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. https://doi.org/10.1016/j.scitotenv.2018.09.350


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.


And the Oscar for best alga in a supporting role goes to …


I know that the focus of this blog can meander, depending on what takes my fancy week-to-week.  My core business is, however, writing about the hidden world of algae so, having written about Sam Mendes’ use of the River Tees Upper in his film 1917 in my previous post, I thought that I ought to take a trip up Teesdale to take a closer look at what is growing in the river at this time of year.   With Storm Ciara looming ominously on the forecast, I knew that if I did not sacrifice my Saturday morning it might be a while before I had another opportunity (there’s a graph at the end of this post which confirms this hunch).  And so I found myself buffeted by the wind with clouds scudding across the sky and the peaty water of the Tees thundering across the sequence of cascades that make up Low Force.

The main river was, even after a period without much rain, too deep and fast-flowing for me to venture far in so my activities were confined to the margins.   The rapid current, however, means that there were few of the small and medium-sized stones that I would normally remove and inspect.  Most had been picked up and transported further downstream leaving wide expanses of the Whin Sill bedrock.   In the shallow areas towards the edges that were not exposed to the full force of the current, there were dark green patches that I picked at with a pair of forceps.   When I was able to look at these under my microscope, I saw that they were Ulothrix zonata, a common inhabitant of northern British streams during the winter, and an alga that I have written about previously (see “The intricate ecology of green slime …” and “Bollihope Bhavacakra” amongst others).


Ulothrix zonata growing on Whin Sill in the River Tees at Low Force, Teesdale in February 2020.   The upper and central pictures on the left hand side show vegetative filaments and the lower picture shows empty cell walls after zoospores had been released, to which a germling is attached.  Scale bar: 20 micrometres (= 1/50thof a millimetre).   

The rocks were very slippery, even when not covered by green patches of Ulothrix zonata.   My usual approach to collecting specimens is to remove the whole stone and scrub the top surface with a toothbrush.  That, however, was impossible here so I had to resort to brushing the surface of the Whin Sill and hoping that enough of the slippery film remained attached to my toothbrush, which I then agitated in a bottle containing some stream water to shake the gunk off before repeating the process.  The small amount of material that I did manage to transfer from the rocks imparted a chocolate-brown hue to the water that signifies that diatoms were present.

Sure enough, when I did get a drop of the suspension under my microscope, there were diatoms aplenty, mostly wedge-shaped cells of Gomphonema growing at the end of long, branched mucilaginous stalks.  These, like Ulothrix zonata, are very common in northern British streams at this time of year.  I described similar assemblages from the River Wear at Wolsingham although, in that case, the Gomphonema shared their habitat with motile Navicula species as well (see “The River Wear in January”).   The Gomphonema in the River Tees is most likely G. olivaceum or a relative but I will need a closer look to be sure.  If I used an old Flora such as Hustedt’s 1930 Süsswasser-flora Mitteleuropas, I would have been able to be more assertive in naming this “Gomphonema olivaceum” but we now know that diatom systematics are more complicated than was thought to be the case in Hustedt’s days.


Gomphonema olivaceum-type colonies growing on Whin Sill in the River Tees at Low Force, Teesdale, February 2020.  Scale bar: 20 micrometres (= 1/50th of a millimetre).   

The sequences of 2017 were filmed in June not January so George Mackay would not have found the bedrock of the Tees to be quite as slippery as it was on my visit.   As the water warms up, grazers become more active and, as a result, the biofilms in the summer are much thinner than those in January.  That means that fewer slippery, slimy polysaccharides are produced, making it easier to keep your balance when walking at the edges of the river.

As I mentioned in my previous post, the sequence in 1917 involves George Mackay falling into a river in Picardy but crawling out of a river in Upper Teesdale.   I know less about the rivers of Picardy than I do about those in northern England, but a combination of low relief, extensive canalisation and the presence of heavy industry and coal mining in the area will mean that the algae found there will be very different to those in the Tees.   However, if 1917 can get 10 Oscar nominations (including for best sound editing) despite having the call of a Great Northern Diver echoing over No-man’s Land, then we can be fairly sure that the Wrong Sort of Algae is a level of detail that Sam Mendes and Roger Deakins thought they could safely ignore.


