Disunited Kingdom?

Alert readers may have spotted a flaw in my last post about the forthcoming UK General Election. I wrote that, in my next post, I would consider the environmental policies of the regional parties.   “But,” I hear you all shouting “responsibility for the environment has been devolved to the regional assemblies, so the Scottish, Welsh and Northern Irish parties will not be campaigning on this issue in this election.”   Correct.   However, I have tried to show in my writings on the election, that policies on a wide range of other issues has knock-on effects on the environment, so we still need to consider the policies of these parties, particularly as the likely outcome is unlikely to be an outright majority.   One or more of the regional parties could well hold the balance of power and, in the process, influence environmental policy directly or indirectly.

The two big factors are the economy and Europe.   Any sort of pact between a minority Labour or Conservative government and a regional party, whether it is Labour and Scottish Nationalist Party or the Conservatives and the Democratic Unionist Party, would inevitably involve a deal that leads to more money being spent in Scotland or Northern Ireland.   And that, in turn, would put a further strain on the finances for other sectors of government, including the environment. Just as for the other parties (see “A plague on both their houses” and “The political landscape isn’t very green …”), the manifestos of the regional parties are not short of fine words on environmental protection, so perhaps the best we can hope for is slightly more expenditure in Scotland or Northern Ireland, albeit at the expense of England.

My biggest worry, however, is UK’s relationship with Europe (see “What has the European Union ever done for us?”) and, on this point, most of the major regional parties are firmly pro-Europe. The only exception is the Democratic Unionist Party in Northern Ireland who support the idea of a referendum on our continued membership of the European Union.   I do believe that several elements of the EU need significant reform and that those countries that have opted out of the Euro may need different terms of membership to those that are in the Eurozone. But I don’t think that a referendum on UK membership is a good idea.   If I thought a referendum would stimulate a sober debate on the pros and cons of our membership, I would have no qualms. The reality, I suspect, would be that Eurosceptic elements of the Conservatives would unite with UKIP and media barons to create a feeding frenzy of scare stories that could precipitate an anti-EU victory.

Please excuse this series of posts on the election.   I am a floating voter by inclination but my constituency (City of Durham) has an entrenched Labour majority and a sitting MP (Roberta Photo-Opportunity) who has shown herself to be a loyal and ambitious apparatchik unlikely to deviate from official party policy.   So I can read every manifesto, ruminate on the budgetary implications of every pronouncement and cast my vote without ever shaking the foundations of Westminster. I am to UK politics what a eunuch is to the survival of the human race. However, having lived in Nigeria at a time of military rule when democracy was just a dream, I know that we should not dismiss the privileges that we have lightly.   So I’m typing away here hoping that someone out there who reads my blog lives in a marginal constituency and has the chance to influence things in a bigger way than I can.  Though, as you may have noticed, I am not expecting a major improvement in the state of the UK’s environment, whoever gets elected on May 7th.

A busman’s holiday in Malta

You are never far from the sea in Valletta, Malta’s tiny capital city. You can gaze across the Grand Harbour and admire the yachts in the marina, or look out to sea and watch the sun setting. The temptation, as always, is to go for the grand, panoramic views. Perhaps, occasionally, it is worth adjusting your focus to take in some smaller scale delights?


Mats of Cystoseira sp. in the Grand Harbour at Valletta, Malta, April 2015.

My eye was caught by mats of brown seaweed at the water’s edge which, on close inspection, was not a type that I recognised from my limited experience of the UK. The fronds resembled pleurocarpous mosses – or leaves of cypress trees – except that they were swollen and brown in colour rather than green.   These belong to the brown alga genus Cystoseira and play an important role in the littoral ecology of areas of the Mediterranean where the substratum is rocky.   The mats that fill the foreground of the first picture are actually the upper canopy of a submerged “forest” and, just as in terrestrial forests, numerous other organisms, both plant and animal, are able to thrive in the different levels, from encrusting organisms living in deep shade on the rocks at the base of the forest to the seaweed equivalents of “herbs” and “shrubs” living amidst the Cystoseira.   All these, in turn, create many microhabitats for invertebrates which, in turn, support the fish that, probably, ended up on the tables of Valletta’s restaurants, supporting the local economy. The Malta Environment and Planning Authority have some useful web pages explaining more about marine habitats around the island.


