Not quite a coral reef …


Working on the principle that we usually pass only a handful of people during our walks in Upper Teesdale we decided that this counted as “social distancing” and headed off to the hills.  Whether this is still deemed to be acceptable behaviour this week is another matter, but I can report that Teesdale in midweek was certainly far less crowded than the tourist honey-pots that were the focus of so much bad press over the weekend.   But I digress.

Our regular beat follows the Pennine Way for a long stretch with the River Tees on our left and the looming cliffs of Falcon Clints on our right.   Just before the Pennine Way gets to this section, however, the valley is broader, with a flat floor that is used as grazing land by Widdybank Farm.  A small stream, Fold Sike, flows off Widdybank Fell and crosses the Pennine Way at an oblique angle before joining the River Tees.   I’ve walked past it many times, mentally noting prolific growths of a broad leafed Potamogeton as I press on, but little else.  Today, however, my eyes were caught by light-coloured crusts on many of the basalt stones just below the surface of this shallow stream.   If you look closely at these crusts you’ll see that they are not homogeneous: there are distinct nodules on their surfaces and they are more prominent on the edges, rather than the tops, of the stones.  You’ll also see a distinct green tinge in some areas.


Potamogeton and Homoeothrix crustacea growing in Fold Sike, Upper Teesdale (NY 834 292) in March 2020.   The photograph at the top of the post shows the view looking back down the valley from Fold Sike with Widdybank Farm in the distance.


A basalt cobble from the bed of Fold Sike showing the surface nodules and the greenish tinge to the crust.  

This crust is distinctive: I know from previous encounters that it is formed, primarily, of the cyanobacerium Homoeothrix crustacea, a member of the Oscillatoriales (see “Shuffling the pack”).  I also know that it is a beast to photograph, having very narrow filaments and, in this case, also is extensively calcified.  I describe the process of calcification of Chara in “Everything is connected” and the same principles are likely to apply here too.   the I did try to dissolve away the calcite with some vinegar, but without much success in this case.  I’ve included some photographs of another species below, and you can see yet another species of Homoeothrix in “Algae from the Alto Duoro”.   The microscopic image shows the characteristic tapering filament combined with the absence of a heterocyst.  In the far past, Homoeothrix was thought to be a heterocyst-free relative of Calothrix, rather than a tapering relative of Oscillatoria and Phormidium.


Some images of Homoeothrix: a. Homoeothrix crustacea encrusting a boulder (approximately 40 cm across) from a calcareous stream in Cumbria, UK; b. filaments of H. fusca from a crust on Whitbarrow tufa stream, Cumbria (scale bar: 100 micrometres, 0.1 millimetre); c: close-up of a single trichome from the same stream. Note the distinctive tapering and absence of a heterocyst (scale bar: 10 micrometres, one hundredth of a millimetre).

The greenish patches on the surface of the crust were mostly composed of the green alga Bulbochaete (discussed in more detail in other posts – see “A winter wonderland in the River Ehen“) and I also saw a number of diatoms, principally Achnanathidium minutissimum and Delicata delicatula.  The latter, formerly included in Cymbella, is a common species in streams hereabouts, though relatively uncommon in the UK as a whole.  I also saw a few trichomes of a member of the Rivulariaceae, though did not find any intact colonies.  Were this a warm, shallow maritime environment a few dominant calcifying algae that create a habitat for a range of other species would be called a “reef”.  That word stretches the imagination when applied to a small windswept sike in upland County Durham, but the processes are the same even if scale and context are very different.   However, what with all the travel restrictions and closed borders at the moment, this might be the closest any of us will get to a coral reef for quite some time …


Delicata delicatula (?) from Fold Sike, March 2020.   Scale bar: 10 micrometres (= 1/100th of a millimetre).

Some other highlights from this week:

Wrote this whilst listening to: Bob Dylan’s first two albums.  One of my projects for the next weeks is to listen to all Bob Dylan’s albums sequentially.  Tony Allen and Hugh Masekela’s latest album, Rejoice, is also well worth a listen.

Cultural highlights:  The Perfect Candidate.  A Saudi film about a female doctor battling misogyny to get elected to the local council.   Under normal circumstances we would probably have ventured up to the Tyneside Cinema in Newcastle to see this.  Instead, we streamed it via Curzon Home Cinema.