You can find some information about the diatoms of Picardy rivers in this paper:

Prygiel, J. & Coste, M. (1993).  The assessment of water quality in the Artois-Picardie water basin (France) by the use of diatom indices.  Hydrobiologia 269: 343-349.

This week’s other highlights:

Wrote this whilst listening to:  Michael Kiwanuka and other acts who will be playing at the Green Man festival in August.   I’ll be there too, talking about slimy algae, at Einstein’s Garden, the on-site science festival, along with (I hope) a gang of volunteers from the British Phycological Society.

Cultural highlight:   Two picks this week.  The first was Monteverdi’s Vespers performed at Durham Cathedral.  The cavernous interior of the cathedral joins the choir and orchestra as part of the experience, providing resonances that raise the experience beyond anything that a CD can offer.   The second is Bong Joon-ho’s film Parasite, a strong contender, along with 1917, at this evening’s Oscar Awards Ceremony.

Currently reading:  John le Carré’s Mission Song

Culinary highlight: a Napoli pizza cooked with locally-grown flour (www.gilchesters.com), part of a push this year to source more of our ingredients locally.  There’s obviously more to a Napoli pizza than can be grown in the UK but it is a start.


River levels at the Tees at Middleton-in-Teesdale (x km downstream from Low Force) in the week from 3 to 9 February 2020. The arrow shows the time of my visit; note the steep rise in level a few hours later, coinciding with Storm Ciara moving through the region.  Graph from the excellent https://riverlevels.uk website.

1917 and all that


If you haven’t seen it already, Sam Mendes’ film 1917 is well worth a trip to the cinema, particularly for the way it appears to have been filmed as a single take, which gives it a very immersive view of the brutality of trench warfare.   The result is a sense that we, the audience, are there alongside the protagonists that lasts up until the point when a small detail intrudes to break the spell and you find yourself sitting up and wondering what is going on.   This may be, I admit, a niche concern but, for me, this happens at the point at which the lead character, played by George Mackay, jumps into a quiet, slow-flowing canalized Picardy river to escape a pursuer.   As he enters the water, it transmogrifies into a fast-flowing rapid-strewn torrent, through which he struggles to keep his head above water until eventually crawling out onto rocks beside some woodland and, from there, back into Picardy and the trenches.

Was it just me, or was that an outcrop of Whin Sill in the background as Mackay thrashes around trying to keep his head above water?   I am no geologist but I had passed signs warning walkers that filming was taking place as I drove up Teesdale a few months ago and the rumours were that this was a location for a major film.  I guess even a geological dunce can start to recognise geological formations when he has seen the paraphernalia of a film set at precisely the point on the River Tees where Whin Sill outcrops create a cascade waterfall.


Filming 1917 at Low Force, Teesdale, June 2019.   The photo at the top shows Low Force on the River Tees (credit: Heather Kelly)

I am not alone.  A listener to Simon Mayo and Mark Kermode’s film programme on BBC Radio 5 wrote in to say that he had been discombobulated by the sound of a Great Northern Diver as, earlier in the film, Mackay and a fellow soldier had made their way across No Man’s Land.   The listener pointed out that the closest locations where the Great Northern Diver was found was northern Scotland, and that the haunting call of this bird appearing out of place had jarred with the film’s otherwise close attention to period detail.   A few years ago, I had a similar experience in a performance of Alan Bennett’s A Question of Attribution when a backdrop supposed to represent the Queen’s picture gallery at Buckingham Palace included Leonardo da Vinci’s Lady with an Ermine, which I knew to belong in a gallery in Krakow.   Such details can undo the hard work of cast and crew to create a particular atmosphere.   Instead of being immersed in the drama, you find yourself scratching your head and asking questions that the director had never anticipated.

As I said above, this is all very niche stuff.  A few ornithologists will have noticed the wrong birdsong (strange synchronicity to use that word in a post about trench warfare), almost everyone else will have benefited from the haunting call’s contribution to the overall atmosphere. And a very few river ecologists will have been disconcerted by the seamless transition from Picardy to Teesdale and back.  Everyone else (the vast majority) will have been grateful that Sam Mendes did not let Mackay float in a muddy, almost stationary French canal while German soldiers took potshots at him, and thus depriving the story of any sense of resolution.

