Form without function?

The latest copy of FBA News includes an article I wrote, along with Catherine Duigan, on the scientist Geoffrey Fryer, who celebrates 50 years as a Fellow of the Royal Society this year.   Geoffrey Fryer spent his early career working on the cichlid fish of the Great Lakes of East Africa’s rift valley.  He moved back to the UK in 1960 and spent the rest of his career working mostly on planktonic crustaceans at the Freshwater Biological Association’s laboratory at Windermere, where I first met him.    

When he arrived at Lake Malawi in 1953, the existence of “species flocks” – relatively large numbers of closely related species confined to a narrowly circumscribed region – of cichlid fish had already been recognised but the reasons that led to their evolution was barely understood.    These were piscine analogues – albeit significantly more diverse – of the finches that Darwin observed on the Galapagos Islands, and which provided crucial evidence for his theory of natural selection.  Swimming in Lake Malawi and observing cichlid fish close quarters through a face mask, then dissecting fish caught by local boys enabled Geoffrey to show how morphology was linked to function (especially feeding behaviour) and explained preferences for sandy or rocky shores.  It is one of the great examples of “adaptive radiation”.

Some of the many cichlid fish from Lake Malawi studied by Geoffrey Fryer. Top left: Pseudotropheus greshakei; top right: Ramphochroumus ferox; bottom left: Lethrinops sp.; bottom right: Copadichromus virginalis.   Photos: Ken Irvine, Institute of Hydrology, Delft.   The photographs at the top of the post show Geoffrey Fryer in the 1950s and earlier this year.

“Species flocks” have been found for other organisms including, some claim, diatoms.   The evidence is not quite so clear-cut but most of the criteria (several closely-related species within a limited geographic area) are fulfilled, and there are reasonable grounds for assuming a common ancestor.   Interestingly, too, several of the purported flocks come from areas with ancient lakes (the African Rift Valley, Lake Ohrid in North Macedonia and Lake Baikal in Siberia, for example).  What is missing from the studies on species flocks in diatoms, however, is the link between form and function. We can infer radiation of several species from a common ancestor, but we cannot explain why it is that one lake is able to support so many close relatives.  We are, once again, confronted by Hutchinson’s Paradox of the Plankton (rephrased for surface-dwelling organisms as “Baffled by the benthos”).

The plate below shows four species of the genus Epithemia from Lago di Trasimeno in Italy.   These do not represent a “species flock” because they are not confined to a limited geographical area but they serve to make a point about our understanding of diatoms in general.   Epithemia is not a particularly common genus but, when you find one species from this genus, there is a good chance that you will find another in the same sample.   I’ve found E. sorex and E adnata, in particular, together in samples from the Shetland Islands to Italy and Greece in the Mediterranean Basin.    In this sense, they are like Geoffrey Fryer’s cichlid fish: two closely related species living in close proximity.

Epithemia species from Lago di Trasimeno, Italy, September 2022.   a. E. sorex; b., c.: E. adnata (two focal planes); d. E. turgida, e. E. frickeri.   Scale bar: 10 micrometres (= 100th of a millimetre).  

But in another sense, they are nothing like cichlid fish.   Fryer, dabbling around in the shallows of Lake Malawi, was able to explain how form linked to function, enabling each species to exploit different resources.  The literature on Epithemia mostly focuses on form, also addresses geographical differences but is almost silent on the subject of function.   We learn that Epithemia, as a genus,  is capable of nitrogen-fixation but not how individual species differ in their habitat preferences.   Clearly, if two species occur side-by-side in a sample, then the chemical composition of the water (the go-to explanation for diatom ecologists) is not going to tell us the whole story.    And it is not just Epithemia: similar patterns can be found in many other genera.

The study of diatoms is certainly not dormant.   We have learned a huge amount about their diversity and evolution over the past few decades.  We also know a lot about why apparently closely-related species live in different places (geological/chemical conditions and biogeography).   What we are less sure about is why two or more closely-related species share a habitat.    Diatom science seems to have become stuck in a cul-de-sac where diversity is celebrated but rarely explained, at least not in the functional ecology terms that motivated Geoffrey Fryer all those years ago in East Africa.   

References

Two good general introductions to “species flocks” are:

Goldschmidt, T. (1996).  Darwin’s Dreampond.  Drama in Lake Victoria (translated by S. Marx-McDonald).  MIT Press, Cambridge, MA.

Weiner, J. (1994).  The Beak of the Finch: a Story of Evolution in Our Time.   Knopf, New York.

Other papers:

DeYoe, H. R., Lowe, R. L., & Marks, J. C. (1992). Effects of nitrogen and phosphorus on the endosymbiont load of Rhopalodia gibba and Epithemia turgida (Bacillariophyceae) 1. Journal of Phycology28(6), 773-777.

Kociolek, J. P., Hamsher, S. E., Kulikovskiy, M., & Bramburger, A. J. (2017). Are there species flocks in freshwater diatoms? A review of past reports and a look to the future. Hydrobiologia, 792: 17-35.

Stelbrink, B., Jovanovska, E., Levkov, Z., Ognjanova‐Rumenova, N., Wilke, T., & Albrecht, C. (2018). Diatoms do radiate: evidence for a freshwater species flock. Journal of Evolutionary Biology 31:1969-1975.

Some other highlights from this week: 

Wrote this whilst listening to:   And in the Darkness, Hearts Aglow, new album by Weyes Blood

Currently reading:   Nadime Gordimer’s A World of Strangers

Cultural highlight:   The Wonder,  adaptation of a 2016 novel which I have not read, featuring Florence Pugh.   The lighting palette often recalls Vermeer’s interiors.  –

Culinary highlight:  roast broccoli and plum salad.  Would not have thought of combining these two ingredients before trying it in the café at the Royal Botanic Gardens in Edinburgh.  The secret lies in the dressing, which should evoke hoisin sauce.

Advertisement

More than just hitchhikers …

The Iroquois people of North America believed that the earth rested on the back of a giant turtle swimming around in a vast ocean.   It sounds quaint and fanciful but, during my visit to the Croatian Biological Congress, I learned that marine turtles do, in fact, carry worlds around on their backs, albeit on a somewhat smaller scale than envisaged by the Iroquois.    The image at the top of the post shows a turtle at Pula Aquarium’s Marine Turtle Rescue Centre, with several barnacles clearly visible but Sunčia Bosak of the University of Zagreb gave a fascinating talk on yet smaller organisms living on turtles.   She focussed on the diatoms but also talked about bacteria and a range of other organisms.

