Cover versions …

Lots of good performances are raised by a cover of someone else’s hit, and Slime Time was no exception.  The cover version that we chose was a short film, “Moon, Mud and Microbes” by filmmaker Susi Arnott and University of Westminster scientists Jane Lewis and Dain Son, which shows the algae which live in intertidal mud in the Thames in central London.

It depicts the changes over a single tidal cycle using time-lapse photography to compress the entire cycle into six minutes.   The film opens with a view looking upstream towards Tate Modern as the moon sets over a darkened London and, as dawn breaks, the tide gradually recedes, gradually revealing, first, some old wooden pilings and then the unprepossessing brown tidal mudflats.   The location then shifts to St Saviour’s Dock, just east of Tower Bridge, where we zoom in on one section of the mudflat and the magic starts to happen: patches of green and a darker chocolate brown start to appear on the grey-brown mud.   These, we told our Slime Time audiences, are algae “commuters” who make a daily migration up through the fine sediments, in order to do their important “work” of pumping oxygen into the atmosphere.   Their upward movement is stimulated largely by light, but also by internal body clocks – something to which an audience of campers can relate: we invariably wake up as soon as daylight floods through the thin walls of our tent on the first morning under canvas but, as days go by, our bodies slowly adapt to override this stimulus.  

Two stills from Moon, Mud and Microbes showing the mud at St Saviour’s Dock, approximately 30 minutes apart in real time, showing the algae rising to the surface.   The montage at the top of the post shows the Omni Tent ten minutes before our performance, slowly filling as Rachel Williams, our compère, pulls in the punters, and finally co-presenter Thomaz Andrade gets Slime Time under way.   

The film then cuts from the mud of St Saviour’s Dock to a view of the organisms responsible for the change in colour under the microscope.   We can see large green cells of Euglena ehrenbergii and needle-shaped diatoms, Cylindrotheca gracilis with their yellow-brown chloroplasts.  Other diatoms appear in subsequent scenes, but these were the most abundant types.   The Cylindrotheca cells are about a tenth of a millimetre long, giving our audience a rough idea of the scale of what they were observing.  All these algae were moving around the screen, to the surprise of our audience who assume “plants” to be static and only “animals” to move (apart from the cheerful clever clogs in the second row who pointed out that Venus Fly Traps also move).   We didn’t want to get into the deep technical arguments about whether algae were, in fact, plants (see “Identity crisis”) or into the details of how they move.   Simply revealing an aspect of natural history hitherto hidden from our audience was enough.  

Euglena ehrenbergii and Cylindrotheca gracilis: the two most common algae in the microscopic samples shown in Moon, Mud and Microbes.  The Cylindrotheca cells are about 100 micrometres (= 1/10^th of a millimetre) long.

From looking at specimens using a light microscope the film then moves on to show some stills taken using a Scanning Electron Microscope, allowing details of individual pores (no more than a micrometre – a millionth of a metre – across).   The image below shows one of the diatoms we saw: Hydrosera triquetra.  This is a species that was formerly regarded as a tropical species, but which was found in the Thames in 1971 and which is now common as a golden-brown zone on the lower part of river walls between Greenwich and Putney.   There are also a number of records from other north European estuaries.  

A cell of Hydrosera triquetra from the St Saviour’s Dock mud sample.  Note the smaller diatom growing as an epiphyte on the side of the cell.   Hydrosera triquetra cells are typically about a 10^th of a millimetre in diameter.  A still from Moon, Mud and Microbes.  

For the last 90 seconds or so the film cuts back to views of the mud, showing the algae “commuters” gradually disappearing back into the mud before the incoming tide covers them all with water again.  The wooden pilings which we saw emerge at the start of the film now disappear back underwater and the light slowly fades at the end of the day.   The final shot is a view looking downstream from the South Bank near the National Theatre towards Blackfriar’s Bridge and St Paul’s Cathedral.   The tide is, again, high and the moon is rising.   And so the cycle begins again … 

Reference

Coste, M. & Ector, L. (2000).   Diatomées invasives exotiques ou rares en France: principales observations effectuées au cours des dernières décennies.   Systematics and Geography of Plants 70: 373-400.