Currently reading:  Still ploughing through Hilary Mantel’s The Mirror and The Light.  Oddly, despite the enforced isolation, I don’t seem to be finding much time to read at the moment.

Culinary highlight:   The bad news is that Durham Indoor Market has finally succumbed to the inevitable and closed its doors, taking with it most of our opportunities to buy non-supermarket food.   That means that the risotto we cooked with a stock made from the leftovers from last weekend’s prawns probably wins the “culinary highlight” this week, if only because it may be some time before we can make another.



How to be an anchorite (1)


Having worked from home for almost 25 years, I feel that I ought to have some wisdom to impart as the whole country is encouraged to minimise unnecessary contact with others.  The truth is that I am so normalised to an eremitical working life that it is hard to compare and contrast my experiences with life in an office.   That means that the addition of a “(1)” to the title of this post may be optimistic and I will get back to the core business of this blog next week.

My period of freelance home working has straddled the digital revolution so that, in 1995, almost nobody in ecology communicated by email whilst today, obviously, email is ubiquitous.  In 1995 I often walked to the Post Office twice a day; now, it Is more like once a fortnight.   I regularly travelled up and down the country by train whereas now, I am more likely to join meetings by Skype, Zoom or Teams.   A wise person wrote on Twitter last week “I think what we’ll discover over the coming weeks is both the undiscovered potential of digital tools, and their limitations in the long term as a replacement for literally being physically in the proximity of other human beings”.  I agree totally except that, I think we know enough already to draw some general conclusions.

Online meetings work really well when all involved have stable internet connections and plenty of bandwidth, when the video displays are large enough to detect body language (never the case when many people are involved), when the participents know each other and when all are working to a common goal.   However, much we try to reduce our carbon footprints, I think there are benefits associated with meeting in person at least once a year, and in including some downtime to enable us to get to know each other better.  Working remotely through digital tools proceeds much better when there are also periodic face-to-face interactions..

I wrote about the opposite situation recently in an opinion paper for Metabarcoding and Metagenomics.   There were several layers to the situation I describe but over-reliance on digital communication rather than face-to-face gatherings played a contributory factor, particularly in the latter stages.   Several of the rules I outlined in the previous paragraph were flouted, but most important from this perspective, we were not working to a common goal.  The project we were discussing had several controversial elements and not everyone agreed that the time was right to push ahead.  Additionally, not everyone understood the nuts and bolts of the technical issues that needed to be addressed and the meetings were structured for “deciding”, not “learning”.

Despite this, I’m largely optimistic about the prospects of working with digital tools such as Skype, Zoom and Teams.  The problems lie, as ever, not with the tools themselves but with how they are used.   The problem I discussed in my Metabarcoding and Metagenomics essay was primarily about the management of change which is never easy, even when you are given plenty of time.   The shift to working from home has happened so quickly that mistakes are bound to be made.   However, one easy lesson is that, even with perfect digital set-ups and plenty of bandwidth, now is probably not the time to push ahead with new, contentious or divisive projects.  Put them on hold or, if that is not possible, adjust your deadlines to allow plenty of time for learning and consensus-building.


The picture at the top of the post shows the west end of St Mary and St Cuthbert’s church, Chester-le-Street, County Durham.   A medieval anchorite’s cell (now a museum) can be seen on the right-hand side of this image. []


Some other highlights from this week:

Wrote this whilst listening to: the news.  Isn’t everyone?

Cultural highlights:  The Florida Project, a 2017 film by Sean Baker.  Opinion hereabouts is divided about whether this is as dark as or somewhat lighter than Ken Loach’s recent films.   The underlying story is very dark but there is a vein of humour running through it and it set in the bright Florida sunlight.

Currently reading:  Still reading Hilary Mantel’s The Mirror and The Light

Culinary highlight:   A combination of limited availability of pasta in the supermarkets and abundant time on my hands seems like a good reason to make my own tagliatelle.   Combined it with prawns and rocket (and chilli) following a recipe in a Jamie Oliver cookbook.   The prawn trimmings made a rich stock which we’ll use next week.  Hooray for “slow food”!