I’ve written many times about epiphytes on this blog – organisms that live on the back of other plants (most recently, “Springtime surprises …”).  In the same way, smaller organisms can hitch a ride on the back of animals and studies have shown that these are not just common but, in many cases, the hitchhikers have strong preferences for exactly this type of habitat.  Luc Denys, from Belgium, has found unique genera that live only on the backs of whales and there is now also evidence that some species and genera found on the backs of marine turtles are also restricted to this unusual habitat.  

In a slight deviation from the Iroquois creation myth, diatoms were found not just on the shell (carapace) of the turtle, but also on the skin.   Furthermore, different diatoms were found on skin and shell, and yet more differences were revealed when turtles from different parts of the world were compared.   The diatoms that seem to live exclusively on turtles were more abundant on skin whereas the assemblages on shells were dominated by a range of generalist species.   

The next twist to this story comes with a very recent paper (published in October 2022) that shows that not only do turtles have distinct assemblages of diatoms on their skin and shell, but that these diatoms, in turn, each have distinct assemblages of bacteria.  I’ve talked before about how loose associations between the protozoan and Ophyridium and diatoms can benefit both (see “Intimate strangers …”). In brief, the hitchhikers extend the “metabolic toolkit of the host, giving it greater resilience to the uncertainties of life in the oceans.  Because they, in turn, host a range of bacteria, the turtle-squatting diatoms take this to the next level, facilitating a rich external “microbiome” to complement the gut microbiome whose importance in humans is now recognised.  

This is all part of an emerging field that is, ostensibly, about how species interact with each other in ways other than traditional view of “nature red in tooth and claw”. There are many studies now showing co-operation amongst organisms that challenge received wisdom not just in science.  “Survival of the fittest” contributed not just to an understanding of nature in the late 19th and early 20th century, it also knitted in with ideas such as Nietzsche’s Übermensch to underpin political views that dominated much of the 20th century.   How might a more co-operative view of nature synergise with politics?   How does this challenge the harsh right-wing political views that dominates modern politics?    This type of speculation may seem to be a long way from scraping diatoms off the back of a turtles in the Adriatic, but it is one of a number of studies all pointing to a more co-operative view of species interactions.   Maybe there is a lesson we should all learn from that.  

References

Denys, L. (1997). Morphology and taxonomy of epizoic diatoms (Epiphalaina and Tursiocola) on a sperm whale (Physeter macrocephalus) stranded on the coast of Belgium. Diatom Research 12: 1-18.

Filek, K., Lebbe, L., Willems, A., Chaerle, P., Vyverman, W., Žižek, M., & Bosak, S. (2022). More than just hitchhikers: a survey of bacterial communities associated with diatoms originating from sea turtles. FEMS Microbiology Ecology 98: fiac104.

Holmes, R. W. (1985). The morphology of diatoms epizoic on cetaceans and their transfer from Cocconeis to two new genera, Bennettella and Epipellis. British Phycological Journal 20: 43-57.

Kanjer, L., Filek, K., Mucko, M., Majewska, R., Gracan, R., Trotta, A., Panagopoulou, A., Corrente, M., DiBello, A. & Bosak, S. (2022). Surface microbiota of Mediterranean loggerhead sea turtles unravelled by 16S and 18S amplicon sequencing. Frontiers in Ecology and Evolution doi: 10.3389/fevo.2022.907368

Van de Vijver, B., Robert, K., Majewska, R., Frankovich, T. A., Panagopoulou, A., & Bosak, S. (2020). Geographical variation in the diatom communities associated with loggerhead sea turtles (Caretta caretta). PloS one 15:  e0236513.

Another highlight of Pula Aquarium: a Noble Pen Shell (Pinna nobilis) sanctuary – hosting populations of this large (up to one metre) rare bivalve endemic to the Mediterranean Sea.  

Some other highlights from this week: 

Wrote this whilst listening to: Benjamin Britten’s War Requiem, as it is Remembrance Sunday.  

Currently reading: Barry Unsworth’s Morality Play.  3rd time I’ve read this book which sits with Umberto Eco’s Name of the Rose as masterpieces of Medieval whodunnits, whilst at the same time rising above the limits of this genre.

Cultural highlight:   Midsummers Night Dream at Newcastle Playhouse, featuring Nadine Shah as Titania.   Brilliant production.

Culinary highlight:  sustainably sourced roast saddle of venison from The Wild Meat Company

Hunger games …

My superpower is being able to see bacteria with the naked eye.   This has many advantages, as I am about to show you.  It also comes with a significant downside: confronted with a view such as that looking north-east along Wastwater on a spectacular autumn afternoon, I find myself staring intently at the boulder in the foreground.  If you follow this blog, you will know this boulder well, as it has featured in several posts (most recently “More from the splash zone …”).   Great Gable can wait for another day: there are more intimate landscapes waiting to be explored …

In that earlier post, I wrote about the zonation of algae on this boulder, pointing out a thick layer of green algae below the surface whilst dark crusts of cyanobacteria inhabited the splash zone.   Two months later, the green algae have largely disappeared, apart from a short fuzz on the side of a few stones.   Instead, the area where these were growing is dotted with small brown colonies, most just a few millimetres across.  A close examination, using the macro lens of my waterproof Olympus Tough shows these to be tufts of vertical filaments.

Patches of Tolypothrix distorta var. penicillatus on the side of a granite boulder in Wastwater, October 2022.   The largest are about five millimetres across.  The right hand image shows a close up, with filaments about five millimetres high.

Under the microscope, these tufts reveal themselves to be Tolypothrix penicillatus var. distorta, which I often find in nearby rivers, including the River Irt, which flows out of Wastwater (see “Tangled up under blue skies …”).   I have never seen it growing quite as prolifically in the lake itself.   I always worry, when I make a new discovery, whether it is a genuine new arrival or if I have just missed it in the past.  However, I have stared at this particular boulder on many occasions and am fairly sure that I would not have missed these if they had been there previously.   Whatever happened to remove the green algae presumably created an opportunity for another organism to move in.

The pictures show several of the characteristic features of this genus.   The filaments are composed of rows of cells (“trichomes”) within sheaths, some of which are yellow-brown in colour due to the pigment scytonemin, a natural sunscreen.   You can also see heterocysts (nitrogen-fixing cells) at the ends of several filaments, along with ”false branches”. These occur when a trichome breaks and both sections continue to grow within the same sheath.  

Tolypothrix distorta var. penicillatus from Wastwater, October 2022.   Scale bar: 20 micrometres (= 1/50th of a millimetre).