There are, almost certainly, far more occasions when a wrong detail passes right over me than when I am discombobulated by something that I do notice.  Any kind of specialist knowledge will reveal small incongruities that a film crew did not realise mattered (they probably don’t in the grand scheme of things) or which were deliberately changed to heighten an effect (as Mendes did in 1917).   The few that notice will be temporarily sprung from the world of illusion that the director has striven to create but, for everyone else, the magic will be heightened.   We should, really, be grateful that Sam Mendes didn’t worry too much about a realistic depiction of the hydrology of Picardy.

This week’s other highlights:

Wrote this whilst listening to: Beethoven’s 9th Symphony. What else at this sad time?

Cultural highlight: Welsh harpist Caitrin Finch playing with Colombian band Cimarron at the Sage, Gateshead on Saturday night.

Currently reading:  The Memory Keeper’s Daughter by Kim Edwards

Culinary highlight: a sociable evening cooking Sichuan food with Heather and Rosie, recreating some of our favourite dishes from our trip to Chengdhu last year using Fuchsia Dunlop’s cookbook.   Consumed with two bottles of Durham Brewery’s Smoking Blonde ale

Little pond of horrors …

One of the highlights of the British Phycological Society’s recent meeting in Plymouth was a talk by Sebastian Hess from the University of Cologne about amoebae which preyed upon microscopic algae.  His presentation included several video clips, one of which featured the aptly-named Vampyrella attaching itself to the outside of an alga cell and slowly sucking out its contents.   The clip drew audible gasps from the audience, none of whom had walked into a dryly-named session on “Algal interactions across the tree of life” expecting the tropes of a horror movie to be displayed before their eyes.

The link to the YouTube video below gives you some idea of the predatory nature of these organisms.   They are not technically parasites but “protoplast feeders”, penetrating the cell wall of the victim and consuming the cell contents by a process known as “phagocytosis”.   Although these organisms have been known for a long time (they were first described in 1865), it is only in recent years that the diversity of these organisms has become apparent.  That’s because, like many unicellular organisms, it is difficult to fully appreciate the differences just by peering at them through a microscope.  It has only with the advent of environmental DNA analyses that this has been understood.   We now know, for example, that the species found in freshwater, soil and marine environments are all different and that each vampyrellid is fairly specific to a particular group of algae (more about Sebastian Hess’ work can be found here.

The vampyrellid amoeba Arachnomyxa cryptophaga feeding on the green alga Eudorina elegans, from the German YouTube channel “Nicht interessant”

Those of us who are interested in algae tend to go on about their importance in trapping the sun’s energy via photosynthesis but rather less time thinking about how that energy then passes from the algae through to higher trophic levels.   I often see chironomid larvae feeding on algae when examining samples (see, for example, “More about very hungry chironomids”) but these tend to use the larger filamentous algae as supports while they graze on the smaller epiphytes (mostly diatoms in the streams I look at) which grow on the surface of the filaments.   The vampyrellids, by contrast, have powerful enzymes that can punch holes in the though cell walls of filamentous algae so that they can suck out the contents.   At the simplest level that creates a tasty meal for the vampyrellid but, from a broader ecological perspective, these amoebae are turning large unpalatable chunks of carbon that an insect larva cannot manipulate into its mouth into smaller nuggets that could, in theory, be consumed by small beasts.  These small beasts, in turn, fuel the slightly larger bugs which may be prey for a fish.   The vampyrellids, in other words, help keep carbon pumping through the aquatic ecosystem.

It is not just predatory amoebae that perform this function.  Another talk at the Plymouth meeting by Davis Laundon of the Marine Biological Association showed that microscopic fungi may play a similar role.   Again, I’ve mentioned these organisms before (see “Little bugs have littler bugs upon their backs to bite ‘em …”) but not really reflected on what role they play in an aquatic ecosystem.  Davis worked in marine rather than freshwater ecosystems but the same principle seems to be at play: large chain-forming diatoms such as Chaetoceros are too big for many zooplankton grazers to feed upon but thraustochytrid fungi inadvertently convert these big indigestible hunks of carbon into bite-sized portions which then fuels the ecosystem in Plymouth Sound.

