Blue skies and blue flowers in Upper Teesdale

There was barely a cloud in the sky for my second walk in Upper Teesdale this year, following the same route as my excursion in early March.   I spent most of the walk in shirtsleeves and, as I arrived at the top of Cauldron Snout, had clear views towards Cross Fell, the highest point in the Pennines.  Widdybank Fell, the area around me, was a mosaic of heather moorland and closely-cropped grassland and, dotted around the grass were small flowers with a vivid deep-sapphire blue.  These are the spring gentians, Gentiana verna, which appear for a few weeks in the spring time in Upper Teesdale.   They belong to a group of plants called the “Teesdale rarities”, mostly species associated with arctic-alpine conditions which have survived in the unique environment of Upper Teesdale since glacial times.  To find so many spring gentians in mid-May is a sign of just how cold it has been this year.  I remembered, as I stood on Widdybank Fell, that I was in the same area almost exactly a year ago and there were virtually no gentians at all to be seen.

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The Spring Gentian, Gentiana verna, photographed on Widdybank Fell, May 2013.

But the spring gentians are a distraction today.  My eyes were pulled towards the small stream. Red Sike, flowing off Widdybank Fell and into the Reservoir.  The water was just a couple of centimetres deep, flowing across mostly limestone bedrock with just a few mobile pebbles  The stream surface was freckled with tiny dark brown dots, which represent one more, albeit virtually unknown, addition to the intriguing flora of Upper Teesdale.

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Left hand picture: Red Sike, with Cow Green Reservoir in the distance, photographed in May 2013.   Right hand picture: a pebble from Red Sike with dark-brown, hemispherical colonies of Rivularia.

The usual approach to examining objects under the microscope is to have a very thin layer of the material, so that light can pass through it, and because the depth of field at high magnifications is very shallow.  However, the little dots from Red Sike were resistant to this, refusing to be squashed under my cover slip.  I had to tease out a few fragments with forceps and a needle in order to examine them.  The reason was clear even at a relatively low magnification: I could see filaments of an alga all radiating out from a central point – that was what gave the colony its hemispherical shape – but, amidst the filaments were crystals of calcite.   A superficial examination showed these filaments to be similar to those of the blue-green algae which we have already met, except this time the filaments gradually tapered to a narrow point.   At the base of each filament was a cell with a different, more rounded, shape.  This was the “heterocyst”, specialist cells responsible for nitrogen fixation.  We saw these in the Tolypothrix filaments from the River Ehen (see post of 1 March 2013).

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Filaments of the blue-green alga Rivularia biasolettiana from Red Sike in Upper Teesdale.  The base of each filament is about 10 micrometres (1/100th of a millimetre) across.

Nitrogen fixation is an expensive process for any organism, as it requires a lot of energy.  However, those organisms that can capture atmospheric nitrogen have a competitive advantage, especially in situations where nitrogen is naturally scarce.  A few kilometres downstream, there will be just enough nitrogen leaching into the river from farming and other human activities for organisms such as Rivularia to lose this competitive advantage.  Consequently, the presence of Rivularia in Upper Teesdale is a good indicator that this is a stream in its natural state, filled with organisms adapted to eking out an existence in a perpetually “hungry” state.  Ironically, it is when man starts to “feed” rivers with nutrients and organic matter that the problems start.

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Black Swan #2: McEcology and Steve Earle

I’m still mulling over the contents of Nassim Nicholas Taleb’s book The Black Swan (see earlier post).  He spends many pages (too many, perhaps) unpicking the statistical foundations of the predictive models beloved of economists (and which are similar, in many ways, to the models ecologists use).  Such models, he argues, have a track record of failing to predict the really significant events, because these, by their very nature, often fall outside the expectations of those of us raised to think in terms of “normal” (Gaussian) statistics.   Rather than attempt imperfect predictions of the future, he suggests, we should, build robustness into our institutions to enable them to react to change.

Yet, when I look around, I see the exact opposite happening, as the economic recession (itself the product of Black Swan events such as the subprime mortgage crisis in the USA) forces the public sector to retrench.  All of the agencies with which I work in the UK, and many elsewhere in Europe, are having to survive on smaller budgets than was the case a few years ago.   The mantra is always “efficiency” but let’s dissect this and examine what it means through the lens that Talib has given us.   Efficiency implies a high ratio of useful work to effort expended and, as “effort” has to paid for from our taxes, this all sounds very reasonable.   My problem lies is how this is being achieved.  You can bring about “efficiency” of a sort by adopting the approaches of manufacturing industry: splitting tasks into discrete steps and thinking about how to optimise each of these.   The outcome should be efficient production of a homogeneous product.   Think hamburgers.   And welcome to “McEcology”.

