The “thirty-three percent rule” re-visited

Having expressed some forebodings about UAMRICH in an earlier post (see “The human ecosystem of environmental management …”), I can now re-visit those concerns with the benefit of hindsight and, in particular, see if the “thirty-three percent rule”, which I proposed a couple of years ago, works or not.   If you recall, this is my suggested ratio of academics and end-users necessary to generate fertile discussions in applied science meetings.

There did seem to be some fertile discussions, during both formal sessions and social events, and a willingness to question existing dogmas and to explore new ideas (such as the application of Next Generation Sequencing). Moreover, most of the discussions were firmly grounded in the frameworks provided by current legislation (the Water Framework Directive in Europe and the Clean Water Act in the USA).   The days when someone would stand up and talk for twenty minutes about “biomonitoring” unencumbered by irksome details such as what the legislation actually says do seem to have passed.

So where did all the participants come from?   Analysing the participant list in the back of the abstract booklet, I see that the largest contingent (half of the total) come from universities, with the remainder split almost equally between museums, research institutes, consultants and regulators.   Sorting these into a straight binary divide between “academics” and “practitioners” isn’t straightforward: some university academics are deeply involved in advising regulators and other end-users, whilst some of us in the “consultants” category are capable of writing quite abstract scientific papers from time to time. However, a crude categorisation of “academics” as university and museum staff, and “practitioners” as everyone else gives us a ratio of 41:23, which is pretty close to my thirty-three percent rule.   This assumes that those from research institutes are primarily engaged in applied research. If we include this group with the “academics”, the ratio drops to 49:15, suggesting that my “thirty-three percent rule” should be re-cast as the “twenty five percent rule”.   A few university and museum staff were at UAMRICH primarily for the taxonomic sessions which occurred at the end of the week, and this may have affected the ratio.  Nonetheless, I think my original point still stands: that if you are discussing the application of science to a real-world problem, you have the best discussions, and most beneficial outcomes, if you have both academic and end-user / stakeholders represented in numbers.


Participants at UAMRICH, Trento, broken down by their employment.

AlgArt: MUSE, Trento, June – July 2015


The spectacular Renzo Piano-designed MUSE in Trento, Italy, with the alps in the background. June 2015.

A little more in this post about the AlgArt exhibition, which I mentioned in the previous post, which is on at MUSE, the Museum of Science in Trento, Italy…   The museum building itself is quite spectacular, having been designed by Renzo Piano, best known for the Shard in London.   One of the themes of my scientific contribution to the meeting was the importance of scientists being able to communicate with the wider world, and the AlgArt exhibition provided an opportunity to put this into practice.

Alongside my own work, there was work by two Trentino-based artists, Viviana Puecher and Maria Giovanna Speranza, as well as by two Innsbruck-based artist-scientists, Doris Gesierich and Werner Kofler, who exhibit as “Duo DOWE”. Their work, “Scacco matto” (“checkmate”), which hung in the atrium of MUSE, juxtaposed diatoms, photographed with the scanning electron microscope, against photographs of the macroscopic world, to create surrealistic montages that played games with viewer’s perceptions.


Duo DOWE’s installation, “Scacco Mato”, in the atrium of MUSE, as part of the AlgArt exhibition, June-July 2015.

Upstairs, Maria Goivanna Speranza and Viviana Puecher had worked together to produce a series of large-format works in mixed media that included images of diatoms into settings that exploited the sensuality of these algae. Alongside these were four of my own works, depicting my own interpretations of underwater algae-filled landscapes.   I’ve written about some of these in earlier posts (see “A winter wonderland in the River Ehen” and “Subaquatic landscapes in Pangong Tso”), and you can buy Giclée prints of these from

The three elements of AlgArt all represented very different journeys: Duo DOWE were scientists talking in the language of modern art, Viviana Puecher and Maria Giovanna Speranza were artists exploring science without the restrictions of formal scientific training, whilst I was a scientist trying to use artistic media to represent the real world. Judging by the number of questions that I had to field (via a translator), the exhibition did manage to excite some interest amongst the visitors. A small step, perhaps, towards my wider goal of raising awareness of the importance of algae?


Another view of “Immaginato ma non immaginario” at MUSE, Trento, June-July 2015 with (on the right) a close-up of two of the works on display.

