First record of Navicula supergregaria in the UK?

I encountered a diatom in a sample yesterday that I had not seen before and, after checking some books, am fairly confident that this is Navicula supergregaria Rumrich & Lange-Bertalot 2000 and that this is the first record of the species from the U.K. I found this in a sample collected from the River Alver, close to Kingfisher Caravan Park in Gosport, Hampshire from April 2014.   It was a gritty sample that did not make for easy counting and contained several taxa that suggested that the river at this point is brackish.

As the name suggests, Navicula supergregaria is similar to Navicula gregaria, albeit larger (> 6.5 mm breadth) and the pores in the striae are just about visible with the light microscope (24-28/10 mm).   My previous post mentioned three distinct forms of Navicula gregaria recognised by Eileen Cox; N. supergregaria is an additional form, previously recorded in similar habitats in the Netherlands and Germany as well as in the USA.   In this sample, it mingled with “true” Navicula gregaria and a distinctive population of Navicula salinarum too.


Navicula supergregaria from the River Alver, Gosport, Hampshire, April 2014. Scale bar: 10 micrometres (1/100th of a millimetre).


Navicula salinarum from the River Alver, Gosport, Hampshire, April 2014. Scale bar: 10 micrometres (1/100th of a millimetre).

The sum of things …

A recurring theme in this blog has been the enormous variety of organisms encountered at the less fashionable end of biodiversity and I thought that it would be interesting to see how the numbers of species in these groups compares with the more visible groups. I made a start at this exercise in my book Of Microscopes and Monsters but decided that I really needed to do this more thoroughly if I was to make my point about the enormous diversity of lower organisms.

Even so, I am afraid that I blanched at the prospect of counting all the insects and mollusc species recorded from Britain and (an even worse confession), I resorted to Wikipedia when I could not find a more authoritative source. I offer these numbers as a broad reflection of the diversity of the British flora and fauna, rather than as a definitive survey, and challenge readers to contribute more authoritative sources, where they think mine are lacking. The spreadsheet on which the graph is based can be found here.

The number of species of different plant and animal groups in Britain.

My original goal was to show just how diverse the algae were relative to other groups of plants and this graph makes that point very well. Seven out of every ten photosynthetic “plants” recorded from Britain, for example, are algae, and there are five species of algae for every vertebrate animal (fish, amphibians, reptiles, birds, mammals). But my argument for a phycocentric focus to our biodiversity was brushed rudely aside when I added fungi to the spreadsheet. With over 14000 species (if lichens are included), there are almost three fungi for every algal species in Britain. Mammals, with just 79 native species, are too insignificant to justify more than the faintest bump on my graph.

Why so many fungi? You may be scratching your head for an explanation. Or, maybe, scratching your head is leading us, indirectly, to the answer. Several fungi cause infections on humans (athlete’s foot, thrush, ringworm) and, similarly, fungal parasites can be found on many other organisms (see “Little bugs have littler bugs upon their backs to bite ‘em”). The number of fungi on my chart equates to 1.5 for every other plant and animal species. Remember, too, that I have not included invertebrates (which would decrease this ratio substantially) but, on the other hand, there are probably bigger gaps in our knowledge of fungi (and algae) than there are for many other groups. So a ratio of roughly one fungus for every other species sounds plausible.

Does this tell us very much? The figures are rough and ready and there is often ambiguity about the geographical scope (“Britain”, “UK”, “British Isles” etc), but I hope it gives you some idea of just how much of Britain’s biodiversity is tucked away in dank corners of the country, mostly overlooked by Attenborough’s extravaganzas with their focus on the exciting, glamorous and, often, downright anthropomorphic aspects of life on earth.