Tittley, I. (2014).  Non-native marine algae in southeastern England. Bulletin of the Porcupine Marine Natural History Society 1: 28-32.

Some other highlights from this week:

Wrote this whilst listening to:    Soar, the collaboration between Welsh harpist Caitlan Finch and Senegalese kora player Seckou Keita.   The answer to the question: “what would Bach’s Goldberg Variations sound like if played on traditional West African instruments.   And Nubya Garcia’s first album 5ive.   Audio methadone to help me through post-Green Man cold turkey.   

Cultural highlights:  New BBC series Vigil which is, in essence, a Golden Era crime mystery but set on a nuclear submarine rather than in a country house.  

Currently reading:  The Sea is Not Made of Water: Life Between the Tides by Adam Nicholson.

Culinary highlight:  Lamb henry, a half shoulder of lamb slow cooked until it is meltingly tender and falling off the bone.  Served with a rich gravy and mash in the Shepherd’s Arms, Ennerdale Bridge, our regular fieldwork home-from-home.   Washed down with a pint of Loweswater Gold.  

Jammin’ in the key of algae …

It’s official: I have now performed at a major music festival.  In its 20-year history Green Man has seen countless guitar solos, plenty of saxophone and keyboard breaks and even, yea gods, a few drum solos.  On Friday and Saturday, for the first time, it experienced its first microscope solo.  In the spirit of improvised jazz, I went out on stage with a few themes in mind but from that point on what happened was down to what I saw through the microscope eyepiece (and which the audience saw on a screen behind me) and not to any pre-prepared script.  

Some context: I’ve been to the Green Man festival in the Brecon Beacons a few times in the past as a punter, and there is always a thriving science zone, Einstein’s Garden.  Last time I was here, in 2019, I noticed some unprepossessing flocs of algae floating in an artificial pond close to the impressive Mountain Stage (shown above) and thought: “they would look really good projected on to a big screen”.  And so the idea of “Slime Time” was born.   The second key component of Slime Time is a six-minute film of algae growing on exposed mudflats in the Thames in central London came when I met filmmaker Susi Arnott, but that will be the subject of a future post and I’ll focus on the improvised microscope solos in this one.

We pitched Slime Time to Green Man in early 2020 and they liked it enough to put us on the bill for the festival.   Shortly afterwards a certain pandemic kicked off and Green Man 2020 was cancelled, along with every other cultural event.   For a long while we thought that the 2021 festival wouldn’t go ahead either but, in mid-July, the Welsh Government finally gave the go-ahead and we all had about a month to get everything together ready for the gates opening ot the public on 19 August.  

The pond which had first inspired me to pitch the idea had, however, changed in the two years since I first saw it.  Gone were the floating flocs of algae and, in their place was a dense mat of duckweed.  Underneath this, however, I found some fine filaments, rough rather than slimy to the touch, which turned out to be blanket weed (Cladophora glomerata) when I got back to the tent and peered at it through my field microscope.  This is not the most exciting filamentous alga to show an audience but, fortunately, I had stuffed a small bottle of Spirogyra from Cassop Pond (see “Promising young algae …”) into my cool box just before leaving.

The artificial pond on the Green Man site, showing the dense cover of duckweed (photo: Sophie Perry)

A festival setlist, however, needs more than two tunes so I needed to do some more exploration around the Green Man site before hitting the stage.   First stop was the Monmouthshire and Brecon Canal which runs along the edge of the Usk Valley and is a ten minute walk from one of the festival’s gates.   That, however, was a disappointment.  The propellers from a steady stream of canal boats stir up the fine bottom sediments to create a turbid brown soup within which no respectable algae are likely to survive.   So, after a pleasant walk along the towpath, fuelled by some welsh cakes sold to me in aid of a cancer charity by two young girls and their grandmother, I headed back, still needing a banger to bring the show to a close.  