Coincidentally, my own interest in the microscopic world started when I read about amoebae in school textbooks, and my earliest natural history explorations involved trying to find amoebae in local ponds, usually without success (when I was in Nigeria, protozoans returned the favour … but that’s another story).   Even now, I do not regard amoebae as particularly easy organisms to observe and have not tried to identify them.  However, once your eyes (and mind) are tuned to noticing particular phenomena in nature, there is a positive feedback loop and you start to notice these phenomena more and more.  I suspect I have been suffering from “amoeba blindness” for some time.  Last year I wrote an essay about what we see and don’t see when peering down a microscopeand Marian Yallop, one of my co-authors, included some photographs of amoebae, reminding me of my earlier fascination with these unicellular organisms.  I’ll be watching out for these as I examine samples, and trying to learn a little more about them during 2020.


A plate from showing interactions between algae and other protists from Kelly et al. (2019).  A. A ciliate has consumed a variety of live pennate and centric diatoms and cyanobacterial filaments. B. Algae autofluorescing red and cyanobacterial filaments yellow within the ciliate. C. Other protists e.g. Vorticella select relatively smaller soft-bodied green algae. D. This amoeboid protist had previously consumed two relatively large diatoms E. Some reorganising of the cell contents is required to shuffle these engulfed cells to the periphery. F. Exocytosis takes place to release the partially digested cells, and the amoeba rapidly moves away. This sequence of events lasted a few minutes. Images (A-B, D-F) were taken from biofilm material from Winford Brook, North Somerset, UK by Marian Yallop; Image C was taken from the Danube at Zimmern, Baden-Württemberg, Germany by Lydia King.


Hess, S., Sausen, N. & Melkonian, M. (2012).   Shedding light on vampires: the phylogeny of vampyrellid amoebae revisited.  PLoS One 7: e31165. 

Hess, S.& Melkonian, M. (2013).   The Mystery of Clade X: Orciraptor gen. nov. and Viridiraptor gen. nov. are Highly Specialised, Algivorous Amoeboflagellates (Glissomonadida, Cercozoa).  Protist 164: 706-747.

Kelly, M.G., King, L.. & Yallop, M.L. (2019).  As trees walking: the pros and cons of partial sight in the analysis of stream biofilms.  Plant Ecology and Evolution 152: 120-130.  


This week’s other highlights:

Wrote this whilst listening to: PJ Harvey

Cultural highlight: Tutankhamun: Treasures of the Golden Pharaoh at the Saatchi Gallery in London.   Was looking forward to seeing Girl From The North Country, a musical based around Bob Dylan’s songs, on the same trip to London but it was cancelled 40 minutes before the start due to cast illness.

Currently reading: Nine Lives: In Search of the Sacred in Modern India by William Dalrymple

Culinary highlight: Mildreds, a vegetarian restaurant in London’s Soho.   You can’t book ahead, so we had to wait for a table.   We spent this time at the closest pub, which just happened to be the John Snow, featured in “A drink of water with John Snow”, a post from 2013.  Mildreds was worth the wait, particularly for the desserts.  I was diagnosed as lactose-intolerant last year and normally gaze miserably at dessert menus packed with dairy-rich offerings.  Mildreds, however, is fully vegan throughout January, so the entire dessert menu was there for the choosing.

Quantifying our ignorance …


I am fairly sure that I am not a popular person after my latest choice of slide for the “ring test”, the regular calibration exercise that UK and Irish diatomists perform.   I had noticed a few taxa that we had not seen in previous ring tests in a sample I collected during my visit to the Shetland Islands back in May 2019 (see “Hyperepiphytes in the Shetland Islands”) but, on closer examination, the sample proved to be both highly diverse and very challenging.  The seven experienced analysts who provide the benchmark analyses for the ring test found, between them, over 150 different species: some we could name with confidence, but others we could match to no published description.  Amongst those was the species of Achnanthidium photographed below.   It might be Achnanthidium digitatum or possibly A. ertzii but, then again, it does not quite match the characteristics of either of these so, once again, we have left it unnamed (you can find the original descriptions of both these species in the reference list).