Disagreeable distinctions …

When you look at an organism, how do you know what it is?   That’s a big question that hovers over many of the posts that I write.   I tell you the names of organisms and you believe me. Sometimes I do too.   The truth is that we take the way that our brains process the constant stream of signals that our eyes send us as we observe the natural world without a second thought.   The subject intrigues me, but I only manage to scratch the surface in the posts that I write (see “Abstracting from reality …” and “Do we see through a microscope?” for some of these speculations).

The plate below offers a case study in this process.  It shows a diatom we encountered in a recent ring test, and which most us agreed was either Fragilaria austriaca or something quite similar.   In binary terms, though, we have to be blunt: either it is Fragilaria austriaca or it is not which may have implications for subsequent recording and interpretation (see “All exact science is dominated by the idea of approximation”).   How come a group of experienced analysts can look at the same population of diatoms and reach different conclusions?   I’ve got two suggestions: the first is that we differ in how we process the images, and the second is that there are sources of systematic error which confound our attempts to seek the right answer.


Fragilaria austriaca” from Foreshield Burn, Cumbria, May 2019.

There are three basic strategies that we use to name an organism:

  • Probabilistic reasoning, through the use of keys which, in theory at least, have a logical structure that guides a user to the correct identity of an unknown specimen. In practice, this is not quite as straightforward as it sounds (see “Empathy with the ignorant …”) and, at some point, many of us will abandon the formal structure of a key and switch to …
  • Pattern recognition, which amounts to flicking through images until we find one that matches our specimen. We can then corroborate this preliminary match by checking the written description.  In practice, we will probably switch from probabilistic reasoning to pattern recognition and back again as we home in on the identity of an unknown specimen. Repeating this process several times will lodge a schemata of this species in our memories, leading to a third strategy:
  • Recall. In practice, most of us probably have seen many of the common and even less-common species so often that we can by-pass these first two steps completely because we recognise the species without recourse to any books.

Disagreements, then, arise partly because we use different books as part of our naming process, our prior experiences differ and because our discipline in checking measurements of our own specimens against descriptions is not always as good as it should be.   In many cases, especially with modern understanding of diatom species, boundaries between species are frequently being redrawn and descriptions of newer species can only be found in obscure journal articles, often behind paywalls, and knowledge of these often diffuses through the community of diatomists more slowly than it should.   However, our discussions about the identity of the mystery Fragilaria also revealed a further issue, which I’ve illustrated in the graph below.

When we switch from “pattern recognition” to “probabilistic reasoning” we often base decisions on categoric distinctions of continuous variables such as length and width.  In this case, the literature quotes a maximum width of four micrometres for F. austriaca, and this was an important factor contributing to decisions about the correct identity.  However, there were differences in our measurements which means that some decided that the population was too broad to qualify as F. austriaca whilst others decided that it fell within the correct range.   The likelihood, based on these graphs, is that at least some of us were making incorrect measurements but, at this stage, we don’t know who they are.


Measurements of width, stria density and length of the population of “Fragilaria austriaca”.  Six analysts were involved in total, using either the eyepiece (“E”), an image projected onto a screen (“S”) or a measuring program (“P”) to make measurements (some used more than one approach). The dashed lines show the upper and lower limits for each parameter.

But that, itself, brings me to another point: do we know the correct size range of Fragilaria austriaca?  In order to be sure, we would need measurements of both initial cells (the largest in a cell cycle) and cells at the point where they are about to undergo sexual reproduction (the smallest in the cell cycle), ideally from several populations.  As this is rarely the case, we actually have three problems: first, is the description reliable? Second, are your measurements accurate? Third, we are using a point on a continuous scale as a criterion for a categorical judgement which implies perfect knowledge of the size range of the target population.  Even if you are sure of your microscope’s calibration, the best you can say is that the largest valve that you saw in the sub-sub-sub-sub-sub-sub sample of the population that lived in the stream you sampled exceeds (or not) the largest valve that the original author measured in the sub-sub-sub-sub-sample that s/he examined.   Several of our measurements just tip over four micrometres, the maximum width quoted in the literature for Fragilaria austriaca but, given these other factors, is that enough to drive a decision?   Statisticians are more comfortable predicting means, modes and medians than predicting extreme values.   Taxonomists, by contrast, seem to have undue reverence for maxima and minima.

