The “thirty-three percent” rule

I’m deep into organisation of an informal workshop, entitled untangling the “causal thickets in river health assessment” which will bring together a number of people who are asking questions about the state of UK’s rivers to consider where we are, and think creatively about where we need to be.   My post of 1 June introduced “causal thickets” as a means of thinking through complex problems, so this post does not need to retread that ground.  Instead, I want to make a link with another post: Colourless green ideas sleep furiously (17 April 2013).

The point I was making in that post was that much so-called “applied science” misfired because it failed to consider the broader context within which science has to function.   It is a problem that I encounter often at scientific meetings attended mostly by academic scientists yet, equally, I also often find myself at meetings where the opposite is true: where a group of practitioners, rather than academics, discuss an issue without a detailed knowledge of recent advances in the field.  It led me to a very rough rule of thumb, the title of this post.

Broadly speaking, if you are discussing a topic which involves 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.   My rule-of-thumb is that you need to have about a third of the group are academics, engaged in research an d aware of current developments, and a third who are end users / stakeholders, aware of practical issues, the nature of underlying legislation, economic realities and so on.   Too few of representatives of either constituency makes it harder for voices to be heard.

The good news is that we do seem to have a mix at the workshop that I’m organising, so I am anticipating some interesting discussions some of which, I hope, will find their way onto this blog.  Watch this space.

My first “selfie”


News today that the word “selfie” is among the new words added to the Oxford Dictionary has prompted me to get in on the act.   My understanding is that a “selfie” is a self-portrait taken on a mobile phone or similar device, so I got out my iPhone and took a photograph of a self-portrait.  That’s the idea isn’t it?  If not, I’m sure my kids will put me right.  They usually do.

Stream of Consciousness …

A couple of Saturdays ago I picked up a book from the Durham-Palestine Educational Trust’s second-hand book stall in Durham Market.   It was a hardback copy of The Stream by Brian Clarke (Black Swan books, ISBN 978-0552770774), a book I had vaguely registered in my sub-conscious when it was first published in 2002 but never got around to reading.   The Stream is a novel, telling the story of a fictional chalk stream in southern England as an industrial park is developed within the catchment.  It was, I am pleased to say, a very well-spent pound and I would recommend tracking down a copy.

The term “novel” does not really do the book justice.  The perspective swings between human protagonists – the multinational industrialists, local and national politicians and environmental activists – and the life in the stream itself.   Brian Clarke is a fly fisherman so we meet the trout and salmon that live in the stream and are told their stories.  We also meet the mayflies and some of the other invertebrate inhabitants of the stream.   The Stream includes vivid descriptions – perhaps the first in literary history – of trout and mayfly orgasms (perhaps it should be reissued as 50 Shades of Grayling?) and even has some chapters where the algae take centre stage.  The human drama is set against this on-going soap opera in the stream itself.

The human drama, however, is inevitably inter-weaved with the life of the stream itself.   The strength of the book is the way that Clarke manages to do this.   He does not take the sensationalist option; there are no pipes gushing with toxic effluent here.  Rather, there are allusions to slight changes in practice – a decision to take more water from a borehole some distance from the stream itself, a farmer grubbing out hedges to make larger fields that will move the farm into profit – and the subtle chains of causation that are precipitated.  The water table drops … the springs that feed the stream have less water, the bankside vegetation where adult mayflies congregate to breed are lost, and so on.  Finally, the fish themselves struggle to feed and breed and the stream slowly changes its nature.

It is, quite simply, one of the best lay introductions to stream ecology, and their vulnerability to human activities, that I have ever read.   I am becoming increasingly aware that there is a gulf between what environmental professionals want to achieve, and the aspirations of the wider public.  The professionals are often not doing enough to explain their work in terms that the public – who will have to pay for the improvements via higher water charges – can understand.  Books like The Stream are one way that we can do this.

More from the River Ehen

When I was visiting the Ehen back in February, I found tufts of a blue-green alga called Tolypothrix tenuis (see post).  I also found that these were smothered, in turn, by a smaller blue-green alga, Heteroleibleinia rigidula (which, until recently, was included in the genus Lyngbya, which we met in the previous post).  I had another look at the Tolypothrix during my last visit and was surprised to see that the Heteroleibleinia had disappeared and had been replaced by another epiphytic blue-green alga, Chamaesiphon (probably) incrustans.   The entire surface of the filament was smothered by the short, club-shaped cells of this species.   I said it is “probably” C. incrustans because there is another species with very similar appearance, C. minutus, but this is not illustrated in the Freshwater Algal Flora of the British Isles so I cannot be 100% sure.


