Lake Lakelake Lake

Lake Lakelake Lake


This post is my small contribution to the Greek economy, as the words “rain”, “August” and “Yorkshire” may occur in sufficiently close proximity to encourage any readers contemplating a holiday in the UK to consider putting their pennies into the pockets of Greek hoteliers instead.   I’m just back from a break, walking in the Yorkshire Dales, having dropped off my youngest son at the Lord of the Flies theme park that is the Leeds Festival.   As you may have noticed if you follow this blog, I don’t really do “holidays”, at least not in the traditional sense of “stop thinking about work” so here goes …

The photograph above shows Semer Water, the second largest lake in the Dales, after Malham Tarn although, this being limestone country, neither is particularly large in absolute terms. It is a glacial lake less than a kilometre long and no more than 10 metres deep. We parked our car at the village of Bainbridge, about 3 km to the west, then circumnavigated the lake, alternately putting on and taking off waterproofs at the whim of the passing clouds.   The photograph above captures the lake at one of the sunnier moments during the day. Not complaining, just commenting.


Semer Water, photographed from the approximate location where J.M.W. Turner painted his view of “Simmer Lake” in 1816 (inset).

Just beyond the east end of the lake there is a sign encouraging visitors to sit at the location where J.M.W. Turner sat to paint his view of “Simmer Lake” in 1816.   The low clouds in Turner’s view show that the weather was no better in July 1816 than it is today.   My view along the lake, however, was obscured by a row of trees. Note the relative positions of the large boulder with respect to the lake then and now: sometime between Turner’s visit and ours the lake level was artificially lowered (using explosives to remove some of the terminal moraine at the outfall, I was told) in order to expose the low-lying area to the west so that they could be used for grazing.   That may explain why the boulder today is so much further from the lake shore than in Turner’s day.

The name of the lake itself is quite interesting: it is variously reported as “Semer Water” (Ordnance Survey maps), Semerwater (Natural England documents) and even Lake Semerwater (interpretation board at west end of lake).   The word “Semer” is, itself, derived from two Old English words for lakes: “sæ” (close to the German “see”) and “mere”, so Semer Water is, effectively, “Lakelake Lake” and Lake Semerwater is just plain ridiculous.   It is enough to drive a man to drink and, fortunately, the Moorcock Inn at Garsdale Head serves Wensleydale Brewery’s Semer Water beer, a refreshing light ale that you almost certainly cannot buy in Greece.   So there is one reason why it is worth visiting Yorkshire in August after all…


What we expect is often what we get …

In a recent post I posed the question of whether healthy ecology in rivers could be considered to be a “steady state” (see “Making what is important measurable …”). I asked this question because, following pioneering work by Brian Moss and others on the Norfolk Broads, the idea of “alternative steady states” in shallow lakes is well established. However, there is a deep-seated assumption that changes in rivers, and many other ecosystems, are gradual shifts along a continuous gradient: increase the “dose” of a pollutant or other pressure, and there is a concomitant “response” in the biology.   My earlier post referred to “good ecological status” as the goal of water management in Europe – implying that we should be trying to achieve a “state”.   Most of the approaches to ecological assessment define this state simply in terms of a threshold on a gradient but could there be other ways of interpreting such data?

Suppose that, for the sake of argument, algae in rivers exist in three “states” with respect to nutrients:

  • Low nutrients, high oxygen concentration – the natural “state” in most cases, where the river is naturally nutrient-poor and algae adapted to living with low concentrations of nutrients are selected.
  • High nutrients, high oxygen concentration – concentrations of inorganic nutrients are elevated due to agricultural or other enrichment, and conditions now favour competitive algae such as Cladophora over algae adapted to living in nutrient-stressed conditions.
  • High nutrients, low oxygen concentration – conditions associated with organic pollution, where there is substantial heterotrophic activity using up dissolved oxygen; conditions favour species of algae (such as some Nitzschia species) that can tolerate reducing conditions and which are facultative heterotrophs.   As this state is often associated with highly polluted conditions, nutrient concentrations will be higher than in the “high nutrient, high oxygen concentration” state.

If this model is true and we sampled diatoms across a number of similar rivers along a phosphorus gradient, then we might expect similar results from locations that shared the same state, as illustrated in the Fig. 1.   Note how the ranges for the different states overlap along our nutrient gradient.   Changes from one state to another are not driven solely by nutrient concentrations but may be induced by changes in other factors (e.g. grazing intensity).


