An inordinate fondness for … algae*

Looking back through my records I counted 152 different algae species from my observations and samples from the five kilometre of the River Ehen between the outflow from Ennerdale Water and the village of Ennerdale Bridge.   This might sound like a large number until you look at the relative numbers of algae compared to other types of plant.   Adding together all the flowering plants, native conifers, ferns, mosses and liverworts recorded from Britain and Ireland gives a figure of 2333 species.   By contrast, just under 6000 species of algae have been recorded.   This figure is almost certainly an underestimate for two reasons.  First, some habitats, particularly offshore coastal waters, have not been as thoroughly documented as others.  Second, there has been a recent rapid increase in numbers of records of algae not because people are looking in different places but because our idea of what a “species” of alga is has changed dramatically.

The classic definition of a “species” is a group of organisms capable of interbreeding and producing fertile offspring.  However, sex is hard to observe in many algae, so we assume that organisms capable of interbreeding will look the same, because they are sharing the same genes.   However, this brings human perception into the equation, exacerbated in the case of microscopic organisms by the limitations of optical technology (see earlier post).   Recently, we have discovered that many algae which look almost identical (and which were classified as a single species in the past) are, in fact, genetically-distinct species (see illustration below).


The diversity of freshwater diatoms.  Each image shows a valve (half a cell wall) that would have been classified as “Sellaphora pupula” in most 20th century diatom Floras but which has subsequently been shown to be a genetically-distinct species in its own right.  Images are from the ADIAC database (

This means that, as well as 6000 species of freshwater algae that we already know about, there is also a category of “known unknowns” – species that will, undoubtedly, need to be split into several distinct entities at some point in the future.   Doubling the figure of 6000 would not be unreasonable.   By contrast, the figure of 2333 higher plants is probably not going to change that much over the next few years, as these organisms have generally been more thoroughly studied and recorded.   This means that algae could represent over 80% of all plant diversity in Britain and Ireland.

But here’s the problem: there is almost no-one doing this work in the UK at the moment.  24 people contributed to the second edition of the Freshwater Algal Flora of the British Isles.  Of these, nine were not from Britain or Ireland, a further ten are retired, and two of the remainder are not currently in research roles.   Whilst most of the retirees are still active, this situation raises yet another spectre: that of knowledge loss.   These are people that could look at a sample and notice subtle differences in an organism that may indicate a new species.  These are people that keep up to date with literature from around the world that might help them match this new species to one described elsewhere.  The book they wrote encapsulates the “known knowns” (to use Donald Rumsfeld’s terminology) but we need active (and funded) researchers to explore the “known unknowns”, let alone the “unknown unknowns”.   Not far behind the “cutting edge” of research is a trailing edge where knowledge is no longer challenged by experience and, I’m afraid, some areas of algal taxonomy in the UK may already fall into that category.

* the title is an adaptation of J.B.S Haldane’s response when asked if anything could be concluded about the creator from the study of creation.  Haldane replied: “an inordinate fondness for beetles.”   Donald Rumsfeld’s quotations come from a press briefing in 2002 about the presence (or otherwise) of weapons of mass destruction in Iraq


2 thoughts on “An inordinate fondness for … algae*

  1. Pingback: More from the River Ehen | microscopesandmonsters

  2. Pingback: Reflections from the trailing edge of science | microscopesandmonsters

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