Rust Coloured Green Alga

Nope, I'm not on about seaweeds. On this occasion I'm referring to Trentepohlia algae. Trentepohlia is a genus of filamentous green alga, usually found as tiny clumps of bright orange fluff on tree trunks and on shaded rocks or concrete posts. What on earth am I jabbering on about, I hear you ask. The easy answer is to check out this page which has far better images than I do.

The tiny clumps of orange fluff on rocks and on tree trunks are Trentepohlia aurea and T.abietina. They differ microscopically, though essentially look identical to each other through a handlens. As a guide, but only as a guide, T.abietina generally prefers tree trunks and T.aurea generally prefers rocks. But they do sometimes swap around. There are a total of eight species on the British list, the aforementioned two being by far the most recorded. But there's a third species that I also see quite regularly here on Skye. And here it is in all of its glory!

Trentepohlia iolithus - seen here covering an entire wall

Here's the Google Street View image of the same property in November 2021

Slightly less coverage in the 2021 image, though clearly still very extensive. The only other Street View imagery is from 2009, when the housing estate was still quite new. In that image there's not a hint of Trentepohlia. But look at it now, what an absolutely magnificent display! Which, I imagine, probably echoes the exact same sentiment of the adjoining neighbour...

There is a confusion species which could also occur on Skye, Trentepohlia umbrina. However, that species tends to favour exposed stonework and forms thick, felted mats. The diffuse and widespread infestation shown in my image is across painted render, not exposed stonework, and has not formed crustose felted mats. I feel confident that this is Trentepohlia iolithus. 

There are three records for Trentepohlia iolithus on iRecord, two from 2015 and one from 2019. None of them have been verified yet. I've added my record, but I won't be holding my breath awaiting verification. 

In other news there have been no reports yet of yesterday's Orcas. I've nailed a handful of aquatic hyphomycetes collected from stream foam yesterday. Four species identified, three of them being lifers for me, and there were three December Moths inside the light trap when I checked it this morning. Oh, and there's an Ivory Gull on Faroes. It's heading this way, I just know it.