This is fine if your product is data, as burger chains achieve a level of reproducibility in their outputs that most ecologists only dream about.   However, if your product is “knowledge” or “advice”, then perhaps splitting the task into several steps and making the ecologists spend less time in the field, will be counterproductive.  It depends if you think of ecologists as data monkeys or as professionals.

Taleb’s term for this process is “naïve optimisation”, though he approaches the topic from a different angle.   He believes that organisations cope with the unexpected by having innate robustness and, interestingly, given my context, uses analogies from ecology.  Robustness and stability arise from having many interdependencies within systems.  This may look like redundancy to an outsider (why do we have two kidneys, for example?) and, therefore, fair game when savings have to be made.   Yet viewed from another perspective, this “redundancy” is insurance against things going wrong.   The human body can cope, for example, with only one kidney.  The “optimised” ecology teams I meet in my work  struggle to cope when colleagues are off sick or on maternity leave and, as important for professionals who need to offer advice and opinions, have little time for reflection and ad hoc investigation of issues that fall outside scheduled activities.

These thoughts came together last night when I went to see the American singer Steve Earle.  He had a role in the TV series Treme, about New Orleans in the months following Hurricane Katrina and three of the songs in his set were written for the show.   Introducing these songs, he reminded us how the aftermath of Katrina – a classic example of a Black Swan event – had been prolonged because the federal agencies responsible had had their budgets slashed by the Bush administration.   All looked fine on paper … until the one time they had to respond to a real crisis.

In the footsteps of a Victorian microscopist …

I embarked on a pilgrimage, of sorts, last weekend, driving to the Druridge Bay, on the Northumberland coast, about 30 kilometres north of Newcastle.   On a sunny day, this is a wonderful horseshoe-shaped expanse of wide, and often almost empty, beach backed by sand dunes and facing into the North Sea.   It was, however, unseasonably wet and windy during my visit,  which robbed it of much of its charm.

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Druridge Bay at low tide on a wet Saturday afternoon in May 2013.

I was following in the footsteps of Arthur Scott Donkin, lecturer in Medical Jurisprudence at King’s College, University of Durham in the middle of the nineteenth century.   King’s College was the medical school attached to Durham though it was in Newcastle, rather than in Durham itself.  It eventually broke away from Durham to become the independent University of Newcastle, where I currently teach.   Details of Donkin’s professional life are vague but would have involved the application of medicine knowledge in legal fields.   This predates the establishment of forensic science as a distinct discipline (the first Sherlock Holmes story did not appear until 1887) so perhaps his main interests were pathology and autopsies?

Donkin’s hobby, and his legacy, was microscopy, and he published about half a dozen papers describing the diatoms of north-east England and we know that Druridge Bay was one of his favourite collecting grounds.  There is one very common diatom, Navicula gregaria, whose original description was based on material collected by Donkin from here, and another, less common diatom which is actually named after Druridge Bay.  It was a curiosity to see this diatom that had brought me here at low tide.

I scooped up enough wet sand to fill a mussel shell, put this into a large plastic bottle. added about 250 millilitres of seawater and screwed on the top.  I then shook the bottle hard for about two minutes then allowed a few seconds for the sand to sink to the bottom before pouring the now-cloudy seawater into a smaller bottle.   Back at home, I stood this bottle in the fridge overnight to allow the particles to settle, poured off the clear water and siphoned up a few drops of the settled material to examine under my microscope.

I went through this rigmarole in an effort to dislodge some of the algae that live attached to the sand grains, as it was here that I hoped to find some cells of Druridgia compressa, the species that Donkin had described back in 1861.  However, I seemed to be out of luck, finding mostly just particles of organic matter of indeterminate origin until one lone diatom cell glided into view.   By coincidence, this was a diatom belonging to a genus called Donkinia – named after Arthur Scott Donkin by one of his fellow microscopists.  This was not growing on the sand grains but, instead, moves through the gaps between grains.

