The democratisation of stream ecology?


About a year ago, I reported on the development of a rapid assessment method for assessing the condition of rivers using algae that are visible to the naked eye (see “Ecological assessment in the fast lane …“).   Last week, our first paper on this subject was published in Science of the Total Environment, a journal which also requires authors to submit a “graphical abstract” (“a single, concise, pictorial and visual summary of the main findings of the article”, according to the Elsevier website). I’ve put our graphical abstract at the head of this post to spare you, dear readers, of the need to read the article.

On the left we have a river then, moving to the right, there are two options: the upper image shows diatoms, followed by a stopwatch indicating the passage of time, and finally a block of five colours which are supposed to indicate the five ecological status classes specified by the Water Framework Directive (blue= high; green = good; yellow = moderate, orange = poor; red = bad). Underneath, we have a picture which is supposed to indicate visible algal growths (green filaments and a crust of Hildenbrandia), followed by a stopwatch indicating the passage of rather less time than is the case for diatoms, leading, again, to the five ecological status classes.   It is, in brief, a concise pictorial and visual summary of why you should not assume that someone with a Fine Art degree can do something that is, strictly speaking, the specialism of someone with a degree in Graphic Design. I make no excuses.

I am, to be honest, rather proud of this paper, largely because it is a piece of “bottom up” science, driven by the needs of end-users rather than, as is often the case, by an agenda set by the high-ups.   It is also a piece of science that eschews the trend to confuse complicated methods with intellectual sophistication.   Unfortunately, this did not endear us to one of the referees.   Only after suggesting, diplomatically, to the editor that perhaps peer review required the reviewer to actually read the paper properly before writing down all of his prejudices, did we scrape through and get our manuscript accepted.

The big change in RAPPER since I last wrote about it, is that we now have two “maybe at risk” categories.   The first (“maybe (1)”) represents situations where there are genuinely ambiguous combinations of algae present at the site, suggesting that there may be some enrichment, but not so much that the sensitive species have disappeared.   The second (“maybe (2)”) represents situations where we did not get a strong signal either suggesting good conditions or enrichment. This happens sometimes, for example when the stream is strongly shaded or (in a few cases) where the dominant algal genus has a very broad ecological tolerance.   In earlier versions, we referred to this latter case as “no data” but, on reflection, it represents a different type of uncertainty and there are usually good reasons why few algae are present at a site.


Graph comparing the TDI (Trophic Diatom Index) scores for sites classified by RAPPER as not at risk, maybe at risk or at risk.   There is a significant difference between TDI scores for the four categories. From Kelly et al. (2016).

One other reason why I am proud of this work is that it is a step towards reconnecting science with non-technical water users. I wrote about this last June (see “So what?”).   I have been concerned for some time that the science of assessing the state of rivers has become so complicated that it now means little to the average angler or to a man walking his dog along the bank.   RAPPER focusses on visible growths of algae, and so there is a more direct link between the outcome of the assessment and what these people actually see.   The “at risk” category, for example, largely consists of sites with a blanket covering of green algal growths on the stream bed and links into some work in the USA which demonstrated how such growths impact upon public opinion of the health of streams and rivers.

This, in turn, raises some further questions about whether the method can be used by people with an interest in the state of rivers but who are not specialist biologists.   The problem is that not all green algal growths necessarily indicate bad conditions (although persistent growths are usually indicative of a problem of sometime). This, in turn, means that the identity of the algae needs to be checked.   At the moment, everyone who has used RAPPER has access to a good microscope.   How well can the method be used by someone with just a hand-held microscope (which rarely exceed 100x magnification)?   That’s the next question that we need to address.   I have been working with a student to explore the potential for modifying the method so that it can be used for “citizen science”, and have some encouraging results.   I’ve also had some useful discussions with a river trust in the north of England and am hoping to meet with angler’s groups too.   That would be a step towards making ecological assessment “a priesthood of all believers” rather than the exclusive preserve of nerds …


Kelly, M.G., Krokowski, J. & Harding, J.PC. (2016).   RAPPER: a new method for rapid assessment of macroalgae as a complement to diatom-based assessment of ecological status. Science of the Total Environment

Suplee, M.W., Watson, V., Teply, M., McKee, H., 2009. How green is too green? Public opinion of what constitutes undesirable algae levels in streams. J. American Water Resources Association 45: 123–140.