Algae and reactive-nitrogen air pollution
Judith Allinson writes:
Have you noticed the spread of Klebsormidium crenulatum -“Nuisance Alga”?
Judith Allinson recounts how she got to know this filamentous green alga which is increasing over gritstone and siliceous rocks and fences especially in upland Britain… due to blanket reactive nitrogen (ammonium and nitrogen oxide) pollution
Fourteen years ago an algologist and lichenologist friend (Allan Pentecost) showed me a filamentous green alga growing on a 50 year old wooden gate in Malhamdale, in the Yorkshire Dales.
“Look at it under a hand lens” he said . “You will see it is filamentous.” And indeed it was – it looked velvety.
Many algae are single celled organisims. But some grow in unbranched threads – as did this.
I photographed it, proud that here was an alga I could easily recognise and give a name to, and duly showed it to friends the following week when I led a walk on Algae and Lichens of Malhamdale
I looked it up on the Internet – most references were to it in Germany. But it said it was spreading in England. And that it was a sign of pollution by nitrogen compounds – nitrogen oxides from car fumes, and chemicals going onto the air from fertilizers, manure and chicken factories. (e.g. Ammonia)
(Elsewhere on this website I have written a post celebrating the Haber Bosch Process, and about nitrogen footprints . It is now 112 years since the process of making artificial nitrogen fertilizer was developed to be run on an industrial scale (in 1913) – which has enabled our world population to increase, by at least an extra (3.5 to) 4 billion more than it would have done had this process not been invented. So we have a world population of over 8 billion (as of Jan 2025) rather than just 4 billion. There are twice as many people alive today as there would have been had not this process been invented. And the Haber-Bosch process today consumes more than 1% of all the world’s energy.
But back to the Klebsormidium
Since then I have noticed more and more each year.
Two years later Allan pointed it out to me on the walls of the sandstone of Malham Tarn House. “Nuisance Alga” he called it — I think because it grows on top of the lichens he would rather be studying.
I saw it on the millstone grit walls above Settle, whilst marshalling for the Settle Harriers Hill Race in 2011. and nearby whilst on a Craven Conservation Group walk in 2012
I saw it on the grit /greywacke wall between Helwith Bridge and Austwick
Both these places are high exposed places – where one would expect the air to be pure and clean. I can only presume that because they are windy places, that lots of air blown across from wherever ~both Yorkshire and Lancashire. Even if the pollution is dilute, then a lot of air will eventually deposit a lot of nitrogen compounds.
Last year I found it in Wales, this year in Scotland.
A trip to Pen y Ghent – over 2000 ft above sea level in February 2014 to get the view above the fog .. revealed Klebsormidium at the very summit.
Here we are finding it on a slate gravestone at Ingleton
On Aug 24 2013) it made a bright green backdrop to the blackberries I collected.
This is the wall where the brambles were. It was on a species rich country lane on millstone grit geology, in the Forest of Bowland. But a glance through into the fields show they have been reseeded and well fertilized to give a second (or third?) crop of silage
Should we be worried? I am surprised the story of the spread of Klebsormidum is not all over internet, with tales of gloom.
But meanwhile I am delighted I can recognise the stuff, that I can get joy out of appreciating (some) different types of alga.
And can now (2015) recognise more types of lichen. Those Lichen species that like high nitrogen compounds are spreading too.. but that is for another post.
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Two years later (Sept 2014) here are links to more places I have noticed it:-
Sannet Hall, above Stainforth, N Yorks Nov 2014
Near The Locks , Langcliffe Oct 2014
Have you noticed Klebsormidium where you live?
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