We were in the Lake District at the turn of the month to collect some of our regular samples and measurements and our reward for some very cold water and slightly higher river levels than was ideal was a day of cloudless, still weather with some inviting vistas of the peaks. That invitation will, however, have to wait, as we have work to do and, having dragged our eyes away from the distant view of Great Gable, we peered at the algae in the littoral zone of Wastwater and then made our way to the two sites on the River Irt, which flows out from the lake.
I wrote about one of these sites after our visit in December (see “As old as the hills …”) and was intrigued to see how the situation that I described there had changed over the intervening two months. The cyanobacterial growths that I described back in December were, if anything, more prolific now, and whilst I was puzzling over their identity then, I am now almost certain (having shown the material to Brian Whitton) that it is Tolypothrix distorta var. penicillatus. Last time, I saw enough double false branches to suspect a species of Scytonema; this time, the branches were almost all single and the general habit of the plant also pointed to T. distorta var. penicillatus.
These growths were still associated with an acrocarpous moss (probably Racomitrium aciculare), presumably gaining some support and protection from stems and leaves. The key difference this time, however, was that the Tolypothrix itself seemed to have been colonised by other organisms. In addition to some very small cyanobacterial cells (guessing Chamaesiphon – see “More from the River Ehen”), there were also a few longer filaments (likely Heteroleibleinii – see “River Ehen … again”) as well as a few diatoms (mostly Fragilaria gracilis). Those earlier posts also highlight the relationship between Tolypothrix and aquatic mosses and were written at approximately the same time of year.
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I’ve tried to capture this relationship in a painting, with Tolypothrix filaments entangled around Racomitrium aciculare leaves (note the characteristic wavy outline of the cells) . The false branches typically have a heterocyst (cell responsible for nitrogen fixation) at the base, and then run almost parallel to the main filament for some time. The epiphytes grow on the thick colourless sheath. Compare the images in this post with those taken in December to see just how the abundance of epiphytes has changed in two months.
This is the second post in a row in which I’ve mused about the relationship between bryophytes and algae. When I was writing about Riccia fluitans and Epithemia, I speculated that the liverwort may gain some nitrogen from the relationship and the same possibility must exist for Tolypothrix and Racomitrium. In both cases, we are probably looking at an arrangement that is too loose for the term “symbiosis” to be appropriate but general proximity of organisms in environments where resources are scarce must lead to mutual benefits. I would go further and suggest that patchy distributions of algae is a common property of nutrient-poor streams, and these patches are often composed of more than one species. So it is fair to speculate that they may gain both physical support and opportunities to share nutritional and other benefits too. It would, alas, also be very difficult to prove.
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Once we had packed away our samples from the Irt our fieldwork was finished. The sky was, however, still blue, the wind still absent, and the fells tempting. Our only constraint was the limited amount of daylight left to us. Rather than attempt anything too ambitious, we drove to the Honister Pass, between Buttermere and Borrowdale, parked at the slate mine at the top and headed up the steep fell to the south. Our car had done half the climbing for us and we were on Grey Knott and striding through the rough grassland towards Brendreth within an hour of parking. The views down the Ennerdale and Buttermere valleys were quite spectacular, with the lakes shimmering in their respective valleys. Forgive me if I end the post with a couple of memories of those very special views.
Some other highlights from this week:
Wrote this whilst listening to: Omega, debut album by jazz saxophonist Immanuel Wilkins. And Julio Iglesias singing Begin the Beguine at the funeral of an elderly aunt.
Cultural highlights: My Donkey, My Lover and I: a French comedy set in the Cévennes.
Currently reading: Lightseekers, by Femi Kayode, a crime novel set on a Nigerian university campus.
Culinary highlight: definitely not the food I encountered on the journey to and from the funeral I mentioned above. I am now definitely inoculated against fast food chain burgers for several months at least.
![](https://microscopesandmonsters.wordpress.com/wp-content/uploads/2021/03/ew_from_brandreth_mar21_2.jpg?w=1024)
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