“Imagined but not imaginary”

One of my tasks during the UAMRICH meeting was to participate in an art-science event at the Museum of Science and Technology (MUSE) in Trento.   I had been wondering what to say at this event and, to be honest, had been so busy with preparing for other meetings and talks, that I arrived in Italy assuming that I would have to make it up as I went along. However, by a fortunate coincidence, I was in Milan at the same time as an exhibition of Leonardo da Vinci’s work was showing at the Palazzo Reale. If one is talking about the art-science interface, what better role model can there be?

What I did not manage to do whilst in Milan, was visit the Last Supper.   Admissions are strictly limited in order to protect this delicate fresco and I left it too late to try to book.   It is, however, sufficiently well known that we barely need an illustration. I did manage to see another of his frescos: the less-well known Salla della Asse in the Castello Sforza, which he covered with depictions of intertwined vegetation. In doing this he created the impression that you were in a pergola, rather than a room inside a castle.   There was no direct link between this room and the Palazzo Reale show but there was a drawing of a lily in the Palazzo Reale that shows how large works such as the Salla delle Asse are informed by his close observation of nature.   He uses drawing as an analytical tool, supporting his observations, and building up an understanding of the interactions between form and function.


The ceiling of the Salla della Asse in Castello Sforza, Milan, June 2015.

We can make links between his anatomical drawings, preparatory drawings where he tested poses and expressions, and his finished works. In our secular age, the symbolism within a work such as The Last Supper is hard to understand, so we look at it purely as a pictorial representation of a mythical event. To unlock the picture, we need to look at it again, from the point of view of a Catholic monk who believes in the real presence of Christ during the Eucharist, and to remember that it was painted on the wall of a refectory. Suddenly, all those hours of observation start to make sense: an anatomically-and perspectively-correct portrayal that brings this most significant of meals into the centre of life in the monastery. The ‘facts’ of his detailed drawings, in other words, build up into a ‘reality’ that is more than the sum of its parts.

If had had a microscope, I am sure that he would have taken the opportunity to examine the floral structure of the lily in yet more detail because his curiosity greatly exceeded the need to inform his painting. But over a century would pass before the first microscope was invented. It means that Leonardo’s concept of ‘reality’ was confined to what he could see with naked eye which, in turn, means that he knows how all of the parts relate to one another when the time comes to reconstruct these into his finished picture.

Many of us in the sciences deal with similar problems, insofar as we have to build the data we collect into a coherent story. Those who read our accounts of this research can then test these stories against their experiences of the natural world. But that is not a luxury that those of us who deal with the microscopic world always have. The process of collecting the sample wrenches the organism from their natural habitat. The material is further distorted as we squash it onto a microscope slide in order to see what we have caught.   We also use unnaturally high light intensities and a suite of other optical tricks. For most scientists, the view down the microscope is the only reality that is available. We try to be objective, which usually involves naming and counting what we see, which is actually a step away from reality and, especially after we have applied our statistical tools, towards abstraction.   That’s okay but, unlike our colleagues who deal with the visible world, we have no mental images of the intact community to help us decode the outcomes.


“Immaginato ma non immaginario”: my contribution to AlgArt at MUSE, Trento, June-July 2015.

I make few claims for my pictures, except to say that they are my own personal view of what these microscopic underwater worlds might have looked like before I disrupted them. I say that they are “imagined but not imaginary” because the pictures are constructed from numerous components that are real. In this way, they are no different from the reconstructions of dinosaurs that we can see elsewhere in MUSE.   They are certainly not definitive descriptions of the three-dimensional structure of the microscopic world.   I invite viewers to disagree with my interpretations, if they wish. That, at least, means that I have made you think a little more about what you see when you peer down a microscope.

Postscript: I wrote this on a coach during a post-conference excursion around some twisting mountain roads. Then, 20 minutes before the event started, I abandoned it and spoke off the cuff instead.

Second term?


The picture above shows myself with Taurai Bere from Zimbabwe at the Use of Algae for Monitoring Rivers meeting in Trento.   Taurai gave an interesting talk on the use of diatoms for biological monitoring in Brazil and Zimbabwe, ending with a call for better interactions between scientists and the general public and decision-makers.   It was a theme that others had already echoed (see previous post) and, for me, is a positive sign that the ecological assessment community is getting more realistic.

His final clarion call deserves repeating: “Those who want a second term need to be convinced that the environment, too, needs a second term.”   The relative indifference of politicians to the environment at the moment seems to be common both in the UK (see “A plague on both their houses …” and “The political landscape isn’t very green …”) and Zimbabwe. That is probably a comparison that David Cameron will not welcome.