Fig. 1.   Hyptothetical data assuming that algae in rivers exist in three alternative but overlapping “states”, which are expressed as three values of the Trophic Diatom Index (TDI): low nutrient, high oxygen (closed circles); high nutrient, high oxygen (open circles) and high nutrient, low oxygen (closed squares). Arrows indicate changes between the overlapping states.

Now let us assume that there is a second factor that can influence the composition of the diatom assemblage and, therefore, indices such as the TDI.   Local geology is known to have such effects, and can be summarised in terms of variables such as alkalinity or calcium concentration.   Let’s apply this variable at random by up to six TDI units to each level and plot the results:


Fig. 2. The same data as for Fig. 1 but this time with TDI values varying by ± 6 units due to a random variable.   Regression statistics: F: 48.8; P < 0.001; adjusted r2: 0.77.

This now looks less like three distinct stable states and more like the gradients that most stream ecologists like to see (especially if you ignore the three different symbols that I used to define the stable states). Gradients are, after all, amenable to all sorts of statistical methods including regression analysis and it is even possible to start contemplating predicting how the diatom assemblage might change if the phosphorus concentration was reduced by a known amount.   Of course, good ecologists should be aware of such factors, and control for them in any models that they construct but this does not always happen …

Finally, let’s assume that our second variable does not vary randomly but is, itself, weakly correlated with nutrients.   This time, the scatterplot looks even more impressive (see below). Yet it is the same scenario as in Fig. 1, only with some additional “noise” stirred in.   And I have only included a single additional factor when, in reality, there will be a number of different physical, chemical and biological factors working to influence the composition of the algal assemblage at any point in time and disguise the existence of three states.


Fig. 3. The same data as Figs 1 and 2 but this time with TDI values varying by ± 6 units due to a variable that is correlated with the x axis. Regression statistics: F: 152; P < 0.001; adjusted r2: 0.92.

As I said earlier, a good ecologist should understand these factors and control for them when building a model. However, this only ever works up to a point. Firstly, we can only control for what can be measured, and these additional measurements are limited by the resources available to a researcher as well as by the assumptions that s/he brings to the study design.   But this leads into my second point: we too often bring the assumption that we are observing changes along a gradient which, in turn, can make us blind to the possibility that the situation is more complex, and that we may be dealing with alternative stable states. The final point is that most of the studies from which inferences about algal ecology are made are based on spatial surveys with limited temporal coverage.   Any community that we observe in a river is the product both of the environment that we can try to capture with our measurements, but also of its history, and of events that may have taken place upstream. As Louis Pasteur once said, “fortune favours the prepared mind”. If we approach our data expecting to see a gradient then we are not surprised when, after some gentle cosseting with statistical package, a gradient usually appears.


I should point out, for the sake of completeness, that there is also a significant relationship between TDI and P for the data plotted in Fig. 1 (F: 46; P < 0.001; adjusted r2: 0.77).   My point is that it does not look like a gradient and a viewer is more likely to contemplate the possibility of alternative stable states.

I also suspect that these states can co-exist at the same site but more about this in a future post.

A good introduction to the application of alternative stable states to shallow lakes can be found in: Moss, B. (2010). Ecology of Freshwaters: A View for the Twenty-first Century. 4th Edition. Wiley-Blackwell, Chichester.

Hilda Canter-Lund photography award winner, 2015


Octopus’ Garden: Günter Forsterra’s winning image in the 2015 Hilda Canter-Lund photography competition.  

I’m pleased to be able to announce the winner of this year’s Hilda Canter-Lund photography competition: Günter Forsterra, for his stunning image of the undersea world of the Beagle Channel in Chilean Patagonia.   Large portions of the rocky benthos along the Beagle Channel are dominated by communities of macroalgae. These provide a habitat for a variety of invertebrates as well as shelter and food for fish.   The principal alga in this photograph is the brown alga Lessonia negrescens. The image was taken during a study of rocky benthos in summer 2010 when water temperatures were around 5°C, using a Canon EOS5 Mark II camera with a 24mm wide angle lens and a Sealux underwater housing.  Günter’s picture is on display, along with all the shortlisted entries, at the European Phycological Congress in London this week, after which it will be exhibited in the Angela Marmot Centre in the Natural History Museum.