The upper image in the second plate shows a filament with what appear to be cyanophycin granules.   These store nitrogen and their presence in some filaments suggests that these cells had recently experienced conditions when phosphorus was scarce.  This meant that the nitrogen obtained by the heterocysts could not be used to fuel growth, so it is stored in these granules (made of amino acids).  Understanding nutrient dynamics in lakes such as Wastwater is difficult because concentrations are so low that you have to push equipment to its limit when measuring nitrogen and phosphorus.  Concentrations of both also fluctuate so that you need a high sampling resolution.   Together, these create serious logistical barriers to understanding what is going on.   

I use the analogy of baking cakes when explaining nutrient limitation to students.   You need everything on the list of ingredients to make a cake.   If you have no eggs, you can’t make the cake with just flour, sugar and margarine, and if you have no flour, you can’t make a cake with just eggs, sugar and margarine.   The same is true for algae: if one nutrient runs out, the algae cannot grow regardless of how much of the other nutrients are present.   In a lake such as Wastwater there will be times when there is enough phosphorus but not enough nitrogen, and other times when there is enough nitrogen, but phosphorus is short.   Having the capacity to capture the nitrogen it needs gives a cyanobacterium such as Tolypothrix a temporary advantage over other algae when phosphorus is available, but when phosphorus is scant, it is not going to let that hard-won nitrogen go to waste.   The cyanophycin acts as a nitrogen larder, ready for whenever the cell needs it.   This can even happen over the course of a day: nitrogen-fixation typically happens at night, because the process is very sensitive to the oxygen produced by photosynthesis.  

Tolypothrix distorta var. penicillatus from the River Irt, October 2022.   Scale bar: 20 micrometres (= 1/50th of a millimetre).

This fieldworker fully empathises with cyanobacteria.  Long days in the field lead to nutritional fluctuations and I have evolved a strategy when out in the field whereby museli bars, crisps and bananas are secreted around me as human equivalents of cyanophycin granules.   As the habitats I am studying are invariably “hungry” in their natural state, I guess this is a sort of ecological “method acting”.   In an urban setting, I would have ready access to coffee shops, cafes and restaurants.  I would be perpetually saturated with nutritional opportunities, just like an alga in a eutrophic lake.  Out here, I live a more feral existence and my strategies shift accordingly.  So not only do I see bacteria with my naked eyes, I am also beginning to think like them.   Maybe I’ve been doing this job for too long … maybe I need a break …

References

Li, H., Sherman, D. M., Bao, S., & Sherman, L. A. (2001). Pattern of cyanophycin accumulation in nitrogen-fixing and non-nitrogen-fixing cyanobacteria. Archives of microbiology 176: 9-18.

Lu, Z., Ye, J., Chen, Z., Xiao, L., Lei, L., Han, B. P., & Paerl, H. W. (2022). Cyanophycin accumulated under nitrogen-fluctuating and high-nitrogen conditions facilitates the persistent dominance and blooms of Raphidiopsis raciborskii in tropical waters. Water Research 214: 118215.

Watzer, B., & Forchhammer, K. (2018). Cyanophycin synthesis optimizes nitrogen utilization in the unicellular cyanobacterium Synechocystis sp. strain PCC 6803. Applied and environmental microbiology 84: e01298-18.

Some other highlights from this week: 

Wrote this whilst listening to: Nick Cave’s Murder Ballards, one track on which is Henry Lee, a duet by Cave and PJ Harvey …

Currently reading: Orlam by PJ Harvey …

Cultural highlight:   PJ Harvey reading from Orlam at the Fire Station in Sunderland.  

Culinary highlight:  fish and chips sitting beside the River Eden in Appleby on the way back from fieldwork

All change …

For the first time since the start of the pandemic I’m travelling to a conference, to give a plenary talk about the UK’s experience with applying metabarcoding to ecological assessment.   I’ve not written about this on the blog for some time (see “Dispatches from Plato’s cave …”) so I’m taking the opportunity of preparing a talk, and sitting around in transit lounges, to summarise some of my thoughts.  I’ve also put in a few of my photos from this trip to break up the text.

The UK was the first country in Europe where the regulatory bodies got involved, alongside academics, in the application of metabarcoding to environmental regulation.  From the outset, we have had funding from the government agencies responsible for regulation, and had their representatives looking over our shoulders as results started to emerge.  That was mostly a constructive relationship between research scientists, but we had more than our fair share of tense moments, sometimes feeling like pawns in wider inter- and intra-agency squabbles.  What I came to realise, however, was that these discussions about the science often missed broader issues about how the new technology would affect whole organisations.  The introduction of metabarcoding, I came to see, was a case study in managing change in organisations that make decisions using ecological data.  

I wrote about this in an online paper a few years ago, and some of my reflections gained further traction when I listened to an episode of Tim Harford’s excellent Cautionary Tales podcast [https://timharford.com/2019/12/cautionary-tales-ep-6-how-britain-invented-then-ignored-blitzkrieg/].  This is about tank warfare rather than ecology, explaining how, he following the invention of the tank, commanders in the British army tried to fit it into the existing approaches to warfare rather than redesigning battle formations to make full use of the tank’s capabilities.   It was left to the German army to do this more radical restructuring in the 1930s, resulting in the “Blitzkrieg” tactics that overrun much of Europe in matter of weeks in 1940.  Harford related these changes back to a paper on business strategies for managing change.   This classified change in two ways: whether or not the core concepts and components that underlay processes in an organisation were changed by a new innovation, and whether or not this affected the linkages between these, which can be visualised as a table:   

Over the course of this podcast, I realised that the same analysis could be applied to the work that we were doing.  Until our metabarcoding projects, the Environment Agency had been using light microscopy to analyse diatoms for about 20 years, using an index that I developed in the early 1990s.   That first version had undergone several changes over the years as our understanding techniques and taxonomy has developed, but these could all be regarded as “incremental innovation” insofar as each development reinforced the way that the data produced was used by the organisation as a whole.   Environment Agency managers, meanwhile, were tinkering with linkages, moving from a structure where almost every area had in-house capability combined with local knowledge to one where diatom analyses were focussed around a few “hubs”.  That counts as an “architectural innovation” because the pathway from sample collection to the use of the data in decision-making changed.  

Arch of the Sergii, a Roman triumphal arch in Pula, dating from approximately 27 BC.  The photograph at the top of the post shows the first century Roman Arena.

