Michael Gove has made a sensible suggestion …

I found myself buying the Sunday Telegraph for the first time in my life a few days ago, as Michael Gove chose this newspaper to announce his plans for a new environmental regulator.   His proposal links back to points I have made previously about a need for a new type of regulator to take over the role of the European Commission and European Court of Justice in holding the UK governments to account once we have left the EU (see “(In)competent authority” and “Who will watch the watchmen now?”).

Gove is in a difficult position in his role of Secretary of State for the Environment, Food and Rural Affairs.  His instincts, as a leading architect of the “leave” campaign, are against the European Union yet, for the environment at least, he cannot deny that there are many benefits that the EU has brought.   He acknowledges this: “Some of the mechanisms which have developed during our time in the EU which helpfully scrutinise the achievement of environmental targets and standards by Government will no longer exist in the same way, and principles which guide policy will have less scope and coverage than they do now”.   Too right.

His proposal is for a “world-leading body to give the environment a voice and hold the powerful to account, independent of government and able to speak its mind freely”.  That sounds promising, in the same way that Gordon Brown’s decision to make the Bank of England free of political control back in the late 1990s.   Of course, such bodies are never completely independent (witness the way that John Redwood, Jacob Rees-Mogg and others turn on the Bank of England whenever it dares contradict the most optimistic post-Brexit forecasts) but it is a step in the right direction.

So I will await, with interest, the consultation that Michael Gove promises in his Sunday Telegraph article.  I am hoping that this means that the Environment Agency will still be the tool of official government policy whilst this new body will be independent and able to point out shortfalls in performance.  I’m hoping, too, that this will bring some new thinking into environmental regulation, preserving the best of the EU systems whilst, at the same time, shaking up some of the aspects – such as the integration of environmental and agricultural policy – where the EU was notoriously weak.

The elephant in the corner of the room is finance.  The Environment Agency is currently working on a shoestring and, unless more money from Government is forthcoming, they and this new Agency will simply be unable to afford to be “world-leading”.   Somehow the Environment Agency muddles along, thanks to well-motivated staff, but corners are being cut and monitoring the state of the environment – one of the cornerstones of any effort to giving the environment “a voice” – has been a major casualty.

All this is going on whilst Parliament debates the EU (Withdrawal) Bill and we should, perhaps, see Gove’s announcement as a tactical move to head off rebellion in the Tory ranks.   Issues such as whether existing legislation will be amended by primary or secondary legislation under particular scrutiny.   I and others saw the prospect of the fine print in European environmental legislation being quietly written out of the statute books as a particular risk of Brexit so, even if this is a cynical manoeuvre, I am encouraged by Michael Gove’s words.   If nothing else, it demonstrates that even arch-Brexiteers know that they have to make some concessions.   However, we need to watch this story closely as it unfolds over the next few months …


Murder on the Barcode Express …

A long time ago, Agatha Christie imagined a train coming to a halt in a snowdrift somewhere in Croatia.  By the morning, one of the passengers was dead.   Eighty years later, a group, only slightly larger than Hercule Poirot’s pool of suspects, gathered in a room in modern Zagreb to plot another fiendish murder.   The victim, this time, would be  …. traditional diatom taxonomy.

“Murder” is far too strong a term for this particular whodunit; maybe I should say “aiding and abetting” rather than actually committing the crime, but I think the outcome might be the same.  The conspirators in Zagreb are all involved in developing methods that use molecular barcoding to identify diatoms and have been busily collecting sequences of the many diatom species in order to establish the libraries that we need to link these barcodes to the appropriate Linnaean binomial.   Some years into this, we still have no more than about 15% of freshwater diatom species matched to barcodes.  We are starting to think about ways of filling in the gaps more quickly than is possible using the conventional approach of isolating a diatom, growing it in culture and then sequencing the appropriate marker genes.