But we should not be complacent. The problem is, at least in part, the fault of ecologists who are not able to move their information through the political and administrative “ecosystem” (see “The human ecosystem of environmental management”).   Sorting this one out is going to take a long time, but I’m leaving Trento with some stimulating conversations on which to dwell and a renewed impetus to make sure that everyone understands the importance of algae as a vital component of healthy ecosystems.

So what?


And so to Trento, and the Use of Algae for Monitoring Rivers symposium.   I approached with mild trepidation (see comments in “The human ecosystem of environmental management …”).   The last time I attended, Diatom Jihad was just getting started, and hordes of fundamentalists were swarming over the plains of scientific reason, eliminating any apostates who dared suggest alternative methods of evaluating the condition of freshwaters.   To be honest, I was probably part of that horde, certainly in the early days, though I think that the True Believers always doubted my ultimate loyalty to the Holy Books produced by Lange-Bertalot, Krammer, Witkowski and their acolytes.

I have, indeed, had my own vision on the Road to Damascus (forgive me for mixing my religious metaphors).   It was, in reality, the culmination of several conversations and much thinking but it can be encapsulated by a comment made by a biologist from Wessex Water, one of the utility companies who operate sewage works in the UK. I had been part of a team working on the River Wylye in Wiltshire and we were discussing our results.   She looked up and said (I am paraphrasing now): “I’m not disagreeing with what you are telling us [i.e. that the river had higher concentrations of nutrients than was ideal for the ecology]. But we need to justify the price rises that would result from improved effluent treatment, and the public don’t know what diatoms are”.   She had put her finger on a very major issue: that many of us involved in applied ecology are so focused on the fine details of the ecosystems that we study, that we lose sight of the bigger picture.

I tried to emphasise this in my talk and the cartoon above follows Billy Wilder’s maxim: “If you’re going to tell people the truth, be funny or they’ll kill you”.   And, to be fair, I was not the only person who made this point.   Jan Stevenson from the University of Michigan gave us a good overview of the current situation in the USA and also emphasised the need to relate the changes in diatom assemblages to ecosystem services and, if possible, to determine thresholds in responses that help to develop consensus amongst stakeholders. So perhaps the winds of change really are now blowing on both sides of the Atlantic?

Towards the end of my talk, I used the phrase “healthy streams are slippery streams”, used by Emma Rosi-Marshall of the Cary Institute for Ecosystem Health in New York.   She is using this phrase as part of a campaign to raise awareness of the role that benthic algae play in ecosystem health. Phil Harding, the co-author of my talk, saw this written on one of my slides and commented that one of the sampling locations that his team visit regularly in the English Midlands is called “Slippery Stones” – a beautiful site on the edge of the Peak District. Is it too fanciful to suggest that this place actually has a name that reflects the quality of the freshwater ecosystem?


“Slippery Stones”, the actual place name of a site on the upper River Derwent in Derbyshire, UK.

An image with which to conjure …

I worry that my ruminations on how ecological information flows through the “human ecosystem” of scientists, regulators and policy makers contradicts some of my earlier statements about the importance of field-based biology (see, for example, “Slow science and streamcraft”).   It lies at the heart of another problem: that the need to create reproducible, comparable data across an entire country leads to biologists being reduced to “data monkeys”, optimised to operate as part of a production line that grinds inexorably from sample collection to delivery of results (see the flow chart in the preceding post). How do we ensure that organisations have access to all the knowledge and wisdom that a professional biologist accumulates, and not just to the digestible chunks of “information” that I talked about earlier?

I’m going to try to answer these questions by stepping outside of biology and into the world of organic chemistry, because I think that we need to think from the perspective of an outsider looking into our cherished world. I gave up chemistry at age 16 and was force-fed just enough subsequently to get through my degree and PhD.   However, it is not a world in which I feel comfortable. Yet the regulation of toxic chemicals is just as vital to the well-being of our freshwaters as management of biological communities. The Water Framework Directive, for example, set out some general principles on the management of chemicals which present a significant risk to or via the aquatic environment.   Guidance on these “priority substances” was developed through a series of Decisions and Directives (e.g. 2008/105/EC – see below). The list includes heavy metals such as cadmium, but also a long list of organic chemicals. Let’s take one of these at random: di(2-ethylhexyl)-phthalate, which is widely used as a plasticiser.   No, I didn’t know that either. And, yes, in light of what is to follow, I really did choose it at random.