When we started the metabarcoding project, there was an assumption that, at some point, metabarcoding would replace analysis by light microscopy, much as you might upgrade a component in your computer: the old component is taken out, the new one dropped in, and everything proceeds as before. In Henderson and Clark’s terminology, this was a “modular innovation”.   Unfortunately, this turned out to be a naïve assumption. Replacing light microscopy by metabarcoding has implications that go beyond the analysis of samples and is, in fact, another example of “architectural innovation”.  The “linkages” (how data/information flowed through the organisation) also need to change if full value from the new method is to be obtained. Here are three examples:

  • Area staff found they had much less agency in the production of data in the metabarcoding era.   There were often long lags between samples being collected and results being available because samples were batched up and sent to remote laboratories where finite analytical capacity created a bottleneck at the times of year when samples were collected.   Previously, area staff could either prioritise particular samples themselves (if they were investigating a local river, for example) or telephone the people that were doing the analysis and ash them to fast-track these samples. 
  • Time spent collecting and analysing samples is valuable unstructured learning that gives ecologists the experience that they need to interpret data.   You slowly learn to associate particular organisms with certain habitats and, gradually, build up a “sixth sense” about when you have encountered an unusual sample.  This was particularly the case in the UK system where a biologist might have had quite detailed knowledge (invertebrates, macrophytes, diatoms) of a single catchment.   In the metabarcoding era, the first time a biologist encounters an organism is as an entry in a spreadsheet or database containing processed sequencing output.   One option is to automate data interpretation; however, this raises more questions.  What is gained and, more importantly, what is lost by not having expert field ecologists involved at this stage?
  • Finally, metabarcoding for ecological assessment is still a very young science and new developments appear regularly in the literature.  However, you cannot keep tinkering with a system that, ultimately, drives multi-million pound/dollar/euro investment decisions.  The regulators want to “lock down” a particular method in the interests of stability and transparency.  However, in the time it takes to pass all the stages of approval in government bureaucracy, improvements on the method are likely to have become available.  Given that we know that there is always uncertainty in predictions of ecological status, any improvement ought to bring us, incrementally, towards more robust decisions.  Too much faith in “stability” simply entrenches avoidable errors.   There is, in the UK, recognition of a need to embrace “incremental innovation” within regulation, but the process is not very systematic and certainly not regular enough.   At the moment, the mantra of “stability” is putting the cart before the horse, and some genuinely bad decisions will slip through the net as a result.   

I tried to capture some of these issues in the title of my paper.  Characterising molecular ecology as “fast-moving” is not controversial.   Characterising environmental regulation as “slow-moving” might appear pejorative but there are good reasons why this should be the case.  None of us would be happy if the speed limits changed overnight on our local roads without good reason and due warning and the same applies to environmental regulation.   This mismatch between science and regulation, however, means that the gap between what is possible and what is allowed is set to widen.  Up to now, we have been expected to squeeze the science into outdated regulatory models.  What we need to think about now is how regulation can evolve to embrace this new potential.

References

Henderson, R.M. & Clark, K.B. (1990).  Architectural innovation: the reconfiguration of existing product technologies and the failure of existing firms.  Administrative Science Quarterly 35: 9-30.

Kelly, M. (2019). Adapting the (fast-moving) world of molecular ecology to the (slow-moving) world of environmental regulation: lessons from the UK diatom metabarcoding exercise. Metabarcoding and Metagenomics, 3, e39041. [https://mbmg.pensoft.net/article/39041/]

Santa Maria Formosa, a Byzantine chapel dating from the 6th century.   The best views are from beside a busy road in bright sunlight.   The view from a nearby café was not as good but I was able to sit in the shade and sip beer whilst I sketched.

Some other highlights from this week: 

Wrote this whilst listening toThe Rest is Politics podcast with Alistair Campbell and Rory Stewart.  Strictly speaking, writing this blog was delayed while I absorbed unfolding political events in the UK.  The implications of economic and fiscal policy will have knock-on effects for all government departments and, therefore, for the subject I write about here.

Currently reading: Act of Oblivion, latest novel from Robert Harris book, set at the time of the Restoration and the revenge enacted on those responsible for the execution of Charles I.  

Cultural highlight:  See How They Run, whose plot involves murders on the set of Agatha Christie’s The Mousetrap.   Gentle, old-fashioned humour channelling the Ealing Comedies of yore.

Culinary highlight:  Currently in Croatia and eating hotel buffet food, which is plentiful though hardly a “highlight”. It has, however, removed any inclination to search out any IrIstrian cuisine that might otherwise replace this as the top gastronomic experience of my trip.

Reflections from Lago Trasimeno

There are two types of ecologists: those who can spend a holiday in an apartment overlooking a lake and forget about work, and those who are compelled to scan Google Scholar to find out all they can about that lake.   I’m in the latter group and the lake in question is Lago Trasimeno, in Umbria, central Italy.   I worked on crater lakes in central Italy in the late-1980s (see: “How to make an ecologist #10“) and had assumed that Trasimeno was another of these.   Whilst it is the result of tectonic activity in the region, and has the circular outline that I associate with crater lakes, it does not sit within a crater.  It does, in fact, have an outflow, which is a big clue, as true crater lakes do not (the technical term is “endorheic”).   But therein lies a tale …

As Lago Trasimeno has a very small catchment and is very shallow, it is very vulnerable to rainfall conditions, with both dramatic floods and droughts over the centuries.  There is an outflow in the south-east corner and, at various points in history, this has been lowered to increase the land available for agriculture as well as to alleviate the effect of floods.   Water has also been taken out of the lake for irrigation and this has meant that the water level has often been lower than the outlet, meaning that the lake is effectively endorheic.  Combine this with a gradual warming of the climate leading to greater evaporation, and salt levels in the lake have started to increase too.   The lake, like many in the Mediterranean region, is at risk of becoming brackish at some point in the future unless steps are taken. 

I took a closer look at the lake during a visit to Isola de Maggiore, the only inhabited island in the lake.   There were tufts of Cladophora glomerata on stones in the littoral zone and, tellingly, bleached filaments on exposed stones on the foreshore, suggesting that the lake level at the time of my visit was low.  The presence of Cladophora also suggests that the lake is enriched with nutrients.  This is borne out by a quick scan of the literature, with the phytoplankton suggesting that the lake is moderate or poor status according to WFD definitions.   It still supports a commercial fishery, and we ate fish from the lake in local restaurants.  The enriched nature of the lake means that these are mainly cyprinids such as tench which, to be honest, do not offer not great gastronomic potential.   I did, however, have some very tasty smoked eel with gnocchi at one restaurant in Tuouro sur Trasimeno. 