The most radical of these alternatives is to by-pass Linnaean binomials altogether and classify diatoms by their barcodes alone – as “operational taxonomic units” or OTUs.   Most of us have spent most of our careers using morphology-based taxonomy and any move away seems like an act of treachery towards a fundamental tenet of our craft.  But the time has come to take a dispassionate view and ask what a species name brings to ecology.   At a very practical level, the use of Linnaean binomials makes it much easier for us to compare data with colleagues and with records in the literature.    Taxonomists would argue that their work helps us to understand the relationships between species but, unfortunately, in this particular branch of science, we make little use of these relationships, and the role of taxonomy is primarily to give us a consistent means of organising the myriad tiny pieces of silica which we find in our samples.

That business of consistent naming could, in theory, be performed for barcodes just as efficiently using digital tags as OTUs and this would also work for the 85% of species where the link between traditional morphology-based taxonomy and marker genes has not yet been established.   So what about the link that Linnaean binomials give us to established knowledge?   Here, again, we need to be brutally frank: ecological information for most freshwater diatoms is limited to information about preferences for hardness/alkalinity, inorganic nutrients, organic pollution, acidity and salinity and that information can be replicated very easily by linking files of metabarcoding and environmental data.  There are very few experimental studies that offer insights into the ecology of freshwater benthic diatoms beyond that gained from looking for associations between diatom distribution and a few common variables.

The plotters plotting …  DNAqua-net workshop in Zagreb, November 2017.  The top photograph shows Zagreb cathedral against the skyline.

The problem is not that we do not see the merits of traditional Linnaean taxonomy, it is that we cannot make a strong case for the funding necessary to collect barcodes for all species.   The final downward thrust of the dagger will, in other words, be inflicted by the bureaucrats whose budgets will not stretch to cataloguing the enormous breadth of algal diversity.   Diatoms sit in the awkward middle ground between larger organisms such as fish where any suggestion of not using traditional taxonomy would be greeted with derision and the microbial world where the idea of applying Linnaean binomials to the enormous diversity uncovered by molecular techniques is equally risible.   Diatom names mean little to the bureaucrats who manage our environmental agencies and, given the choice between a spreadsheet of incomprehensible Latin names or one of equally incomprehensible OTUs, all else being equal, they will choose the cheapest.

“All else being equal” is the key phrase.   I think that there is growing awareness now that one downside of barcoding is that it risks sidestepping the need for trained biologists at all: samples will be collected by technicians, processed in high-throughput laboratories and results churned out through black box computer programs.   The situation for diatoms is worse than for most groups of organisms used for ecological assessment because so much attention is given to the laboratory stages of producing a list of taxa and relative abundances.  We are, however, now approaching the point when DNA sequencers can produce data of equivalent sensitivity to that produced by light microscopy.   The message that barcoding has the potential to be a good friend but a poor master could be lost as our paymasters recognise the potential for reducing costs.   What we need to do now is use those “little grey cells” to ensure that good biological insight is not the victim of a heinous crime.

The underwater world of Ennerdale Water …

I’ve tried to capture the world of microscopic benthic algae many times but never, until now, attempted the same effect with plankton.   The picture below illustrates the problem that I face: whereas the benthic flora are organised with, for the most part, a clear three-dimensional structure and known dependencies amongst organisms (species A, for example, being epiphytic on species B), plankton are randomly distributed in a very dilute solution.   My picture  below, which is based on four phytoplankton samples collected by the Environment Agency in the summers of 2014 and 2016.

A representation of the phytoplankton of Ennerdale Water with cells of Rhodomonas and Kephyrion depicted at a realistic density (c. 1000 – 2000 cells per millilitre).