Suppose someone tells me that the annual average concentration of di(2-ethylhexyl)-phthalate in a local river is 5 micrograms per Litre.   What do I conclude?   Not a lot, unless I also know that the Environmental Quality Standard (EQS) for this compound is 1.3 micrograms per Litre.   In fact, as a non-chemist, all I really need to know is that this river fails the EQS for di(2-ethylhexyl)-phthalate.   In other words, whilst the biologist part of me balks at the idea of reducing detailed data about the composition of the algal community down to a simplistic metric, I am quite happy when other people do this for chemicals, in order to make my life easier.   I can scan down a long list of priority substances, and quickly spot those that present a problem in any particular river.

Let’s take a closer look at what is happening: the EQS is based on a lot of toxicological data.   It is good to know that this has been done, but I don’t actually need any of the details. Nor do I need to know much about the way analytical chemists measure di(2-ethylhexyl)-phthalate.   There is probably a CEN or ISO standard detailing the procedures but for me, as a token end-user, these are details that I don’t need.   All I need to know is whether or not the di(2-ethylhexyl)-phthalate concentrations represent a problem or not and, perhaps, a qualifier (“definitely”, “probably”, “maybe”).   I can then take this desiccated nugget of information and “rehydrate” it (as it were) with appropriate context when needed.   Suffice it to say that there is toxicological evidence linking this compound to decreased penis width. Fifty percent of my readers are now forming a mental image that converts the concentration of this obscure organic compound into a genuine threat to the future of humankind. Don’t pretend that you are not.

The same kind of process should happen in ecology. We take a lot of data that represents a complex idea (the ecological health of a river), distil this into a nugget of information (an Ecological Quality Ratio), then hope that our “customers” (that word again, I’m afraid) can conjure the appropriate mental images in order to use it appropriately.   My colleague Nigel Willby addressed this in an editorial in the journal Aquatic Science and Conservation a few years ago. He pointed out that ecologists work at a level of detail that is far too esoteric for the average manager, let alone the man in the street to comprehend easily. He went on to say that “Our basic currency needs to be far more generic, transferable and indeed utilitarian if we are to argue more effectively for the resources to manage or restore degraded aquatic habitats”. Just as decreased penis width gives us a mental image that 5 mg/L of di(2-ethylhexyl)-phthalate will never supply, so we need a “guiding image” of the state of ecology. Nigel was arguing for this image for larger plants, but the same point applies, I believe, for microscopic organisms too. The idea of algae as the “back room staff” of healthy ecosystems, converting sunlight into carbon, reoxygenating water and generally acting as a “supporting ecological service” needs to pop up in a manager’s head whenever s/he sees one of the nuggets of information that our hard work and training has produced. More often than not, algae are regarded as a potential nuisance that needs to be kept at bay, rather than as an asset with both local and global benefits. And I think that there is little point in producing better methods of assessing ecological health using algae unless we can overcome this limited potential for our information to be interpreted by non-technical colleagues and stakeholders.

I’m drawing closer to Trento, and my plenary talk, spatially, temporally and mentally. One more post on this subject to come …


European Union (2008). Directive 2008/105/EC of the European Parliament and of the Council of 16 December 2008 on environmental quality standards in the field of water policy, amending and subsequently repealing Council Directives 82/176/EEC, 83/513/EEC, 84/156/EEC, 84/491/EEC, 86/280/EEC and amending Directive 2000/60/EC of the European Parliament and of the Council. Official Journal of the European Union L 348: 48-97.

Kelly, M.G. (2012). The semiotics of slime: visual representation of phytobenthos as an aid to understanding ecological status. Freshwater Reviews 5: 105-119.

Swan, S.H. (2008). Environmental phthalate exposure in relation to reproductive outcomes nad other health endpoints in humans.   Environmental Research 108 (2): 177–184.

Willby, N. (2011). From metrics to Monet: the case for an ecologically-meaningful guiding image. Aquatic Conservation: Marine and Freshwater Ecosystems 21: 601-603.