Close-ups of Cystoseira sp from the Grand Harbour in Valletta, April 2015.

Cystoseira seems to prefer the part of the shoreline that is permanently submerged (there are virtually no tides in the Mediterranean so there is virtually no intertidal zone). However, on the pitted limestone just above the permanently submerged area, there were several patches of reddish algae which turned out to be composed of mats of intertwined filaments.   It is a member of a red algal genus called Polysiphonia, possibly P. urcolata (suggested by Mike Guiry).   This is a species of the mediolittoral zone, which will be periodically submerged.   My immediate impression of this was of a two-dimensional mat, but exposure from the water has meant that the filaments have collapsed in on themselves, so any sense of a three-dimensional structure is lost.


A patch of Polysiphonia cf urcolata on exposed limestone at the edge of Grand Harbour, Valletta, April 2015.

The microscopic views show that the branched filaments are composed of several rows of elongate cells. Also visible were some large, more opaque cells within the filaments. These are, I think, tetrasporophytes. The plants I was looking at in Valletta are, like most algae, “haploid”. That is, they each contain only a single set of chromosomes.   Most higher organisms spend most of their lifecycle with two sets of chromosomes (“diploid”). In the case of humans, it is just our sperm and eggs that are haploid, but these quickly fuse to form a diploid zygote, which develops into a baby and, thence, to the adult.   The tetrasporophyte is the diploid phase of the red alga, living piggy-back (as it were) on the haploid phase. The life-cycle of red algae is particularly complicated (see “The schizophrenic life of red algae …”) and details differ between orders.   There is also a lot of specialist terminology … all in all, not ideal material for a blogger to use to enthuse his audience.   Malta, on the other hand has plenty of botanical delights packed into a small space (and an excellent bus service, with day tickets costing just 1.50 Euros).   Somewhere, on a blog not very far away, someone might even be writing about some of these …


Microscopic views of Polysiphonia cf. urcolata, from Grand Harbour, Valletta, April 2015: a. vegetative filaments, showing multiple rows of elongate cells; b. two tetrasporangia (?) on a vegetative filament. Scale bar: 25 micrometres (= 1/40th of a millimetre).

The political landscape isn’t very green …

My pre-election review of the environmental policies on offer continues with an overview of the parties who are likely to hold the balance of power if, as is predicted, no-one has an outright majority. In this post, I’ll look at UKIP, the Green Party and the Lib Dems.   After that, I’ll consider the regional parties.

UKIP first. For anyone with an interest in environmental policy this is a no-brainer. As I wrote back in December, leaving the EU would be a disaster for the environment (see “What has the European Union ever done for us?“).   Repealing the Climate Change Act, whatever they regard it’s faults to be, also sends out the wrong signals when the great majority of scientists are convinced that major changes in climate are taking place.

Surprisingly, the Green Party do not do very much better, in my opinion. The problem, here, is not the insistence on sidestepping any issue beyond a few core dogmas, as UKIP do, but a propensity for vague generalisations lacking in detail. It may seem odd to say this when the Greens devote so much of their manifesto to the environment and climate, but it is a frustrating read, stuffed with good intentions but short on practicality. Here’s an example: “Because of the interaction between water supply and the wider environment, require Ofwat … and the Environment Agency to work together to create a healthy water environment and long-term low prices for consumers.” That is pretty much what happens at present, so what, exactly, are the Greens offering other than a continuation of the status quo?   What is more worrying is that, tucked away in the financial appendix, we see that the Green’s plans are, in part, funded by “efficiency savings on base government expenditure”.   No guarantee, then, that Ofwat and the Environment Agency will actually get any more funding to work towards this healthy water environment.

And, finally, what about the Liberal-Democrats? Their standings in the polls are not good, and many feel that they are tainted by their involvement in the coalition. Reneging on 2010 promises about university tuition fees leaves a bitter taste for many but perhaps we in the UK are not yet fully attuned to the give-and-take of coalition politics? If anything, I think that the Lib-Dem manifesto has a pragmatism borne from their experience in government.   There is less rhetorical grandstanding than in some of the manifestos, and a clearer sense of the steps needed to translate dogma into practice. They recognise the important role that the EU plays in creating environmental law, and that working at this level helps to maintain the UK’s competitiveness. I was particularly taken by the proposal to set up a commission to research back-to-nature flood prevention schemes. As I have mentioned before (see “Beware the modern day Cnuts”), political meddling did not help during the 2014 floods and removing the issue to an independent body seems to be a sensible way forward.