Molecular biologists are approaching similar questions with considerable vigour.   The arrival of metabarcoding and high throughput sequencing means that they have had to write complicated computer code (“bioinformatics pipelines”) to sort the millions of sequences that emerge from sequencers, matching as many as possible to sequences from organisms whose names we already know, in order to turn those sequences into data that biologists can use (see “When a picture is worth a thousand base pairs …”).   We are conscious that decisions about software and settings within packages contribute to variations in the final output for reasons that we cannot always answer to our satisfaction.  But, whilst engaged in these discussions about cutting-edge technology, I’m conscious that old-school biologists such as myself each perform our own private “bioinformatics” every time we try to name an organism and we don’t always agree on the outputs from these thought processes.   Molecular biology, in a roundabout way, holds up a mirror to the way that we’ve been used to operating and should make us ask hard questions.

Some other highlights from this week:

Wrote this whilst listening to: my elderly vinyl copy of Mike Oldfield’s Tubular Bells

Cultural highlights:  Milton Jones at Newcastle City Hall

Currently reading:  Hilary Mantel’s The Mirror and The Light

Culinary highlight: polenta served with a mushroom and cheese sauce.

Finally, breaking news: I’m going to be live at the Green Man festival this August.  More details of our event “Slime Time”, and all the other performers at Einstein’s Garden can be found here


When a green alga is not necessarily a Green Alga…


I will end this short series of posts on the organisation of the major groups of algae with a look at the Xanthophyceae, or yellow-green algae.   My old copy of West and Fritsch’s Treatise on British Freshwater Algae from 1927 includes this group of algae with the green algae, although we now know that, apart from a generally green appearance, these two groups of algae have very little in common.  The big differences lie, however, in the types of details that are beyond the purview of the casual natural historian, so you may well find yourself flicking back and forth between “green algae” and “yellow-green algae” as you try to put a name on a specimen.  The definitive test is to add some iodine to your sample, as the Xanthophyceae do not produce starch as a storage product, and so do not produce the characteristic blue-black colour in the cells.  However, iodine is messy stuff and most of us will struggle along without for as long as possible.

The five orders of Xanthophyceae are shown in the table below.   In contrast to the case for most algal groups where molecular studies have led to many revisions of traditional classifications, the Orders of the Xanthophyceae have proved to be quite robust when subjected to this type of scrutiny.   Two of the Orders have siphonous organisation, though the form that this takes is very different in each (see “The pros and cons of cell walls” for more about siphonous lifestyles).  Tribonematales is an Order of filamentous algae that can be difficult to differentiate from filamentous green algae, whilst the Mischococcales are easily confused with small Chlorophyceae.


The organisation of the Xanthophyceae into five orders.  Organisation follows Algaebase.   The image at the top of this post shows Tribonema smothering the surface of a pond in Norfolk (photo: Geoff Phillips).

That’s one of the mysteries of freshwater algae: to the lay observer, an organism such as Vaucheria looks very similar to Cladophora or another green alga.  Yet they are distant relatives, belonging to different Kingdoms (Chromista and Plantae respectively).  That means that they share the same genetic affinity to one another as they do to us, which is a staggering thought (see “Who do you think you are?”).   What we are seeing is two organisms supremely well adapted to living in similar habitats, which means that natural selection has, gradually, shaped two quite distinct gene pools in quite different ways to arrive at the same end-point.   Just as motor manufacturers have, in the hatchback, found a style of car that is well-adapted to urban living, so the rival algae manufacturing corporations (“Plantae Inc” and “Chromista plc”) have come up with two broadly similar models that are both well-adapted to life in lowland streams.  Just as, in the case of hatchbacks, you can lift up the bonnet and see differences in the engine (petrol, diesel, hybrid, electric) but within the same basic shape, so many of the big differences in algal groups concern their internal machinery not outward appearances.


Reproductive structures growing from a filament of Vaucheria frigida (photo: Chris Carter)


Maistro, S., Broady, P.A., Andreoli, C. & Negrisolo, S. (2009).  Phylogeny and taxonomy of Xanthophyceae (Stramenopiles, Chromalveolata).  Protist 160: 412-426.