Günter Forsterra: this year’s Hilda Canter-Lund competition winner

Günter Försterra is originally from Germany but is now the Research Coordinator at Huinay Scientific Field Station in Chilean Patagonia. He studies fjord ecosystems and is especially interested in the ecology of cold-water corals and the forces which determine species distribution within Chilean Patagonia. He co-edited a field guide to the marine benthic fauna of Chilean Patagonia and sits on several advisory committees concerned with marine conservation. Since 1994 he has used his underwater photos to promote the beauty of Patagonian marine life to the public and to governmental institutions. He is married to Vreni Häussermann, whose image was also shortlisted this year.

John Tunnard: Nature, Politics and Science


The DLI Musem and Art Gallery in Durham, August 2015

I’ve written about my interests in the borderlands between science and art several times before (see ““Imagined” but not “imaginary”” amongst other posts) so an exhibition entitled “John Tunnard: Nature, Politics and Science” at our local art gallery is not something that I can ignore.   The exhibition, at the DLI Gallery, is an overview of the career of John Tunnard, a modernist painter active during the middle of the 20th century, and the relevance to a blog that focuses on algae is that the exhibition was curated by, and contains many  paintings owned by, my PhD supervisor, Brian Whitton.


John Tunnard: Nature, Politics and Science at the DLI Museum and Art Gallery, August 2015

Tunnard worked in a variety of styles, but the picture below is a good summary of his work, which often hovers on the borderlands between realism and abstraction.   There are identifiable elements within the painting (the sea on the right hand side, a moon suspended in a night sky towards the centre?) but also abstract shapes that veer towards surrealism (though, apparently, Tunnard himself did not formally associate himself with this movement).   Other pictures include references to the natural world, particularly around his home in Cornwall but, again, he pushes our expectations of what this natural world looks like, teasing us with alternative, more abstract, realities. In Cliff Tops, amongst near-recognisable flowers, we see a rock formation that bears an uncanny resemblance to the head of a whale.   Does this borderland between realism, imagination and abstraction exist in the head of the artist or the viewer, or does it depend on a synergy between the two?   Or is it out there, all the time, just waiting for an open mind to approach it?


John Tunnard: Holiday, 1947, lithograph, 42 x 68 cm.

In his later paintings his interest in science branches out and space motifs, in particular, start to appear in his paintings. The parabolic bowl of a satellite earth station dominates some whilst one painting, from 1969, shows moon craters. This brings the issue of realism and the imagination into sharp focus: before the Apollo missions, we had ideas about the moon; from 1969, lunar landscapes had a reality against which the efforts of an artist could be verified.   As is often the case, abstraction and reality are not mutually exclusive; perception and experience play a part in determining the limits which, consequently, can vary from person to person, and from subject to subject.

The exhibition runs until 4 October 2015


Peat, A. & Whitton, B.A. (1997).   John Tunnard: His Life and Work. Scolar Press, Aldershot.

Whitton, B.A. (2015). John Tunnard: Nature, Politics and Science. Exhibition Catalogue, DLI Museum and Art Gallery, Durham.

Making what is important measurable …

I heard an interesting discussion on Radio 4 a couple of weeks ago that set me thinking about the theoretical basis of ecological assessment. The discussion, paradoxically, was about education rather than ecology, but I have mentioned in the past that there is common ground between these two disciplines (See “The madness that is “British values”).   The discussion involved a comparison of the education systems of the UK and China.   In many measures, the education system in China appeared to be outperforming that in the UK, but one contributor questioned whether the measures being compared were actually appropriate.   China appeared to perform better than the UK because the measures being used were crude assessments of the proportions of students that passed exams and which, therefore, favoured rote-learning over more interactive approaches to education. The contributor went on to suggest that this search for easily quantified measures of school performance was part of a more general problem.   The telling distinction that he used was “making what is measurable important” versus “making what is important measurable”.