The human ecosystem of environmental management …

I’m travelling towards Trento in Italy, where I am to give a plenary talk at a symposium on the Use of Algae for Monitoring Rivers (and comparable habitats). This series of meetings has been organised at roughly two or three year intervals since 1991 although I have not been to any for the last ten years. There is a variety of reasons for this but I often felt that the meetings were some way divorced from reality, failing my “thirty-three percent rule” which suggests the ideal ratio of academics and end-users necessary to generate fertile discussions.   There will, undoubtedly, be some interesting papers, and some that are good science but not practicable from the point of view of end users. That is one of the big dilemmas in working in the “applied sciences”.   I approach conferences with Lord Lever’s maxim to hand: “I know half my advertising isn’t working, I just don’t know which half.”   Replace “advertising” with “scientific papers” and you can, at least, approach a scientific meeting with a suitably stoical mind-set.   And, of course, my audience might well be applying exactly the same test to my talk.

One topic that I want to address in my talk is how we ensure that the results from ecological assessments are as effective as possible.   I will, I am sure, not be the only person addressing this topic, though I hope that I will open out the debate beyond the technical aspects of our science. The figure below, for example, is a simple flow diagram showing how a sample of diatoms that is collected from a river is converted into the information that a “customer” needs. I don’t like using the word “customer” in this context but it helps to remind ourselves that we are working towards objectives that go beyond simply “curiosity-driven science”.   I have used diatoms as my example as half the papers being presented at the meeting deal with this group, to the exclusion of all other types of algae.

What I wanted to illustrate with this diagram was that much applied ecology is, by necessity, a set of very standardised steps. Otherwise, it would not be possible to make comparisons between different water bodies, or the same water body at different times.   These steps are, in turn, supported by a much wider knowledge base that gives us the taxonomy that we need to identify diatoms, as well as ecological understanding that helps us to interpret data. Much of what happens at the Use of Algae Meeting will contribute to the knowledge base, which is great, but what is the broader impact of our work?


Diatom analysis as a process that converts the complex reality of organisms growing in the field to useful information for customers (e.g. catchment managers, regulators).

One of the points I wanted to make in my talk was that we must not consider the algae in isolation but, instead, remember that they are one part of a larger ecosystem, with many interactions between the different components.   This, then, led me to start thinking about the “human ecosystem” within which the work that we do is situated. The next figure, therefore, shows this human ecosystem, expressed in the style of a “trophic pyramid” but with the traditional categories of primary producers, herbivores and carnivores replaced by different levels of organisation within a bureaucracy.   In ecology, we think in terms of how energy flows through the different trophic levels; in the human ecosystem, energy is replaced by information.

This visualisation is also a useful way of reminding ourselves that we are just one small part of a much larger process: the data we collect about algae has to be considered alongside chemical measurements, data concerning other groups of organisms (invertebrates, fish, higher plants) and so on.   As a result, the effects of any changes we make to our methods will be damped down, when we consider them in terms of the system as a whole.   Very few of the papers that I read which argue for more detailed taxonomy, for example, step back and consider what effect (if any) their proposed changes will have, when viewed in this broader context.

However, just as energy has to be first converted to carbon-based compounds in order to be stored (and, later, transferred to a higher trophic level), so the data we collect is not, itself, a very useful property and needs to be synthesised into information if it is to be useful.   Much as we specialists like to dig into the minutiae of what species lives where, the reality is that this level of detail is not very “digestible” (to continue my food chain metaphors) to the higher  levels in organisations.   Even the indices that we use to summarise our data are not especially useful unless the outcomes can be expressed in a very generic manner. In the UK, this process has been taken quite a long way as part of a “weight of evidence” approach that expresses many different biological and chemical elements of water bodies in a simple, readily comparable manner.   It means that we quickly lose a sense of the biological reality (as described in my previous post, for example) but this is offset to some extent by the ability of this pared down nugget of information to move smoothly through the “human ecosystem”.   It is possible for the field scientists to invest the information with some “added value” in their reports, providing context, but we should probably accept that this level of detail is not going to move far beyond the first tier of management.   I think that we should also ask questions about the extent to which we compromise our insights into the state of the natural world as soon as we drop our samples into strong oxidising agents and digest away everything except the empty silica shells of diatoms.


The “human ecosystem” of environmental regulation, expressed as a trophic pyramid. Diatom analysis (circled) is one small part of the lowest level of this ecosystem and the information produced then needs to flow upwards in order to influence decision-making whilst, at the same time, it is influenced by “top down” factors such as policy and resources.

