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_The eye always knows more than it sees. Kenneth Clark_ I have been watching the weather forecast and the river levels closely for the past three weeks, trying to find a window of opportunity when I can get back to the Lake District for some fieldwork. Each pulse of heavy rain over this period has sent river levels to a point where entering the river would be foolhardy then, just as levels drop towards a workable point, the next weather front arrives, and the rivers are in spate again. The longer this cycle of wet weather and high flows persists, the more curious I become about the effects this is having on the algal communities in rivers and streams in this area, which just adds to the frustration. Meanwhile, I am busy rearranging schedules to make the most of the time when I should have been out on fieldwork, and also taking the opportunity to reflect on some of the patterns that I have recorded from these sites in the past. I have just been reading about how Anton van Leeuwenhoek pioneered new ways of “seeing” in the 17th century through his use of microscopes to explore a hitherto completely unknown and invisible world in his local ponds. Yet another way of “seeing” emerged just over a century later when William Playfair started using graphs as ways of presenting information. The microscope, by itself, is a fine way of exploring the here and now but graphs, in their many and varied forms, let us take those immediate sensations and compare them with observations at other locations, or at the same place over preceding months and years. Whether Van Leeuwenhoek would have embraced graphs is a moot point. The impression I get from his biographies is that he was extremely curious but had a relatively short attention span and was forever flitting between subjects that caught his imagination (see: “The invention of microscopy …”). He was curious in the same way as the explorers of his age who were travelling to the far-flung corners of the world, rather than in the theory-driven sense of science emerging at the same time through he work of Descartes and Bacon. In a way, graphs brings these two approaches together because you can not only marvel at the world the microscope reveals, you can also wonder at the changes you see in these observations in space and time and speculate about causes and consequences. We live in an age where Cartesian hypothesis-driven science prevails but sometimes there is a place for doodling in R Studio and seeing where your curiosity takes you. So, confined to base by the vagaries of the weather, I made a mental journey back to Croasdale Beck (see “Sick note …” and links therein). Many of the stones on the bed of this turbulent stream have dark brown or black patches of a Cyanobacterium _Chamaesiphon fuscus_ (see: “Spotting spots …”) and we have often noticed, whilst out in the field, that our BenthoTorch (portable fluorimeter) records more diatoms on stones with obvious Cyanobacterial crusts than it does on those that are bare. This observation is largely substantiated by the patterns we have recorded over the past decade. First, the quantity of _Chamaesiphon_ in Croasdale Beck shows a distinct seasonal trend with more biomass recorded in the summer. This is interesting because our estimates of the cover of Cyanobacterial crusts do not tend to fluctuate, so they must be getting thicker and thinner as seasons change. Second, the quantity of diatoms seems to show a dependency on the amount of Cyanobacteria measured on the same stone. **Left hand graph: annual trends in the abundance of Cyanobacteria (measured as chlorophyll concentration) in Croasdale Beck between 2015 and 2025; right hand graph: relationship between abundance of Cyanbacteria and diatoms in Croasdale Beck. Diagonal line indicates 1:1 slope (i.e. equivalent concentrations of both groups). The photograph at the top of the post shows Croasdale Beck in April 2025.** What we may be seeing is diatoms taking advantage of the way that the _Chamaesiphon_ alters the substrate. One possibility is that, by creating texture across an otherwise flat cobble, _Chamaesiphon_ creates opportunities for the diatoms to escape the constant mechanical stress exerted by the current. A second possibility is that the habitat they create is less conducive to the marauding invertebrate grazers that we know are abundant in this stream (see: “Curried diatoms …” and “Mayfly mayhem …”). Maybe _Chamaesiphon_ is producing toxins that serve as deterrents (there are a few hints in the literature suggesting that _Chamaesiphon_ does produce such toxins, but no unambiguous evidence. However, this capacity is widespread within the Cyanobacteria so it must be a possibility). This interaction between diatoms and _Chamaesiphon_ may explain some of the patterns that I described in “Entrances and Exits …” where diatoms with a high-profile habitat were more abundant in the summer, which is counterintuitive in a stream where we often see grazing invertebrates. It is possible that the _Chamaesiphon_ creates patchiness in the habitat at a finer scale than most biologists typically sample stream algae. The next two diagrams, then, show what I think may be happening; first, inside a _Chamaesiphon_ patch where _Fragilara gracilis_ and _Meridion constriction_ are nestled amongst the cells and, then, a wider view showing low-profile diatoms (_Achnanthidium_ spp. and _Cocconeis lineata_) growing alongside the _Chamaesiphon_ crust. **A schematic diagram showing how _Chamaesiphon fuscus_ may create microenvironments for diatoms (_Fragilaria gracilis_ and _Meridion constrictum_) to thrive in turbulent stream habitats.** There is quite a lot of conjecture in this because it is difficult to recreate the higher level structure of the algal community on a stream bed from what we see under a microscope (see: “Imagined but not imaginary”). The _Chamaesiphon_ species that live as crusts are particularly difficult to observe to the point where the three “standard works” that I consulted (Desikachery ‘s _Cyanophyta_ from 1959; Brian Whitton’s chapter in the _Freshwater Algal Flora of the British Isles,_ 2011,__ and Komárek & Anagnostidis’s revision of the _Süsswasserflora von Mitteleuropa_ from 1999) all rely on the same drawings in Lothar Geitler’s first edition of the _Susswasserflora_ dating from 1925. Playfair’s inventions ushered in a new era for science, one that meant that we were no longer constrained by the forms of the organisms we are studying. At the same time, though, he introduced abstraction to scientific thought process, with reality described by patterns on graphs rather than by tangible phenomena. This unlocked a whole range of possibilities, many of which I use in my work. It does mean, however, that we sometimes forget to “see” in the way that van Leeuwenhoek understood, at all. **An alternative visualisation of the relationship between _Chamaesiphon fuscus_ and diatoms in a turbulent stream such as Croasdale Beck. The _Chamaesiphon_ on the right hand side creates physical shelter and, possibly, an unfavourable habitat for grazing invertebrates. On the left-hand side, an assemblage of diatoms typical of grazed habitats (_Achnanthidium_ spp and _Cocconeis lineata_) develops.** Some other highlights from the past week (or so): **Wrote this while listening to:**. Rosalia’s _El Mal Querer_ and _Lux_. Flamenco (hint of Fado, too, perhaps?) meets electronica meets rap meets … **Currently reading:** NoViolet Bulawayo’s Glory. An _Animal Farm_ -type allegory of recent Zimbabwean history. **Cultural highlight:** the film _Manchester By The Sea_ on Netflix. **Culinary highlight:** trial runs for Christmas week cooking. ### Share this: * Click to share on X (Opens in new window) X * Click to share on Facebook (Opens in new window) Facebook * Like Loading... ### _Related_

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