Looking after their own …

Much has changed in the two months since I was last at the River Irt.  The conspicuous yellow-brown patches of diatoms that attracted my attention in Cold Comforts have gone, but other algae have appeared: clusters of dark brown filaments, each a couple of centimetres long, on the upper surface of boulders.   These tufts are the red alga Lemanea fluviatilis, which I’ve written about before (see“Lemanea in the River Ehen”).   Interestingly, I did not see Lemanea at Lund Bridge, the focus of the posts about winter diatoms, but at Cinderdale Bridge, a few kilometres further downstream.  Lemanea is also not found in the River Ehen close to the outfall of Ennerdale Water but becomes abundant a few kilometres further downstream.  There must be something about proximity to a lake that does not favour this genus.  

Young shoots of Lemanea fluviatilis along with green algae on a boulder in the River Irt at Cinderdale Bridge, February 2023.   The boulder is about 40 centimetres long.    The photograph at the top of the post shows the River Irt at Cinderdale Bridge.

These filaments (which are actually hollow tubes of cells) had some growths which looked remarkably like another red alga common in streams hereabouts, Audouinella hermainii.  But we could also turn that argument around and say that Audouinella looks remarkably like juvenile stages of several red algae (see “The complicated life of simple plants …”).  Unravelling the identities of these simple filaments has kept taxonomists busy for over a century and molecular analyses are still presenting us with surprises.   I’m going to assume that these are young gametophytes of Lemanea until someone convinces me otherwise, simply because of their proximity to so many other young shoots of Lemanea.  

A filament of Lemanea fluviatilis with young epiphytic gametophytes.  Scale bar: 100 micrometres (= 1/10^th of a millimetre).  

Close-up of young gametophytes on a filament of Lemanea fluviatilis in the River Irt, February 2023. 

These were not the only residents on Lemanea.   There were also some thin, unbranched filaments belonging to a cyanobacterial genus Chamaesiphon.   This is a genus with two very distinct habits: some species form dark brown/black crusts on rocks (see “A bigger splash …”) whilst other species live as epiphytes.    I last wrote about the epiphytic forms in “Whatever doesn’t kill you …”.  In that post, I was circumspect about naming the species because I could only see a single “exospore” at the end of filaments.   The population in the River Irt, however, has several filaments with a very characteristic stack of exospores so I can use the name C. confervicola with more confidence.  

A young filament of Lemanea fluviatilis with epiphytic Chamaesiphon confervicola. A stack of exospores is visible on the filament to the left of centre.  Scale bar: 20 micrometres (= 1/50^th of a millimetre).  

The last image in this post is a graph showing the changes in the cover of Lemanea fluviatilis in rivers in West Cumbria over the course of a year.   This shows very clearly that Lemanea is most prolific in winter and spring, becoming very sparse in summer through to autumn.  It is a similar pattern to that shown by Gomphonema.   There are algae that have pronounced summer peaks but we tend not to see these in the very nutrient-poor streams of the Lake Disrict.   My theory is that these small streams tend to be shaded and to have healthy populations of (hungry) invertebrates which are most active in the warm waters of summer.   Consequently, winter offers the best opportunity for an alga to grow relatively unmolested.   And, just as I showed how Gomphonema created a “housing estate” for other diatoms to inhabit, so Lemanea might well be determining the fluxes of the tiny Chamaesiphon confervicola filaments too.  

Seasonal changes in the cover of Lemanea fluviatilis in rivers in West Cumbria, 2019 – 2023.   Cover is expressed on the 9-point scale used for macrophyte surveys in the UK.   Vertical lines separate the twelve months.

Some other highlights from this week: 

Wrote this whilst listening to: In a Silent Way, by Miles Davies.   My favourite of his many records. 

Currently reading:   Animal, Vegetable, Miracle: Our Year of Seasonal Eating by Barbara Kingsolver.  

Cultural highlight: finally got around to seeing BAFTA-winning and Oscar nominated film Aftersun, starring Paul Mescal.  

Culinary highlight:   homemade prawn, crab and fennel cannelloni.   

All change …

We can just about fit a tour of 15 sites spread across four catchments in the Lake District into a single day of fieldwork if we start early and take only a short break for lunch.   However, my task on these trips is to survey the visible algal communities and, as the day progresses, I am conscious that my concentration wanes as tiredness sets in.   It can be a struggle to keep focus for the River Irt, the final river we examine.   Fortunately, it is one that usually has some conspicuous and unusual algal growths to hold my attention.  