All manifesto statements about the environment have to be read with a healthy degree of scepticism. If we assume that the major battle will be over the economy and the deficit, and remember that the NHS and education expenditure are ring-fenced, then the room for manoeuvre during coalition negotiations becomes very limited. Proposals from the minor parties will, moreover, have to dovetail with the political philosophy of the major party in a coalition (so any proposals involving greater European collaboration, for example, will be less likely to succeed if the Tories win). Proposals that require significant expenditure are also less likely to be part of a coalition agreement than those that are cheap to fulfil. Yet it is unrealistic to expect significant improvements to the state of the UK’s environment if our statutory bodies are not properly funded. All of which leads me to suggest that the best thing to do right now is to enjoy the soothing, optimistic words of the manifestos. Because delivery is going to be a whole different, and far more uncertain, game.

No longer a dispassionate observer of nature …

I wrote my previous post whilst on an EasyJet flight to Malta and, yes, I did feel pangs of guilt writing about climate change at the same time that I was adding significantly to my carbon footprint. That’s one of the great conundrums of my life: on the one hand, I need a global (or, at the very least, a European) perspective in order to do my job. Yet, in gaining that perspective I become part of the problem.20150417-082337.jpg

A pond at Argotti Botanic Gardens, Valletta, Malta, April 2015.

So here I am in Valletta, capital of Malta, a country whose properties as summarised by Luke in the Acts of the Apostles still remain true (ch. 28 v. 2: “… the natives showed us unusual kindness …”). And, Lo and behold, I find myself at the University of Malta’s Argotti Botanic gardens, (which may well be coming to a blog near you before too long) where there is a pond into which I stare. And in that pond I see a mass of vegetation that, from a distance, resembles duckweed in appearance. However, in close-up they resolve into a series of tiny overlapping leaves with, hanging beneath them, a bunch of roots, a couple of centimetres long. Most of the leaves are green but several are reddish in colour. This is Azolla, which is, despite appearances, an aquatic fern, very common in the warmer parts of the world. It contains a symbiotic nitrogen-fixing Cyanobacterium (blue-green alga) which means that, like terrestrial legumes, it can grow in situations where most other aquatic plants cannot thrive. There has been a lot of research over the years into the potential for encouraging Azolla to grow as a “green manure” in paddy fields.



Azolla sp. in a pond at Argotti botanic gardens.  There are a few leaves of Lemna in the foreground to give an indication of scale.

A little further on, I saw another pond whose surface was covered by another aquatic fern, Salvinia. This is larger than Azolla and lacks a nitrogen-fixing partner, but it is also very common in warmer parts of the world. Both grow by extending and branching their underwater stems and adding new leaves in such a way that they can rapidly cover large areas of a pond’s surface if conditions are favourable.



Salvinia sp in a pond at Argotti botanic gardens.

And there is evidence that conditions are getting increasingly favourable for both Azolla and Salvinia. Azolla filiculoides is not native to the UK but was introduced during the 19th century and, for a long time, the scattered records were confined to the south and midlands. The latest distribution maps, however, suggest that it is now widespread in these areas and has also been recorded from the north of England and Scotland.

Salvinia has not been recorded from the UK but there is an interesting study from Poland where this species, too, has been introduced and is on the increase. There is good evidence from northern Poland of warming associated with the North Atlantic Oscillation. This allows spores of Salvinia to germinate earlier in the year and, crucially, fewer frosts in the Spring means that the delicate young stages are more likely to survive. The fronds are also able to continue to grow – and spread – later in year too. All these factors combine to help this alien species extend it’s distribution not just in Poland but elsewhere in northern and Central Europe where it has not previously been seen.

There lies the irony. Plants such as Azolla and Salvinia are opportunists, adapted to spreading fast when conditions are favourable. You can find evidence for many other plants and animals whose distribution has changed in recent years. And, yes, I can’t avoid the comparison with the opportunism of humans, offered a cheap flight for a brief escape from the chilly British spring. At times such as these it is better that I accept that I am not a dispassionate observer of nature and, in fact, a small part of the systems that I study.