The final point to make is that this “human ecosystem” is subject to top-down as well as bottom-up controls.   A naïve assumption lies behind many papers on ecological assessment that I read: that there is a smooth and logical flow from an ecologist’s data to a diagnosis of a problem to the implementation of a solution.   The reality is more complicated: the situation I have faced over the past five years or more is that resources have been limited (a top-down decision) which has meant that they have been thinly spread and, in many cases, the outcome is not enough replication to ensure certainty in outcomes.   The challenge to the research scientists then becomes very specific: can we get greater confidence in outcomes at the same or lower cost?   But that, in turn, raises a different set of very human challenges, because the scientists whose career depends on producing “cutting edge” science in high impact journals are unlikely to be enthusiastic about re-shaping what we already know in order to fit a bureaucrat’s unrealistic budget.

More about this in my next post.

More about Croft Kettle

In my post on Croft Kettle, I commented on the long stalks possessed by Cymbella cymbiformis. These were difficult to capture with my camera, partly because the Cymbella cells readily detach themselves from their stalks and partly because the tangle of stalks exceeds the depth of field available to the microscopist. Instead, I have tried to capture the view through the microscope eyepiece in a drawing.


Croft Kettle, epiphytic algae associated with Chara hispida stems, May 2015. Drawn at x400 magnification.   The narrow stalks on the left hand side are about five micrometres in diameter.

There is a tangle of stalks on the left hand side, along with two cells each of Cymbella cymbiformis, Navicula radiosa and Rhopalodia gibba. Note, too, the narrow filament of Oedogonium, complete with oogonia (see “Love and sex in a tufa-forming stream …”).   The Rhopalodia cells have glided free from the tangle of stalks.

As I looked at these rich communities of algae I started to wonder if would make a good subject for a painting, so I have been continuing to examine the material I collected in order to build up a sense of what the three-dimensional community around the Chara stems would have looked like. One interesting observation came when I had a look at some of the narrow branchlets of Chara. I wanted to see which algae were directly attached to the Chara surface (more about this in a moment) but the feature that was most noticeable was the quantity of calcite crystals deposited around the stems.   These give Chara its characteristic stiff stems that are rough to the touch.   The calcite is deposited as a by-product of photosynthesis; intriguingly, Chara shares this property with many tufa-forming algae and bryophytes but not with its close relative Nitella, which is much softer to the touch (see “Finding the missing link in plant evolution…”).


Calcite crystals deposited around the tip of a branchlet of Chara hispida from Croft Kettle, May 2015.   Image composed using Helicon Focus stacking software. Scale bar: 10 micrometres (= 1/100th of a millimetre).

One of the questions that was puzzling me was the habit of the diatom Rhopalodia gibba within the community of algae on and around the Chara stems.   In many of my specimens, Rhopalodia seemed not to be attached to the Chara but, instead, glided amidst the tangle of Cymbella stalks growing around the Chara stems; however, I also saw a few cells directly epiphytic on the Chara stems, and this also seems to be the habit that Chris Carter has captured in some of his images of Rhopalodia. I suspect that Rhopalodia, and many other diatoms are opportunistic and can adopt slightly different habits depending upon the prevailing conditions. There is no point, for example, in doggedly sticking to an epiphytic habit if this m

eans sitting in the deep shade cast by a Cymbella forest. Whatever the textbooks say.


Rhopalodia gibba associated with Chara hispida stems in Croft Kettle, May 2015. b. is a valve view; e. is a girdle view and a.,c. and d. are intermediate between the two positions. Scale bar: 25 micrometres (= 1/40th of a millimetre).


Rhopalodia growing on Chara. Photographs by Chris Carter.

Rhopalodia is a genus with an unusual morphology. The raphe follows the dorsal margin (i.e. the left hand side of b. in the figure above) but this means that, in girdle view (i.e. looking from above), both raphes are on the same side of the valve.   I have often assumed that having raphe slits on opposite sides assists motility, by giving the cell two planes by which it may attach (much like a climber working his way up a narrow chimney).   It is possible that being attached to the surface is the preferred habit; motility would become an advantage only when the energy that this process consumes is offset by that supplied by the extra photosynthesis that can take place when it moves away from the shaded areas and into the canopy.   I have never seen any work done to address this topic, but it would make an interesting study.