This time, I noticed some brownish-green growths on the tops of granite boulders.  I had not seen them here before, although that is not quite the same as saying that they are new arrivals (see “On fieldwork …”).  Let’s just agree that they are conspicuous enough that, even at the end of a busy day, I should have noticed them if they were there on previous visits.   I could not identify them with confidence in the field but, when I got a specimen under my microscope, my first thought was that it as a species of Batrachospermum (see “algae … cunningly disguised as frog spawn”) although this one looked different to most I had seen previously.

Torularia atrum growing on a submerged boulder in the River Irt.   The largest clumps are about 3 – 4 centimetres across.  The photograph at the top of the post shows Cinderdale Bridge over the River Irt, June 2022.

Batrachospermum usually has a characteristic “beaded” appearance, caused by whorls of side branches along a main stem.   This one had much shorter lateral branches and longer internodes, so the beading was not visible with the naked eye, and only just visible with a hand-lens.  Evidence pointed to Batrachospermum atrum, according to the Freshwater Algal Flora of Britain and Ireland, but that book is now a decade old and, as happens frequently in algal taxonomy, names have changed.   

In this particular case, there are two reasons for the change in name.  The first is that molecular analyses have revealed that variation within the genus Batrachospermum is greater than previously expected, leading workers to pick off some of the groups and put them into newly described genera.  That’s data-driven science and, as in this case, molecular evidence makes us think again at traditional criteria used in classification.  In the time since the Flora was published, some UK and Irish Batrachospermum species have been moved to Sheathia, whilst B. atrum is now Torularia atra.    

The other aspect is the niggly bureaucracy of taxonomy.  In this case, the scientists who recognised that B. atrum was distinct from other Batrachospermum created a new genus, Setacea, which was later found to be invalidly published.  They then tried again with another genus name, Atrophycus, but then Michael Wynne pointed out that B. atrum had, itself, been placed in a separate genus, Torularia, way back in the 19^th century, rendering all these modern names irrelevant.  And, just to stir in a little more confusion, the name Torularia was also used for a genus of flowering plants until relatively recently.

Torularia atrum from River Irt, Cinderdale Bridge, June 2022.  Top picture: taken with macro lens; scale bar: 1 cm; lower picture: 100x magnification; scale bar: 100 micrometres (= 1/10^th of a millimetre).  

Frequent name-changes was a frequent cause of confusion during our algae identification course at Windermere.  We pointed out that, in many cases, there are good grounds for re-evaluating the limits of traditional genera (as is the case here).  Nonetheless, these name changes make it difficult for anyone (beginners especially) using older identification guides.   The Freshwater Algal Flora of Britain and Ireland, hardly counts as “old”, a mere decade after publication.  However, an update has just had to be published, detailing the many nomenclatural changes since the book went to print. Almost inevitably, that update will, itself, be out of date very soon too.   For this reason, we point our students to Algaebase, an excellent resource that keeps track of the taxonomic literature and allows you to check very quickly whether a name is current usage or has been superseded.   In the case of Torularia atra, there are no less than six synonyms each with a separate entry and each with a hyperlink that takes you back to T. atra.   

Torularia atrum from the River Irt, Cinderdale Bridge, June 2021 at 400x magnification.   Scale bar: 20 micrometres (= 1/50^th of a millimetre).  

This short tale encapsulates the history of algae studies.   We’ve spent the last 350 years trying to make sense of what we see as we peer through our microscopes.   Over that time, microscopes have gradually improved and, each time, we’ve seen a little more.   Whenever that happens, ideas about what constitutes a “species” have shifted.  That might bring us a little closer to scientific truth but, seen from the perspective of those for whom the species are a means to understand habitats, each change of name sows a little more confusion.  Within the last 50 years, this process has speeded up inexorably with the introduction of, first, electron microscopy and, then, molecular genetics to the taxonomist’s toolkit.  What we “see” – in the sense of light patterns hitting the retina – does not change; what we “see” – in the sense of how our brains process messages from the optic nerve – is forever shifting (see “Do we see through a microscope?”).   Some confusion is inevitable: better that we learn to live with this rather than expect to be presented with a naively simplistic view of the world.

References

John, D. M., Guiry, M. D., Wilbraham, J., & Krokowski, J. (2022). The 2011 edition of “The Freshwater Algal Flora of the British Isles”: additions, corrections, nomenclatural and taxonomic changes. Applied Phycology 3: 36-71. []

Léonard, J. (1986). Neotorularia Hedge & J. Léonard nom générique nouveau de Cruciferae. Bulletin du Jardin botanique national de Belgique/Bulletin van de Nationale Plantentuin van Belgie 56: 389-395.

Rossignolo, N. L., & Necchi Jr, O. (2016). Revision of section Setacea of the genus Batrachospermum (Batrachospermales, Rhodophyta) with emphasis on specimens from Brazil. Phycologia 55: 337-346.