According to Algaebase there are 116 species of Achnanthidium that are currently accepted but descriptions of these are scattered through the literature so it is really hard to be confident that you have found a new species during a routine survey.  This is particularly the case when we only have light microscopical analyses with which to work, as the small size of Achnanthidium species means that you really need a scanning electron microscope to see the fine details clearly.  This, however, assumes that the pool of unnamed Achnanthidium species is finite and that the 116 species on Algaebase is a significant proportion of the total number of Achnanthidium species.  A recent study by Eveline Pinseel and colleagues based on samples from Arctic regions offers hints that there is still plenty of diversity within the genus that cannot be linked to named species

This may, however, be a naïve assumption.   My colleague Maria Kahlert, who works in Sweden, comments that she is quite happy looking at samples that I send her from polluted sites in the UK as she can name most of the species (Achnanthidium and otherwise) from her own experience.   It is the samples from pristine habitats that fox her because so many of the forms are different to anything she has encountered in Sweden.  We have, in other words, a neat reversal of the opening line of Anna Karenina (“All happy families are alike, each unhappy family is unhappy in its own way”), with very high beta and gamma diversity of diatoms (probably other microalgae too) as a characteristic of regions with low population density (see “Baffled by the benthos (2)”).  We often miss this in our enthusiasm to fit all that we see down the microscope to published descriptions, but when we take time to look hard, that diversity – and those differences between sites – start to mount up.


The unknown Achnanthidium species from Petta Water, Mainland, Shetland Islands (pictured at the top of the post).  Scale bar: 10 micrometres (= 1/100th of a millimetre).   Photographs: Lydia King

Let’s think of this as an ecological experiment to understand the diversity of Achnanthidium, following the capture-mark-capture approach.   Capture-mark-recapture is a technique used by ecologists to assess the size of a population.   As it is rarely possible to count all individuals, a portion of the population is collected, marked (a dab of paint on a snail’s back, for example) and released.   Some time later, the population is sampled again, and the proportion of those that bear the mark in this second sample is used as an indicator of the proportion of the population captured by the original sample.   Though devised for population biology, some have used the same principles to understand diversity in other contexts too so might it work as a means of understanding the yet-to-be discovered diversity of diatoms?

What we have in the scattered taxonomic literature is a record of all the Achnanthidium species that have been “captured” (i.e. observed) and “marked” (i.e. described) by taxonomists.   Suppose we now go some locations not previously visited by taxonomists, take some new samples and see 1) how many different forms of Achanthidium we can see and b) how many of these are “recaptured” (i.e. forms that align with previously described species).   Or, thinking about the problem in a different way, the number of named species could be compared with the number of distinct “operational taxonomic units” (“OTUs”) detected by metabarcoding.   More relevantly, how many extra OTUs are added when more lakes and streams are added to the dataset?   There are well-established methods for deriving “rarefaction curves” that might be useful in understanding regional diversity of diatoms, and modifications of “capture-mark-recapture” have been used to understand taxonomic diversity in palaeobiolgoical contexts, so why not in contemporary ecology too?

The Shetland Islands would make an ideal test ground for such a study as they are geologically-diverse habitats providing the types of conditions where Achnanthidium species thrive (low population density and agricultural intensity.   The diatoms of the region were studied about 40 years ago by my late mentor John Carter and although one of his samples yielded the type material for Achnanthidium caledonicum there have been so many developments in Achnanthidum taxonomy subsequently that this archipelago represents a tabula rasa for a modern taxonomist.   Its many remote lochs and streams offer the setting for a natural experiment which sets out, to put it bluntly, to quantify our ignorance.


Achnanthidium caledonicum from Loch Osgaig, Highland Region, Scotland.   Originally described as Achnanthes microcephala f. scotica Carter & Bailey-Watts 1981 (Scale bar: 10 micrometres (= 100th of a millimetre).  Photographs: Lydia King.


Carter J. R., Bailey-Watts A. E. (1981). A taxonomic study of diatoms from standing freshwaters in Shetland. Nova Hedwigia. 33: 513-630.

