Return to Cyprus …

A few weeks ago I described some of the algae that I found during a visit to the Avgás Gorge (pictured above) in Cyprus, including a chain-forming Ulnaria (see “Cypriot delights …”).   I’ve now had a chance to prepare cleaned valves from this material so we can take a closer look.

The chain-forming habit had already led David Williams to suggest Ulnaria ungeriana (Grunow) Compère 2001 and more detailed observations have confirmed this.  This is a species that was actually first described from Cyprus (actually Northern Cyprus) and it was also recorded quite extensively during a survey of the island’s diatoms a few years ago.   Unfortunately, some of the key diagnostic characters – such as small marginal spines and striae composed of single rows of pores – cannot be seen with light microscopy but the former, at least, can be inferred from the chain-forming habit.   Note, too, how the long chains that dominated the population in the live state, fell apart when the sample was cleaned with oxidising agents and I did not see more than three cells joined together in the new preparation.

Ulnaria ungeriana from Avgás Gorge, Cyprus, April 2018.   Scale bar: 10 micrometres (= 1/100th of a millimetre).

The Ulnaria ungeriana cells are mostly about 100 – 150 mm long and 7-8 mm wide, with a striae density of 9-10 / 10 mm.   They have parallel sides, narrowing to rostrate to slightly sub-capitate ends, and central areas that reach to the valve margin and which are slightly longer than they are broad.   Unfortunately, most of these characteristics overlap with those of Ulnaria ulna in all but most recent identification guides.   This species was first described by Nitzsch in 1817; it would have been one of the more conspicuous diatoms visible with the relatively basic equipment available at the time, with a magnification of about 150x.  His drawings are of live cells, mostly in girdle view, which means that many of the details which modern diatomists use to discriminate species are not apparent.   Moreover, the material on which these drawings are based is no longer available so we cannot go back to this in order to ascertain the characteristics of the original Ulnaria ulna and, to increase the confusion yet further, it is possible that Nitzsch has illustrated more than one species (see the reference by Lange-Bertalot and Ulrich below).

It would be, in short, very easy to look at a population of Ulnaria ungeriana in the cleaned state and match it to the descriptions of Ulnaria ulna which, under various names, have appeared in the identification literature over the past 100 years or so.   You might just detect the small marginal spines if you have a good microscope and know what you are looking for.  In the live state, however, the ribbon-like colonies are a very distinctive feature yet these do not survive preparation, putting anyone who only encounters this species on a permanent slide at a distinct disadvantage.   It is a good example of how examination of live material can add valuable information to an understanding of a diatom species yet, inevitably, many diatomists make little time for examination of their samples before dropping them into their bubbling cauldrons of oxidising agents.

High magnification views of the ends and central portions of Ulnaria ungeriana valves.   Scale bar: 10 micrometres (= 1/100th of a millimetre). 

What do we know about the ecology of Ulnaria ungeriana?   Our survey of Cypriot streams a few years ago yielded 11 records, forming up to four percent of all diatoms in the sample.  This means it is both less widespread and less dominant in samples than some other Ulnaria species.   It was often found along with other Ulnaria species, in particular U. mondii and, though generally not associated with reference sites (one out of the 11 records), it was mostly found in relatively clean conditions.   It was also associated with sites with high conductivity, which corresponds with the limestone geology that we saw in the Avgás Gorge.   On the whole, these environmental preferences are similar to those of other Ulnaria species from Cyprus that we’ve studied (see reference in earlier post).

The last question is perhaps the hardest to answer.  What benefit does the chain-forming habit confer upon Ulnaria ungeriana?   Ulnaria often forms tufts of upright cells sharing a common pad of mucilage at the base, and it is often (but not exclusively) found as an epiphyte on other plants.   We can’t rule out the possibility that the Ulnaria ungeriana chains are not also attached at one end, but it is also possible that the chain-forming habit means that they are easily entangled with the Chara and filamentous green algae that I described in the earlier post.   Both mucilage pads and entangled chains fulfil the same role of keeping the alga in the same spot in the stream, particularly where there are other plants and filamentous algae to offer extra protection from the current.

