As opportunities for field work are still limited, I have returned to the banks of Lough Down for this post. Lough Down, as some of you will have worked out for yourselves, is not somewhere that can be defined in terms of exact geographic co-ordinates, rather it is a state of mind. However, that means that, in ecological terms, it is as diverse as I want it to be and, as such, it offers plenty of opportunities for writing about algae that I would not otherwise come across. Thankfully, Chris Carter is another habitué of Lough Down and its environs, so I can use his pictures to illustrate these posts.
I used a Pasteur pipette to suck up a likely-looking patch of algae growing over some fine sediments in the littoral zone of Lough Down and brought this back to examine under my microscope. When magnified, I was presented with the view of blue-green coloured helices twisting and turning across my field of view which means that this is almost instantly identifiable as the Cyanobacterium genus Spirulina. It is, in effect, a helical cousin of genera such as Phormidium and Oscillatoria which we have encountered many times in this blog. If you look closely, you’ll see that there are no heterocysts – the specialised cells responsible for nitrogen-fixation – whilst this particular population also has no gas vacuoles. These are structures inside the cell which make the cells buoyant. Many of the Spirulinaspecies found in warmer parts of the world have these, enabling them to live suspended in the water, whereas the temperate species tend to live at the bottom of lakes and ponds. Whilst a few species definitely prefer freshwaters, most are associated with brackish and marine habitats, including saline lakes in Africa such as Lake Chad.
Spirulina is not a particularly common alga in UK and Irish freshwaters, but there is one habitat where it can be conspicuous: the shelves of health food stores. All sorts of claims have been made for its health-giving properties – some supported by evidence, others not – earning it the epithet “superfood”. There is, for example, evidence that women from communities around Lake Chad who regularly ate Spirulina (“Dihé”) had higher levels of Vitamin A than those who did not. However, vitamin A deficiency is common in the region and the effects would not be pronounced in regions where there was a greater range of sources of vitamin A in the everyday diet. On the other hand, Spirulina comes from the same sub-class as a number of Cyanobacteria known to produce neurotoxins, and there is some evidence (admittedly much less than for other genera) for it also producing toxins. The aggressive marketing of Spirulina is enough to make me wary: there is no such thing as a “superfood”, except as one small part of a balanced diet. Buy it and use it, by all means, but do not expect miracles.
I should mention, in closing that “Spirulina”, as commonly understood, is actually two genera: Spirulina and Arthrospira. Much of the material sold as health food actually belonging to the genus Arthospira, which is broader than Spirulina and has more distinct cross-walls. Looking at the Freshwater Algal Flora of the British Isles, I see a record for Arthrospira jenneri from a pond just a short cycle ride from my house from 1938. Maybe I should make a trip one day soon to see if it is still there …
McCarron, P., Logan, A. C., Giddings, S. D., & Quilliam, M. A. (2014). Analysis of β-N-methylamino-L-alanine (BMAA) in Spirulina-containing supplements by liquid chromatography-tandem mass spectrometry. Aquatic Biosystems. https://doi.org/10.1186/2046-9063-10-5
Roy-Lachapelle, A., Solliec, M., Bouchard, M. F., & Sauvé, S. (2017). Detection of cyanotoxins in algae dietary supplements. Toxins. https://doi.org/10.3390/toxins9030076
Soudy, I. D., Minet-Quinard, R., Mahamat, A. D., Ngoua, H., Izzedine, A. A., Tidjani, A., … Sapin, V. (2018). Vitamin A status in healthy women eating traditionally prepared Spirulina (Dihé) in the Chad Lake area. PLoS ONE. https://doi.org/10.1371/journal.pone.0191887
Wrote this whilst listening to: Bob Dylan’s Live at Budokan, Slow Train Coming and Saved. Also, Big Thief’s new single Love in Mine. Still not sure how I missed their set at Green Man 2019.
Cultural highlights: Enjoyed the film Peanut Butter Falcon, an indie hit last year which we missed first time around. Also discovered a podcast on Spotify called Winds of Change by American journalist Patrick Radden Keefe. It might be about American soft power and psy-ops at the end of the Cold War or it might just be a loopy conspiracy theory. Not sure I know myself yet.
Currently reading: Just about to start Sarah Walter’s The Paying Guest.
Culinary highlight: Either a Yotam Ottolenghi recipe for tamarind and tomato braised chickpeas from the Guardian [https://www.theguardian.com/food/2020/may/09/tamarind-tomato-braised-chickpeas-savoury-porridge-browned-butter-lime-rice-pudding-yotam-ottolenghi-thrifty-recipes] or an improvised East-meets-West better-than-it-sounds risotto topped with steamed sea bass with ginger and spring onions.