Another interesting feature of Rhopalodia is the presence of cyanelles, organelles derived from cyanobacteria or similar prokaryotic algae. We also encountered these in Epithemia (see “A return to Cassop”) where I also mentioned that they may be involved in nitrogen fixation.   Cyanelles deserve a post all of their own at some point in the future, so I will just leave you for now with another of Chris Carter’s excellent photographs, in which the cyanelles of a Rhopalodia sp. are highlighted.   They are near-transparent, with thin membranes and are easy to confuse with the vacuoles that contain the polysaccharide chrysolaminarin (these tend to be more refractive). Very easy to overlook.

As I was putting this post together, I noticed that West and Fritsch noted that Rhopalodia gibba was “common in all kinds of localities.”   This surprised me, as I have only ever seen it at a handful of sites in the UK. It did make me wonder if West and Fritsch, writing in 1927, were right, and that it has declined significantly subsequently. A species that has a competitive advantage at low nitrogen concentrations will not have had an easy life in the period after West and Fritsch wrote, as agricultural intensification and widespread use of fertilisers led to increases in the concentration of nitrogen in surface water.


A girdle view of Rhopalodia sp. with cyanelles indicated by arrows.   Note, too, the characteristic lobed chloroplast. Photograph by Chris Carter.


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

The Hilda Canter-Lund Prize


The Hidden World of Algae, showing winners and shortlisted entries for the Hilda Canter-Lund prize, 2009-2011, at the Great North Museum, Newcastle, January 2012.

The 2015 Hilda Canter-Lund competiton is well under way (deadline: 24 June, full details at and the winner this year has the honour of seeing their image displayed in the Angela Marmot Centre, at the Natural History Museum in London.   This will not be the first time that prize winners have had their images on public display: in 2012 the Great North Museum in Newcastle hosted the “Hidden World of Algae” exhibition, with 18 images from the shortlists on display along with four of Hilda Canter-Lund’s own images.

The staff at the Great North Museum did a great job, tactfully editing the captions to remove all the jargon that they knew their audiences would not understand, and using their expertise to put on a really professional display.   One of their suggestions was to place QR codes alongside some of the images so that visitors could listen to the photographers conveying their enthusiasm about their subject matter.   Great idea, I thought (once I had looked up “QR code” on my computer – this was 2012, remember, eons ago in the fast-moving world of the internet).   I asked some of the photographers to record a couple of minutes of audio and send it to me to pass on to the museum. They, then, uploaded the audio file to YouTube and set up QR codes to point to their locations.

The only problem was that the gallery where our images were displayed had very poor mobile ‘phone reception, which meant that few of our visitors got any further than pointing their ‘phones at the QR codes and waiting … and waiting … for something to happen.   Consequently, these audio files have sat on the Great North Museum’s YouTube channel ever since, without the audiences that they deserve.

So here they are, in all their multimedia glory:


Gordon Beakes talks about his personal memories of Hilda Canter-Lund and also about his image of algae from Langdale Tarn in the Lake District, shortlisted in 2010.


Chris Carter talks about the origins of his fascination with algae, and about his image of the red algae Balbiania, shortlisted in 2012. Chris won the competition in 2013.


Eileen Bresnan talks about her image Chaetoceros Chaos, shortlisted in 2010.


John Huisman talks about his image of the red alga Dictyomenia sonderi, which was shortlisted in 2011 (John was also the winner in 2014).


Mariano Sirioni talks about his image of a southern Right Whale swimming through an algal bloom off the coast of Argentina, the winning image in 2009.

Remember: the closing date for the competition is 24 June, so there is still plenty of time to find a favourite image to submit.   The BPS website has all the details.


The desert shall rejoice and blossom …


The Nordic Diatom Meeting, Ratnieki, Latvia, May 2015.  

The motivation for my recent trip to Latvia (see “Following in Arthur Ransome’s footsteps …”) was to attend the Nordic Diatom Meeting, which took place in the University of Riga’s conference centre, Ratnieki, set in the Latvian countryside. It was a small, informal and very friendly meeting, fuelled by enormous quantities of food and enlivened by an excursion that managed to compress an overview of Latvian history from the Iron Age to the present into one afternoon of sightseeing.