Links to posts describing representatives of the major groups of Xanthophyceae 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
Botrydiales Botryidium: The littoral ecology of Lough Down
Mischococcales Watch this space …
Rhizochloridales Watch this space …
Tribonemetales Tribonema: Survival of the fittest (1)
Vaucheriales Vaucheria: When the going gets tough …

Some other highlights from this week:

Wrote this whilst listening to: Two Hands, by Big Thief

Cultural highlights:  Jon Hopkins at the Sage.  What Radio 3’s Ibiza night might sound like.

Currently reading: the last few pages of Bill Bryson’s The Body: A Guide for Occupants (454 pages) prior to starting Hilary Mantel’s The Mirror and The Light (904 pages)

Culinary highlight: fish pie.  Spécialitié de la maison.


Shuffling the pack


The next group of algae I’m going to consider in my review of higher taxonomy and systematics, the Cyanobacteria, or “blue-green algae”, present some significant challenges.  Not least of these is a shift over the past forty years from being classified according to the rules of botanical nomenclature to being classified according to the International Code of Nomenclature of Bacteria.  The former assumed species could be defined from field material on the basis of morphology, with “type specimens” preserved in herbaria; the latter uses axenic (i.e. pure) cultures as the basic taxonomic unit, and allows a wider range of attributes than just morphology.   In recent years, as those who follow this blog will know, properties such as gene sequences have also been used to define species although the Code of Botanical (now Biological) Nomenclature still requires a description of the any new species that are described, with an expectation that the morphology will take a prominent role in that description.  As this post will show, morphology is no longer such a reliable indication of how Cyanobacteria are organised as it was in the past.

For practical purposes, many Cyanobacteria fall into the same size range as other algae, live in communities that include many protist groups and can be identified using similar techniques as would be employed to identify other algae.  They also have a form of photosynthesis that produces oxygen as an exhaust gas, in contrast to other bacteria which are capable of photosynthesis. This means that a default view of the Cyanobacteria as “algae” is a reasonable starting point for a field ecologist.   However, at an intercellular scale, the Cyanobacteria are very different to other algae, and we should never lose sight of the fact that they actually belong to a different Domain to other algae.

The problems are clear when I compare the morphology-based classification that I used when I first taught classes on algae in 1990 with the classifications that are accepted now.  Then, Cyanobacteria were divided into three or four orders, typically:

  • Chroococcales – single cells or cells loosely-bound into irregular gelatinous colonies
  • Oscillatoriales – filamentous forms lacking heterocysts
  • Nostocales – filamentous forms with heterocysts

The high-level classification, in other words, was based solely on whether or not the organism formed filaments and, if so, whether or not it possessed heterocysts (specialised cells responsible for nitrogen fixation).  This made logical sense when your primary source of insight is morphology.  Unfortunately, more recent studies have shown that it bears little relationship to the genetic relationships amongst the organisms that have been revealed over the past thirty years or so.   A more recent organisation is given in the diagram below.

First, note that this shows subclasses, rather than orders, within the class “Cyanophyceae” (the only class in the division Cyanophyta).   There is rarely unanimity amongst experts on the appropriate organisation of high-level classifications so just bear with me on this one.   Of the four sub-classes, one, Nostocophycidae, contains a single order (Nostocales) which includes all the heterocyst-bearing forms.  No change there.   However, the other two classes diverge very much from the older classifications in that they both contain a mixture of filamentous and non-filamentous forms.


The organisation of the Cyanobacteria (blue-green algae) division into four sub-classes.  Filled boxes indicates the classes that are represented in UK and Irish freshwaters.   Organisation follows Algaebase.   The image at the top of this post shows a Microcystis bloom at Ladybower Reservoir (photo: Chris Carter)

The Oscillatoriophycidae is a good example, with five sub-classes, four of which are represented in the UK and Ireland.  Two of these have featured in several posts (see Appendix) so you can see for yourself just how different they are in appearance.  The Oscillatoriales includes filamentous forms without heterocysts whilst the Chrococcales has taxa that either exist as single cells or in masses loosely-bound within gelatinous colonies.    A similar situation exists within the Synechococcophycidae; indeed, some genera that would formerly have been considered to be relatives of taxa within Oscillatoriales (e.g. Schizothrix and Heteroleibiana) are now included in families in this group.   There is, however, still more work to be done to unravel all the relationships within this sub-class.   The current understanding is that there is a single order (“Synechococcales”) but a great number of families.  Similarly, all the heterocystous forms are grouped into a single order, the Nostocales, within the Nostocophycidae, also divided into a large number of families.