I had to address two issues in producing this image, which is based on four phytoplankton samples collected by the Environment Agency in the summers of 2014 and 2016: depicting the phytoplankton cells at approximately the correct density and making sense of the list of names that appeared on the list.  Ennerdale Water is a very nutrient-poor lake and cell concentrations during the summer are in the order of 1000 to 2000 per millilitre.  That sounds a large number until you consider the scale at which we are working.   For simplicity, I assumed spherical cells of about 20 micrometres diameter (= 1/50th of a millimetre) at a density of 1000 cells/ml.    That equates to one cell per micrometre which is 1 mm x 1 mm x 1 mm.   Using these assumptions, each cell is 50 diameters distant from its nearest neighbour, which means the foreground of a picture should contain only two small cells and a lot of blue paint.

Next, I need to know what algae to paint and the problem here is that 85 per cent of the cells in the Environment Agency phytoplankton analyses were described as “picoplankton < 2 micrometres diameter” or “nanoplankton 2-20 micrometres diameter” (the latter divided into flagellates and non-flagellates).  There are, apparently, big difficulties in naming many of the cells found as preservation with Lugol’s Iodine coupled with the long time in storage before analysis can lead to loss of useful diagnostic features.   Cells in the nanoplankton category can, in theory, belong to any one of a number of groups of algae but If I focussed just on those organisms that could be named, I see that the Cryptophyta Rhodomonas lacustris var nannoplanctica (formerly R. minuta var. nannoplanctica) predominates, followed by Chrysophytes, of which Kephyrion is the most abundant.   So these are the two cells that I have put in the foreground.

I subsequently turned up a paper from 1912 by the father and son team of William and George West who looked at the phytoplankton of Ennerdale Water and a number of other lakes in the Lake District and Scotland.  The range of taxa that they found was quite different to that recorded in these recent surveys with samples dominated by desmids and almost no Chrysophytes or Cryptophytes recorded at all. That may, in part, be due to differences in methods – they collected samples using a “silken tow net”, which would probably have missed the very small Chrysophyta and Cryptophyta (an earlier paper by them tells us of the size of the nets but not the mesh itself) .  Some desmids that they found were found in the recent surveys but in much smaller quantities and it is possible that this was partly an artefact of the differences in sampling technique.  The idea of comparing count data from old papers with modern records is appealing but, in most cases, separating genuine changes in composition from differences introduced by sampling and analytical methods is always difficult.

Excuse these ramblings … there is, as you can see, not a lot of pictorial interest in the underwater world of an oligotrophic lake.   If you want excitement, tune into Blue Planet II, David Attenborough’s latest series for the BBC You will find sex and violence galore there.  The underwater world of Ennerdale Water is a quieter, more serene and certainly less televisual place.  Maybe that’s not such a bad thing …


Lund, J.W.G. (1948) A rarely recorded but very common British alga, Rhodomonas minuta Skuja. British Phycological Bulletin, 2:3, 133-139.

West, W. & West, G.S. (1909). The British freshwater phytoplankton, with special reference to the desmid-plankton and the distribution of British desmids.   Proceedings of the Royal Society of London Series B 81: 165-206.

West, W. & West, G.S. (1912).  On the periodicity of the phytoplankton of some British lakes.  Journal of the Linnaean Society, Botany 40: 395-432.

The green mantle of the standing pond* …

One of the highlights of a wet and windy weekend at Malham Tarn Field Centre for the annual British Diatomist Meeting was a talk by Carl Sayer on the ecology of a small pond in Norfolk.  The work was not new to me, as I had been the external examiner for Dave Emson’s PhD thesis on which the work was based.  I remember, at the time, making a mental note to write a post once the work was fully in the public domain, and Carl’s talk has finally jogged me into action.

Carl’s starting point was the observation that small ponds are often covered with dense growths of floating aquatic plants such as duckweed (Lemna minor).  Repeated visits to ponds in north Norfolk, close to where he grew up, had shown that this cover of duckweed often lasted for a few years before disappearing, only to reappear some years later.   As this duckweed blocks out sunlight, periods of dominance are likely to have unfortunate consequences for other aquatic plants in the pond and, as these pump oxygen into the water as a by-product of photosynthesis, life for other pond-dwelling organisms – such as the Crucian carp (Carassius carassius) that Carl likes to catch from the pond – will also get tougher.