The Monmouthshire and Brecon Canal near the Green Man Festival site, August 2021.

The River Usk, which runs along the northern edge of the festival site, provided the inspiration for my closing number.   This is a river of high conservation value for several reasons, including the presence of the Twaite Shad (Alosa fallax).  Pete, the security guard watching the exit to the Green Man site as I left, told me that he had seen a large brown trout resting in a backwater close to the bridge, as well as spotting a salmon leaping.  As we chatted, there was the briefest of flashes of iridescent blue as a pair of kingfishers flew low along the water and my journey down to the river’s edge also disturbed a dipper.   These, I felt, were all good signs, reflecting Natural Resources Wales’ (NRW) assessment of the ecology here as “good status”.  

The River Usk looking upstream towards the entrance to the Glenusk estate, August 2021

Down at the water’s edge, however, the omens did not look so good, with stones smothered by a thick film of loosely-attached brown flocs which disintegrated to the touch.   Under the microscope these revealed themselves to be mostly made of the chain-forming diatom Melosira varians, along with Diatoma vulgaris(abundant in rehearsals with the field microscope, less common during my live set …) and a chain of Fragilaria(abundant during the live set, not apparent when photographing the diatoms on my return).   Overall, the impression that these algae gave me was that NRW’s overall assessment of “moderate status” is about right, reflecting concerns about the elevated concentrations of nutrients present in the river. To be fair to NRW, rivers never look at their best in late summer (see “Summertime Blues …”).   A combination of low flows, warm water and long hours of bright sunshine create ideal conditions for algae to grow and to outpace the invertebrates that feed upon them.  

As with a guitar solo, there comes a point when you pass from embellishing the main theme into self-indulgence and, with an audience composed largely of primary-aged children and their parents, I felt that my improvisations around the theme of the River Usk had reached a natural conclusion.   And, in the time-honoured festival fashion, it was time to say “that’s all we’ve got time for, you’ve been a great audience, enjoy the rest of the festival …” before throwing my microscope against an amplifier and leaving the stage to an overwhelming howl of feedback.    In my dreams …

The margin of the River Usk at Glenusk (beside the Green Man festival site) in August 2021 showing the thick film of Melosira-dominated biofilm smothering the rocks.   

River Usk diatoms: photographs taken on the same sample as I used for the live show, but stored in my tent for three days before I had a chance to examine it again. Consequently the chloroplasts of some diatoms are past their best.   a., b.: Ulnaria ulna; c. Diatoma vulgaris; d., e.: Didymosphenia geminata; f. Cymbella cf. neolanceolata; g. Achnanthidium minutissimum; h. Navicula tripunctata; i., j. Navicula sp (possibly N. cryptocephala, but N. gregaria was also present in the sample); k. Placoneissp., l. Cymatopleura solea; m. Melosira varians; n. Cocconeis pediculus growing on a filament ofOedogonium.   Scale bar: 20 micrometres (= 1/50^th of a millimetre). We did not see Didymosphenia geminata, Cymbella neolanceolata, Cymatopleura solea or Oedogonium/Cocconeis pediculus during either of the live shows, so these are included here as “studio overdubs”.

Note: I was asked, after our show, for some guidance on how to buy a microscope.  If you are interested in exploring the microscopic world for yourself, this post, “Getting started with microscopy” offers some hints on buying your first microscope.

Some other highlights from this week:

Wrote this whilst listening to:    the Far Out Stage at Green Man which was about 200 metres from our tent as the crow flies.  The first draft of this post was written longhand into my notebook whilst Crack Cloud and Porridge Radio were on the stage on Sunday afternoon.  Other highlights of the weekend include Wet Leg (opening the festival on Thursday afternoon), Nubiya Garcia’s excellent jazz, Thundercat, Laura Marling’s LUMP, Richard Dawson, Big Joanie, interplay between harp and kora from Caitlan Finch and Seckou Keita,  and headline sets from Caribou and Mogwai (whose soundcheck provided a backdrop to our Saturday show).  The overwhelming memory of Green Man 2021 will be the joy on musician’s faces as they played to live audiences again; in many cases this was their first show since the start of the pandemic.