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A cell of Donkinia collected from Druridge Bay in May 2013.  It is about 50 micrometres (1/20th of a millimetre) long.

Druridgia reminds me of a line from Henry IV part I that I was forced to learn at school: “… Being wanted, he may be more wondered at ….”   One of my books describes Druridgia as being “rarely recorded”. Apply this criterion to a bird or a higher plant and it would become a cause célèbre for the conservation movement.   Yet Druridgia is a microscopic alga, so is unlikely to elicit the same level of attention even though it represents an evolutionary lineage as long and as fascinating as those of the more charismatic creatures that fill our television screens.

Black Swans #1: rolling stones gather no moss …

I’ve recently finished reading Nassim Nicholas Taleb’s book The Black Swan and am slowly digesting the implications for the work that I do.  “Black swan events” are occurrences that are unexpected (by the observer) but which have a disproportionately large impact on the observer.   Taleb points to 9/11 as a classic example of a Black Swan event, insofar as it came out of the blue and led to a seismic shift in foreign policy thinking in the US and beyond, the reverberations of which are still with us.   He also adds one other characteristic of Black Swan events: that once the event has occurred, it is rationalised by hindsight, as if it could have been expected.  And, again, the media in the weeks following 9/11 was full of just such “I told you so” articles.

The problem, Taleb argues, is rooted in Western epistemology – the philosophy of the nature and scope of knowledge.   The emphasis in Western thought since the age of the Enlightenment at least has been to draw general conclusions from specific observations.   Modern scientists make heavy use of statistics to provide the links between observations and conclusions yet the statistics we use – and the normal distribution in particular – are good at predicting “average” or “typical” conditions, but are far less reliable at predicting consequences of low probability events – those that occur in the “tail” of the bell-shaped normal distribution curve.   Yet the crux of Taleb’s argument is that it is often these events that have the most profound impact.

The main focus of Taleb’s ire are the financial analysts whose sophisticated models consistently fail to predict the various market-shaking events of the last thirty years or so.  However, I saw much that was of at least tangential relevance to ecology.   My fellow practitioners won’t like me saying this but ecology is a discipline which hovers between the “hard” and “soft” sciences.  We can isolate particular components of the highly complex systems that we study and subject them to controlled experiments, following all the tropes of rigorous, quantitative science.  Yet the very act of isolating components often means that we have created simplified, artificial situations and there is no guarantee that the components will act in the same way in the complicated and often unpredictable ecosystem from which they were plucked.  So we often resort to soft science methods such as taking measurements in the field and then looking for correlations and associations.  Our science advances from piecing together these various strands of evidence to make a convincing narrative.

Reading “The Black Swan” brought to mind a conversation I had had with colleagues a few years back.  We were contemplating the ecology of submerged mosses in rivers.  The data we had consisted of associations between these mosses and water chemistry.  We were particularly interested in the consequences of reducing nutrient concentrations.  Would this, we were wondering, lead to significant changes in the ecology of the river?  As mosses often form a major part of the plant biomass in the rivers in which we were most interested, a change in these might have been expected.  Some mosses, indeed, did inhabit rivers with higher nutrient concentrations than others.  The question was exactly that which Taleb was posing for financial markets: did our models allow us to make predictions?  Or, as they were based on correlations and associations with current conditions, were they descriptive, with very limited predictive power?   The point that dawned on us was that one factor not included in our equations was the rare but catastrophic flood that would have the power to turn over the stable boulders which were the preferred substratum of the mosses and scour away many of the plants.   These are the Black Swan events in rivers that would provide the tabulae rasa on which new species could establish themselves.

But this, in turn, runs into another set of problems: the need for “evidence-led policy”.   Models which do not include the possibility of “Black Swan events” may have low predictive power and, therefore, an excuse for those policy makers and industry sceptics who want to avoid expenditure, especially where there is low confidence in a positive outcome.  Yet, as Taleb, points out, the very nature of low probability, high impact events, means that it is difficult to build them into models.  The dilemma is exacerbated by the short-termism which permeates many areas of science and science-policy.

