attribute.  British Phycological Journal 16: 115-132.

Domozych, D. S., & Domozych, C. R. (2008). Desmids and biofilms of freshwater wetlands: Development and microarchitecture. Microbial Ecology

Sorentino, C. (1985). Copper resistance in Hormidium fluitans (Gay) Heering (Ulotrichaceae, Chlorophyceae). Phycologia 24: 366-388.


The little tarn of horrors …

In addition to desmids, we found several other algae in the samples collected from Cogra Moss.  One of these consisted of colonies of cells in mucilaginous masses attached to floating mats of vegetation (which looked like terrestrial grasses).  We decided that these were probably Chrysocapsa epiphytica, the second representative of the Chrysophyta I’ve described in this blog this year (see also “Fade to grey …”).  As is the case for Chromulina, much of what we know about Chrysocapsa epiphytica is down to the patient work of John Lund who first described this species back in 1949.


Colonies of Chrysocapsa epiphytica growing on submerged vegetation at Cogra Moss, Cumbria, September 2019.  Cells are 7.5 – 15 micrometres long and 7.5 – 12 micrometres wide. 

He described the various mucilaginous lobes as “reminiscent of the …. human brain”.  The spherical, oval or ovoid cells form a layer, two to four cells deep, at the surface of the colony.   The cells have the typical yellow-brown colour of chrysophytes and, though it is hard to see the chloroplasts in this photograph, John Lund says that there are usually two, sometimes four, in mature cells.

Its presence in a soft-water lake probably means that it is a species that relies on dissolved carbon dioxide rather than bicarbonate as its raw material for phytosynthesis (see “Concentrating on carbon …” for some background on this).   We know, from laboratory studies, that most chrysophytes rely exclusively on carbon dioxide, and lack the capacity to use bicarbonate.  This confines them to water where the pH is low enough to ensure a supply of carbon dioxide (the chemistry behind this is explained in “Buffers for duffers”. It may also explain why Chromulina lives in surface films rather than submerged in the pond (the locations where we’ve it found are unlikely to have sufficiently low pH).

One extra twist to the story is that many chrysophytes are “mixotrophic”, meaning that they can switch between using photosynthesis as a means of getting the carbon they need to grow from inorganic sources, and “feeding” on other organisms.  Our Chrysocapsa epiphytica, in other words,  has parked itself beside a convenient supermarket of pre-packaged carbon in the form of decaying vegetation and associated bacteria which it then ingests by a process known as “phagotrophy”.

Phagotrophy is, in fact, a very ancient characteristic, insofar as the very first eukaryotic cells were the result of Cyanobacteria-type cells being ingested by larger heterotrophic cells and being retained as on-board “energy farms” rather than digested and treated as one-off vegetarian dinners.   However, the shift to a permanent role for chloroplasts within a eukaryotic cell involved a lot of rewiring of intercellular machinery, and effectively “switching off” the intercellular mechanisms involved in phagotrophy.   Retaining the ability to “feed” on bacteria alongside a capacity for photosynthesis is the cellular equivalent of a hybrid car: there is a lot more to cram under the bonnet.  Flexibility, in other words, comes at a cost.

On the other hand, phagotrophy does not just result in extra carbon for the Chrysocapsa cells in Cogra Moss.   In an oligotrophic tarn such as this, the extra nutrients that are obtained when the bacteria are absorbed will also be a useful boost.   Once again, though, you can see that, in environments where nutrients are more plentiful, the cost to the cell of maintaining the equipment required for phagotrophy outweighs the benefits.

I’m sure that a close inspection of the land around Cogra Moss would have revealed insectivorous plants such as Drosera(sundew) and we also recorded Utricularia minor, an aquatic insectivorous plant, in another tarn we visited whilst desmid-hunting (see “Lessons from School Knott Tarn”).  Chrysocapsa is, in many senses, a microscopic equivalent of these carnivorous plants.   OK, so it has a taste for bacteria rather than flesh but, somewhere out there, there must be a sub-editor in search of a headline …


Lund, J.W.G. (1949). New or rare British Chrysophyceae. 1.  New Phytologist48: 453-460.

Maberly, S. C., Ball, L. A., Raven, J. A., & Sültemeyer, D. (2009). Inorganic carbon acquisition by chrysophytes. Journal of Phycology 45: 1052-1061.

Raven, J. A. (1997). Phagotrophy in phototrophs. Limnology and Oceanography 42: 198-205.

Saxby-Rouen, K. J., Leadbeater, B. S. C., & Reynolds, C. S. (1997). The growth response of Synura petersenii(Synurophyceae) to photon flux density, temperature, and pH. Phycologia 26: 233-243.

Saxby-Rouen, K. J., Leadbeater, B. S. C., & Reynolds, C. S. (1998). The relationship between the growth of Synura petersenii (Synurophyceae) and components of the dissolved inorganic carbon system. Phycologia 37: 467-477.