Tolypothrix tenuis from the River Ehen, smothered by epiphytic Chamaesiphon cf incrustans.   Scale bar: 10 micrometres (1/100th of a millimetre).  The inset shows a single cell of Chamaesiphon with its characteristic exospore.

It is hard to make out the individual Chamaesiphon cells in the photograph so I have sketched a single cell to illustrate the main features.  It is attached by the narrow end to the host organism and many of the cells have a characteristic “exospore” at the other end which buds off to produce a new cell.

About a dozen different species of Chamaesiphon have been recorded from the UK.  A few of these are epiphytes, but most form colonies on submerged rocks.  Most are just brown patches that sometimes resemble lichens but more often look like … brown patches.   Consequently, they are easily overlooked and, probably, under-recorded.  Back in March, I commented on the “trailing edge” of science where we were forgetting more than we were learning (see post) and the ecology of Chamaesiphon is a good example of this.

The River Ehen in August

I was back at the River Ehen last week, fully expecting to find rocks scoured clean of algae following the heavy rain that had preceded our visit.   Two surprises were awaiting me: first, almost all the stones had a cover of algae that was thicker than on several of my previous visits and, second, these particular green films were composed of different species to those that I had found on those visits.   The most abundant species were a form of Oedogonium (though not the same one as I had seen in the Wear a few weeks ago) and a close relative of Oedogonium, called Bulbochaete.

Bulbochaete shares Oedogonium’s characteristic rows of barrel-shaped cells but differs in two important respects: the filaments of Bulbochaete have several short side-branches and several of the cells have long, colourless hairs protruding from them.   The function of the hairs has never been investigated, to my knowledge but, like the hairs we saw on Draparnaldia, they could be associated with nutrient acquisition.  Indeed, looking at the prolific growths in the Ehen, I did wonder if the recent heavy rain had flushed nutrients off the surrounding fells, giving the normally hungry algae the brief feast which allowed this dramatic flourish on the stream bed.


A branched filament of Bulbochaete from the River Ehen, August 2013.  Scale bar: 10 micrometres (1/100th of a millimetre).

A kilometre or so downstream, I picked up a stone from the river bed that had a distinct blue-green tinge.  However, this was not a film lying on top of the rock: it seemed that the rock itself was coloured.   I had seen this before but never in a stream with such soft water as the River Ehen.   I had to scrape the rock with a razor blade in order to remove some of this crust and, once under the microscope, it was difficult to get a clear view due to the quantity of rock particles that had come off along with the film.  However, there was enough for me to make out some narrow filaments, similar to the Phormidium and Oscillatoria filaments we have seen in earlier posts.  This is a species called Lyngbya vandenberghenii.   The inset photograph shows some of the empty “sheaths” which surround the filaments of cells – the possession of a distinct sheath is the main character which distinguishes this genus from Phormidium and Lyngbya although, as the right hand picture shows, the filaments often glide free of this sheath.


Left: Lyngbya vandenberghenii growing on a limestone cobble in the River Ehen, August 2013.  Right: individual trichomes (the technical term for the chain of cells) as seen under the microscope (the rock particles make crisp focus impossible) and, inset, empty sheaths of L. vandenberghenii.   Scale bar: 10 micrometres (1/100th of a millimetre).

Although it looks as if the alga was growing in the rock, it is actually growing on the surface of the rock but depositing calcite crystals as it grows.   I was surprised to see this species here as I generally associate it with harder water.   However, the stone itself was a surprise: a single piece of limestone amidst a river bed composed almost entirely of the igneous rocks that underlie the Ennerdale catchment.  I presume that some limestone had been imported, perhaps for a building, and that this piece had somehow found its way into the river.  It had, in the process, created a tiny microenvironment which enabled this exile from harder water to survive.

When I use a word …

Ending my previous post with a quote from Alice in Wonderland was a trifle unfair on my taxonomist colleagues but it does help make the point that taxonomy – the classification of living organisms – is largely an edifice constructed by humans.  Within this edifice, there is one level – the species – that should be unambiguous: members of the same species are able to share genetic information amongst themselves.   If two organisms cannot reproduce and produce fertile offspring, they don’t belong to the same species.  Full stop.   You should, in other words, be able to define any species “beyond reasonable doubt”.  The reality for the freshwater algae is, as we have seen in earlier posts, that this is not always practicable as many can thrive without needing to undergo sexual reproduction.   Taxonomy then becomes a process of assembling information about properties that can be seen or measured leading to a species concept that is based on the “balance of evidence”.   Of course, shared properties implies shared genes which, in turn, implies a shared heritage, so we should expect the “balance of evidence” approach to give us the right answer most of the time.  My point is that we need to remember the limitations.