There’s a lot of questions that could be asked about what’s going on here, and not all can be answered in a single study, but establishing whether these periodic episodes of duckweed dominance were one-offs or if they were regular events is a good place.  Here Carl and Dave  were able to use a well-known association between a diatom – Lemnicola hungarica – and duckweed to track changes in Lemna over time.   Lemnicola hungarica grows attached to the roots of duckweeds and similar species and seems to be unusually fussy about its habitat compared to many diatoms, which means that when Lemnicola is found in the sediments of a pond, that is a fairly good indication that Lemna was abundant when those sediments were being laid down.   In the process, they also discovered another diatom, Sellaphora saugerresii, also seemed to be strongly associated with Lemna, at least in this habitat (it is also common in many rivers were Lemna is sparse or absent).

The relative abundance of a) Lemnicola hungarica and b) Sellaphora saugerresii in surface sediments of north Norfolk ponds with and without Lemna dominance.   The two species are illustrated on the right hand side (S. saugerresii is typically about 10 micrometres  (= 1/100th of a millimetre) in length).

Armed with this information, Dave and Carl went back to one of Carl’s local ponds and extracted a core of the sediments from the middle in order to see how numbers of Lemnicola hungarica and Sellaphora saugerresii changed through the length of the core.   Because they were also able to date the core, they were able to show that the period when there are documentary records of duckweed dominance coincides with both of these indicators being abundant in the pond sediments.  Below these levels (i.e. further back in time), the relative abundance of these two species waxes and wanes several times, suggesting that the duckweed cover, too, had come and gone over the years.

Left: Dave Emson and the core from Bodham Rail Pit; right: changes in the relative abundance of Lemnicola hungarica and Sellaphora saugerresii at different levels of the core.    The grey rectangle indicates the period during which Lemna is known to have been dominant in the pond.

Quite why this is so is not clear.   There are several species of floating aquatic plant (water hyacinth and Salvinia, the floating fern are two good examples) that are able to cover large areas of standing water bodies in a short period of time and they often do this by vegetative growth rather than by seed.   This means that the plants are mostly clones of a very small number of plants that first colonised the water body.   And this, in turn, may mean that a virus that infects one frond will be able to infect every other frond as well as there is a very narrow range of genotypes within the population.  That’s one possibility but there may be others.

But back to the story: knowing that Lemna abundance fluctuates is not quite the same as being able to describe the consequences of this for the rest of the organisms that inhabit these ponds.   The Crucian carp was the species that attracted Carl to the pond in the first place so it would be good to know whether this species can survive the dark, oxygen-poor years when the surface is covered with duckweed.   They did find scales of Crucian carp in the cores right through the pond’s dark ages suggesting that this tough little fish had managed to hang on.  In 2008, a few years after the most recent duckweed episode, they found just a single carp when they cast their nets out into the pond but there were three by the following spring and, in 2011 there were over 200 juveniles.  So it looks like the carp populations definitely retrench during the duckweed episodes but that they do, eventually, recover.   And, maybe, another generation of north Norfolk natural historians will become enthralled by the aquatic world as a result?

* King Lear Act III scene IV


Buczkó, K. (2007).  The occurrence of the epiphytic diatom Lemnicola hungarica on different European Lemnaceae species.  Fottea, Olomouc 7: 77-84.

A very dilute compost heap …

It is hard to believe that this idyllic view is within a kilometre of the centre of Newcastle.   We are standing in Jesmond Dene, a steep-sided valley that is now, thanks to the largesse of Lord Armstrong in the 19th century, now a public park.  From the point of view of someone teaching freshwater ecology to undergraduates it is a godsend, as it means that we have a fine location for fieldwork within walking distance of the university.  And, because I teach Geography undergraduates, all I need to do is tell them the location and assume that their spatial awareness will lead them to the right place at roughly the right time.  It usually works.