It is a little unfair to pick out one of the presentations, but there was a moment on the first afternoon when I sat up with a start as the story of a fossil lake in the Saharan desert unfolded.   There is, in the middle of the Western Great Erg (a huge sand-covered area of the Sahara in southern Algeria), within which there are several depressions. Some of these contain deposits that suggest that they were once lakes.   An Algerian PhD student, Nassima Yahiaoul, told us about her study of an outcrop in one of these depressions, Guern Touil, which was composed largely of diatomite, a rock consisting largely of the remains of dead diatoms.   This is good evidence that, in a moister period perhaps 7000 years ago (the precise date is not yet known), this area was not a bleak, unforgiving desert, but a freshwater or brackish lake.

What made me take particular notice, however, was the diatoms that she found when she analysed these deposits.   These included Cymbella cymbiformis, Epithemia argus, Denticula tenuis, three species of Mastogloia and Navicula oblonga, a very large and distinctive species.   None of these are particularly common in the streams and lakes that I study in temperate Europe but, curiously, several of these occur together in a small pond about 30 kilometres away from where I lived. This pond is, itself, botanically quite distinctive, and it was a strange sensation to sit in the Latvian countryside and hear about another with such an uncanny resemblance but which is so far distant in both space and time.


The outcrop of diatomite in the Guern Touil depression, Western Great Erg, Algeria, studied by Nassima Yahiaoul.

The place that Nassima’s description evoked for me is Croft Kettle, a small pond is fed by subterranean springs emanating from the Permian limestone.   It is fringed by the saw sedge, Cladium mariscus but the edges of pond then shelve very steeply and the submerged vegetation is dominated by Chara hispida and C. vulgaris.   Whether Nassima’s pond ever looked like the illustration below is debatable (there are fossil forests near Guern Touil so the idea of a tree-fringed oasis at some point in the Holocene is not wholly fanciful). The bare evidence that palaeoecologists produces often needs to be catalysed by the imagination, and the imagination, in turn, feeds off analogies. So long as we treat these speculations with a healthy dose of caution, all is good.


Croft Kettle, a Site of Special Scientific Interest in County Durham, just south of Darlington, photographed in May 2015.

As the pond is fed by subterranean springs, the water in Croft Kettle is very clear, allowing the dense Chara beds to extend into the depths.   I could only reach the very edge of these beds when I visited a few days ago, but I was struck by the large quantity of yellow-brown diatom growths that smothered the Chara.   Under the microscope, these proved to be composed of a dense tangle of a stalked diatom, probably Cymbella cymbiformis, within which other diatoms such as Rhopalodia gibba and Navicula radiosa were moving.   The Cymbella is the same one that Nassima found in Guern Touil and I could also see representatives of three of the other genera that she described. I have recorded some of the other species that Nassima recorded from here, but they were not showing themselves today.


An underwater view of the margins of Croft Kettle, showing the dense beds of Chara, smothered by growths of diatoms, May 2015.

The quantity of diatoms that I saw in Croft Kettle was surprising, especially as I normally expect grazers to be very active at this time of year.   The yellow-brown growths resembled those that I reported from the River Ehen in April (see “Diatoms and dinosaurs”). Those were of a Gomphonema species which, like Cymbella cymbiformis, grows on the end of long stalks. These, in turn, create a tangled matrix within which other species of diatom can live.

The Cymbella cells become detached from their stalks very easily, which means that it is easier to photograph isolated cells than the complete stem plus stalk complex.   The tangle of stalks is also difficult to capture in a photograph due to the very shallow depth of field available when you are using medium-and high-magnifications.   That brings me back to the topic of imagination: the microscopist needs this just as much as the palaeoecologist, if s/he is to gain an insight into the nature of communities that have been wrenched out of their natural habitat and squashed under a cover slip.   More so, indeed, for the diatomist, who habitually marinades samples in a sauce of oxidising agents to leave just the silica frustule behind.   But here I go again … droning on about the need to understand diatoms in their living state.   Forgive me …

Enough for today: Croft Kettle is a pond with many fascinating – and one or two very unexpected – stories to tell.   Plenty to keep me going for a few more posts …


Cymbella spp. growing on Chara in Croft Kettle, May 2015; a. – c.: Cymbella cf. cymbiformis; d. – e.: two as yet unknown Cymbella sp. Scale bar: 10 micrometres (= 1/100th of a millimetre).


Wheeler, B.D. & Whitton, B.A.(1971). Terrestrial and Sub-aquatic vegetation. The Vasculum 56: 25-37.

Hudson, J.W., Crompton, K.F. & Whitton, B.A. (1971). Ecology of Hell Kettles; 2. The Ponds. The Vasculum 56: 38-45.