Cladophora glomerata on stones on the foreshore of Isola de Maggiore, Lago di Trasimeno, September 2022.  Scale bar: 100 micrometres (= 1/10th of a millimetre).   Isola de Maggiore is on the right hand of the picture at the top of the post. 

Another feature of the lake, which can just be seen in the picture above, is its turbidity.  Fine sediments are very easily stirred up by wind and wave action due to the shallow nature of the lake, and the result is a milky-coloured water that did not look inviting for bathing.  The turbidity is a double-edged sword: on the one hand it stirs up the sediments, releasing their nutrients into the water.  On the other hand, the limited light penetration as a result of all this suspended matter reduces the potential for harmful blooms to form.  

Submerged stones that were within reach had a thick slimy biofilm, and I brought a sample back (preserved with a generous shot of grappa) to examine under the microscope.  There were plenty of diatoms, typical of hard water habitats, and a few that might tolerate mildly brackish conditions.   Epithemia and Rhopalodia were both conspicuous, and suggest nitrogen limitation.   A full account of the diatoms will follow once I’ve had a chance to examine them at high magnification.  I also saw some tapering cyanobacterial filaments which I suspect were once part of Gloeotrichia colonies (see: “Rewriting history at Talkin Tarn …”).  The literature reports that both planktonic (G. echinulata) and epiphytic forms (G. pisum) are present in the lake, and I am not going to speculate which these are.  Like Epithemia and RhopalodiaGloeotrichia is capable of fixing atmospheric nitrogen, suggesting that this is the nutrient limiting growth at this time of year.  

Gloeotrichia filaments from the littoral zone of Lago di Trasimeno, September 2022.

The tranquil images that top and tail this post, in other words, are misleading.  This is a lake where there is a lot going on.  There is a history of human habitation dating back to Etruscan and Roman times.  Humans are drawn to lake shores because these can be sources of water, protein and power.   Yet these demands can, in turn, lead to degradation of the lake.   In the case of Trasimeno, tourism also contributes to the local economy but, at the same time, puts yet more pressure onto the lake.   In more recent years, Trasimeno is also having to contend with the impacts of global warming.   This is a widespread problem, but shallow lakes in the Mediterranean region are especially sensitive to this pressure.   I think I knew when I booked the apartment that this was going to turn out to be a busman’s holiday.   I brought back bottles of local wine and olive oil, pictures of the Tuscan countryside, and some broader perspectives on shallow lake functioning.  That’s not a bad haul of mementos, is it?

References

Bresciani, M., Pinardi, M., Free, G., Luciani, G., Ghebrehiwot, S., Laanen, M., Peters, S., Della Bella, V., Padula, R. & Giardino, C. (2020). The use of multisource optical sensors to study phytoplankton spatio-temporal variation in a Shallow Turbid Lake. Water 12: 284.

Gasperini, L., Barchi, M. R., Bellucci, L. G., Bortoluzzi, G., Ligi, M., & Pauselli, C. (2010). Tectonostratigraphy of Lake Trasimeno (Italy) and the geological evolution of the Northern Apennines. Tectonophysics 492: 164-174.

Ludovisi, A., & Gaino, E. (2010). Meteorological and water quality changes in Lake Trasimeno (Umbria, Italy) during the last fifty years. Journal of Limnology 69: 174-188.

Mugnai, M., Angela Margheri, M., Cristina Sili, C., Turicchia, S., Soldati, E., Maffettone, E., … & Ventura, S. (2008). The cyanobacterial community of Lake Trasimeno. Algological Studies, 37-64.

Some other highlights from this week: 

Wrote this whilst listening to: Public Service Broadcasting, who I saw earlier in the week at the Fire Station in Sunderland, as well as lots of Bob Dylan (see below)

Currently reading: Lustrum, part two of Robert Harris’ Cicero trilogy

Cultural highlight:  Girl from the North Country.   Back in January 2020 we had gone to see this musical based around the songs of Bob Dylan, but the production was cancelled 40 minutes before curtain up due to cast illness.   We finally had a chance to see what we missed when a touring production came to the Theatre Royal in Newcastle.

Culinary highlight:  Khai Khai, an Indian restaurant in Newcastle whose vegetarian/vegan food is so good that a flexitarian such as me feels no inclination to look at their meat offerings.  Their Signature Tandoori Broccoli is out of this world.

Lago di Trasimeno from Passignano sul Trasimeno, September 2022.   Mixed media (watercolour/pastel/conté)

 

Walking with St Francis

I’m travelling in Umbria this week, reflecting on the life of St Francis and his relevance for the modern world.   St Francis is often considered to be a pioneer environmentalist, although I’m wary that this involves projecting modern ways of thinking onto him.   He lived in a time when many saw a stark dichotomy between good and evil, with the physical world embodying all the forces that were bad and which had to be resisted.   Francis, by contrast, saw nature to be the mirror of God in the world.   For the first time in the Christian era, humans were joined in confraternity with the natural world, rather than sitting apart from it.   It was an important step, theologically, but not one which fundamentally changed the nature of the day-to-day encounters with nature for Medieval people.  

Francis’ contemporary relevance, then, is less to do with explicit proto-environmentalism, and more with the way that he lived his life.  Back in 2019, I quoted US environmental lawyer Gus Speth in a post.   He argued that the top environmental problems were not the stresses on ecosystems that we usually think about – climate change, pollution etc, but selfishness, greed and apathy (see “The limits of science”).  We can study systems and understand more about how they work and how they should be managed, but actually bringing about that change is largely beyond the capabilities of scientists.  

It is also, unfortunately, largely beyond the capabilities of politicians, partly because most of the messages of modern ecological and environmental research can be distilled into two precepts: consume less and intervene more.  By contrast, the dominant political dogma is to promote economic growth and to limit the role of government.   A further problem is that, borrowing a phrase from Robert Harris: “Power brings a man [sic] many luxuries, but a clean pair of hands is seldom among them”.   Politicians, in our age, rarely have the moral authority to bring about the changes that are needed. 

Statue of St Francis of Assisi at Le Carceri hermitage, just outside Assisi.  The photograph at the top shows the view over Assisi from the tower of the Cathedral of San Rufino.

We need, in other words, “saints” to whom we can look up towards, and whose lifestyles we aspire to emulate.  In the case of Francis, it is not the extreme poverty per se but the attitude that lay behind this.  There is no intrinsic worth in poverty, but nor is there intrinsic pleasure in wealth or the accumulation of material possessions.   Happiness arises through living a virtuous life.   In the modern world, a virtuous life means being sufficiently well informed that you can make judgements so our list of contemporary “saints” might include individuals such as David Attenborough.  Greta Thunburg set an example by crossing the Atlantic in a boat rather than flying.   She lives the life she preaches.  Indirectly, her example contributed to our decision to travel to Italy by train rather than fly.  