There is some speculation in the final couple of sentences but that’s never a bad thing for an ecologist.  If nothing else, it provides me with a reason to return one day …

Ecological preferences of Ulnaria ungeriana at running water sites in Cyprus.  a. pH; b. conductivity; c. total nitrogen (TN) and d. total phosphorus (TP).  Arrows indicate the mean value for each variable, weighted by the relative abundance of Ulnaria ungeriana in the sample.


Krammer, K. & Lange-Bertalot, H. (1991).   Süsswasserflora von Mitteleuropa 2 Bacillariophyceae, 3 teil: Centrales, Fragilariaceae, Eunotiaceae.   Spektrum Akademischer Verlag, Heidelberg, Berlin.

Lange-Bertalot, H. & Ulrich, S. (2014).  Contributions to the taxonomy of needle-shaped Fragilaria and Ulnaria species.   Lauterbornia 78: 1-73.


Cypriot delights …

I could not return from my visit to Cyprus without an algal sample and a fine opportunity presented itself early last week when we visited the Avgás Gorge, on the Akámas peninsula at the west coast of Cyprus, just north of Pathos.  This is a spectacular limestone ravine whose steep sides offered welcome relief from the Mediterranean sun.  At points, as in the photograph above, the ravine narrowed to just a few metres wide, reminiscent of the siq which guards the entrance to Petra except that instead of exquisite carvings we stumbled across a Russian team conducting a glamour shoot.

A small stream made its way down the gorge.  The presence of woody debris at intervals suggested a considerable head of water during the winter months but, at this time of year the water has reduced in power, tumbling across a series of boulders into stagnant pools, interspersed with short runs shaded either by the high cliffs or the vegetation that flourished away from the harsh glare of the sun.

In the sections where water was still running there were clumps of Chara tangled up with filamentous algae, with plenty of bubbles of oxygen as evidence that both were busily photosynthesising away.  The filamentous algae was a coarse unbranched filament that was clearly a relative of Cladophora but which did not match any of the genera or species that I had encountered before (see “Fieldwork at Flatford” for similar situation).   There were pebbles and cobbles between these clumps, their surfaces criss-crossed by the galleries of caseless caddis larvae – probably Psychomyiidae, according to Richard Chadd.

Chara growing in the stream at Avgás Gorge in western Cyprus, April 2018.

Cladophora or a relative growing in the stream at Avgás Gorge in western Cyprus, April 2018.  The scale bar is 50 micrometres (= 1/20th of a millimetre). 

There were a number of diatoms present too, the most abundant of which was a chain-forming Ulnaria.  Unfortunately, despite having just co-authored a paper on Ulnaria from Cyprus, I cannot name the species, as I saw no cells in valve view.  I will have to return to this subject once I have prepared a permanent slide from the sample that I brought back.   The chloroplasts in the illustration below are not in a very healthy state because the sample lived in a fridge for almost a week before I was able to get it under a microscope.  Had I looked at this sample 20 years ago, I would have assumed that I was looking at a species of Fragilaria, as most keys then stated categorically that Synedra (the former generic name) were solitary rather than chain-forming.  However, we now know that there are several Ulnaria species that form chains although most that I see in my regular haunts in the UK do not.   Our paper states that the species we describe form short chains although, as we worked from cleaned samples collected by other people, I now wonder if that was an artefact of the preparation process and whether these, too, formed longer chains in their living state.

A chain of Ulnaria from the stream at Avgás Gorge in western Cyprus, April 2018.  Scale bar: 20 micrometres (= 1/50th of a millimetre).

Though it is rare for me to stray into describing the invertebrate life of streams, the Psychomyiidae are actually an important part of the story here, as the larvae graze algae from the surface of the stones.  They create a silk tube and this, in turn, becomes covered with fine sediment to create the galleries that are visible in the picture.   We know that invertebrates can change the composition of the attached algae by grazing but I sometimes wonder if the caseless caddis larvae also change the composition by creating myriad patches of very fine sediment across the rock surface.   If you look closely you can also see a couple of Simuliidae (blackfly) larvae.  These attach themselves to the rock by a circle of hooks at their last abdominal segment (I think that is “bum” in entomological language) and then use fan-like structures around their mouths to filter tiny particles from the water.  However, I have also seen Simuliidae larvae bent double on rock surfaces in order to hoover up particulate matter and algae that live there.