Gałka, A. & Smezja, J. (2012). Phenology of the aquatic fern Salvinia natans (L.) All. in the Vistula delta in the context of climate warming. Limnologica 43: 100-105.


A plague on both their houses ….

Back in January, I promised to scrutinise the election manifestos as they appeared, and to evaluate the promises made by the major parties regarding environmental protection (see “122 days to go …“). My worry, three months ago, was that the election campaign would be so dominated by the economy and the NHS that the environment would be largely pushed to one side. Now that I have seen the Labour and Conservative manifestos, I fear that my pessimism was well-founded.

The problem is that few of us would argue with the core arguments laid out by both of the major parties: that we need to reduce the fiscal deficit whilst, at the same time, increase spending on health and education. Every other promise in both manifestos has to be evaluated against this backdrop and there is frustratingly little in either manifesto on which to make a decision. The Conservatives make more reference to the “environment” (15 references to Labour’s 4) whilst Labour are ahead, in rhetoric at least, on “climate change” (14 references to 5 in the Tory manifesto). Labour give very few details of environmental policy in areas other than climate change; on the other hand, the Conservative pledge to “spend £3 billion from the Common Agricultural Policy (CAP) to enhance England’s countryside over the next five years, enabling us, among other things, to clean up our rivers and lakes …” sounds impressive until you bore into the details. Elsewhere in the manifesto we learn that the plan actually is to push for reform of the CAP as well as to “liberate farmers from red tape”. Is this a funded proposal or a negotiating position with Brussels? It is not clear.

A little further on we read that the Conservatives will be “… building 1400 new flood defence schemes, to protect 300,000 homes.” Flood defence is an expensive business, and a responsibility of DEFRA so if this is a firm pledge, we have to expect other activities in DEFRA to be curtailed. Floods are also classic examples of “Black Swan” events in that they are both devastating and unpredictable (see “Black swan #2: McEcology and Steve Earle“). However much is spent on flood protection, there is no guarantee that the next monumental downpour will sidestep these altogether and flood a different catchment. We are still paying the price for the floods in early 2014 which had the temerity to hit marginal Tory constituencies disproportionately (see “Beware the modern day Cnuts”).

Labour also fall into the trap of playing a populist card arguing that “[the] water industry, too, also requires reform.” Fair enough, up to a point, but they go on to say that this will be achieved by strengthening “the power of the regulator to change licenses, limit price rises and enforce industry standards.” First of all there are three regulators of the water industry (OFWAT, Drinking Water Inspectorate and Environment Agency), not one. Second, there is general recognition (underpinned by European legislation) that the costs of environmental improvements should be passed on to consumers because all of us are, ultimately, polluters. The quid pro quo for limiting price rises will be less investment in sewage works and, ultimately, limited improvements to our rivers. But, to be fair to Labour, they make no concrete promises to improve our environment so there is no internal contradiction in their manifesto. Just a nagging fear that things are probably not going to get better.

Next time, I’ll look at the manifestos of the minor parties. If the pollster’s predictions are correct and neither Labour nor the Conservatives will win an outright majority, then policy areas such as the environment may become useful bargaining chips during negotiations following the election itself. Spoiler alert: my dissection of UKIP’s environmental policy will, by necessity, be brief.

Diatoms and dinosaurs


Ennerdale Water, looking north from the outflow to the River Ehen, April 2015

My monthly visit to the River Ehen coincided with a week of warm weather, clear skies and low flows.   There were some glorious views of the Lake District fells shrouded in early morning mist when I first arrived and I spent a few minutes trying to capture them with my camera before turning my attention to work.

We are now into our third year of regular sampling and are beginning to get a feel for the seasonal dynamics of the algae in the stream. By this time of year, we expect to see the biomass falling as the invertebrates start to become more active and browse away the luxuriant winter growths (see “A very hungry chironomid”). Many of the stones do appear to have less algae growing on them but, at one site, there were still some very conspicuous growths of diatoms. I did wonder if these were growths of Didymosphenia geminata (see “A journey to the headwaters of the River Coquet”); I have never seen this species in the Ehen but several aspects of the habitat here are such that it is possible that it could thrive.   However, when I got a sample under my microscope, the growths turned out to be long-stalked Gomphonema species, with a variety of other diatoms, including Tabellaria flocculosa, Fragilaria spp., Hannaea arcus, Brachysira neoexilis and at least a couple of members of the Achnnathidium minutissimum complex.