Terrado, R., Pasulka, A. L., Lie, A. A. Y., Orphan, V. J., Heidelberg, K. B., & Caron, D. A. (2017). Autotrophic and heterotrophic acquisition of carbon and nitrogen by a mixotrophic chrysophyte established through stable isotope analysis. ISME Journal.


Desmids from Moss Dub


I’d like to say that this post is about an excursion I made beyond Ennerdale Water and along the valley of the River Liza in order to find some different habitats from those that I usually write about in this blog.  I’d like to but, in truth, I was sitting by a road about ten miles away waiting for roadside assistance whilst my compatriots on the Quekett Microscopy Club / British Phycological Society algae weekend went up the valley on a glorious mid-September afternoon without me.  Whilst I was sitting waiting for a tyre to be replaced in a garage in Egremont they were casting plankton nets and squeezing handfuls of Sphagnum beside Moss Dub, a small tarn set amidst woodland close by the River Liza.

Moss Dub is set within one of Britain’s oldest and most ambitious rewilding schemes, Wild Ennerdale, where nature is allowed to shape the landscape as far as possible free from human interference.  However, Moss Dub, as we found out, is far from a natural water body.  A path forks and the two arms act as bunds encompassing a shallow pond, now partly overgrown with aquatic vegetation.   There is evidence of past mining activity – for iron and copper – in the area and my guess is that Moss Dub was, in the far past, a reservoir associated with the Lingmell mine located on the hillside above the River Liza and active in the late 19thcentury.     Whatever its history, it proved to be a rich location for desmids, and we spent a happy Saturday dipping Pasteur pipettes into the vials of peaty water that they collected and peering through our microscopes (If you want to know more about how to collect desmids, look at the post I wrote after our last excursion to the Lake District: “Desmid masterclass”).

There were some conspicuous green growths suspended in the water at the margin of the pond.  Even without a microscope, their filamentous nature was obvious.  When magnified, we saw chains of green cells set within a distinct mucilaginous sheath.  Each filament was composed of short cells with a distinct notch on either side.   This is a representative of Desmidium, one of a relatively small number of filamentous desmids.  We met D. schwartziion our previous excursion (see “Lessons from School Knott Tarn”); that species was present here along with D. grevillei, which is similar in many respects but the cross-section is lemon-shaped rather than triangular.


Desmidium grevillei from Moss Dub, Ennerdale Valley, September 2019.  a. shows a macroscopic view of filaments in a Petri dish; b. shows a filament of cells, along with a distinct mucilaginous sheath whilst c. shows a cell in cross-section.  I forgot to bring my graticule so cannot add scale bars to any of the images in this post.   Instead, I will quote dimensions from the Freshwater Algal Flora of Britain and Ireland to give an indication of size.   Cells of D. grevillei are 30 – 56 micrometres wide (50 micrometres is 1/20thof a millimetre).   The photo at the top of this post is a view of Moss Dub, taken by Zeneb Henderson

There were numerous other desmids in the sample.  A couple are illustrated below, and we’ve sent the sample off to David Williamson for a more thorough examination, and some definitive names.  On the right-hand side of the plate there is a different green alga, Coelastrum pulchrum, a member of the Chlorophyceae that forms spherical colonies with a fixed number of cells (“coenobia”).  We met Coelastrum microporum in the River Wear last summer (see “More green algae from the River Wear”): cells of C. pulchrum, by contrast, have a blunt projection.


More algae from Moss Dub: d. Micrasterias radiosa (142 – 191 micrometres across); e. Euastrum pinnatum (65-75 micrometres across; 125 – 170 long); f. Coelastrum pulchrum (about 100 micrometres in diameter). 

The final desmid I’ve illustrated is Closterium lunula, large by desmid standards as it can reach half a millimetre or more in length.  Members of this genus have prominent vacuoles at each end of the cell within which small crystals can be seen.  Because C. lunula is so large it is easy to see both vacuole and watch Brownian motion move the crystals within.   Studies have shown that these are crystals of barium sulphate and also that the crystals are scattered throughout the cells, just happening to be easier to see I the vacuoles.  Quite what role they play remains speculation: barium is not required for plant nutrition and is, indeed, toxic in high concentrations.   It is also scarce in the soft waters where Closteriumis most often encountered, both in absolute terms and relative to other trace metals, which only adds further to the mystery.

That’s enough about Moss Dub for now.  A few words about Ennerdale Bridge, where we were based before I sign off from this post.  I usually stay at the Shepherd’s Arms when I am in the area and Keith and his staff hosted most of us and fed all of us.  It is a comfortable, unprententious inn, living mostly off walkers doing the Coast-to-Coast walk and with a menu that managed to put a smile on the faces of vegetarians and non-vegetarians alike.  Our daytime events took place in the community room of The Gather, a community-owned and run café and shop,  That gave us the satisfaction of knowing that the money we paid for the room was going to good use.   Their coffee keeps me going during long days of fieldwork in the area so I’m keen to make sure that they thrive!