Pinseel, E., Vanormelingen, P., Hamilton, P. B., Vyverman, W., Van de Vijver, B., & Kopalova, K. (2017). Molecular and morphological characterization of the Achnanthidium minutissimum complex (Bacillariophyta) in Petuniabukta (Spitsbergen, High Arctic) including the description of A. digitatum sp. nov. European Journal of Phycology 52: 264-280. https://doi.org/10.1080/09670262.2017.1283540

Van der Vijver, B., Jarlman, A., Lange-Bertalot, H., Mertens, A., de Haan, M. & Ector, L. (2011).  Four new European Achnanthidium species (Bacillariophyceae).  Algological Studies 136/137: 193-210.

Liow, L.H. & Nichols, J.D. (2010). Estimating Rates and Probabilities of Origination and Extinction Using Taxonomic Occurrence Data: Capture-Mark-Recapture (CMR) Approaches.  The Paleontological Society Papers 16: 81-94).

This week’s other highlights:

Wrote this whilst listening to: Sheku Kanneh-Mason’s recording of Elgar’s Cello Concerto.   Taking me back to his performance at the proms on a warm evening last summer.

Cultural highlight: Sam Mendes’ film 1917 which, coincidentally, uses the River Tees (as featured sporadically in this blog) as one of its locations

Currently reading: I have just finished Good Economics for Hard Times by Abhijit V. Banerjee and Esther Duflo, which I mentioned a couple of weeks ago.  It left me with the feeling that, had both Boris Johnson and Jerermy Corbyn read it and taken on its messages, the election campaign and the UK political landscape might have been very different.

Culinary highlight: OK Diner on the southbound side of the A1 near Grantham.  Felt like we were walking into the opening scene from Pulp Fiction (the one where Tim Roth jumps up onto a table and attempts to rob all the customers).   Escaped with wallet intact.


Hooray for hippo dung …


I’ve only seen hippopotami in the wild once in my life, and then only at a distance in the Yankari game reserve in northern Nigeria.   I took some photos, but these were taken with only a moderately-powerful telephoto lens and crocodiles basking a few metres from where our Land Rover was parked were a more pressing concern.  In any case, the prints from that holiday (years before digital cameras) are now lost.   The photo at the top of this post is, in fact, a pygmy hippopotamus – a different genus to the common hippopotamus (Hexaprotodon liberiensis rather than Hippopotamous amphibious) – taken at smaller wildlife park (a glorified zoo, really) near Jos but it will do for my purposes. 

A couple of years ago, I wrote about the role that bears may play in the transfer of essential nutrients from the ocean to the forests of north-western North America (see “Ecology’s bear necessities”).  I recently came across a paper that described a situation where hippos were responsible for a significant movement of nutrients in the opposite direction: from land to water.   We think of hippopotami as beasts that wallow in muddy water, but that is because they are filmed and photographed when there is enough light.   Hippos are actually nocturnal animals, coming out of the water to feed on the savannah grasslands when it is dark, and resting in pools during the day.    As they rest in their pools, the grass that they eat during the day is slowly digested (hippos are “pseudoruminants”) and, eventually, passes out of their colons as faeces.   That is an important source of carbon, nitrogen and phosphorus for the river, but also of silicon, an essential nutrient for diatoms.   Diatoms form the base of the food chain in Lake Victoria so, consequently, depend upon a constant supply of silica from the surrounding catchment, and the hippos are inadvertent vectors for this.

There is plenty of silicon in the natural environment (it is the second most abundant element on earth, after oxygen) but most is tightly-bound in particles and so is not in a form that is accessible to other organisms.   Some plants, especially grasses, however, use silicon as a means of strengthening and supporting their cells.  In the process, they also provide a measure of protection (as anyone who has been cut by the sharp edge of a grass leaf will know).  The silicon is taken up by the plant’s roots, but is then laid down in the cells as structures called “phytoliths”.  When these phytoliths are released back into the environment via a tortuous path through the hippo’s digestive system, the silicon they contain is in a much more accessible form than when it was trapped into minerals in the savannah soil.

