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.

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Unmasking the faceless Eurocrats …

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My own small contribution to the campaign to keep the UK in the European Union takes the form of a scientific paper. This will probably not raise many eyebrows outside the small band of specialists amongst whom I work but it offer it as an antidote to the rhetoric of the anti-EU campaigners and their scaremongering about the Brussels bureaucracy. I have made no secret that I am pro-EU (see “What has the European Union ever done for us?”) and that I think the UK benefits from EU environmental legislation. What one person thinks to be sensible regulation can easily be portrayed by the disingenuous as excessive red tape peddled by faceless, unelected Brussels bureaucrats.

Our paper deals with about half a sentence in an annex of an 80 page Directive that deals with how EU Member States should assess the quality of lakes.   Should the suspended algae, the attached algae and the larger plants be used to assess lake condition, or can you get the same outcome by just using two of these three components? Interpretation of those few words can, however, result in considerable and recurring expense for a large Member State such as the UK.   Opinion on how they should be interpreted differed between the 28 countries of the EU.   How do you find the balance between the environmental risks associated with lax interpretation of EU law and the extra costs that a stringent reading of the Directive would entail?

I was contracted, along with two colleagues, by the European Commission’s Joint Research Centre to look into this issue by examining the datasets of those countries that had analysed all three components to see how much extra information additional types of monitoring added to a manager’s overview of lake condition.   One additional twist to the problem was that my own particular specialism, the attached algae, was the Cinderella at this particular ecological assessment Ball, with about 60% of EU states deciding that these were not necessary.   Ironically, my career as Fairy Godmother to fellow algal specialists was extremely short-lived, as the outcome of our analyses was that, if a lake had a problem, it could usually be detected using the suspended algae and higher plants (the “ugly sisters” … metaphor overload .. no more of this, I promise).   There are situations when all three are needed to understand how to manage a lake but, for strategic overviews of the condition of a country’s lakes, little was gained by including them.

So what has all this got to do with our EU referendum?   In brief, this was a matter of interpretation discussed by representatives of all Member States at meetings mediated by European Commission representatives.   Having identified a difference of opinion, they brought us in to work on an evidence-based solution which was then discussed, in depth, at another meeting of national representatives (mostly ecologists). Many agreed with our conclusion; a few made the case for continuing to use all three components.   Ecological arguments were put forward by both sides but, in essence, we were debating whether this was an issue that should be decided within or between Member States.   Most were happy that this level of detail could be determined within Member States.   Even if the outcome had been in favour of imposing a more rigorous interpretation of the Directive, it would have been the consensus of Member States enacted through the Commission, not a blanket edict from these (hypothetical) faceless bureaucrats that the right wing press constantly demonises.

An interesting coda to this story is that after our report had been circulated and discussed my colleague at JRC was contacted by people from one Member State who were slightly alarmed by the conclusion.  The point that they made was that devolving responsibility to individual countries would lead to many dropping the use of attached algae, simply on the grounds of financial expediency. I had some sympathy (one of the authors was a fellow consultant who, like me, makes part of his living from this type of work) but it also touched on something that has been exercising my mind over recent months.   Do countries use this type of monitoring because they have to (i.e. the Directive tells them to) or because they need to (i.e. it contributes valuable information to lake management)?   It shifts the onus on us, as advocates of a sub-discipline, to make a reasoned case for the continued use of attached algae, rather than simply assume that “Brussels” will guarantee our livelihood.

Note: the photograph shows Derwent Water in the English Lake District, looking south from Friar’s Crag, July 2015.

Reference

Kelly, M.G., Birk, S., Willby, N.J., Denys, L., Drakare, S., Kahlert, M., Karjalainen, S.-M., Marchetto, A., Pitt, J.-A., Urbanič, G. & Poikane, S. (2016). Redundancy in the ecological assessment of lakes: Are phytoplankton, macrophytes and phytobenthos all necessary? Science of the Total Environment http://dx.doi.org/10.1016/j.scitotenv.2016.02.024.

