What Constable never saw …


This picture depicts a landscape painted from a position within a few metres of that used by John Constable for his painting Flatford Mill, now in Tate Britain (see “Fieldwork at Flatford”).   It shows part of the same scene almost exactly 200 years after he painted his picture, albeit at a somewhat larger scale (the leaves in the background are only a few millimetres long).   It is based upon the handful of pondweed that I pulled out of the River Stour on 30 December, and the algae that are associated with it.   In the foreground, there is a filament of a green alga that we have not named to our complete satisfaction, but which is either an unbranched Cladophora or Chaetomorpha e linum. Also present in the foreground is a chain of the diatom Ellerbeckia arenaria (see “Ellerbeck and Ellerbeckia”) and, at top left and bottom right there are chains of Melosira varians.   The pondweed leaves are smothered with Cocconeis placentula cells and, at the top right there is a cell of Gyrosigma attenuatum gliding across the pondweed leaf.   Proportions are roughly in line with what I saw down my microscope and the cells of Melosira are approximately 20 micrometres (1/50th of a millimetre) in diameter.

Constable never saw this particular scene on the River Stour partly because he was not (as far as we know) a microscopist, but also because Elodea canadensis, whose leaves that create the backdrop for the image, was not introduced to the UK until after he died. The river would have been different in other ways, too: lower concentrations of nutrients and agrochemicals, in particular. There would have been different submerged plants, but maybe some of the algae growing on their leaves would have been different too?   I was involved in a study a few years ago that looked at this question, using aquatic plant specimens from herbaria. None dated back as far as Constable, but we did see some significant shifts in composition of the attached algae in samples from 100 years ago, compared with now.

The Greek philosopher Heraclitus once said: “no man ever steps in the same river twice, for it’s not the same river and he’s not the same man.”   Perhaps we can also say that no-one looks at the same landscape twice, for it, too, is always changing.   There is a paradox here, because landscape has, at its core, a geological form that change infinitesimally slowly whilst at the same time being cloaked in an ever-changing raiment of vegetation. Rivers are a curious mix of a fixed landscape feature and, as recent floods have reminded us, highly dynamic systems.   And landscape is also a matter of scale: Constable lifted his eyes to the horizon and showed a naturalist’s passion for the clouds that scudded over the Vale of Dedham as he painted.   Sometimes he focussed on more intimate events but not with the level of detail that a botanist craves.   We can look across the River Stour towards Flatford Mill and see the view almost unchanged from when Constable was alive. Yet, at the same time, it is almost wholly different. It is a matter of perspective …


Yallop, M., Hirst, H., Kelly, M., Juggins, S., Jamieson, J. & Guthrie, R. (2009). Validation of ecological status concepts in UK rivers using historic diatom samples. Aquatic Botany 90: 289-295.


Fieldwork at Flatford


If you look just behind the horse in Constable’s landscape (on display at Tate Britain) showing the River Stour with Flatford Mill in the background (1816-1817), you’ll see a man crouching down.   He’s just disconnected the rope between the barge and the horse to enable the barge to pass under Flatford Bridge but, by coincidence, it is roughly the point where, on 30 December, I crouched down to pull out a handful of weed from the River Stour for some post-Christmas natural history.

I pulled up a handful of Canadian pondweed, Elodea canadensis, which happened to have some filaments of a green alga tangled around it.   It was tough, wiry stuff and, as far as I could see with the naked eye, unbranched, which ruled out the most likely candidate, Cladophora glomerata, so I stuffed a handful of the weed into a sample bottle that I had brought along and brought it back home for a closer look.   However, what I thought would be a straightforward identification task proved problematic.   Rhizoclonium hieroglyphicum is an unbranched alga in the same order as Cladophora (Cladophorales) but the Flatford material was too broad to fit the description. Another candidate, a marine/brackish species occasionally found in freshwaters, is Chaetomorpha linum. The Flatford material was broad enough to qualify as this species, but the cells of C. linum are typically less than twice as long as broad, whereas the Flatford alga had cells with a longer length:breadth ratio.   So, even after consulting Dave John, who wrote the relevant section of the Freshwater Algal Flora of the British Isles, I am still not confident that I know the genus, let alone the species.


Flatford Mill algae: a. the tangle of Elodea canadensis and filamentous algae that I pulled from the River Stour; b. the unidentified alga with epiphytic diatoms (Cocconeis spp. and Rhoicosphenia abbreviata); c. a filament of Ellerbeckia arenaria, also tangled amidst the E. canadensis. Scale bars: 10 micrometres (= 100th of a millimetre).