So what is the answer?  It is probably not bigger and better models, particularly if we are dealing with low probability events.  The simplest solution may be to stop making inferences about ecological dynamics from spatial studies and shift the focus, instead, to monitor those situations where changes should be expected.  There are numerous cases all over the country where water quality improvements are being enacted yet the ecological monitoring both before and after is often extremely limited.   Yet it is only by following changes at these sites over a number of years – long enough to allow Black Swan events to exert their effects and with adequate spatial and temporal replication – that we will build up reliable evidence on which policy should be based.   Long-term environmental monitoring by UK’s statutory agencies?  Forget Black Swans: that would be a Pig’s Might Fly event.

Phworrrrhhh …. algal sex in 3D!

I commented in a post back in March that many algae lived quite happily in an asexual state and that it was rare to see sexual reproduction in “wild” populations.  This, in turn, makes it difficult to identify many species (imagine a garden in which the plants only ever produced foliage and never, or rarely, produced flowers).  A couple of weeks later I received an email and some photographs from a friend, Chris Carter, who had found some Vaucheria in full “bloom” growing in his garden pond in Northampton.  Although it is often bright green in colour, Vaucheria is actually a member of the group of algae called Xanthophyta, and is more closely related to the diatoms than it is to the other green algae.   It is another of the annoying filamentous forms that can only be identified to genus in the vegetative state but the presence of sexual organs had allowed Chris to name this population as Vaucheria taylorii.

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The vegetative filament (running diagonally from left to right in this image) is a long, hollow tube (about a tenth of a millimetre in diameter in this example) without cross walls dividing it into separate cells.   The chloroplasts lie just inside this tube, leaving a large empty vacuole in the middle of the cell.  On the outside of the tube there is a rich growth of other algae (mostly diatoms).  The sexual organs are on the short lateral branch in the centre of the image.  This species is monoecious, meaning that male and female organs grow on the same plant.  The oospores, the female reproductive cells, are the dark green ovoid structures growing in a whorl whilst the male organ rises above these and looks, well, male….

The crispness of this image is due to a special technique used by Chris called “stacking”.  All microscopists face problems when trying to capture three-dimensional objects because of the low depth of field associated with highly magnified images.   “Stacking” involves taking a series of images, adjusting the focus very slightly between each, so that you end up with a series of images of the same object, but each with a different part of the object in crisp focus.   Chris then uses a piece of proprietary software to select the sharply-focused parts of each image and combine these into a composite image with apparently greater depth of field than is possible from any single image.

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Chris then goes one step further by taking a series of images from two slightly different viewpoints (not as easy as it looks, as the subject has to be tilted slightly between the two sets of images.  He then combines each of these to give a composite image, as above, but then he manipulates the image further to remove red from the left image and blue and green from the right image.   When the two images are superimposed, the outcome is an “anaglyph”, a stereoscopic image.  You’ll need a pair of 3D glasses to see this image properly (the old-fashioned type, with one red and one blue lens).  He has made a speciality of this type of photography, producing images of the microscopic world that leap off the page in a dramatic fashion.  Of course, like a true artisan, Chris is never happy and commented in a recent email to me that “this seems to be another genus whose 3D characteristics and (messy) environment needs the artist’s brush.”  Whereas I, struggling always with brush and paints, look at Chris’ anaglyphs and wish I had his dexterity with a camera.   The grass, I guess, is always greener on the other side…

Healthy streams are slippery streams …

I couldn’t resist repeating this phrase after reading it in a press release and then to dig a little deeper into the research that it was reporting.   The phrase is a succinct summary of what I want to convey through this blog: that the microscopic life which coats submerged surfaces in lakes and rivers is an essential component of aquatic ecosystems.  Anyone interested in long-term sustainability of freshwaters cannot afford to ignore the composition and functioning of these “biofilms”.  Yet it is, undoubtedly, slippery and slimy and, consequently, sometimes unsightly and often a nuisance.

But “nuisance” is, itself, a loaded term with no more definitive quality than something in the wrong place at the wrong time.   Perhaps the angler who slips on these films in search of recreation is, himself, the nuisance, as he assets himself as an unnatural top predator in the river food chain?   Except that the angler is, in modern parlance, a “stakeholder” and the fishing that he enjoys is an “ecosystem service”, thereby converting the often abstract business of conservation and environmental protection into a tangible benefit for society.

The press release led me to a paper by two US ecologists, Emma Rosi-Marshall and Todd Royer, on the effect of pharmaceuticals on aquatic systems.    The story goes something like this: your doctor prescribes antibiotics to fight a bacterial infection which you dutifully take.   Most of the antibiotics are absorbed by your body and you recover from your infection.  However, a portion of the antibiotic passes through you, into the sewerage system, then through a sewage works and into a river where it continues to exert its antibacterial activity but now on the natural microbial communities which play an essential role in nutrient cycling.