Constructing a stalk …

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Shortly after I posted my piece on calcification in Chara last week (see “Everything is connected …”), I came across another paper that discussed similar processes in a very different organism.   I’ve written about the diatom Didymosphenia geminata before (see “A journey to the headwaters of the River Coquet …”) and commented on the long stalks that it produces.   I mentioned in this post that the stalks were composed of carbohydrates and that this may be part of the reason why Didymosphenia can growth in such large quantities in rivers that are naturally nutrient-poor.   As carbohydrates are composed of just carbon, hydrogen and oxygen, they can be built by the miraculous rearrangement of carbon dioxide and water that we call photosynthesis.

Although other diatoms produce stalks too, the stalks produced by Didymosphenia are intriguing because they are so much larger than those of other species.   An organism that is only a tenth of a millimetre long can produce a stalk ten times as long – enormous, by the standards of the microscopic world.   Just as a builder might need to adjust his methods when building a skyscraper, compared to a normal-sized house, so it may be that Didymosphenia has acquired some structural reinforcements to make sure that the polysaccharide stalk can support the cells amidst the rigours of a fast-flowing stream.

A paper by a large team of researchers from Germany, France, USA, Russia and Poland sheds some intriguing light on this subject.   At the heart of the story is the same inorganic chemistry that we encountered for calcification in Chara, and the same enzyme, carbonic anhydrase, to enhance the process. In the case of Didymosphenia, however, there are some intriguing differences.   The researchers suggest that the stalk of Didymosphenia is strengthened by calcite nanofibres within the polysaccharide matrix.   They pointed out that the “foot” of the Didymosphenia cell is rich in mitochondria, which provide the energy for the production of the stalk.   Carbonic anhydrase is an enzyme that can both produce bicarbonate and protons from carbon dioxide and water, and the reverse. This means that it can regulate the concentration of carbon dioxide, ensuring a constant supply for photosynthesis whilst, at the same time, preventing a build-up in those parts of the cell that are busily respiring. The same carbonic anhydrase-mediated process that we saw in Chara can take place inside the Didymosphenia cell to capture calcium to build the nanofibres for the stalk.   However, intriguingly, a parallel reaction can take place outside the cell.

A long stalk is no advantage to an organism unless it is well-anchored and the suggestion now is that the carbonic anhydrases can generate localised patches of acid conditions that erode the rock surface and allow the stalk to form rhizoid-like “holdfasts” within the substrate. About half of all the carbonic anhydrase activity seems to take place outside the cell, and so contribute to these processes.   It is an interesting hypothesis that makes sense when the substrate contains a high proportion of limestone; whether it explains the success of Didymosphenia on other rock types (such as basalt, found in Didymosphenia-rich streams of the Cheviots) remains to be seen. The researchers (who approach the topic from the perspective of materials scientists rather than ecologists) describe the outcome as “mechanically stable and simultaneously very flexible under challenging hydrodynamic conditions of rivers with especially strong flow”.

Other evidence points to stalk production being at least partially controlled by the need to acquire nutrients, so a picture is starting to emerge of a single-celled organism with a range of physiological adaptations that enable it to survive in fast-flowing nutrient-stressed environments where relatively few other organisms can survive.   Having grumbled a few times in the past about diatom scientists wanting to know the shape of everything and the meaning of nothing, it is great to see that, in a few cases at least, we are beginning to get a more rounded understanding of the ecology of these fascinating organisms.

Note: the picture at the top of the post shows Didymosphenia stalks smothered in epiphytes, based on material collected from the headwaters of the River Coquet, Northumberland, May 2011.

References

Bothwell, M.L. & Kilroy, C. (2011). Phosphorus limitation of the freshwater benthic diatom Didymosphenia geminata determined by the frequency of dividing cells. Freshwater Biology 56: 565-578.

Ehlich, H., Motylenko, M., Sundareshwar, P.V., Ereskovsky, A. et al. (2016). Multiphase biomineralization: enigmatic invasive siliceous diatoms produce crystalline calcite. Advanced Functional Materials DOI:10.1002/ADFM.201504891.