That, I thought, was just about enough natural history for one day.   I put my toothbrush and bottle back into my rucksack and made my way back down until, turning the corner, I stumbled across the Russian glamour models.   I’ve often written about the similarities between freshwater ecosystems in different parts of Europe but you don’t often see a bikini – or less – in April in my cold, damp corner.

Galleries of Psychomyiidae larvae on the top of a limestone cobble from the stream at Avgás Gorge in western Cyprus, April 2018.


Cantonati, M., Lange-Bertalot, H., Kelly, M.G. & Angeli, N. (2018).  Taxonomic and ecological characterization of two Ulnaria species (Bacillariophyta) from streams in Cyprus.   Phytotaxa 346: 78-92.

Wallace, I. (2003).   The Beginner’s Guide to Caddis (order Trichoptera).  Bulletin of the Amateur Entomologists’ Society 62: 15-26.

Letter from Cyprus


Travel can be one of the most rewarding forms of introspection ….
Laurence Durrell, Bitter Lemons, 1957

When I stepped off flight EZY1973 from Manchester to Paphos on Saturday night I passed a personal milestone. Arriving in Cyprus means that I have now visited all 28 Member States of the European Union. Starting with (West) Germany in 1972 on an exchange visit before the UK was even a member of the European Economic Community, followed shortly after by a family holiday to southern Austria (where my father had been stationed just after the war) with a day trip to Slovenia (then part of Yugoslavia), the number started to increase in the late 1990s when I became involved in the work of CEN, the European Standards Agency and, from the mid-2000s onwards, with the intercalibration exercise associated with the Water Framework Directive. A few years ago I made a list and realised just how many I had visited, after which, I have to admit, my choice of conference and holiday destinations was driven by this rather childish whim. Latvia, Malta and Bulgaria, all subjects of posts on this blog, were ticked off, leaving just Cyprus. This year, a family holiday to celebrate my mother’s 80th birthday provided the opportunity and, after some shameless lobbying, we had booked a villa near Paphos via AirBnB and were on our way.

How Europe has changed in the 47 years since my first overseas trip. Twelve countries were behind the Iron Curtain, three of the remainder were right-wing dictatorships. Two have merged (East and West Germany) whilst seven have become disentangled from previous relationships (the Baltic States from the USSR, Slovenia and Croatia from the former Yugoslavia and the two former constituents of Czechoslovakia from each other). Cyprus, from where I am writing, was in political chaos in the early 1970s. A former British colony whose territory was argued over by Greece and Turkey, it was soon to be split into two, separated by a buffer zone. I used to browse my Collins World Atlas assuming national borders to be fixed and immutable; the older and wiser me wonders where (and when) the next changes will come from.

The intercalibration exercise, in particular, was an opportunity for an exchange of ideas and I counted co-authors from 23 of the 28 EU states on my publication list. Looking back, these papers show remarkable consistency in some aspects of ecology across Europe whilst, in other respects, I am much more cautious about assuming that knowledge gained in my damp corner of north-west Europe can be applied to warmer and more continental regions. This publication list includes, incidentally, two papers about Cyprus, despite never having either visited before or having a native Cypriot on my list of co-authors. In the first paper, we worked with an Austrian employed by the Ministry of the Environment but, for the second, the samples were collected and analysed by Italians and Germans whilst I helped out with data analysis. Scientific colonialism is not, perhaps, dead?

My favourite? I don’t think I should single one of the 28 out. The food and culture of the warm lands of the Mediterranean basin draw me but I think that the parched summer landscapes would lose their appeal if I was there for too long. I find the grey, damp climate of my own corner of Europe wearisome but the greenness of the Spring and Summer, and the Autumn colours almost compensate. My ideal, in other words, seems like it should be a semi-nomadic existence but that, too, would pale with time. The truth is that, for me, elsewhere, being wanted, is always more wondered at ….