Don’t be misled by the Arcadian scene in this photograph: for most of its length the Ouseburn is an unprepossessing stream with a multitude of problems, which is one of the reasons why I bring the students here in the first place.  We get them to sample the water, which they analyse in the laboratory over the next couple of weeks, and also collect a sample of invertebrates from the stream bed.  But, most importantly, I just want to get them to start thinking about the factors that driver a river ecosystem.

In the lectures beforehand, I make the point that we need to think beyond the stream channel itself if we are to understand its ecology and the visit to the Ouseburn helps to reinforce this.   That sun-dappled scene above is conveying an important truth: that a lot of the sunlight is intercepted by the leaves of the surrounding trees before it can reach the stream itself.   If we thought about ecology solely in terms of the stream channel we might conclude that this means less energy to fuel the stream ecosystem.  However, look at the photograph below of some of my students peering into the tray containing the invertebrates they have just collected.  Around them in the stream are leaves shed by the surrounding trees.   And, in that tray, we find a range of invertebrates but, most commonly, freshwater shrimp (Gammarus pulex), freshwater hoglouse (Asellus aquaticus) both of which are as happy feeding on the rotting remains of leaves from the surrounding trees as they are on food produced within the stream.

Left: Invertebrate sampling at Jesmond Dene, October 2017. Note the dead leaves in the stream, creating a natural food supply for the bugs.  Right: a Petri dish containing the contents from one pond net.  Note the large numbers of freshwater shrimp, Gammarus pulex (see inset).  

This is the time of year when gardeners are raking up piles of leaves and dumping them on their compost heaps.   When I peer into our compost heap I see a writhing mass of invertebrate animals also feeding on dead and decaying vegetation.  There are many segmented worms in both our compost heap and the samples we get from the Ouseburn, although most of the other animals are quite different (slugs, mostly, in our compost heap).   They may not be as exciting as the hyenas and vultures that perform similar functions on African savannahs but they play an essential role in driving nature’s cycles, turning death back into life (or, at least, into the raw materials on which new life will grow).  All flesh is grass…

Two compost bins: useful metaphors for how energy flows through stream ecosystems.

That’s the first lesson that I want to get across to the students: a river, in its natural state, is really a very, very dilute compost heap, full of organisms custom-built to recycle dead and decaying organic matter.   What I don’t tell them is that bringing them to the Ouseburn is a cop-out for me, as a lecturer whose real skills lay with algae rather than invertebrates.  If I took them to a stream further up the Tyne Valley where the hand of man was less obvious, we would have found many more types of invertebrates, and would have been able to demonstrate a much wider range of ways of feeding than we saw in the Ouseburn.  In particular, I would have expected to see stonefly nymphs and caddisfly larvae, some of which have tough jaws capable of ripping apart leaves, as well as mayfly nymphs, some of which will graze directly on algae.

The idea of a “grazer”, however, needs a little qualification.   Freshwater ecologists like to classify bugs into neat categories based on their food preferences as this helps them understand how energy flows through ecosystems.  The bugs-eye view of algae, however is that they are just one of many types of digestible energy found on and around the stream beds they inhabit.  Some ecologists prefer to lump “grazers” into a larger category of “collector-gatherers” that are relatively unfussy about what type of organic matter they eat and will cheerfully hoover up detritus that other organisms have left behind.

That “detritus” is, by the way, a euphemism for, amongst other things, the downloaded remains of the stonefly nymph’s vegetarian dinner.  Freshwater ecologists refer to this as “fine particulate organic matter” but the rest of us have a wealth of scatological language on which to draw.   That’s another lesson that I want to convey to my students: streams contain a lot of small organisms investing a lot of their valuable time searching for and eating other animal’s poo.   And that means that trout and other predators in these aquatic food-webs are eating a mixture of herbivores (the “shredders” plus the bugs that feed directly on algae) plus a lot of invertebrates that are a lot less fussy about food hygiene.   Next time you sit down to eat grilled trout, remember that you are basically eating reprocessed poo.