Cultural highlights:  Green Man (see above)

Currently reading:  Pie Fidelity by Pete Brown: a paean to British Food.   Bought at Book-ish, the excellent Crickhowell independent bookshop that operates a pop-up shop on the festival site.

Culinary highlight:  Green Man is also a street food and beer festival.   From the many stalls on offer, the highlight (by a small margin, because all were very good) was Taste Tibet, finalists in the streetfood category of the BBC Food Awards.   Of the beers on offer, Stouty McStout Face, from Mad Dog Brewery, Porthcawl, is worth the price for the name alone, but is also a very decent pint.   

Duckweed delights …

I’m hopping around in both time and space in recent posts.  The previous one was based on a visit to the Lake District in June whilst this one crosses the Pennines to report on a visit to Cassop Pond in May.   There is always a lag when studying diatoms, because of the preparation steps involved, but it has been longer than normal this time due to the pressure of other work.   In The Diatoms of Cassop Pond, I wrote that I had found 98 different species in samples collected in January, February and March.  Having looked at samples from April and May, this list has now been extended to 134 species but this is about more than just “twitching” because I’m also intrigued by how habitats around the lake margin differ in the diatoms they host.  

One of the most distinctive features of Cassop Pond are the extensive flocs of the liverwort Riccia natans, and I’ve noted the predilection of nitrogen-fixing diatoms (principally Epithemia adnata) for this substratum in previous posts (see “Working their passage …”).   One part of the margin, however, is dominated by duckweed (Lemna minor).   There is always some duckweed mixed in with the Riccia flocs, but it is usually a minor component.  How different, I wondered, were the diatoms when I looked at an almost pure growth of duckweed?  

Monoraphid diatoms from Cassop Pond, April and May 2021.   a., b. Cocconeis euglypta; c.,d. C. lineata; e. C. pseudolineata; f.g. Cocconeis euglypta/lineata/pseudolineata raphe valves; h.-l. Lemnicola hungarica (two raphe and three rapheless valves).   Scale bar: 10 micrometres (= 1/100^th of a millimetre).

I had a hunch that I knew the answer, because I wrote about the epiphytes of duckweed in a previous post (“The green mantle of the standing pond …”), describing work in a Norfolk pond that had identified two species as being particularly characteristic epiphytes: Lemnicola hungarica and Sellaphora saugeressii (formerly S. seminulum).   I had found both of these in other samples from the pond, but they were more abundant on the Lemna than elsewhere.  L. hungarica accounted for five percent of the total number of valves, whilst S. saugeressii accounted for three percent.   By contrast, the Lemna samples had much less Epithemia (a single valve, compared to ten percent in the sample from Riccia) whilst the assemblages on the two plants were both dominated by Cocconeis spp.   The difference in representation of Epithemia is intriguing, based on what we know about its ecology, as it suggests that the Lemna assemblages are less nitrogen-limited than the assemblages on Riccia.   My hunch is that the most Lemna-rich area of the pond is a heavily-shaded inlet and, with the light needed for photosynthesis in such short supply, the plants grow more slowly and, as a result, the demand for nitrogen is lower.

One other species that I found for the first time in the May sample was Adlafia bryophila, a small diatom whose habitat is described as “locally frequent on intermittently wet bryophytes, aerophilous”.  In Cassop Pond it seems to show an opposite tendency: avoiding the bryophyte (Riccia fluitans) and inhabiting a fully aquatic habitat.   A good lesson in the need to treat ecological notes in the taxonomic literature with a healthy dose of scepticism.   

Biraphid bisymmetrical diatoms from Cassop Pond, April and May 2021.  a. Brachysira neoexilis; b. Navicula cryptotenella; c. N. cf. reichardtiana; d. Cavinula cocconeiformis; e. Adlafia bryophila; f.-h. Sellaphora saugeressii.   Scale bar: 10 micrometres (= 1/100^th of a millimetre).