The phytoliths released by the hippos form about three quarters of all the biologically-available silicon in the hippo pools and, when these have made their way down the stream, may also have an effect on the ecology of Lake Victoria.  At this point, the paper gets rather speculative, but noting that there has already been a significant decline in hippo numbers in recent decades, the authors suggest that this may have had an impact on the ability of diatoms to compete with other algae, contributing to the greater dominance of cyanobacteria that has been observed in recent years.

Even allowing for a little academic hyperbole, this is a useful reminder that trying to keep ecology neatly compartmentalised is never a good idea.  Everything is connected to everything else: lakes, rivers, terrestrial systems.  We sort of know this instinctively but, at the same time, scientists spend so much time absorbed by their specialisms that they often forget this too.   The hippopotamus seems to be an unlikely benefactor of tiny diatoms, but maybe that is the fault of our imagination rather than of nature.


Schoelynck, J., Subalusky, A. L., Struyf, E., Dutton, C. L., Unzué-Belmonte, D., Van De Vijver, B., Post, D.M., Rosi, E.J., Meire, P. & Frings, P. (2019). Hippos (Hippopotamus amphibius): The animal silicon pump. Science Advances 5: https://doi.org/10.1126/sciadv.aav0395


A baboon, photographed at Yankari game reserve in 1990.  The photograph at the end of the post shows a waterbuck, photographed on the same visit.

And, once again, some notes on what else I have been up to this week:

Wrote this whilst listening to: Keith Jarrett’s Köln Concert

Cultural highlight: Keith Jarrett’s Köln Concert is so good that I am prepared to enter it under two headings.  Worth listening to Tim Harford’s Cautionary Tales Podcast (Episode 7: Bowie, jazz and the unplayable piano) to learn more about this remarkable piece of music.

Currently reading: Raynor Winn’s The Salt Path.  I’m in south-west England so a book about walking the South West Coast Path seems appropriate.

Culinary highlight: yet to happen.  I’m at a conference at the University of Plymouth, subsisting on breakfast from a chain hotel and lunch from a university catering service that offers few options for those who are lactose-intolerant.




Fit for purpose?



It is sobering to think that the Water Framework Directive (WFD) will be twenty years old this year (23 October, to be precise).  The 70 pages of legalese that comprise this directive have, to a large extent, determined the course of my career over the past two decades (it is a few sentences in Annex V, to be precise, but unravelling and interpreting these has been enough).  Just before this anniversary arrives, however, the European Commission has published a “fitness check”, giving the Directive a thorough once-over before reaching a mixed verdict on its performance.

The report’s conclusion is that the WFD has provided a governance framework for water management but, overall, the condition of Europe’s water bodies has shown little significant improvement since the WFD passed into law.   The original objective – grossly optimistic in hindsight – was for all Europe’s water bodies to be at least at good status by 2015.  Instead, we are still in the situation where less than half are at good status.  There is no doubt that there have been local improvements, and the rate of deterioration may have decreased but this is not the same as a general trend towards better ecological quality in our water bodies.   I’ll offer three possible reasons for the shortcomings, based on my own experience of WFD implementation, in the hope that lessons learned from turning a well-intentioned policy instrument from theory into practice will have some broader lessons as we tackle the climate emergency.

The first lesson is that complex problems, by necessity, spawn complicated legislation.  The Water Framework Directive arose from an attempt, in the early 1990s, to produce a directive addressing the Ecological Quality of Waters.  As debates about this progressed, people realised that you cannot consider the state of the aquatic environment in isolation, without also considering broader economic issues such as water pricing and, indeed, all aspects of catchment management that respects the rights of other legitimate users.  Each of these issues requires a small army of bureaucrats to unpack and apply within the 28 Member States.   In some countries and for some aspects of the legislation, there were procedures in place that simply needed tweaking to be fit-for-purpose.  Some other aspects were, however, completely new for almost everyone.

The whole idea of using the health of an aquatic ecosystem (“ecological status”) as a measure of the long-term sustainability, for example, was something never attempted on such a scale before.  It had been advocated in the academic literature, and there were a few localised attempts to apply the system (RIVPACS in the UK, for example) but, as the sun rose on 23 October 2000, the task of working out how the fine words of Article 4 had to be translated to a practical reality that was both faithful to the intentions of the WFD and that worked within public sector budgets had to start.