Diatom hunting in the Pirin mountains

I started 2018 peering down my microscope at a sample that I collected whilst in Bulgaria back in the summer.   I have written about my trip to the Pirin mountains before (see “Desmids from the Pirin mountains”) but the diatom sample that I collected from Lake Popovo had remained unexamined since I got back.

I had waded into the littoral zone of this steep-sided corrie lake and picked up a few of the smaller stones, which I had then scrubbed with the toothbrush stowed in my rucksack to remove the thin film of diatoms.  These, like most of the algae that I collect on my travels, get treated to a bath in local spirits to ease the journey back to the UK.  This is not an ideal preservative for soft-bodied algae but is not a problem when your primary interest is diatoms with their tough silica cell walls.  Once I got back, I had them prepared and mounted ready for inspection, but then got distracted by other things and have only just got around to having a proper look.

The two most abundant taxa were the Achnanthidium minutissimum complex (probably at least three species) and Cymbella excisiformis.  Together, these constituted over eighty per cent of all the diatoms in the sample.  Ten years ago, I would have called the organism I was calling Cymbella excisiformis by a different name, Cymbella affinis, but opinions have shifted more than once.  The original Diatomeen im Süsswasser-Benthos von Mitteleuropa has images of C. affinis that are actually C. tumidula, and also describes C. excisa as a separate species.   However, the most recent view is that C. affinis and C. excisa are two names for the same species, with C. affinis taking precedence.   To confuse matters yet further, the population illustrated below shows a gradation of features from “C. affinis” to “C. excisiformis”, suggesting that the use of length:width as a discriminating factor is over simplistic.  Krammer tried to explain his rationale for distinguishing between these species in his 2002 monograph but he uses the name “C. excisa” for the organism called “C. affinis” in our 2017 English edition.  Confused?  You will be ….

Cymbella excisiformis” from Lake Popovo, Pirin Mountains, Bulgaria, August 2017.   Based on Lange-Bertalot et al. (2017)’s criteria of length:breadth 4.2-5.3 in C. excisiformis compared to 3.1 – 3.8 in C. affinis, images a., b. and c. are C. excisiformis whilst d., e., f. and g. are C. affinis.   Scale bar: 10 micrometres (= 1/100th of a millimetre).

This is another good example of points that I have made several times before: that we should always try to identify populations rather than single cells, and that we should treat dimensions stated in the literature as indicative rather than definitive (see “More about Gomphonema vibrio”).    Length:width, in particular, can change a lot during the life-cycle of the diatom.

Species of Gomphonema were also present in the sample.  Though not numerically abundant (none constituted more than one per cent of the total count), they included some large cells which, in addition, have extensive mucilaginous stalks, so their contribution to total biomass is greater than their low abundance suggests.   I’ll write more about the ecology of these species in the next post.   Finally, I also found other Cymbella species, as well as some Encyonema and Encyonopsis, and a few valves of Eucocconeis flexella, a relative of Achnanthidium and Cocconeis which has a distinctive diagonal raphe.

Gomphonema spp. from Lake Popovo, Pirin mountains, Bulgaria, August 2017.   h., i.: G. acuminatum; j.: G. truncatum; k.: unidentified girdle view; l.: G. pumilum.  Scale bar: 10 micrometres (= 1/100th of a millimetre).

There is, at this point in time, no official Bulgarian method for assessing the ecological status of lakes using diatoms so I have evaluated Lake Popovo as if it were a low alkalinity lake in the UK instead.  Using the method we developed, this one sample has an Ecological Quality Ratio of 0.92, which puts it on the border between high and good status.   Looking around the lake, I see no reason why it should not be firmly in high status but, at the same time, I am using an evaluation method that was designed for lakes 2000 kilometres away, so maybe we should not expect perfect results.    However, I have performed similar exercises at other lakes far from the UK and also got similar results (see “Lago di Maggiore under the microscope”) which points to a basic robustness in this approach.