Rossignolo, N.L., Necchi, O., Jr. & Guiry, M.D. (2017). Atrophycus, a new genus name for “Setacea (De Toni) Necchi & Rossignolo”. Notulae Algarum 26: 1-2.

Wynne, M. J. (2019). Torularia Bonnnemaison, 1828, a generic name to be reinstated for Atrophycus Necchi & Rossignolo, 2017. Notulae algarum 89: 1-4.

Some other highlights from this week:

Wrote this whilst listening to: Nick Cave’s Seven Psalms and Gwenno’s Tresor

Currently reading: The Girl at the Lion d’Or by Sebastian Faulks.  Just finished Gillian McAllister’s Wrong Place, Wrong Time which is a crime novel with an intriguing difference.

Cultural highlight:   Durham Miner’s Gala (below), back for the first time in three years.

Culinary highlight:  home-cooked vegetarian Sichuan meal: fish-fragrant aubergine, gon bao mushrooms, smacked cucumber.

Springtime surprises …

My last few trips to the Lake District have been plagued by indifferent, if not inclement, weather.  High flows are the ultimate curse of anyone working on rivers, and recent trips have all been uncertain until almost the last moment as I watched the fluctuations of weather forecasts and hydrographs.  Even once we had arrived, clouds were low and we never seemed to be out on one of those crisp winter days that offers views of distant, snow-capped peaks.   Finally, last week, the sun was able to break through the clouds, at least occasionally, daffodils, primroses and cowslips were in flower and the woodlands were heady with the scent of wild garlic.   

Life under water, however, follows a different trajectory to life on land.   At this time of year, stream beds in West Cumbria tend to look less, not more, verdant.   The algae that are so prolific during the winter were still there, but nowhere near as prolific now.   That was the case at several of the sites we examined but one – the River Cocker just below Crummock Water – bucked this trend in quite a dramatic way.  Peering through my bathyscope, I saw bright pink-red growths, particularly on fronds of the moss Fontinalis antipyretica.   These turned out to be filaments of the red alga Audouinella hermainii, which also smothered many of the stones.

Audouinella hermainii epiphytic on the moss Fontinalis antipyretica in the River Cocker, just downstream from Crummock Water, April 2014.  The photo at the top of the post shows the site where this photograph was taken.

The growths on the stones looked different to those on the mosses, with longer filaments and a brownish, rather than red, colour.  The colour difference may simply be due to the balance between reflected and transmitted light in the two locations; however, the difference in growth form between the two habitats is harder to explain.  In the River Ehen the same alga (so far as I can tell) has the habit shown in the top photo, but here growing on rocks rather than on mosses (see “Not so bleak midwinter?”)

The other complication is that, in the River Ehen, Audouinella hermainii is extremely abundant in the winter and early spring but is not visible between about May and August, after which it starts to become obvious again.   The growths I saw last week were not the first records from this site, but they are both the most abundant records and the only time it has been so prolific this late in spring.   I also found one record from the River Crake, just below Coniston Water, where A. hermainii was prolific in June.  What’s more, neither the Freshwater Algal Flora of the British Isles nor West and Fritsch’s Treatise on the British Freshwater Algaemakes reference to this species having a particular predilection for winter and spring.   The former says it is “… most common as an epiphyte on … bryophytes” whilst the latter says “… usually attached to rocks and stones in rapid rivers”.   Both agree, however, that it is more likely to be encountered in streams and rivers than in lakes.  It is the Ehen that seems to be the outlier, but it is also the river where I find it most often, hence my inference about its seasonality.   

Audouinella hermainii on stones in the same stretch of the River Cocker as the epiphytic growths in the previous photograph.   

Another reason for treading cautiously is that the red algae present us with some particular challenges when it comes to identification (see “Something else we forgot to remember” and “Reflections from the trailing edge of science”).   Although the view through a microscope shows similarities amongst these populations, these differences in habit and seasonality make me question whether I am looking at the same organism across all these locations. 

I’m conscious that my understanding of this species is drawn from records from a limited geographical area.  On the other hand, the “big picture” for other people may encompass different sites to mine but, I suspect, will include fewer records from the depths of winter.   Then again, mid-winter and early spring in rivers flowing out of lakes will have quite different thermal and hydrological characteristics to the same seasons in unregulated streams flowing off the Alps, for example.   Is anyone’s “big picture” ever big enough to make generalisations?

Vegetative filaments of the red alga Audouinella hermainii from the River Cocker, just downstream from Crummock Water.   Scale bar: 20 micrometres (= 1/50^th of a millimetre).  

There are certain other algae that I also associate with late winter and early spring (Ulothrix zonata, Draparnaldia glomerata, for example).  However, most of these turned out to show similar patterns to Audouinella hermainii when I collated my data, with just enough outliers to confound my expectations.  The likelihood is that these plants do not have circannual rhythms hard-wired into their physiology, but are opportunistic, reacting to circumstances.  Their optimal conditions may be more likely to occur at particular times of the year, but there are also exceptions, giving rise to my observations last week.   