A second big issue that was relatively under-acknowledged in the fitness check is that solving environmental problems cannot be achieved without engaging other sectors as well.   A recent review, to which I contributed, highlighted this, emphasising the need, first, to integrate water policy with other sectors (such as agriculture) whilst, at the same time, emphasising the need to demonstrate tangible benefits that extend beyond the subtleties of shifts in ecological parameters.  Bring agriculture on board to achieve more sympathetic management of catchments, in other words, recognise the contributions that farmers make (“public money for public goods”) but also back this up with substantial demonstrations of reduced flood risk for urban areas downstream.   That calls for a level of joined-up thinking across sectors that has not yet been achieved in Europe and which is, perhaps, an opportunity that the UK, shortly to be freed from the leviathan that is the Common Agricultural Policy, may be in a better position to address.  We live in hope.

The third reason may be that the ambition of the WFD may be higher than many politicians and civil servants are happy with.   Article 1 sets out the objective of promoting “sustainable water use based on a long-term protection of available water resources”.  A phrase such as that could have appeared in any of the party manifestos for our recent election but when the scientists unpack this and explain that this will mean that every river in the country needs to have average phosphorus concentrations of well under 0.1 milligrams per litre, and the water planners put a price on this, alone, that runs into hundreds of millions (if not billions) of euros, then that ambition falters.   More particularly, the noisy nature of much ecological and environmental data gives ample opportunity for bureaucrats to prevaricate rather than take steps that are unlikely to play well with the media (the WFD enshrines the “polluter pays” principle and, as we all contribute to urban wastewater loading, this translates to “voter pays”).

As its 20th anniversary approaches, the WFD will have spanned four electoral cycles (assuming national parliaments have five-year terms), at each of which policy wonks will have been thinking less about long term sustainability of water resources and more about short-term swings in voting preferences.   Moreover, since 2008, much of Europe has felt the consequences of the banking crises, with public sector finances often badly affected.  Again, the scientific challenges that the WFD creates provides easy excuses for cash-strapped regulators to kick the can down the road rather than make potentially unpopular decisions.

Governance may be in place, in other words, but a willingness to push this governance to deliver may be lacking.  That, in turn, reflects a perceived unwillingness on the part of the electorate to accept the costs.  Imperfect democracies will always deliver imperfect solutions, particularly when the underlying problems are complex and the opportunity costs are high.


Pictures in this post are from a New Year’s Day walk around the riverbanks in Durham.  New feature for 2020 is a few notes on what else I’ve been up to during the week in which this post gestated:

Wrote this whilst listening to:  Bob Dylan’s John Wesley Harding; Bruce Springsteen’s Nebraska

Cultural highlight: Greta Gerwig’s Little Women.

Currently reading: Good Economics for Hard Times by Abhijit V. Banerjee and Esther Duflo – two Nobel Prize winners setting global problems into a broader economic framework.  Not an easy read but very stimulating.   A good follow-up to Kate Raworth’s Doughnut Economics, which I mentioned in a couple of posts last year.

Culinary highlight: followed a recipe in The Guardian which involved cramming all the leftovers from our Christmas dinner (turkey, stuffing, roast potatoes, parsnips, brussel sprouts) into a loaf tin along with some breadcrumbs and two eggs to bind.  This created a meatloaf which I froze and then produced on New Year’s Day to provide a final reminder of the festive season before the realities of 2020 intruded.  Doubly enjoyable as West Ham had their first win of the Festive Season as it was being demolished.


Carvalho, L., Mackay, E. B., Cardoso, A. C., Baattrup-Pedersen, A., Birk, S., Blackstock, K. L., Borics, G., Borja, A., Feld, C.K., Ferreira, M.T., Globevnik, L., Grizzetti, B., Hendry, S., Hering, D., Kelly, M., Langaas, S., Meissner, K., Panagopoulos, Y., Penning, E., Rouillard, J., Sabater, S., Schmedtje, U., Spears, B.M., Venohr, M., van de Bund, W. & Solheim, A. L. (2019). Protecting and restoring Europe’s waters: An analysis of the future development needs of the Water Framework Directive. Science of the Total Environment 658 1228-1238. https://doi.org/10.1016/j.scitotenv.2018.12.255