That summarises my series of posts from June (see “The human ecosystem of environmental management …” and the two subsequent posts).   We have made progress over the last two or three decades towards developing criteria that are “important” rather than just “measurable”.   Go back to the early 1990s and being able to demonstrate that the composition of the diatom assemblage was significantly related to the concentration of phosphorus in the water was a step in the right direction but there was little “added value” compared to just measuring the phosphorus concentration (which was a necessary part of the regulation process).   During the 2000s we took this a step further, driven by the precepts of the Water Framework Directive (WFD). By the end of the decade we had a good idea of what diatom assemblage could be expected at any river or lake site and use that to measure how far the present state of a site deviated from this ideal. The question that bugged us throughout, though, was how much deviation was acceptable.   The problem with an ideal is that it is probably unlikely to be attainable, so we need to infuse our ideals with a spoonful or two of pragmatism (supporters of Jeremy Corbyn, please note …).   This is, in fact, at the heart of the WFD, encapsulated in the definition of “good ecological status” (GES). The problem is that GES, itself, is an elusive concept.

The outcome of this is that is has tended to be defined in terms of the “measurable” rather than the “important”. By this I mean that various statistical approaches have been used to determine a point along the index scales that we have developed that we thought met the definition of good ecological status as set out in the WFD.   This describes GES as a “slight change” from the community structure associated with the ideal state (“reference conditions”).   What has concerned me for some time is that this “slight change” does not necessarily have deep foundations in ecological theory, and does not necessarily guarantee the long-term sustainability of Europe’s waters, the ultimate goal of the WFD.   We could argue that a “slight change” leans towards precaution, but the downside is that it is hard to justify the expense of restoration when your argument is littered with “probably” and “maybe”. So where should we look in order to find these deeper foundations?

I came across an interesting new paper that points us in some new directions, if stopping short of giving detailed answers.   It focuses on the concept of ecological resilience, defined as “the amount of disturbance that an ecosystem could withstand without changing self-organized processes and structures” (see the reference by Gunderson, below).   “Ecological resilience” is no more than preserving the natural homeostasis of a system; just as a healthy human should have the resilience to recover from a minor infection, so an ecosystem should have the capability to recover naturally, without management intervention, from minor natural or anthropogenic perturbations. What this then does is set us some new challenges to understand what we mean by “resilience” in freshwater ecosystems and then to develop some ways of measuring this.   I made some suggestions in a post back in January (see “Baffled by the benthos (2)”) and there is scope for other approaches too. These, then, would let us re-examine how we set the limits for GES and, in turn, give us stronger justifications for their restoration.   Of course, all this assumes that GES is a steady state that fulfils this definition of possessing “self-organized processes and structures”, but that is the subject for another post …


My own thinking on the ecological theory behind good ecological status is described in:
Kelly, M.G., King, L. & ní Chatháin, B. (2009).   The conceptual basis of ecological status assessments using diatoms. Biology and Environment: Proceedings of the Royal Irish Academy 109B: 175-189.

The other two papers I refer to are:
Gunderson, L.H. (2000). Ecological resilience in theory and application. Annual Review of Ecology and Systematics 31: 425-439.

Spears, B.M., Ives, S.C., Angeler, D.G., Allen, C.R., Birk, S., Carvalho, L., Cavers, S., Daunt, F., Morton, R.D., Pocock, M.J.O., Rhodes, G. & Thackeray, S.J. (2015). Effective management of ecological resilience – are we there yet?   Journal of Applied Ecology DOI: 10.1111/1365-2664.12497

Return to Pangong Tso


Pangong Tso, from the Indian shore, looking towards China, July 2015 (photograph: Heathe Kelly).

You may remember that a year ago I wrote some posts about a high altitude lake on the India-China border (see “Subaquatic landscapes in Pangong Tso” and references therein).   This year, Heather made a second trip to Pangong Tso (described here) under the auspices of Indus Experiences and brought me back another sample from the littoral zone.   There was a beautiful thick biofilm here, an unusual bright yellow-brown colour and a jelly-like consistency, but bubbling away as the algae photosynthesised busily.   Once again, local vodka was pressed into service as a preservative and, once again, peering through my microscope a few days later, I could see that the sample was dominated by the same long-stalked Gomphonema species that I recorded a year ago (see “Diatoms from Pangong Tso”). The jelly-like consistency did worry me, as this is not what I would expect of a pure growth of diatoms and I did wonder if there were cyanobacteria growing amongst the diatoms that had not survived the journey home in their marinade of cheap vodka.


Growths of diatoms (predominately a long-stalked Gomphonema sp) on a boulder in the littoral zone of Pangong Tso, India, July 2015. The right hand image is a close up showing oxygen bubbles being produced by the the jelly-like masses. Photographs: Heather Kelly.