The outflow of Lake Popovo leads into a cascade that ends in the first of a series of lakes, the “Fish Popovski” lakes.   I wrote about the desmids in this lake back in September (see “”Desmids from the Pirin mountains”) and will return to this sample in order to describe the diatoms in another post.   But, meanwhile, the assemblage at Popovo reminded me of the littoral algae in another lake that I really should tell you about …

Miscellaneous diatoms from Lake Popovo, Pirin mountains, Bulgaria, August 2017.   m.: Cymbella sp.; n.: Encyonema neogracile; o. and p.: Eucocconeis flexella (raphe valve and girdle view respectively).  Scale bar: 10 micrometres (= 1/100th of a millimetre).

Lake Popovo, photographed from close to the location from which my sample was collected.  The brass plate on the rock at the right hand side gives the altitude as 2234 metres above sea level.  The photograph at the top of the post shows Lake Popovo against a backdrop of the Pirin mountains.


Hofmann, G., Werum, M. & Lange-Bertalot, H. (2011).   Diatomeen im Süßwasser-Benthos von Mitteleuropa. A.R.G. Gantner Verlag K.G., Rugell.

Krammer, K. (2002).  Diatoms of Europe volume 3: Cymbella.   A.R.G. Gantner Verlag K.G., Ruggell, Germany.

Lange-Bertalot, H., Hofmann, G., Werum, M. & Cantonati, M. (2017).   Freshwater Benthic Diatoms of Central Europe: Over 800 Common Species Used In Ecological Assessment (edited by M. Cantonati, M.G. Kelly & H. Lange-Bertalot).   Koeltz Botanical Books, Schmitten-Oberreifenberg.

The UK lake diatom assessment method is described in:

Bennion, H., Kelly, M.G., Juggins, S., Yallop, M.L., Burgess, A., Jamieson, J. & Krokowski, J. (2014).  Assessment of ecological status in UK lakes using benthic diatoms.  Freshwater Science 33: 639-654.

Details of the calculation can be found in the UK TAG method statement.

The kindness of strangers …

A matter of days after we arrived in Nigeria (see “How to make an ecologist #11”) a battered old Peugeot 504 station wagon pulled up alongside us as we walked from our hotel to get a bush taxi across Jos to the university campus. A North American voice called through the open window (we were later to discover that it never closed properly) and asked if we wanted a lift. We clambered in gratefully, the vehicle crunched into gear and pulled out into the traffic again. As the car lurched forward a whisky bottle rolled across the foot well and the driver, a lean man in his fifties, introduced himself as Alvin, a worker with CUSO, the Canadian equivalent of the Peace Corps or VSO. The whisky bottle, he explained, contained local honey (invariably sold with honeycomb and a few dead bees included). By the time we had made the mile or so journey to the centre of town where our routes diverged, he had invited us back to his house for dinner the following evening.

A week at the Plateau Hotel had been enough to exhaust our enthusiasm for their rather limited menu so we accepted with alacrity and, the following evening, his Peugeot grumbled up the driveway to the Plateau Hotel to collect us for the short drive to his house on the edge of the town where we met his wife Sylvia and ate her home-cooked food. They had had a furniture business in Kenora, Western Ontario, we learned, but had sold up to take a career break teaching in a technical college. Officially, Alvin taught woodwork (which he wryly summarised as showing students how to make long pieces of wood shorter) but he had an unofficial sideline in demonstrating how random acts of kindness made the world a better place. They and we bonded despite the age difference and, at weekends, we joined them in their elderly Peugeot to explore the region.

Fishermen on the River Benue, early 1990.   The photograph at the top of the post shows rock formations near Riyom, south of Jos (but taken some months later, during the wet season).