Clumps of diatoms – mostly Gomphonema – on a stone from the River Ehen, April 2015.

The Gomphonema species in the River Ehen have perplexed us before. Our best bet is that the larger ones, in particular, are G. gracile.   However, we are straying into areas where names abound although the limits between species are often described in vague terms in the literature. Dawn Rose and Eileen Cox described an experiment recently in which they grew two cultures of a different diatom, Gomphonema parvulum, in culture.   Diatoms, you may remember, get smaller with successive cell divisions (see “Diminishing with age…”) until a point is reached when sexual reproduction is initiated.   When this happened with one of their cultures, they were surprised to see cells that our Floras would have called Gomphonema gracile emerge from the auxospores. They continued to grow these and watched as the G. gracile cells diminished in size until they resembled G. parvulum again. The problem is, as they point out in their paper, most diatomists base their opinions on the structure of the cleaned frustule rather than the behaviour of the living cell.


Gomphonema cells from the River Ehen, Cumbria, April 2015.  The five images on the left show a size reduction series in valve view; the right hand image shows two cells in girdle view with the stalk just visible.   Scale bar: 10 micrometres (1/100th of a millimetre).

Why, you may ask, don’t more people do experiments of this type in order to define the limits between species of diatoms?   It is a good question. The day before my visit to the Ehen, I had read an article in my newspaper about a similar study that had confirmed that the dinosaur Brontosaurus was probably a distinct genus rather than being part of the genus Apatosaurus, as had been assumed for most of the 20th century.   The scientists based their conclusion on careful measurements of different properties of dinosaur skeletons, just as most diatomists measure and describe the diatom frustule. What else can a palaeontologist do?   Their material is, after all, long dead.   Diatomists work with the living world. It is, admittedly, fiddly and time-consuming work to prepare cultures of single species from field communities, and you need special incubators to grow these cultures once they have been isolated. But it is not impossible.

Most of us who study diatoms are over-anxious to get rid of the organic constituents of the cell in order to focus on the silica remains. We are, in effect, contemporary palaeontologists. Most palaeontologists would love the opportunity to get some definitive evidence of species limits (mating experiments on Brontosaurus: that would be quite a sight!).   They must think that us diatomists are a bizarre bunch indeed.


Rose, D.T. & Cox, E.J. (2014). What constitutes Gomphonema parvulum? Long-term culture studies show that some varieties of G. parvulum belong with other Gomphonema species. Plant Ecology and Evolution 147: 366-373.

Tschopp, E., Mateus, O. & Benson, R.B.J. (2015). A specimen-level phylogenetic analysis and taxonomic revision of Diplodocidae (Dinosauria, Sauropoda).   PeerJ 3: e857 [https://dx.doi.org/10.7717/peerj.857]


The fine art of marine biology …

I am, as regular readers will know, curious about how art and science can work symbiotically.   I have written both about how science can inspire art (see “Anselm Kiefer and the art of algae…”) but have also tried to show how the tools of the artist can help ecologists gain insights into the communities that they study (see “More about Very Hungry Chironomids”).   A chance conversation has led me to another scientist who used his artistic background to great effect in his work.

A retired clergyman who I know well was talking about his own encounters with Sir Alister Hardy when he was running the Religious Experience Research Centre in Oxford.   The name rang some bells with me, though in very different contexts to those that we were discussing.   When I got home, I checked on my computer and confirmed that this was the same Alister Hardy who I knew as a marine biologist and who, in fact, wrote one of the very first ecology books that I read.   This was the New Naturalist volume The Open Sea 2: Fish and Fisheries, written in 1959.   Of more interest to me now is the first volume of The Open Sea: The World of Plankton (1956).   The science in this book is now rather dated but this can be forgiven for the enthusiasm with which he communicates his interest.   He also illustrated his own books, drawing on a background that included a period designing camouflage schemes during the First World War.


Two plates from Alister Hardy’s The Open Sea: the World of Plankton.   Left: “Plants of the Plankton”; right: “More Hydrozoan Jelly-fish”.