Closterium lunula (400 – 663 micrometres long) from Moss Dub, showing the terminal vacuole (ringed) and (below) a close up showing rectangular crystals of barium sulphate inside the vacuole.


Brook, A. J., Fotheringham, A., Bradly, J., & Jenkins, A. (1980). Barium accumulation by desmids of the genus Closterium (Zygnemaphyceae). British Phycological Journal 15: 261-264.


Quekett Microscopy Club and British Phycological Society members getting stuck into analysis of samples from Moss Dub and the Ennerdale valley at The Gather, Ennerdale Bridge, September 2019.

Close to the edge in Wastwater …


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

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

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


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

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

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


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

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

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


Maberly, S. C., King, L., Dent, M. M., Jones, R. I., & Gibson, C. E. (2002). Nutrient limitation of phytoplankton and periphyton growth in upland lakes. Freshwater Biology.

Moss, B., Jeppesen, E., Søndergaard, M., Lauridsen, T. L., & Liu, Z. (2013). Nitrogen, macrophytes, shallow lakes and nutrient limitation: Resolution of a current controversy? Hydrobiologia.

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

Notes from Windermere


Just before the trip to the Shetland Islands I wrote about in the previous post, I spent two days in the Lake District teaching a course on identifying macroalgae for the Freshwater Biological Association.  It coincided with a period of gorgeous weather, showing Windermere at its absolute best (as the photo at top of the post shows).  Only a month ago my wheels were spinning in the snow on Whinlatter Pass (see “How to make an ecosystem (2)”).

Looking up Windermere towards the high peaks of the Lake District’s volcanic centre, I find myself reflecting on how geology creates the diversity in landscapes and aquatic features that, in turn, creates variety in the microscopic flora and fauna (see “The Power of Rock”).   A nuanced understanding of the aquatic world requires one to view the grand panorama at the same time as focussing on organisms that are scarcely visible with the naked eye.

One of the locations that we visited during the course was Cunsey Beck, which flows out from Esthwaite Water and, a few kilometres later, into Windermere.   Esthwaite is one of the more productive of the lakes in this region and we usually find a healthy crop of algae in the beck.   This year was no exception and, amongst the different forms we collected were some long straggly growths that had a slighty gelatinous feel.  Back at the laboratory we put part of one of these growths under the microscope and saw a large number of individual cells set in a jelly matrix.   This identified the alga as Tetraspora gelatinosa, a green alga that I have written about before (see “More from the Atma River …”) although not for some time.


Tetraspora gelatinosafrom Cunsey Beck, Cumbria, May 2019.   The picture frame is about five centimetres wide.

The genus Tetraspora gets its name from a mode of division that leaves many of the daughter cells in groups of four (visible in the lower illustration).  These, in turn, are embedded in mucilage, and repeated divisions can lead to growths becoming visible with the naked eye.   Three species have been recorded from Britain and Ireland, of which the Cunsey Beck population is most likely to belong to T. gelatinosa.   In the past, it might have been called Tetraspoa lubrica, which has a more tubular thallus; however, this is now thought to just be a growth form of T. gelatinosa that is associated particularly with fast-flowing rivers.  As far as I can tell, no-one has performed any detailed molecular genetic studies on this genus to better understand the relationships between these different growth forms so we will have to go with current convention for now.


Tetraspora gelatinosaunder the microscope.   Cells in the foreground are about ten micrometres in diameter.   Photograph by Hannah Kemp.

I’ve seen Tetraspora in a wide range of habitats – on stones in fast-flowing, relatively soft water rivers in Norway and growing on plant stems in the littoral zone of hard water ponds in Ireland.   Most of my records are from the spring, though I should add that spotting some of the smaller gelatinous colonies (barely more than near-transparent dots on the stone surface) does take some practice and I suspect that I have missed it on a few occasions too.

The microscopic image of Tetrasporawas taken during the course using a Carson Hookupz, a neat device which allows a smartphone to be attached to a microscope (or any other optical device).   It takes a little fiddling to get the set-up right but, once this has been achieved, the quality of pictures we obtained was excellent.   My microscope engineer tells me that he is selling large numbers of these to schools and colleges as it means that students can capture images during practical classes that they can subsequently use in reports or just (as was the case during our course) as an aide mémoire.


The Carson Hookupz 2.0 as it comes out of the box (left) and (right) in action during the Identifying Macroalgae course at the Freshwater Biological Association.


Looking north from Miller Ground towards the central Lake District peaks as the sun sets.  The photograph at the top of the post was taken from nearby but shows the view in early morning.  


More about measuring biomass …

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

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


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

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

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

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