More algae from Shetland lochs …

Lamba_Water_May19

I’m taking you back in the Shetland Islands for this post, and onto the remote moorlands of northern Mainland.   When I visited this particular loch in 2016, I noticed a lot of slippery filaments of Batrachospermum attached to the sides of the cobbles in the littoral zone (see “Lucky heather …”).   This time around, I explored further around the edge of the loch and, in the south-west corner noticed prolific growths of algae in the shallow peaty water.  Closer inspection showed that these, too, were the red alga Batrachospermum and, though they were not fertile, Dave John suggests that they are likely to be B. turfosum Bory.

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Tufts of Batrachospermum turfosumin the littoral zone of Lamba Water, north Mainland, Shetland Islands, May 2019.   The picture frame is about 15 centimetres across. 

If you have a hand lens you can just about make out a bead-like structure when observing Batrachospermum in the field; however this becomes much clearer with higher magnification.   I think it looks like a bottle-brush when seen under the microscope at low magnification, with whorls of side-branches arising from the central filament.  At higher magnification, these filaments can be seen to have a bead-like structure, with cell size gradually reducing with distance from the centre.

What you cannot do in the field is separate Batrachospermumfrom the closely-related genus Sheathia(see “News about Batrachospermum… hot off the press”).   I usually tell people that, for a general overview of the condition of a stream or lake (for example, as part of the UK macrophyte survey technique), then simply recognising that you have “Batrachospermum” (meaning Batrachospermum or Sheathia) should be enough.   In my experience, the presence of Batrachospermumis usually a good indication that the water body is in a healthy condition.  However, I have been told that Batrachospermumis often found growing prolifically in very enriched conditions in southern chalk streams, which would challenge this assumption.   This may be because the species that are found in southern chalk streams are different to those that I encounter in my more usual haunts in northern England and Scotland.  But it is also possible that the factors I described in “The exception that proves the rule …” pertain in those cases too.

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Filaments of Batrachospermum turfosum from Lamba Water, north Mainland, Shetland Islands, May 2019.   The upper photograph shows a low magnification view of a filament (about 350 micrometres, or 0.35 millimetres, wide) whilst the lower image shows a whorl of side branches arising from the main stem.  Scale bar: 20 micrometres (= 1/50thof a millimetre).  

We often run into this dilemma with filamentous freshwater algae: it is reasonably straightforward to identify the genus but we need reproductive organs to determine the species.  As they seem to survive quite happily in the vegetative state our understanding of the ecology of individual species (rather than the genus as a whole) is scant so it is hard to tell whether there is value in that missing information or not.   In a few cases – this is one – better taxonomic understanding has revealed that we may not even be dealing with a single genus but the lists used for applied ecological surveys still persist with the old concepts.

This creates a toxic spiral of consequences: it is hard to split into species so most people don’t bother. Because we don’t bother, our interpretations are based on generalisations drawn from the behaviour of the genus.  This means we don’t generate the data needed to demonstrate the value (or otherwise) of the effort required to go from genus- to species-level identifications.   So we carry on lumping all records to genus (or, in this case, a pair of genera) and accept a few records that our out of line with our expectations as “noise”.  The situation is probably worse in the UK than in many places because there are very few people in universities specialising in these organisms and, as a result, no-one is producing the data that might break us out of this spiral.

We found Batrachospermum turfosum in a few other locations during our visit, but nowhere, even in nearby lochs, was it in such quantity as we saw in Lamba Water.   Chance might play a part in determining its distribution on a local scale but that ought to be the explanation of last resort rather than the go-to answer when we are worryingly short of hard evidence.

 

 

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How to make an ecologist #7

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Casting a plankton net to collect algae, somewhere in Scotland (possibly Loch Earn), April 1985.

At some point between leaving Westfield as a rookie ecologist with an enthusiasm for Sphagnum, and finishing a PhD on mosses at Durham I started the slow metamorphosis into a phycologist.   Brian Whitton expected his PhD students to help out in undergraduate practicals and my lack of phycological training up to that point was not regarded as sufficient reason to excuse me from this duty.   It was a steep learning curve but, in turn, it opened windows onto new worlds that have kept me fascinated ever since.

Brian had an old school natural historian’s approach to undergraduate practicals.   Technicians were sent out to local ponds and came back with handfuls of vegetation which were squeezed and scraped to yield rich harvests of algae. At the start of the practical, no-one had any idea which species might be present; three hours later, with the help of a handful of books in a range of languages (we just looked at the pictures) and cajoling from Brian, the demonstrators, at least, emerged older and wiser.

Straight after Easter, the third year botany students were taken on a week-long field trip to Loch Lomond, staying at University of Glasgow’s Rowadennan Field Centre, and learning about algae at a time when most of them would really have preferred to be getting on with revision for their finals.   However, once they arrived at the field centre, set amidst the forests on the east shore of Loch Lomond in the shadow of Ben Lomond, they usually mellowed.   It was a glorious location. We went out to various lochs and streams, sampled different habitats, collected a few environmental measurements, and then spent time in the laboratory trying to name what we had found.   In the evenings most of us made the three kilometre walk to Rowardennan Hotel for a pint of beer.

On one of the days we made a long excursion, down the east shore of Loch Lomond, then up the west shore, making a short diversion at Tarbet to Loch Long, the only sea loch we visited during the week. Then it was back into the vans and up to the north end of Loch Lomond, stopping at a stream in Glen Falloch before sampling Loch Lubhair and Loch Linhe. The final leg swung south past Loch Venachar to Lake of Menteith in the Trossachs (‘the only lake in Scotland’) before returning to Rowardennan in time for dinner. In one long day we had seen marine and freshwater habitats, sampled hard and soft streams and lakes, planktonic and benthic habitats and seen seaweeds as long as our arms and microscopic algae a 100th of a millimetre in diameter.

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Durham University botany undergraduatest getting to know freshwater algae at Rowardennan Field Centre, April 1985.

At this time, the Durham botany degree was strong on biochemistry and molecular biology and notoriously light on traditional botanical skills.   There was a running joke during my postgraduate years that some of our molecular biologist colleague’s plant identification skills ran no further than reading the label on a packet of seeds. Reductionism ruled, with teaching on whole plants and their interactions with the environment pushed to the edges of the course.   The honours botany students were taken on a two week field course to Austria at the end of their second year to learn about alpine plants. This week in Rowardennan dealt with the 75 per cent of UK’s plant diversity that has now dropped off most undergraduate curricula over the past couple of generations. And, once again, the demonstrators, acting as intermediaries between Brian’s extensive knowledge and the near complete ignorance of the students, were probably the principal beneficiaries.

There were other beneficial outcomes to the course. I spent long hours walking to and from the pub sharing our experiences of travelling in the Himalayas with one of the students.   This same individual (and her distinctive orange cagoule) cropped up in more of my photographs than a hypothesis concerning the random distribution of students on 35 mm film would predict.

Reader, I married her.

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Durham undergraduates sampling a stream in Scotland during the algae field course, April 1985.