This is not a completely novel idea: there have been reports of antibiotic resistance in natural communities of bacteria for some time now, and the effects of constituents of birth control pills have been widely reported.   Most of these papers have adopted a traditional toxicological approach, looking at effects on a single organism. Rosi-Marshall and Royer go one step further by pulling together the few fragments of evidence of effects at the ecosystem level. For example, antibiotics can influence the decomposition of leaves, leading to fewer bacteria and more fungi which in turn, made the leaves more palatable to some types of invertebrates. The result is a series of small, but potentially consequential, shifts in how energy moves through ecosystems.  Stir in the whole cocktail of healthcare products – antihistamines (inhibit neurotransmitters in invertebrates), birth control pills (inhibit reproduction of fish), even antidepressants (induce spawning in bivalves) – and a picture emerges of aquatic ecosystems subject to a multitude of individually small but cumulatively significant changes.

Where does this leave us?  Two undeniable points are that pharmaceuticals and other health care products bring major benefits to society, and that the cost of removing all traces from wastewaters would be very high.  Balanced against these, the costs to ecosystems might seem a fair price to pay.  Maybe.   Trade-offs such as this happen all the time.  But the trade-off is only valid IF you understand the costs and accept that there may be situations where the consequences are unacceptable.  Nonetheless, simply recognising that these compounds might be a problem is a step in the right direction.  That said, it is yet another stressor to include in the “causal thickets” that we have to untangle when trying to understand river ecology.   “Causal thickets”?  That’s a subject for another post.

Reference

Rosi-Marshall, E.J. & Royer, T.V. (2012) Pharmaceutical compounds and ecosystem function: an emerging research challenge for aquatic ecologists.   Ecosystems 15: 867-880.

Return to Kilmartin Burn …

Back in early April I was looking into Kilmartin Burn, in Argyllshire, and noticing the water milfoil (Myriophyllum alterniflorum) smothered in epiphytes.   Having looked at the various components separately under the mciroscpe (see post of 5 April), the next step was to put the various components together again, in an attempt to visualise the community of algae growing in and around the finely-divided leaves of the water milfoil.  It took longer than expected but here, at last, is the finished product.

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The epiphytic life on the finely-divided leaves of Myriophyllum alterniflorum from Kilmartin Burn in April 2013.  The long needle-like cells of Ulnaria ulna are about one tenth of a millimetre in length.

The picture shows the finely-divided leaflets of Myriophyllum, each bearing numerous needle-like cells of Ulnaria ulna which, at one tenth to almost a quarter of a millimetre in length, are giants amongst the other diatoms.   The Ulnaria cells generally occur in small clusters, radiating out from a mucilage pad at their base.   There are also many fan-shaped colonies of another, smaller, diatom, Meridion circulare, some of which stood erect on the surface of the Myriophyllum leaflets whilst others were lying flat.   Finally, you can also see a small number of elliptical cells of Cocconeis placentula, which grow flat on the surface of the Myriophyllum, and a few cells of Achnanthidium minutissimum.   You can see photographs of Ulnaria, Meridion and Cocconeis cells from Kilmartin Burn in the 5 April post, and we also met Cocconeis placentula growing on the underside of duckweed in Cassop Pond back in the 26 January post.   Achnanthidium minutissimum is an extremely common diatom, particularly in clean waters, and there are several illustrations of this on my website, www.martynkelly.co.uk.

All of these algae are thriving in the relatively-sheltered conditions created by the finely-divided Myriophyllum leaves.  Had I hunted harder, I would also have found many invertebrates living here too, so the Myriophyllum creates a self-contained world within the wider stream environment.  But this has a cost as the mass of diatoms intercept the sunlight before it reaches the Myriophyllum leaves.  People have suggested that one way that eutrophication – the artificial enrichment of lakes and rivers by nutrients – can disrupt ecosystems is by increasing the mass of these epiphytic algae and ultimately “shading” the host plant until it can no longer survive.  There is also some evidence of submerged plants secreting chemicals which attract invertebrate grazers which, in turn, stop the epiphytes attaining such damaging quantities.