Of microbes and mountains …

I spent a few anxious days last week watching the weather forecast in anticipation of fieldwork.   It was not clear from the forecast whether there would be enough rain to lift river levels to a point where I could not safely collect samples or if, rather than rain, there would snow, which may make the roads slippery but would, at least, mean that river levels were low.  The best I thought I could expect was to be working in near freezing conditions amidst flurries of snow, so it came as an unexpected surprise to find clear skies and sunshine even if April water temperatures were still bitingly cold.   The photograph at the top of the post shows Wastwater, looking towards Scafell Pike and Great Gable on a cold but still April morning, but the focus is on the River Irt, about 500 metres or so downstream from the outfall from the lake.   The landscape overlooking the lake is spectacular but, on a different scale, the subaquatic landscape that I see when I peer at the bed of the River Irt through my aquascope, is equally spectacular, albeit on a vastly smaller scale. 

Underwater landscape in the River Irt, April 2021, with green algae (a.), mosses mixed with Cyanobacteria (b.) and diatoms (c.).   The foreground of the picture frame is about a metre in width.

The flocs of green algae are mostly composed of Spirogyra whilst the mosses and cyanobacteria combos in the background are the same as those that I wrote about in “Tangled up under blue skies” a couple of months back.   The diatoms in the front foreground are the most intriguing.   Here, as at several other locations, we could see and feel distinct biofilms on rocks, but our measurements of chlorophyll concentrations were nearly always very low.  The answer became clear when I looked at some of the biofilm under my microscope: the dominant diatom in these biofilms was a long-stalked form of Gomphonema; probably the same one that I wrote about in “Diatoms and the space-time continuum” a few years back.   The biofilm that covered the patches where other algae and mosses were not dominant was composed mostly of the polysaccharide stalks, with the photosynthetic cells forming a surface layer.  From the point of view of any subaquatic grazer, this roughly equates to a piece of bread with a thin smear of marmite on top.   However, the tangled mass of stalks also works well as a means of trapping organic and inorganic particles that are in transit through this part of the river, and most of the invertebrates that live on stream beds are not particularly fussy about precisely what is on the menu.   I have no data to back this up, but my hunch is that these diatoms make a bigger contribution to the diet of these bugs through these trapped particles than they do through the energy that they have created from trapped sunlight.  

Gomphonema on long stalks, along with a few Achnanthidium, from the River Irt, April 2021.  Scale bar: 10 micrometres (= 1/100th of a millimetre).  

With samples from the River Irt safely packed into the cool box, our field work was finished and, as it had already spilled into the weekend, we felt no compunction about heading back to explore the mountains that loomed over Wastwater.   Our target today was Great Gable, a steep pull up from Wasdale, but a climb that rewarded us with striking views of the lake and the famous screes.   Having started our walk with blue skies and cotton wool clouds, it also gave us a panoramic view of the changing weather as clouds blew in and showers fell along the west Cumbrian coastal plain.   We encountered a few flurries of snow as we approached the summit of Great Gable, but not enough to obscure a view which extended to Windermere to the east, Skiddaw, Helvellyn and Blencathra to the north-east and Crummock Water and the Liza valley to the north.  Somewhat to my surprise, Ennerdale Water was not quite visible from the summit.

The view back along Wasdale towards Wastwater from the flank of Great Gable, April 2021.

We made a steep descent to Styhead Tarn, then followed the track back to Wasdale, passing a group of intrepid mountain cyclists on the way up variously pushing and carrying their bikes.  We could still see showers in the distance but the snow flurries we encountered on the way up did not seem to have come to much.  Consequently, it was a surprise to us when, having driven out of Wasdale and back to our accommodation in Ennerdale, we saw the flanks of the hills around Great Gable to be covered with snow.   Last April, we were basking in unseasonably warm weather at the start of the first lockdown; a year on there is snow, and not just on the high fells either.   Nature continually surprises us, on a whole range of scales, from the minute to the enormous.  That’s what keeps pulling us back.

Wrote this whilst listening to:  Déjà vu, by Crosby, Stills, Nash & Young.

Cultural highlights:   The film The Mauritanean, about the longest serving prisoner at Guantanamo Bay.  

Currently reading:  Spring Has Not Been Cancelled: David Hockney in Normandy, by Martin Gayford.  Reflections on landscape painting by an undisputed master.

Culinary highlight: probably has to be the sandwiches we ate on the way up Great Gable, mostly because of the spectacular views that accompanied them.

Snow over the fells to the south of Ennerdale Water: Heather’s photo taken on the evening of 10 April after our ascent of Great Gable (just out of frame).

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