Intriguingly, the Gomphonema seems to occur in two forms: a fatter form, with a width around eight micrometres, and a narrower form, about six micrometres wide. I’ve written before about how diatoms tend to get shorter over time (see “Diminishing with age”). What I did not make clear in this post is that cell breadth tends to stay relatively constant during this process.   This does not happen with every species but it is interesting to see that the fat and narrow forms have overlapping sizes, so it is not a simple matter of the narrow ones being the far end of the size reduction sequence. More work is definitely needed here although, alas, I don’t think Pangong Tso is on the itinerary for next year’s visit to India.


Gomphonema sp from the littoral zone of Pangong Tso, north India, July 2015.   a. – d. represent the “fat” form; e. – h. are the narrower form(s). Scale bar: 10 micrometres (= 1/100th of a millimetre).

Farewell to our “Green and Pleasant Land”?

I’ve spent the last few days contemplating the implications of a UK exit from the European Union, my thoughts focussed by a stimulating workshop in Birmingham organised by the Chartered Institute of Ecology and Environmental Management.   Reassuringly, many of the other participants echoed the view that I aired in a post at the start of the year: that the immediate implications of a UK exit (I refuse to use the term ‘Brexit’) for the environment will be limited, as most EU law has been transposed into UK legislation (see “122 days to go …”). We also have a strong body of domestic legislation that dovetails with EU Directives to such an extent that it is difficult to unpick the unique contribution that EU Directives have made to the state of our environment. If I had to point to one event that truly marked an upturn in the fortunes for English and Welsh rivers, it would probably be the privatisation of the water industry in 1989 and the creation of a strong, independent regulator, the National Rivers Authority (see “The state of things, part 1”). That was nothing to do with Brussels.

My biggest worry about a UK exit is less tangible, not so easily supported by hard evidence, but no less real. It is that the EU, with the UK as a willing and constructive partner, defines our collective ambition.   Legislation such as the Water Framework Directive (WFD) sets out a vision for the sustainable use of Europe’s water that goes far beyond anything that domestic legislation had ever contemplated.   Maybe it is not leaving the EU that is the major concern, so much as what such a step would say about the mentality of a significant proportion of my fellow citizens? My ‘vision’ will be their ‘red tape’ and, gradually, the ideals enshrined in legislation such as the WFD will be chipped away and watered down.

Let’s be honest and admit that the UK is far from perfect at the moment. It has been dragged into the European Court of Justice for infractions of EU environmental legislation on a number of occasions and, if we vote to stay in the EU, we will probably find ourselves there again.   Think of the European Court of Justice as the speed cameras on the environmental highway.   Simply knowing that there are speed cameras along a stretch of road is enough to quell the temptation to speed and the same principle applies to environmental law.   The ‘No’ campaign will claim the moral high ground but, realistically, the more challenging aspects of EU legislation will be quietly revoked as time passes, without this scrutiny from a higher body. The phosphorus standards for freshwaters, which I helped to develop, would be an obvious candidate. This is partly because they represent the small print in environmental protection, rather than headline-grabbing issues.   More pertinently, they are sufficiently tight (for which read “realistic”) for many utility companies to struggle to achieve them.   Quietly letting them drop from the legislative agenda could even be turned into a PR success (one less reason to raise water charges).

I realise, at this stage, that ‘No’ campaigners will be nodding sagely at what I have just written. ‘Exactly’, they will be saying, ‘that is what we want to happen.’ Leaving Europe is a vote against interventionist approaches to government but, when it comes to matters of environmental policy, the political right has not yet demonstrated a better alternative (see “When Right is not right”).

Of course, the environment will be competing for column inches with high profile issues such as the economy and immigration over the next few months. Immigration presents us with an interesting parallel: when you next consider the free movement of people across European borders, think, too, about the free movement of migratory birds across a continent, and the benefits that joined-up environmental policy has on organisms that cannot be constrained by national borders. You might also like to consider the free movement of atmospheric pollution; again, no respecter of boundaries.

Leaving the EU would be a double whammy for the environment. Not only will it water down our ambition, it will also reduce the amount of independent scrutiny. The ‘No’ campaigners may allude to our “Green and Pleasant Land” in their rhetoric, but don’t expect it to stay that way for long.