My definition of a modern saint is someone who lives well to such an extent that others want to emulate them.  It excludes anyone of a puritan mindset, because they tend to be define themselves by what they do not do.  Saints, then, would be those that change approaches from the bottom up, rather than the top down.   This is the way a democracy should work:  the populace changing the minds of the leaders, not vice versa.   Only when the psephologists tell politicians that the public mood has changed will politicians change their promises.   

Some other highlights from this week: 

Wrote this whilst listening to:   mid-80s power pop.  Can’t escape it.  Every restaurant we go to seems to have this on repeat.    

Currently reading:  Underlands by Robert McFarland, and also Marcus Aurelius’ Meditations, whose Stoic philosophy dovetails neatly with my meditations on St Francis.

Cultural highlight:  long-anticipated visit to the Basilica of St Francis in Assisi, revelling in the frescos by Cimabue and Giotto (only to discover that many of those long thought to be by Cimabue are actually by others)

Culinary highlight:  many good meals, as you might expect in Tuscany and Umbria, but the standout was at Osteria dell’Accademia in Tuoro sul Trasimeno, where I had gnocchi made with raspberries served with smoked eels in a white wine and sweet pepper sauce.  

The Basilica of St Francis in Assisi does not allow photography, so here is a photo from a small church (San Michele Arcangelo) on the Isola Maggiore in Lago Trasimeno showing a lamentation over the dead Christ in the style of Giotto. 

Fifth columnists …

We managed to tag an extra day onto the fieldtrip that I wrote about in “More from the splash zone …”, and we spent it in the Newlands Valley, ascending the ridge that starts with Cat Bells and walking along as far as High Spy, where we could look down into Borrowdale before descending, again, and walk back along the Newlands Valley to our car.  

The track up the valley was cut into the peat moorland.   At some points, the peat was undercut by a small channel of water that ran down one side.   Where this happened, partially-decomposed Sphagnum hung down in straggly dreadlocks or, if you prefer, “stalactites”.   One of these was decorated with some tiny sundew flowers, exploiting this most unusual habitat.  The Sphagnum provided the framework, around which a peaty-brown ooze clung, providing a rooting medium for the Sundew.   Sundews are fascinating plants well adapted to life in nutrient-poor environments (see “It’s a plant eat insect world out there …”) and their presence here made me wonder what else might be growing within this brown ooze.

Drosera rotundifolia growing on a peat “stalactite” hanging beside the Newlands Valley, August 2022.  Photographs: Heather Kelly.   The photograph at the top of the post shows the view south down Newlands Valley.

I teased out some portions of the peat once we had returned and had a look at it through my microscope and, as I expected, there was a wide range of algae present.  The most common alga was Zygogonium ericetorum, which belongs to the same order as  Spirogyra, which we met in the post mentioned above.  Zygogonium is similar to Zygnema in appearance (see “A day out in Wasdale”) but the two chloroplasts are less obviously star-shaped.  Other features are that the cytoplasm is often pink-purple in colour and that it has thick cell walls, often composed of “H”-shaped segments.   Unlike Zygnema and the other Zygnemetales, it is found mostly in terrestrial habitats, often acid in character.  In this mini-habitat, the tangle of filaments provide an extra level of structure which will both retain water through capilliarity and provide a substratum amongst which the sundew’s rootlets can gain a foothold.

Zygogonium ericetorum from the peat “stalactite” in the Newlands Valley.  Scale bar: 20 micrometres (= 1/50th of a millimetre).  

As well as the Zygogonium ericetorum, there were plenty of cyanobacteria too.  Prominent amongst these was a species of Stigonema (possibly S. minutum) – a close relative of the cyanobacterium from the River Liza that I’ve written about previously (see “Fieldwork notes, August 2021” and links therein) but I also saw Tolypothrix tenuis and also some filaments of Scytonema.   All three of these are interesting because they are nitrogen-fixers.   They are faced with the same problem of scarce nutrients as the sundews but have adopted a different solution.  

Stigonema minutum from the peat “stalactite” in the Newlands Valley.  Scale bar: 20 micrometres (= 1/50th of a millimetre).  

Alongside the green algae and cyanobacteria, there were also several diatoms present, most prominently chains of Tabellaria flocculosa and individual cells of Frustulia crassinervia.   There were also several desmids, but I didn’t have enough time to work out what these all were.   If I had worked through the sample in more detail, I’m sure that I could have made a list of twenty or more species from this one inauspicious strand of peat.

This is one more manifestation of a theme that I’ve returned to several times over the year: the role of algae and cyanobacteria as ecosystem engineers (most recently in the Burren: see “Landscape architects …”).   This is another good example of how algae can add both structure and nutrients to a habitat, allowing other organisms to gain a toehold.   Our eyes were drawn to this particular habitat by the colourful sundews, but the same patterns will be repeated across much of the damp peatland that surrounded us.   Algae are the plant world’s fifth columnists, a clandestine faction of organisms that mobilize to prepare the ground for the more overt botanical forces that follow.   

Tolypothrix tenuis from the peat “stalactite” in the Newlands Valley.  Note the heterocyst just above the branch.  Scale bar: 20 micrometres (= 1/50th of a millimetre).  

Some other highlights from this week: 

Wrote this whilst listening to:   J.S. Bach Cantata 77: Du solist Gott, deinen Herren, lieben (Thou shalt love God, thy Lord). 

Currently reading:  Robert Harris’ Imperium.  First part of his trilogy about the life of Cicero.

Cultural highlight:  The Great North Run.  

Culinary highlight:  Linguine picante at La Piazza in Richmond, North Yorkshire, serving the double purpose of loading on the carbs before the Great North Run and getting me in the mood for our trip to Italy.

The view north from the ridge leading towards High Spy, with Catbells in the foreground, Derwent Water, Skiddaw and Blencathra beyond and Bassenthwaite just visible on the left hand side of the image.

