Ardvar to Loch na Mola, an April outing

May 9th 2021

Ardvar to Loch na Mola

Some days out provide interest throughout, others seem to save most of it for our destination.  A walk from Ardvar to Loch na Mola (NC1633-1735) on 3rd April 2021 was an example of the latter.

We parked, with the permission of Field Club member Margaret Payne, near the house, and started off north along the east side of Loch Ardbhair.  Two great northern divers in winter plumage were noted out on the sea loch before we turned inland up an undulating path.  This took us to the south-eastern end of Loch an Fionn Airce or House Loch, where a bank of primroses was admired over hot drinks.

Refreshed

Diverging from the path, we made for a well-grown holly to collect a few dead leaves to check for their usual tiny black fungi (Phacidiostroma multivalve and Trochila ilicina) and then dropped down into a boggy basin.  This had once been dug for peats, and a sample of the rather sludgy vegetation in a resulting shallow pool (NC171348) was collected for desmids.  David Williamson has since sent drawings of 16 species he found in the sample.  He described the variety as ‘quite good, although mostly common stuff’. Two are pictured, Cosmarium canaliculatum, unprepossessing in appearance but ‘unusual’ (photo 1) and Micrasterias papillifera, which is particularly beautiful (photo 2).

A short distance further on we came to a small shingly beach (NC172349), where we disturbed a pair of ringed ploversPrimroses were really frequent here, growing right down into grassy shingle, an unusual habitat.  A small rocky cliff with grass at its base (photo 3) provided shelter for an early lunch, with good views across Eddrachillis Bay.  We were, however, a little disturbed, when gathering up our sandwich boxes afterwards, to find them covered with hundreds of tiny ticks Ixodes sp., all with six legs, indicating the larval stage (photo 4). Although they were probably too small to penetrate human skin, we did give ourselves a vigorous brushing down to stop them trying.  Their normal hosts in such places are presumably small mammals such as field voles.

Back on track

Returning to the path, we found our way across to the south-west end of the crescent-shaped shingle beach which lies between Loch na Mola on its seaward side and the freshwater Loch na Dubh Leitir to landward.  The latter is edged with large beds of great fen-sedge Cladium mariscus, which is presumably salt tolerant (photo 5).

Mayflies (photo 6) were emerging along the edge of the loch (NC174350), leaving the discarded skins of their last nymphal stage on stones (photo 7).  The latter looked like tiny suits of armour, but with conspicuous white trailing tracheal tubes which had previously supplied air to the inside of the nymphs.

Gwen took close-ups of both stages and from these Craig Macadam of Buglife has been able to identify them as the sepia dun Leptophlebia marginata.  It is a widespread mayfly of slightly acid waters, but there are only three previous records from Assynt, all made nearly 40 years ago: River Loanan at Loch Awe, NC2516, 6th May 1981; River Loanan at Inchnadamph, NC2421, 3rd December 1981; River Inver at Little Assynt, NC1525, 3rd December 1981.

We then walked along the landward side of the beach, scanning the edges of vegetated areas for the small adder’s-tongue fern Ophioglossum azoricum, first found here by Gwen on an AFC field meeting on 18th August 2013, and once since, but it was too early in the year.

Rusty rocks

At the far end of the beach an outcrop of rock had the familiar dark, lichen-blotched, look of a mafic dyke (as the geological map later confirmed) and this is where observations went into overdrive.  In places mineral-rich water was seeping out of the rock.  The run-off contains both iron, which had been utilised for energy by specific bacteria, making for colourful rusty oily patches (photo 9) and also calcium salts, which have coalesced into coralline tufa (photo 10).

The presence of plentiful wild thyme Thymus polytrichus indicated the basic nature of the rock, as also did tufts of black spleenwort Asplenium adiantum-nigrum.  However the star finds were rosettes of pyramidal bugle Ajuga pyramidalis, with its striking blue flowers, springing out of otherwise bare crevices or tucked into gritty soil below the outcrops (photos 11-12).

The lichens were also worth a good look. On vertical rock faces were tiny orange-red thalli of a species of Caloplaca (photo 13); Tony Fletcher has had a look at our photos and suggested C. arnoldii, which is found in such coastal situations in the North West, often on slightly basic rocks.  In gulleys where water trickles down were the greyish contorted thalli of Dermatocarpon luridum (photo 14) and, elswhere in crevices, grey cushions of the Felt Lichen Degelia atlantica, which we more often find locally on trees (photo 15).

Another drink

Following this flurry of finds, we had a final hot drink looking back along the beach (photo 16) and then made our back to Ardvar to report our finds, in an appropriately-distanced manner, to Margaret Payne.

Faunal observations from Ardvar to Loch na Mola, other than those mentioned, were sparse: a fox scat on the path and otter spraints on a conspicuous tump at the edge of Loch na Dubh Leitir; mallard off the House Loch, sundry meadow pipits, two pied wagtails and a wren; and six separate caterpillars of the drinker moth.  The last are brightly coloured and quite obvious; they are perhaps protected from predation by being distasteful?

 

Ian M. Evans and Gwen Richards

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