Heteropolar and dorsiventral taxa from Cassop Pond, April and May 2021.  a. Gomphonema capitatum; b. G. exilissimum; c. G. calcifugum; d.,e. Rhoicosphenia abbreviata (raphe and girdle views); f. Reimeria sinuata; g. Encyonema neogracile.  Scale bar: 10 micrometres (= 1/100^th of a millimetre).

There’s a lot more going on in Cassop Vale than just the changes I’ve written about in the pond itself.  You can follow changes in the higher plants in Heather’s blog [https://heatherkelly.blog/2021/08/04/cassop-vale-july-2021/] but our two approaches still miss out great swathes of the biodiversity.  There is a lot more that could be written about the bryophytes, for example, though that is way outside both of our comfort zones.  And we haven’t even started thinking about the animal life.   Nonetheless, we can both agree that the little we have discovered only serves to remind us both about how much more there is to learn, and how difficult it is to make generalisations even about a habitat that we know reasonably well.

Bacillariales and Surriellales from Cassop Pond, April and May 2021.  a. Nitzschia acicularis; b. N. dravillensis; c. N. paleacea; d. N. inconspicua; e. Tryblionella debilis; f. Surirella angusta.  Scale bar: 10 micrometres (= 1/100^th of a millimetre).

Some other highlights from this week:

Wrote this whilst listening to:    As The Love Continues, new album by Mogwai, headliners at Green Man next weekend.  Getting back into the festival vibe …

Cultural highlights:  Shiva Baby, a comedy set in a Jewish community in New York

Currently reading:  Culture Warloads: My Journey into the Dark Web of White Supremacy by Talia Lavin which, by macabre coincidence, includes a chapter on the world of incels.

Culinary highlight: Sunday lunch at a local restaurant.  Good food but, more importantly, the first time the whole family had eaten a meal together since April 2019.

Under the weather …

One of the curiosities of the algal communities of rivers is how much they can change in relatively short periods of space and time, even when major drivers of change, such as season and pollution, can be discounted.   In the River Ehen, for example, there are significant and predictable changes in the quantities of algae recorded over the course of the year, but also, less predictably, changes in the composition of the often-conspicuous green flocs between the lake and Ennerdale Bridge.   The floc in the photograph below, for example, looked very much like the flocs I had seen a few kilometres upstream, but close examination showed that their compositions were entirely different.   And, to add another level of complication, the Oedogonium I saw in July was different in microscopic appearance to that which I saw in June.

Last year, I pondered the reasons behind these observations, speculating that some of the unpredictable changes we see in space and time may be due to pathogens (see “The stream eats itself …”) and, a couple of months back, I found some filamentous algae from streams in the Lake District that were infested with chytrids.  I look at these streams often enough that I know that the algae here are not typically infested to this extent, so it lends some circumstantial support to the possibility that these are driving some of the changes that we see in these streams.   

Oedogonium filaments infested with chytrid sporangia in the River Ehen, June 2021.  Scale bar: 20 micrometres (= 1/50^th of a millimetre).  The photograph at the top of the post shows the River Ehen near the outflow from Ennerdale Water in July 2021

The population of Oedogonium that I mentioned in the first paragraph was heavily infested by chytrid sporangia during my June visit.   Quite a few of the filaments were in an unhealthy state, with many epiphytic bacteria apparent even with a light microscope.   When I came back in July, however, there were lush growths of filamentous algae which turned out, on microscopic examination, to be Oedogonium, but the cells were broader, less elongate (length:breadth mostly < 2) and with fewer cap cells.   Moreover, the cells looked healthier, with no chytrid sporangia and few or no bacterial filaments visible.   I would wager that this is a different population, possibly resistant to the earlier chytrid, possibly even a different species.   It is difficult to identify Oedogonium in the vegetative state, and it is not clear how much of the visible variation between June and July populations is expected within a single species.  We can’t rule out the possibility that this is a case of the much talked about “herd immunity” spreading out from a few resistant strains which, eventually, dominate the community. 