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

I always stress that taxonomy and identification are two distinct crafts: the taxonomist calls on a wide range of tools to find natural groupings of species at different levels whilst an ecologist only needs a parsimonious route to an unambiguous identification.  For the purposes of identification, recognising whether an organism is filamentous or not is a logical early step, even though both options will contain representatives of both Oscillatoriophycidae and Synecchococcophycidae.   We need to recognise that some of the characteristics that contribute to our taxonomic understanding (gene sequences, arrangement of thylakoids) are useless from the point of view of someone trying to name an organism encountered in a field sample but, at the same time, the taxonomist’s standpoint will not necessarily capture all of the features that explain how an organism contributes to energy and nutrient flow within ecosystems.


Calothrix stagnalis: a member of the Nostocales.  Note the heterocysts at the base of the filaments (photo: Chris Carter)


Mai, T., Johansen, J.R., Pietrasiak, N., Bohunciká, M. & Martin, M.P. (2018).  Revision of the Synechococcales (Cyanobacteria) through recognition of four families including Oculatellaceae fam. nov. and Trichocoleraceae fam. nov. and six new genera containing 14 species.  Phytotaxa 365: 1-59.

Palinska, K.A. & Surosz, W. (2014).  Taxonomy of cyanobacteria: a contribution to consensus approach.  Hydrobiologia 740: 1-11.


Links to posts describing representatives of the major groups of Cyanobacteria 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
Synechococcales Chamaesiphon: A bigger splash

Heteroleibleinia: River Ehen … again

Chrococcales Aphanothece: No excuse for not swimming …

Gloeocapsa: The mysteries of Clapham Junction …

Oscillatoriales Microcoleus: How to make an ecosystem

Oscillatoria: Transitory phenomena …

Phormidium: In which the spirit of Jeremy Clarkson is evoked …

Pleurocapsales Watch this space …
Spirulinales Spirulina/Arthospira: Twisted tales …
Nostocales Nostoc: How to make an ecosystem (2)

Rivularia: Both sides now

Scytonema, Stigonema, Tolypothrix: Tales from the splash zone

Some other highlights from this week:

Wrote this whilst listening to: Leonard Cohen’s posthumous album Thanks for the Dance.   And, as I used it to name a post, Joni Mitchell’s Both Sides Now.

Cultural highlights:  David Hockney: Drawing from Life at the National Portrait Gallery.   Great examination of the importance of drawing and observation to artistic practice.   By coincidence, another post I’ve cited is named after one of Hockney’s paintings

Currently reading: Robin Wall Kimmerer: Gathering Moss (Oregon State University Press).  A collection of essays on the natural and cultural history of mosses.

Culinary highlight: dinner at The Sichuan on City Road in London.


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

Policy-based evidence?

In my day job as an ecologist I spend a lot of time thinking about how energy and nutrients flow through ecosystems.  Understand this and it should be possible, in theory, to provide guidelines for how we move to a more sustainable future.  However, communication of ecological principles is often a frustrating business, especially when your audience is government officials balancing scientific evidence with other policy concerns.   The organisations I work for pay lip-service to “evidence-based policy” yet, somehow, fail to react in the way I expect when confronted with strong evidence.

Some of my frustration, I realise, comes from not fully understanding how evidence moves through the complex human ecosystems of government agencies, the businesses whose actions they regulate and the stakeholders whose lives are affected by decisions. I’ve written about this before (see “The human ecosystem of environmental management” and subsequent posts) and find that ecological cycles can form powerful metaphors for understanding information flow and, as a result, how we can communicate important results.   It also, as I will show, helps us understand when to recognise that the argument does not hinge on scientific evidence but on powerful institutional barriers.

The graph at the centre of the diagram below comes from a paper that I co-authored as part of my work with the European Commission and describes the relationship between aquatic plant communities (“Macrophyte EQR”) and total phosphorus in shallow lakes in north-west Europe.  It formed part of a bigger project to help Member States set environmental standards.    The point of my diagram is to show how ecological evidence (represented by our graph) is nested within a series of other considerations which often lead to the decision the evidence points towards being over-ruled.