Bloor, M.C., (2011).  Dietary Preference of Gammarus pulex and Asellus aquaticus during a laboratory breeding programme for ecotoxicological studies. International Journal of Zoology 2011: article ID 294394, http://dx.doi.org/10.1155/2011/294394.

Cummins, K.W. (1983).  Trophic relations of aquatic insects.  Annual Review of Entomology 18: 183-206.

Kelly, D.W., Dick, J.T.A. & Montgomery, W.I.  (2002). The functional role of Gammarus (Crustacea, Amphipoda): shredders, predators, or both?   Hydrobiologia 485: 199-203.

Macus, J.H., Sutcliffe, D.W. & Willoughby, L.G. (1978).  Feeding and growth of Asellus aquaticus (Isopoda) on food items from the littoral of Windermere, including green leaves of Elodea Canadensis.  Freshwater Biology 8: 505-519.

Willoughby, L.G. (1983).  Feeding behaviour of Gammarus pulex (L.) (Amphipoda) on Nitella.  Crustaceana 44: 245-250.

What a difference a storm makes …

I was back at Croasdale Beck last week and noticed a rather dramatic change to the meander just upstream from our regular sampling spot.   If you look at the photograph that heads the post “A tale of two diatoms …”, you’ll see the stream flowing around this meander.  Now, however, it has cut a new, shorter channel that bypasses the meander altogether.   We visited the stream just a few days after Storm Ophelia had passed through although, judging by the grass growing on the gravel of the abandoned meander, it was not necessarily this particular event that reshaped the stream.

Croasdale Beck is an unruly tributary of the River Ehen, rising on the fells above Ennerdale Water and tumbling down across rough grazing land and some semi-improved pasture (as in the picture above) before joining the Ehen in Ennerdale Bridge.   This is not the first time that we have seen conspicuous changes in the channel after a storm.  The magnitude of the flood is illustrated by the hydrograph below, which went off-scale for a period, as the discharge exceeded 3000 mega litres per day (300 MLD is the approximate limit for safe wading, in my experience).   I noticed that there was much less green algae present than we usually record at this time of year, although the diatom film was still quite thick.   Some of the stones that I picked up to sample had the slimy biofilm on the underside, suggesting that they had been recently rolled by the flooded river.   Croasdale Beck has no lake to buffer the rise and fall of the floodwaters and a huge amount of energy is carried down in a short period of time as the water surges downstream.

By the time we had arrived, the floodwaters had subsided and the sheep were contentedly grazing the surrounding land.  The stream itself was almost back to base flow (in contrast to the River Ehen which was still only just wadable).  Only the meander looked different …

The hydrograph for the River Ehen, as the aftereffects of Storm Ophelia make their way downstream.

Winning hearts and minds …

I write several of my posts whilst travelling, though am always conscious of the hypocrisy of writing an environmentally-themed blog whilst, at the same time, chalking up an embarrassing carbon footprint.  Last month, however, I participated in my first “eConference”, in which the participants were linked by the internet.  With over 200 people from all over Europe, and beyond, attending for all or part of the three days, there was a substantial environmental benefit and whilst there was little potential for the often-useful “off-piste” conversations that are often as useful as the formal programme of a conference, there were some unexpected benefits.  I, for example, managed to get the ironing done whilst listening to Daniel Hering and Annette Battrup-Pedersen’s talks.

You can find the presentations by following this link: https://www.ceh.ac.uk/get-involved/events/future-water-management-europe-econference.   My talk is the first and, in it, I tried to lay out some of the strengths and weaknesses of the ways that we collect and use ecological data for managing lakes and rivers.  I was aiming to give a high level overview of the situation and, as I prepared, I found myself drawing, as I often seem to do, on medical and health-related metaphors.