Oedogonium filaments from the River Ehen just above Ennerdale Bridge in June (a.) and July (b., c.).   Note the abundant bacteria and generally unhealthy condition of the June filament compared to the July filaments.  Scale bar: 20 micrometres (= 1/50^th of a millimetre).

A monospecific growth of Oedogonium in the River Ehen, just upstream from Ennerdale Bridge, photographed in July 2021.  A patch of the cyanobacterium Phormidium autumnale is just visible in the foreground. The picture frame is about 30 cm across.

About five kilometres away, also during my June visits, I found a population of Draparnaldia glomerata in Croasdale Beck which also had an infestation of chytrids.  Croasdale Beck is a wilder, more torrential stream than the River Ehen and the harsh hydrological regime means that green algae are rarely as conspicuous as they are in Ehen.  A long period of dry, warm weather had probably encouraged the algae to grow but the patches of algae, in turn, fostered an epidemic of chytrids.  When we came back in July, the Draparnaldia had disappeared, replaced by a population of a different filamentous alga, Microspora amoena.  

Top picture: patches of Draparnaldia glomerata in Croasdale Beck, Cumbria, June 2021.  Lower pictures: chytrid sporangia attached to Draparnaldia filaments.  Scale bar for lower pictures: 20 micrometres (= 1/50^th of a millimetre).  

I’m left scratching my head about the importance of chytrids in changing the composition of filamentous algal assemblages.  My June and July 2021 visits to the Lake District would suggest that they are likely agents of change, but I’ve also seen shifts in composition between visits when there are no obvious chytrid infestations.  And the literature does not help us much either: a quick search on Google Scholar reveals no recent ecological studies on chytrids on river algae.   There is a tradition of looking at the importance of chytrids in determining phytoplankton dynamics but very little on their role in stream ecosystems, so I am left speculating.  It seems like a productive area for research not just to satisfy the rather nerdy curiosity of people like myself, but also because these pathogens are one means by which the scant resources of streams can pass from one organism to another.   Nature is sometimes red in tooth and claw but, we are increasingly realising, it catches whatever bug is doing the rounds and throws a sicky.  Just like us.   

Some other highlights from this week:

Wrote this whilst listening to:   Waltz for Debby, a 1961 recording by the Bill Evans Trio.  

Cultural highlights:  Host, a 2020 horror film set within a Zoom call.  The first film that I’ve seen that was directly inspired by the pandemic.

Currently reading:  The Wind in the Willows, by Kenneth Grahame.  

Culinary highlight: our son is back after three years in China, so all meals over the last week have had a celebratory feel, regardless of what’s actually being eaten.

The view from the north-west shore of Buttermere with Fleetwith Pike and Haystacks in the background, June 2021.

Change of tenants …

July seems to be over almost as soon as it had begun, and I had to combine a brief visit with a therapeutic cycle ride in order to keep to my promised schedule of monthly trips throughout the year.   Temperatures had dropped after a month of very warm dry weather and there was even a smear of rain in the air as I made my way down the hill towards the lake early one morning wondering what I would see.

There is always a “macro” and a “micro” aspect to the changes – the arrival and disappearance of the Spirogyra flocs being one example (see: “Promising young algae …”) and this time was no exception.  Even from a distance, I could see the surface dotted with green-brown flocs of Riccia fluitans that were certainly there last month (see “Cassop Pond in June”) but certainly not as extensive.  The second obvious change was the presence of the aquatic plant Hippurus vulgaris, Mare’s Tail, in the shallow margins of the pond.   The photograph below also shows the prolific Riccia fluitans flocs growing around its base.

Hippurus vulgaris, Mare’s Tail, growing at the margins of Cassop Pond, with prolific Riccia fluitansflocs at the base.   You can see the Riccia flocs in open water in the picture of the pond at the top of the post.