Slipping through my fingers …

Not content with finding freshwater sponges in the Hodder, our search for nondescript green patches on stones continued in other tributaries of the Ribble.  In Wrigglesworth Beck, a small stream that flows off the Forest of Bowland to join the Ribble just south of Settle, we struck lucky.   Small jelly-like patches adhered to several of the cobbles, and were easy to pick off with a pair of forceps and pop into a sample tube.   These turned out to be Tetraspora gelatinosa, an alga that I have written about before (see “More from the Atma River …” and “Notes from Windermere”)

Tetraspora gelatinosa growing on cobbles in Wrigglesworth Beck, August 2022.  The picture frames are approximately 20 cm and 5 cm respectively.   The photograph at the top shows Wrigglesworth Beck during our sampling / survey visit.  

We’ve been given the brief of developing a method for using algae to understand the health of a stream or river that does not need a microscope.   The idea that we are testing is that there are enough visual and tactile clues available even without a microscope to make a judgement on condition.   In particular, we’ve noticed that those algae that are slimy to the touch, or gelatinous in appearance, tend to thrive in cleaner waters than those that are rough to the touch.  Tetraspora is definitely gelatinous, and does tend to be found when levels of external pressure are relatively low, seeming to confirm our hunch. 

The slime that surrounds some algae is a polysaccharide.  As such, it sits in the “debit” column of the alga’s end-of-year accounts.   Photosynthesis brings in most of the profits – in the form of carbon that can be used as fuel or for cell structures, but that has to be offset against the cost of keeping the cells running.   Producing slime has several advantages.   One is that it contains enzymes released by the cell that help it to harvest phosphorus from the water.  The “investment”, therefore, brings a “return”, in the form of a scarce nutrient.   Another benefit is that slimy filamentous algae tend not to have epiphytes (which rob the host of some of the light that it needs for photosynthesis).   Investment in slime, therefore, is also like a business paying for a burglar alarm.   

Tetraspora gelatinosa from Wrigglesworth Beck, West Yorkshire, August 2022.   Scale bar: 20 micrometres (= 1/50th of a millimetre).  

However, it is not quite as straightforward as this.   Slime is an attractive habitat for all sorts of microorganisms.  In “Intimate strangers …” I suggested that mucilage contains microbiomes that were more “friend” than “foe” to the host organism.   In more enriched waters, where nutrients are plentiful and bacteria more abundant, the equation may tilt more towards “foe” and an organism that invests in slime may be outcompeted by tougher species that direct their resources to faster growth.   

There is, of course, experience accumulated over generations that says that eyeballing algal growths with nothing more sophisticated than a hand lens is going to miss a lot of what is going on in a stream.   One response to this is that rapid “citizen science” approaches should never be more than an ecological “triage” that separates locations where there is an easy answer from those that need a more sophisticated approach.   The other is to complement our rapid assessments of algae with other information that can be gathered readily from streams in order to complement our rapid ready assessments of algae.   The photo at the top of the post shows Bill sorting through the invertebrates he gathered with a kick sample whilst Katrina checks the algae: two strands of evidence being, we reason, better than one.

Of equal, or greater, importance, however, is the potential for getting people to look at rivers and their algae.   Britain’s freshwaters e are not well served at present by George Monbiot and others who refer to “algae” as a universally bad thing and leap too quickly to conclusions about causes.   Yes, prolific algae are often the result of nutrients arising from human activities, but there are other reasons too.  This summer, with long periods of low flow and warm weather, have allowed algae to proliferate even when nutrients are present in relatively low concentrations, and otherwise healthy rivers have turned green.  Encouraging people to look more closely at the algae in their local rivers may not only fulfil my ambition of ecological “triage” but also help correct some of the misconceptions that are proliferating about algae.  

Some other highlights from this week: 

Wrote this whilst listening to:   Public Service Broadcasting (see below)

Currently reading:  After Hannibal by Barry Unsworth.   Essential preparation for a holiday in Umbria.

Cultural highlight:  BBC Prom on the iPlayer: 100 years of the BBC with Public Service Broadcasting and the BBC Symphony Orchestra.   Public Service Broadcasting’s drummer is, coincidentally, called “Wrigglesworth” 

Culinary highlight:  an Ottolenghi recipe from the Guardian: roasted cauliflower with a roast pepper and tomato dressing and grape salsa.   

 

Soaking up the sunshine …

Hardly had my field kit dried out following my trip to west Cumbria than I was loading it back into the car for a trip to the Ribble valley.   I’m involved in a small project to develop a citizen science tool for assessing algae in rivers, along with Bill Brierley of the Freshwater Biological Association and Katrina Woodhead, a student at Lancaster University, and Leanne Trough of Ribble Rivers Trust.  We’re looking at streams with different levels of human impact, using the RiverFly method to assess invertebrates and a simplified version of RAPPER (see “The democratisation of stream ecology”) to assess river health.

One of the sites we visited was on the River Hodder, a tributary of the Ribble, which flows off the Forest of Bowland and eventually joins the Ribble just downstream from Clitheroe.   There are no major settlements on the Hodder and, as a result, it is a relatively clean river, with one of the best salmon, trout and grayling fisheries in the country.  On this particular occasion there was a lot of filamentous algae visible but, following the long period of warm weather and low flows, this was not a great surprise.   The big interest here was a few patches of freshwater sponge on submerged bedrock on the far side of the river from where we were working.  They formed distinct patches on the rock, with a green tinge (due to endosymbiotic Chlorella-like algae) and which yielded slightly when pressed with a finger.  

Sponges are very primitive organisms.  There is a well-known trope that if a sponge is passed through a sieve, the individual cells will reform into a new sponge, suggesting some basic cell-to-cell communication (see video here).   Inside the sponge there is also a “scaffold” of long, thin silica “spicules” which give the sponge some structural integrity and which are also useful for identification.   There are only about half a dozen sponges from freshwaters in the UK and Ireland (there are, by comparison, about 300 sponges in marine habitats).  Based on the spicule morphology, I think that the sponge we found was Ephydatia fluviatilis.  

Spicules of Ephydatia fluviatilis from the River Hodder at two magnifications.  Scale bars: 50 micrometres (= 1/20th of a millimetre).   The picture at the top of the post shows the sponge growing in situ.  The picture frame is about 50 cm across.

Identification requires a microscope in order to examine the spicules.   By the time I got home, the green-tinged portions that I had scraped off the stones were beige whilst the overlying water in the vial was green with suspended algae, which suggested that the association was very loose.  There is, however, evidence that the sponges are actively switching genes on and off to encourage the algae to join them.  Maybe is more going on than, perhaps, we first assume.   Studies have shown that the algae do not meet all the energy requirements of freshwater sponges and prolific growths such as those we saw in the Hodder also depend on the sponges’ ability to filter particles from the water.   That, in turn, translates into a broader ecosystem benefit.   Removing particulate matter helps preserve the crystal-clear water that the Hodder’s fish need to thrive.    