The filaments were, in turn, smothered with diatom epiphytes – mostly Cocconeis placentula but also some C. pediculus and Rhoicosphenia abbreviata and there were also a few chains of the large centric diatom Ellerbeckia arenaria (see Ellerbeck and Ellerbeckia) alongside a variety of other diatoms including chains of Melosira varians.   The tangle of Elodea and Cladophorales filaments presumably creates a “micro-backwater” within which these other organisms can thrive away.


Unidentified Cladophorales from River Stour near Flatford Mill, 30 December 2015; scale bar: 50 mm (= 1/20th of a millimetre).

My final picture for this post is a view down my microscope during my examination of this material – a homage to John Constable’s landscapes, of sorts, except that distances in my image are measured in micrometres rather than metres.   You can see a filament of the Cladophorales complete with epiphytes at one side and, on the other, a few cells of the diatom Melosira varians. Understanding of the composition of a sample of algae comes from examination of many fields of view such as this, partly because, as you can see, there is usually a lot of non-algal material present that would obscure the algae if preparations were much denser.   I’ve also taken some liberties with depth of field in putting this sketch together.   The experienced microscopist is constantly adjusting the fine focus to get an insight into the three-dimensional structure of his samples. With microscopy, what you see is rarely what you get … but I’ve written about that quite recently so perhaps it is time for me to stop…


A view down the microscope (400x magnification) whilst examining the material from Flatford Mill. Watercolour, gouache and pencil.

How to make an ecologist #2


My New Year musings over the origins of my professional interest in ecology included a journey along the A12 out of London to the Dedham Vale, on the Essex-Suffolk border.   If the building in the photograph above looks familiar, it is because it forms the backdrop to John Constable’s The Hay Wain.   It is also one of the accommodation buildings for Flatford Mill Field Studies Centre and, for a brief but formative week in the summer of 1979, a temporary home for me whilst I made my first tentative forays into the world of ecology.

This experience came at the end of a year of frankly lacklustre biology teaching during my lower sixth year that had done little to rekindle the adolescent enthusiasms that I wrote about in my previous post.   That the school had chosen an A level curriculum that did not involve a practical examination speaks reams about their genuine interest in our education over easing us smoothly through the bureaucratic hassle of an examination and out of their responsibility.

This first experience of field ecology was no Damascene conversion to the joys of ecology.   If anything, I remember being underwhelmed.   At home, my reading had progressed from Arthur Ransome’s adventures set amidst the hills of the Lake District to Chris Bonnington’s accounts of mountaineering in the Himalayas.   Earlier in the year, David Attenborough’s ground-breaking Life on Earth had been screened on the television.   Somehow, the Essex landscape did not seem to match up with these more glamorous settings.   In retrospect, however, I think Flatford was less an anteclimax and more of an antidote to the drama of high mountains, tropical locations and exotic wildlife.   Flatford taught me that ecology did not need a plane ticket and a huge budget. It could be studied in a saltmarsh in Essex, just as easily as on the Serengeti plains.


Flatford Mill Field Studies Centre, December 2015.

Our group of 20 or so teenagers from east London were part of a varied crowd at Flatford Mill that week, alongside older, and rather more sedate, clientele signed up for classes on watercolour painting and church architecture.   There was, I remember, a scrummage after breakfast when the ingredients for packed lunches were laid out.   It was survival of the fittest – another early but important lesson for a nascent ecologist – albeit with pensioners taking the role of top predators whilst the school groups were left to scavenge on the left-overs.

Evening meals, on the other hand, were rather more sedate affairs, presided over by the warden, Jim Bingley, who adopted the airs of Lord of the Manor.   Once again, our group were the ones left behind as the gong sounded and the sharp-elbowed old ladies rushed in to the dining hall to get the best seats.   Strangely, I cannot remember much about the food itself during that week, only about the behaviour of my elders and betters.

One evening, after our classes had finished, I remember standing in the library with my friend, Stuart, pulling books off the shelf and laughing at the idea that anyone could write an entire book about a subject as obscure as butterflies or earthworms.   We were reprimanded by our teacher for our flippant attitude and I can only smile wryly at this memory.   This disrespectful schoolboy ended up writing one of the Field Studies Council’s identification guides and, I am guessing, a new generation of school children are even now pulling it off the shelves of Field Centre libraries and wondering how anyone can get quite so obsessed by nature …


The cover of my now rather dated booklet, written for the Field Studies Council.