The illustration shows two of the colour plates from the World of Plankton to illustrate his skills. On the left hand side are illustrations of common organisms of the marine phytoplankton, mostly diatoms, but including a couple of dinoflagellates at the bottom right too.   At the top left you can see a chain of cells of a diatom he refers to as Asterionella japonica, but which we encountered last year as Asterionellopsis glacialis (see “Sampling the surf at Alnmouth”).   The right-hand plate is one of several exquisite paintings of jellyfish that he included in The World of Plankton.   The three illustrations at the top of the plate are based on specimens that he collected from Cullercoats, just a few miles up the coast from where I live but, early in his career, he made two expeditions on board RRS Discovery. He describes how he was lowered on a Boson’s chair until he was just above sea level as the ship sailed along, ready to dip his bucket into the sea whenever an interesting-looking specimen came into his reach.   His paintings of these jellyfish are wondrous to behold – more so if you consider that they were made on the deck of a sailing ship under way.   The act of drawing or painting is more than just a means of recording specimens; it is also a meditation on form and function that, perhaps, we lose when we can get fine images simply by clicking a shutter.

In later life, he turned his attention to the study of religion, which is where my friend Theo encountered him.   Hardy’s interest was in the biological and psychological basis for religious instincts, a subject that he wrote about extensively in his later years, and for which he was awarded the Templeton Prize in 1985.   His Religious Experience Research Centre is still going, now at the University of Wales in Lampeter.

Go and find a copy of The Open Sea.   I did mention that some of the science was dated but Hardy’s writing is clear and, what is more, he does not patronise his audience.   He writes with an assumption that the ideas he discusses are well within the grasp of the informed non-specialist, and laces his prose with just enough enthusiasm to draw the non-specialist into the excitement of his discoveries.   There is much here that modern scientists could learn from.

A return to Cassop


Cassop Pond, and Cassop Vale, looking towards Durham, April 2015.

One of my earliest posts described the algae that I found in Cassop Pond, which lies at the foot of the Permian escarpment close to my house in County Durham (see “Cassop”).   I returned there a couple of days ago to grab a couple more samples and see what had changed since my last visit.   The first of these samples was a handful of submerged plant stems, which I crammed into a sample bottle and shook to dislodge the algae.   I pipetted a couple of drops of the brown suspension that this produced onto a microscope slide and put it under my microscope.   Prominent amongst the diatoms that I could see in this sample was a nice colony of Gomphonema truncatum var. capitatum and also a cell of the large diatom Cymbella lanceolata, displaying its characteristic lobed chloroplast. I also saw a few cells of another diatom, Epithemia adnata. This diatom is relatively uncommon in the UK, but it gives us some interesting insights into the ecology of Cassop Pond.


Diatoms from Cassop Pond, April 2015.   a. Gomphonema truncatum var. capitatum; b. Cymbella lanceolata; c. Epithemia adnata, valve view; d. Epithemia adnata, girdle view of two recently divided cells.   Scale bar: 25 micrometres (= 1/40th of a millimetre).

Cells of the genus Epithemia contain small cyanobacteria-type cells that are capable of nitrogen-fixation (the reality is a little more complicated – see the reference by Prechtl et al. below for more information). This means that it can thrive in situations where nitrogen is relatively scarce compared to other nutrients.   I came across it in a small stream in Northumberland, downstream of a forestry plantation. I was interested in the stream because the plantation was being fertilised with phosphorus at the time and I wanted to see what this would do to the stream.   Every time it rained (which was quite often in the Northumberland hills), some of the phosphorus was washed into the stream and, gradually, over a period of about a month after the fertilisation, the proportion of Epithemia in my samples increased from undetectable at the start to over forty percent of all the diatoms a couple of months later.   What I suspect was happening was that most of the algae in this remote stream could not use this extra phosphorus because nitrogen was naturally very scarce. However, Epithemia is one of a very small number of diatoms that can overcome nitrogen limitation and so was able to thrive. Finding it in Cassop Pond is, therefore, a clue that this pond is, periodically at least, limited by nitrogen rather than by other nutrients.

The other photograph I’ve included in this post was taken by Chris Carter and shows Epithemia growing on the surface of Chara virgata. Epithemia is a genus that does often seem to be associated with plants, although I have also seen it growing on rocks. Chris’ photograph also shows the lobed chloroplast very clearly.