This begs a rather obvious question: how good are sponges at cleaning rivers?   It will depend how much sponge is growing in the river and how dirty the water is, but all that filtration must have some effect?   On the other hand, whilst we know the Hodder to be a clean river, sponges are not restricted to unpolluted rivers.  A study in Ireland indicated that Ephydatia fluviatilis is as likely to be found in rivers below good ecological status as they were to be found in high or good status rivers.  Only one of the sponges included in this study (Racekiela ryderi) was largely restricted to clean waters.   It would be unwise to use sponges on their own as indicators of the quality of a river.  That is, however, a very utilitarian view.  Sponges are curious and ancient organisms which are largely overlooked by casual naturalists.  They are worth watching out for whenever you are wading in a river or at the edge of a lake.

References

Cocchiglia, L., Kelly-Quinn, M., & Lucey, J. (2013). Classification of freshwater sponge collection at EPA Kilkenny. Environmental Protection Agency, Johnstown Castle, Co. Wexford, Ireland, 31.https://www.epa.ie/publications/research/biodiversity/Classification-of-freshwater-sponges.pdf

Evans, K. L., & Montagnes, D. J. (2019). Freshwater sponge (Porifera: Spongillidae) distribution across a landscape: environmental tolerances, habitats, and morphological variation. Invertebrate Biology138: e12258.

Hall, C., Camilli, S., Dwaah, H., Kornegay, B., Lacy, C., Hill, M. S., & Hill, A. L. (2021). Freshwater sponge hosts and their green algae symbionts: a tractable model to understand intracellular symbiosis. PeerJ, 9: e10654.

Jensen, K. S., & Pedersen, M. F. (1994). Photosynthesis by symbiotic algae in the freshwater sponge, Spongilla lacustris. Limnology and Oceanography 39: 551-561.

Lucey, J., & Cocchiglia, L. (2014). Distribution of sponges (Porifera: Spongillidae) in southern Irish rivers and streams. In Biology and Environment: Proceedings of the Royal Irish Academy 114: 89-100). 

Some other highlights from this week: 

Wrote this whilst listening to: All of us Flames by Ezra Furman.

Currently reading: Suite Française by Irène Némirovsky.  

Cultural highlight:  Sally Potter’s 1992 film interpretation of Virginia Woolf’s Orlando.

Culinary highlight:  very good takeaway pizza from Flint Pizza in Heaton [https://www.flintpizza.co.uk], eaten al fresco in Heaton Park 

More from the splash zone …

It was unfortunate, but the long spell of hot weather came to an end the day before we were due to head out for our regular fieldwork in the Lake District.  The day started with rain which petered out by mid-morning. Clouds had started to lift by the time we reached Wastwater, although had still not cleared the peaks of Great Gable and Scafell Pike.   The scene in the photograph above may look idyllic, but the water was choppy, with white horses visible on the lake and waves adding an extra complication to my sampling efforts.  

One recurring feature of Wastwater is persistent growths of algae on the rocks in the lake littoral zone.   I’ve never quite been able to explain why this is the case.   We do see visible growths of green algae in other lakes nearby, but these are usually transitory phenomena whereas Wastwater’s margins nearly always have growths that are obvious with the naked eye.  Wastwater is probably the lake with the lowest level of human influence in the region, so the usual kneejerk association between algae and nutrients doesn’t really hold.   It is a conundrum still awaiting an explanation.  

As well as these green growths, however, there are also very dark crusts growing on larger boulders around the air-water interface.  I’ve written about these before (see “Notes from Wastwater …” and “Close to the edge in Wastwater …”) and Allan Pentecost has also made a study of them (see reference below).  Today, with the water levels going up and down as the waves came in, I held my camera underwater and managed to photograph these two communities in situ, revealing their clear zonation.   Spirogyra dominates in the fully-submerged zone whilst the cyanobacterial crusts are in the zone that is often exposed.

Algal zonation on an emergent boulder in Wastwater, August 2022.   The green algae in the lower part of the image is Spirogyra and the black patches in the upper part are cyanobacteria.  The picture frame is about a metre across.

Scraping the crusts off the rocks for later examination was not easy in the choppy conditions.   I just got enough to confirm that the predominate cyanobacterium was a Calothrix species, but not enough to photograph.   The Spirogyra was easier to collect: it was a broad filamentous form with two chloroplasts which is very common in the Lake District.  I’ve never seen it conjugating so cannot put a species name on it.  

This type of zonation is well known in marine environments, where tides exacerbate the effects.   In natural lakes, water levels do not fluctuate to the same extent so the potential for zonation is more limited.  There is some evidence of zonation in deep Alpine lakes (see “Depths of imagination …” and “Life in the deep zone …”) and these studies are useful reminders that our understanding of benthic algal zonation in freshwaters is limited by our capability (I wear chest waders when sampling, the Alpine studies used SCUBA).  The study in the Bodensee I discuss in an earlier post found this zonation most clearly expressed on submerged vertical rock faces which, to the best of our knowledge, do not exist in Wastwater.   Deepwater benthic algae will not be able to establish in depositional environments.  But, from my shore bound perspective, deepwater benthic algae are a subject on which I can speculate but not explore for myself.

Spirogyra filaments from the submerged zone of a boulder in the littoral of Wastwater, August 2022.  Scale bar: 20 micrometres (= 1/50th of a millimetre).

Wastwater empties into the River Irt, to which we travelled straight after our sojourn on the lake shore.  Both of these also had extensive coverage of filamentous algae.  Once again, algae are almost always visible at these sites despite a lack of obvious human drivers.   Quantities were greater today than we usually find at this time of year, most likely because of the long period of warm, dry weather, and this was the case at almost all the sites I’ve looked at recently.   Of note, however, was the absence of obvious growths of Torularia atrum, which was abundant when I visited in June (see “All change …”).   For every constant on this regular tour of Lake District habitats, there seems to be an inexplicable variable too.  The algae change and I learn.   

Reference

Pentecost, A. (2014). Distribution and ecology of cyanobacteria in the rocky littoral of an English lake district water body, Devoke Water. Life4: 1026-1037.

Other highlights from this week: 

Wrote this whilst listening to: Rocket, 2017 album by Americana/Indie artist Alex G.

Currently reading: The Country of Others by Leïla Slimani, about the last days of French colonialism in Morocco.

Cultural highlight:  Hit the Road, a film described as an Iranian Little Miss Sunshine.  

Culinary highlight:  Tasting menu at Peace and Loaf in Newcastle