The microscopic world had changed too, most conspicuously by the proliferation of cyanobacteria – blue-green algae.   There was one form with heterocysts (specialist cells for nitrogen fixation) which I called “Anabaena cf. variabilis” on first encounter, and another without, Pseudanabaena cf. limnetica.   Life in the proximity of Riccia fluitans had changed too: in June I wrote about the presence of Cladophora filaments within the flocs, albeit not always in a healthy state.   In July these filaments had largely disappeared but filaments that I described as “Anabaena” when I encountered them free-floating now seemed to be attached to the Riccia fronds.   I am being circumspect about names because, although there are certainly species of Anabaena that live attached to surfaces rather than in suspension, I am not ruling out the possibility that these actually represent a form of Nostoc.   What I can be sure about is that these were nowhere near as prolific last month as they were in July.

My plate below also includes a cell of Nitzschia acicularis which glided into my field of view whilst I was photographing the Anabaena.   This is a diatom that can live both as plankton and on and around surfaces.  However, the clumps of Anabaena-Nostoc proved very difficult to photograph and a description will have to suffice for now.

Cyanobacteria and a diatom from Cassop Pond, July 2021.   a., b.: Anabaena cf variabilis; c., d.: Pseudanabaena cf. limnetica; e. Nitzschia acicularis.   Scale bar: 10 micrometres (= 1/100^th of a millimetre).  

The presence of Anabaena should not be a great surprise: throughout the year I have been observing diatoms that are capable of nitrogen fixation in the pond; now I see the other major algal group that is capable of nitrogen fixation proliferating.   The warm weather and bright sunshine will have given a boost to many of the plants, and those nutrients that were already scarce will have been in even greater demand.   The supermarket shelves, to use a currently relevant metaphor, have some gaps and the algae have resorted to their equivalent of “panic buying”.  In this case, they are paying well over the normal price (in terms of their energy reserves) for the nitrogen compounds that are essential ingredients of the proteins they need to grow.   

I’ve mentioned before that the nitrogen-fixing diatoms on and around Riccia fluitans are probably paying some “rent” to the liverwort (see: “Working their passage …”) and the same may well be true for the Anabaena/Nostoc that were attached to the Riccia fronds.   There are some references to associations between Nostoc and the genus Riccia, mostly in older literature.  Surprisingly for me, one of the references was in a paper by my mentor Brian Whitton, who observed colonies of Nostoc intermingled amongst fronds of Riccia in terrestrial habitats on the Indian Ocean island of Aldabra.   There is no evidence that the relationship between cyanobacteria and Riccia and other liverworts is as developed as that between them and the aquatic fern Azolla (see “Escape to Southwold …”).  One older paper that I found described Nostoc as a “space parasite”, colonizing cavities and intercellular spaces in the host organism.   A modern interpretation would probably be of mutualism, with both partners gaining and neither losing substantially from the arrangement.  

All this confirms the prediction I made in Cassop Pond in June – that Cladophora might struggle to survive in Cassop Pond as the summer progresses.   But having seen the microscopic changes that have happened so far in these unprepossessing handfuls of wet liverwort, I am beginning to be intrigued by what I might see on my next visit …

References

Duckett, J.G., Prasad, A.K.S.K., Davies, D.A. & Walker, S. (1977). A cytological analysis of the Nostoc-bryophyte relationship.   New Phytologist 79: 349-362.

Nathanielsz, C.P. & Staff, I..A. (1975).  On the occurrence of intracellular blue-green algae in cortical cells of apogeotropic roots of Macrozamia communis L. Johnson.  Annals of Botany 39: 363-368. 

Whitton B.A. (1971).   Freshwater and terrestrial algae of Aldabra.  Philosophical Transactions of the Royal Society Series B 260: 249-255.

Some other highlights from this week:

Wrote this whilst listening to:   Robert Plant and the Band of Joy.  

Cultural highlights:  First night of the Proms, on BBC iPlayer.  In particular, Sibelius’s Second Symphony

Currently reading:  Hannah Arendt’s Eichmann in Jerusalem: a Report on the Banality of Evil.   Gruelling.

Culinary highlight: a lateral tasting of Ardberg whiskies (with the vicar), booty from recent trip to Islay.