Regulation in the face of noisy ecological data: ring 1 represents environmental targets; ring 2 is the regulatory framework; ring 3 is national policy (water pricing and the cost recovery framework in particular) and ring 4 is society’s environmental aspirations.

The process works something like this: ecology is not an exact science, but we could use this graph to justify a maximum permitted total phosphorus concentration of about 60-70 micrograms per litre in these lakes (1: the innermost ring).   This, then, converts into a series of consents and licenses for businesses that discharge into the catchment and, potentially, into encouragement for farmers to sign up to countryside stewardship schemes (ring 2).  The carrots and sticks that make up this regulatory framework then fit into a broader framework of environmental management that embodies the “polluter pays” principle (ring 3).  Finally, this broader framework reflects, to a greater or lesser degree, society’s aspirations for the environment (ring 4).

Protecting and restoring lakes and rivers, then, depends on society as a whole regarding the environment as a high priority (4) and being prepared to pay for this (3).  We could refer to this as an effective environmental aspiration*, as distinct from everyone talking the talk on social media but carrying on with unsustainable practices in their everyday lives.  Once people recognise their own agency, then the “polluter pays” principle should be easier to enact and utility companies will be less inclined to challenge the regulator because they know they can recover their costs (2).

If, on the other hand, the link between rings 4 and 3 is weak, and that there is pressure to reduce utility charges (as is the case in the UK at the moment for reasons that go beyond the subject of this post), then decisions within individual catchments will be less straightforward and the targets themselves will become the subject of greater scrutiny.

The graph at the centre of the diagram is typical of the evidence that we have to use in situations such as these.   There is not a perfect relationship between biology and nutrients (only 43% of the variation in EQR is explained by total phosphorus) so it is hard for catchment managers to tell stakeholders that a reduction in phosphorus loading will definitely lead to an improvement in ecology.  Ecologists never work with the certainty of engineers; we deal in probabilities.  We can say that if this reduction was enacted across the whole country then many lakes would show improvements but may be hard to be specific on a local scale.   Given the costs involved in producing these reductions, the temptation is to play safe.

Playing safe starts with the graph itself.   If you can only explain a proportion of the variation in Y from X then there are, invariably, loose threads that can, with a little tugging, unravel the argument.  In this particular case, there is a substantial body of experimental evidence behind the relationship but, even so, the targets derived from these relationships often translate into significant challenges for both regulators and regulated.    It is often far easier to kick the can down the road: easily achieved these days by prioritising other tasks for the limited pool of technical specialists employed by our environmental agencies.

I started this post by drawing metaphors from ecology in order to understand the process of environmental management.  The analogy I see here is that of equilibrium: imagine the barriers between the rings as a series of membranes: society’s aspirations flow towards the centre and, if these are high and all the intermediate stages are in equilibrium, then our graphs are powerful evidence for moving towards a healthy, sustainable environment.  As soon as there is disequilibrium (e.g. high environmental standards versus a low willingness to pay for improvements in utility infrastructure), however, all the intermediate steps become adversarial rather than consensual and the noise inherent in ecological relationships becomes a pawn in political and bureaucratic games.

* analogous to the economist’s concept of “effective demand”


Poikane, S., Phillips, G., Birk, S., Free, G., Kelly, M. G., & Willby, N. J. (2019). Deriving nutrient criteria to support ʽgoodʼ ecological status in European lakes: An empirically based approach to linking ecology and management. Science of the Total Environment, 650.


This week’s other highlights:

Wrote this whilst listening to: Jeff Beck Group’s Beck-Ola from 1969.   (Just bought tickets to see Jeff Beck at the Sage in May, so celebrations were in order).

Cultural highlight:  The Strange Case of Charlie Chaplin and Stan Laurel at Northern Stage in Newcastle, during which I was hauled up on stage to play piano (photo below).   I can’t play piano but they showed me what two notes to play and when.   Figured that if I can’t face this, then I shouldn’t have signed up to a live microscopy “performance” at Green Man this summer.

Currently reading:  Brooklyn by Colm Toíbín

Culinary highlight: a self-baked lime and coconut drizzle cake.