In the previous post, I discussed two examples where people generally agreed (on balance of evidence) that the organisms each represented distinct species but disagreed on the genus to which each belonged.   The problem we face is that the “beyond reasonable doubt” criterion only applies to species and every higher level taxonomic category – genus, family, order, class etc – are defined entirely by “balance of evidence”.   New approaches based on genetic differences between species may help us but the problem lies as much with the definition of terms such as “genus” as with our ability to allocate each species to the correct genus.   Ironically, it is the higher levels of classifications (e.g. “class”) that may gain the most added clarity from genetic methods, as these can show distinct differences where other forms of evidence are confused by a mixture of convergent evolution and our own pre-conceptions, formed from the biases inherent in the older literature (see reference below).

Postscript: I had planned to make some analogies between the reluctance of many algae to have sex with the love life of giant pandas, who also seem to prefer celibacy to passion.  However, as I was writing the piece, news broke that the female giant panda in Edinburgh Zoo might be pregnant.   That this was achieved by artificial insemination rather than waiting for Yang Guang to do his stuff is, perhaps, a useful lesson for those of us who study algae…


Sims, P.A., Mann, D.G. & Medlin, L.K. (2006). Evolution of the diatoms: insights from fossil, biological and molecular data.  Phycologia 45: 361-402.

Back to Druridge Bay

The weather for my second visit to Druridge Bay this year was rather better than I enjoyed when I was here back in May.  This time around, the sun was shining and the huge expanse of sand spread out invitingly before me.  This was Northumberland at its very best … glorious scenery and just a handful of other tourists with whom to share it.


Druridge Bay at low tide in July 2013. 

There were a series of conspicuous ripple marks on the firm sand of the lower part of the beach and, looking closely at the “valleys” within these ripple marks, I saw a few patches, each just a couple of centimetres across, that were noticeably darker than the damp sand surrounding them.   These, like the chocolate-brown patches I scraped from the mud at Whitburn, were composed largely of diatoms, though a different set of species, as the sand presents a very different habitat to the mud I had sampled there.  The most abundant species here was a thin bobbin-shaped diatom, with two chloroplasts mounted end-to-end in the short “body” from which projected two spines, each longer than the body itself.

This diatom looks very similar to the Nitzschia acicularis that we saw in the River Wear in a recent post.  The arrangement of the chloroplasts is identical, and the cells were also busily moving around the slide, in a similar manner to cells of Nitzschia.  However, when viewed under an electron microscope, there are a number of differences that have led many to classify this into a separate genus, Cylindrotheca.


Patches of Cylindrotheca closterium from the “valleys” formed by ripple marks on the beach at Druridge Bay, close to the low tide mark.   The lowermost patch is about four centimetres across.   A single cell of C. closterium is illustrated on the right-hand side.  Scale bar: 25 micrometres (1/40th of a millimetre).

Scanning around the slide, I found some other species of diatoms including the Pleurosigma that we met at Whitburn, and some cells of a planktonic genus, Chaetoceros.  Another that caught my attention consisted of a chain of cells each with a pyramidal base from which emerged a long spine.  Until 1990 this would have been regarded as a marine species in the genus Asterionella, which we met a few weeks ago.   It shares similar-shaped cells which form similar-shaped colonies although, on closer examination, both cell and colony shape are quite different.   Here, the “spine” is much narrower and the chloroplasts are squeezed into the basal part whilst the colonies are loose helices rather than closed star-shaped colonies.   As a result, this is now regarded as part of a separate genus, Asterionellopsis.


A colony of Asterionellopsis glacialis from the same sample as the Cylindrotheca closterium (above).  The inset shows a single cell.  Scale bar: 25 micrometres (1/40th of a millimetre).

The chain of Asterionellopsis cells is quite hard to make out in the illustration because all that I found in the sample were surrounded by what appeared to be organic detritus.   Perhaps I had stored the sample too long before examining it?  I’ll need to revisit the area to see if I can find some cleaner specimens before too long.

Both Cylindrotheca and Asterionellopsis illustrate an important trend in recent studies of the algae, as our ideas about the affinities between groups of organisms change as we learn more about them.  In both these cases, classifications that made sense to earlier generations peering through light microscopes have been revised as more recent phycologists use scanning electron microscopy and, increasingly, molecular biological methods, to examine them.   Indeed, there is still no consensus about Cylindrotheca closterium, with one very recent identification guide still regarding it as part of Nitzschia.  Faced with a pile of algal identification guides, some old, some new, we are little better off than Alice when confronting Humpty Dumpty:
“When I use a word,” Humpty Dumpty said, in rather a scornful tone, “it means just what I choose it to mean — neither more nor less.”