That unpredictability is what keeps me wanting to head out into the field, even when the weather is not ideal.  It is also a reason to want to keep going back to the same sites, so that I can watch patterns unfold, and also a reason to want to visit different sites, so that I can fit my observations drawn from a limited area into a broader perspective.  Beware the ecologist who speaks with too much confidence.  The chances are that they are not spending enough time getting cold and wet in the field.   

Records of Audouinella hermainii from West Cumbrian rivers and streams, 2020 – 2022.  The y axis shows the cover of the alga using the 9-point scale adopted for macrophyte assessments in the UK.   Vertical lines indicate the twelve months of the year.  

Some other highlights from this week:

Wrote this whilst listening to:  Easter music: Stanier’s Crucifiction and Bach’s St Matthew’s Passion.

Currently reading:   Still Colm Tóibín’s The Magician.

Cultural highlight: The Raphael exhibition at the National Gallery.   

Culinary highlight: Grilled mackerel on Asian salad, prepped and made at the Cordon Bleu cookery school in London during a short course on knife skills.

The first Hilda Canter-Lund competition winner

Before we put the Hilda Canter-Lund competition to rest for another year, I thought I would dig out the very first winning entry to see how much had changed over the ensuing years.  The British Phycological Society ran the first competition in 2008 not as an open competition to which people submitted their images, but as a prize for the micrograph published in their journal, the European Journal of Phycology, that was “judged best with respect to a combination of scientific, technical and aesthetic merit”.  David Mann and I scoured through the 2007 and 2008 issues of the journal and selected the image above as the winner.   It comes from a paper by Conxi Rodríguez-Pieto, D. Wilson Freshwater and Noemí Sánchez on the morphology of the red alga Gloiocladia repens and is shows a fusion cell, one of the early post-fertilisation stages.   The scale bar in the bottom left corner is 50 micrometres (= 1/20^th of a millimetre).

Strip away the explanatory labels and you are left with a pleasing abstract monochrome composition dominated by a vaguely tree-like structure.   You do not need to know anything about the reproductive biology of red algae to find some aesthetic pleasure from this image.  However, images in a scientific journal are not supposed to stand in isolation.   They are loaded with significance which the viewer needs to be able to decode and come alive through interplay between the image and text.  The viewer, indeed, needs to bring considerable prior knowledge to the text itself: the European Journal of Phycology serves as a conduit for new knowledge, not as a means of explaining basic principles of red algal reproduction to the uninitiated.   Whereas the fine artist might regard abstraction as a mental exercise unconstrained by reality, this image, however “abstract” it may appear to the uninitiated is, in fact, representational (see “Abstracting from reality …”).

We recognise images as depictions of particular objects by a mental process of matching our sensory perceptions to impressions (“schemata”) stored in our memories.   Similar processes now take place automatically using computer algorithms and, as an indication of how far this image is from the mainstream, the alternative text suggested by my computer (to be used in situations where the image itself cannot be displayed) was: “A picture containing nature, pizza, rain sitting …”

After this first exercise, we rethought the competition.  Offering the prize only to published images in the European Journal of Phycology was limiting because the images were only ever selected for their role in a larger story.  The aesthetic qualities of the image were always secondary to this purpose and we closed off significant pathways of visual exploration in the process.  So the following year, we ran it as an open competition and invited entries from the entire phycological community.   That attracted over fifty entrants and the format has stayed more-or-less unchanged ever since.

Reference

Rodríguez-Pieto, C., Freshwater, D.W. &  Sánchez, N. (2008).Vegetative and reproductive morphology of Gloiocladia repens (C. Agardh) Sánchez et Rodríguez-Prieto comb. nov. (Rhodymeniales, Rhodophyta), with a taxonomic re-assessment of the genera Fauchea and Gloiocladia.  European Journal of Phycology 42: 145-162.

 

Some other highlights from this week:

Wrote this whilst listening to:   Gaslighter, the new album by The Chicks and Jarvis Cocker’s Beyond the Pale

Cultural highlights:  we’ve been watching Life on Mars, the TV series about a detective who travels back in time to the 1970s.  Like Mad Men, it manages to trigger simultaneously a sense of nostalgia and an awareness of the casual sexism and racism that were rife at the time.  We’ve come a long way, though that does not necessarily mean that we have come far enough …

Currently reading:   Utopia Avenue, the new novel by David Mitchell

Culinary highlight:  I have a painful mouth ulcer, so eating is a chore rather than a pleasure just at the moment, I am afraid.