At its simplest, ecological assessment involves looking at a habitat, collecting information about the types of communities that are present and match the information we collect to knowledge that we have obtained from outside sources (such as books and teachers) and from prior experience in order to guide decisions about future management of that habitat. At its simplest, this may involve categoric distinctions (“this section of a river is okay, but that one is not”) but we often find that finer distinctions are necessary, much as when a doctor asks a patient to articulate pain on a scale of one to ten.  The doctor-patient analogy is important, because the outcomes from ecological assessment almost always need to be communicated to people with far less technical understanding than the person who collected the information in the first place.

I’ve had more opportunity than I would have liked to ruminate on these analogies in recent years as my youngest son was diagnosed with Type I diabetes in 2014 (see “Why are ecologists so obsessed with monitoring?”).   One of the most impressive lessons for me was how the medical team at our local hospital managed to both stabilise his condition and teach him the rudiments of managing his blood sugar levels in less than a week.   He was a teenager with limited interest in science so the complexities of measuring and interpreting blood sugar levels had to be communicated in a very practical manner.  That he now lives a pretty normal life stands testament to their communication, as much to their medical, skills.

The situation with diabetes offers a useful parallel to environmental assessment: blood sugar concentrations are monitored and evaluated against thresholds.  If the concentration crosses these thresholds (too high or too low), then action is taken to either reduce or increase blood sugar (inject insulin or eat some sugar or carbohydrates, respectively).   Blood sugar concentrations change gradually over time and are measured on a continuous scale.  However, for practical purposes they can be reduced to a simple “Goldilocks” formula (“too much”, “just right”, “not enough”).  Behind each category lie, for a diabetic, powerful associations that reinforce the consequences of not taking action (if you have even seen a diabetic suffering a “hypo”, you’ll know what I mean).

Categorical distinctions versus continuous scales embody the tensions at the heart of contemporary ecological assessment: a decision to act or not act is categorical yet change in nature tends to be more gradual.   The science behind ecological assessment tends to favour continuous scales, whilst regulation needs thresholds.  This is, indeed, captured in the Water Framework Directive (WFD): there are 38 references to “ecological status”, eight in the main text and the remainder in the annexes.  By contrast, there are just two references to “ecological quality ratios” – the continuous scale on which ecological assessment is based – both of which are in an annex.   Yet, somehow, these EQRs dominate conversation at most scientific meetings where the WFD is on the agenda.

You might think that this is an issue of semantics.  For both diabetes and ecological assessment, we can simply divide a continuous measurement scale into categories so what is the problem?   For diabetes, I think that the associations between low blood sugar and unpleasant, even dangerous consequences are such that it is not a problem.  For ecological assessment, I’m not so sure.  Like diabetes, our methods are able to convey the message that changes are taking place.  Unlike diabetes, they are often failing to finish the sentence with “… and bad things will happen unless you do something”.   EQRs can facilitate geek-to-geek interactions but often fail to transmit the associations to non-technical audiences – managers and stakeholders – that make them sit up and take notice.

I’d like to think that we can build categorical “triggers” into methods that make more direct links with these “bad things”.  In part, this would address the intrinsic uncertainty in our continuous scales (see “Certainly uncertain …”) but it would also greatly increase the ability of these methods to communicate risks and consequences to non-technical audiences (“look – this river is full of sewage fungus / filamentous algae – we must do something!”).   That’s important because, whilst I think that the WFD is successful at setting out principles for sustainable management of water, it fails if considered only as a means for top-down regulation.   In fact, I suspect that Article 14, which deals with public participation, is partly responsible for regulators not taking action (because “costs” are perceived as disproportionate to “benefits”) than for driving through improvements.   We need to start thinking more about ensuring that ecologists are given the tools to communicate their concerns beyond a narrow circle of fellow specialists (see also “The democratisation of stream ecology?”).   Despite all the research that the WFD has spawned, there has been a conspicuous failure to change “hearts and minds”.  In the final analysis, that is going to trump ecological nuance in determining the scale of environmental improvement we should expect.