Epithemia sp. growing on a stem of Chara virgata.   Photograph by Chris Carter.


DeYoe, H.R., Lowe, R.L. & Marks, J.C. (1992). The effect of nitrogen and phosphorus on the endosymbiont load of Rhopalodia gibba and Epithemia turgida (Bacillariophyceae). Journal of Phycology 23: 773-777.

Kelly, M.G. (2003). Short term dynamics of diatoms in an upland stream and implications for monitoring eutrophication.   Environmental Pollution 125: 117-122.

Prechtl, J., Kneip, C., Lockhart, P., Wenderoth, K. & Maier, U.G. (2004). Intracellular spheroid bodies of Rhopalodia gibba have nitrogen-fixing apparatus of cyanobacterial origin. Molecular Biology and Evolution 21: 1477-1481.

More about mucilaginous algae

Following my post about the increase in algal “gloop” (see “Is algal gloop on the increase?”), I thought it would be interesting to show some of the organisms responsible for this “gloop” at higher magnification.   Chris Carter provided the images.

First of all, there are some images of the green alga Coccomyxa confluens, one of the organisms mentioned in my previous post.   Under the microscope, the mucilaginous masses can be seen to consist of large numbers of solitary cells, each with a single chloroplast wrapped around the margin, embedded in the mucilage.   But what is particularly interesting about these specimens is the fungal hyphae that weave through the mucilage.   Coccomyxa can be found both as a free-living alga but also as the algal partner in a lichen. I wrote about lichens last year (see “Discovering a liking for lichens …” and “It takes two to tango …”) and speculated about their origins.   The image of fungal hyphae weaving through the mucilaginous mass re-ignites this curiosity. Broadly speaking, the lichen symbiosis is not a meeting of equals: the fungal partner cannot live without the alga but the alga can survive without the fungus. The fungal partner is capable of sexual reproduction but once the spores arrive at a suitable habitat, they need to find some algal cells in order to thrive. A free-living mass of Coccomyxa is, therefore, the perfect place for a tiny wind-blown lichen spore to land.   Maybe that is what we are seeing here: the start of a beautiful relationship?


Coccomyxa confluens, photographed by Chris Carter. Left: macroscopic view of mucilaginous masses; right: microscopic view showing individual cells along with fungal hyphae.

The second representative of the “gloop”-forming algae is the desmid Mesotaenium macrococcum.   We’ve met desmids a few times in this blog (see “Hunting for desmids in Upper Teesdale”) but Mesotaenium does not have the elegant, symmetrical outline of most desmids with a central constriction.   It belongs to a group called the “saccoderm (or false) desmids”, which is a family in the same sub-order as the filamentous algae Spiroygra and Mougeotia which we’ve met elsewhere in this blog.   By contrast, most of the desmids such as Closterium and Micrasterias, which we met in Upper Teesdale, belong to the “placoderm” (or true) desmids”.   The exception is Netrium, which is also a saccoderm desmid.   In Upper Teesdale, I was hunting for desmids amongst Sphagnum in bog pools; Mesotaenium, by contrast, is a species that can live in situations where it is not permanently submerged. Once again, the mucilage offers protection against desiccation.


Mesotaenium macrococcum, photographed by Chris Carter: left: medium-power image showing mucilaginous masses; right: high power image showing the simple chloroplast.

Finally, another green alga, though we are not sure what this one should be called.   Chris and I contemplated the genus Palmella but this seems to be a name that has fallen out of favour recently.   Species formerly included in Palmella can be found in both the Cyanobacteria (now species of Aphanothece, Chlorogloea and Gloeothece) and Chlorophyta (now Trochiscia) so we are clearly not the first people to struggle.   However, Chris has highlighted a small eye-spot and also the beginnings of a flagellum, which suggest that this is the resting stage of a motile Volvocale rather than a permanently sessile organism. Chris commented that this specimen came from a wetter habitat than the Coccomyxa and it may be that this is the resting stage of an organism which, when conditions are favourable, lives freely in the water, rather than forming mucilaginous masses.


Resting stage of a Volvocalean alga, photographed by Chris Carter; left: low-power image showing mucilaginous masses; right: high power image with (inset) cells with eye spot and the start of a flagellum highlighted.