A few days ago  we heard news that Alvin had died after a long battle with cancer. Once our initial sadness had passed, we found ourselves smiling again as memories that had faded with time reasserted themselves. One trip, in particular, summed-up Alvin’s indomitable attitude, taking us south off the Jos Plateau into the heat of the northern Nigerian plain. I can’t remember the motivation for this trip, only that we spent the night in a guest house belonging to a mission, but only after a hair-raising crossing of the Benue River. Our first approach to the river was presaged by a sudden improvement in the road surface as we drove up an incline towards a very modern-looking bridge before Alvin stood on the brakes to bring us to a halt just before the road ended abruptly with just a few traffic cones between us and a vertical drop.

From this narrow escape we made our way on smaller roads to the ferry, where a narrow barge barely wider than the car itself was tied up with some planks bridging the gap to the steeply-sloping riverbank. At this point, the rest of us climbed out declaring our intention of recording the occasion on film, leaving Alvin to line-up the car at the top of the slope and then to slither down, across the rickety planks and onto the barge.  We followed him onto the barge and were shown into the open boat lashed to the side, from which the ferryman started up the outboard motor and pointed the ferry towards the line of trees that marked the opposite shore.

Boarding the ferry across River Benue, Nigeria, 1990.

We shared the broad river channel with a few small boats carrying foot passengers and a skiff from which a local fisherman and his son were casting seine nets.  There are reports of manatee and hippopotami from the river, though we did not see any, and there are almost certainly crocodiles too, though they kept out of sight.  Our ferry moved slowly diagonally upstream across the broad river channel towards the southern shore where the exercise was repeated (the river bank on this side was far less intimidating) and we were in Benue State.  This was the heartland of the Tiv ethnic group whose distinctive round huts were the subject of one of my very first watercolours.   The Tiv are the fourth largest ethnic group in Nigeria, a farming people, proud of their yams.  Inside the round huts it is easy to imagine the scenes related by the anthropologist Laura Bohannan in her fascinating article Shakespeare in the Bush.

Having got to Tiv country on the Saturday evening we had to turn our eyes back towards Jos if we were to be back in time for work on Monday.   We took a more circuitous, albeit faster, route this time, crossing the river by the modern bridge and heading back along roads lined with mahogany plantations.   We stopped at a roadside stall beside one of these and haggled for a small pestle and mortar, which our Nigerian friends dismissed as hilariously inadequate and which imparted a tinge of brown boot polish to our first few batches of pounded yam.   And then Alvin was changing down the gears so that the Peugeot could haul itself back up to the milder climate of the Jos Plateau and we were passing familiar landmarks again.

A reconstruction of the Tiv village at the Museum of Traditional Nigerian Architecture in Jos, circa 1990. 

Recalling Alvin and Sylvia at this time of year is apt, as hospitality to strangers is an integral part of the Christmas story.  They helped us find our feet and we, in due course (I hope) followed their example with other new arrivals.   After leaving Nigeria they moved to Minnesota, to be close to their children, where we visited them in November 2012 (I watched Bill Clinton’s first election victory from their front room).  Distances were too great to see them regularly but we kept in touch by letter and email.   Though I had not seen him for over twenty years, I felt the bonds we forged in Nigeria were strong and knowing that he is no longer here to share his dry humour and practicality is enough to give me pause for thought.

In pursuit of Bulgarian diatoms …

Our visit to Rila Monastery was one of the cultural highlights of our trip to Bulgaria in the summer (see “The art of icons …”) with the added bonus that it is set amidst some spectacular scenery.   The monastery was founded by St Ivan Rilski (“St John of Rila”) in the 10th century, though the present structures date from the 19th century.   St Ivan, I gleaned from my reading, shared a love of nature with St Francis and St Cuthbert and Rila’s remote location reflects his desire to live the life of a hermit.

Beyond the monastery the road twists and turns amidst the forest that lines the valley.   Occasionally, the canopy is broken by meadows and orchards of apricot and plum trees.  The apricots were ripe for harvest and at an easy height for foraging as we passed by.   We were too late in the year to find many wild flowers in these meadows but the absence of any of the paraphernalia associated with intensive agriculture made us suspect that these would have been a riot of colour in the spring.    Eventually, we came to a small hamlet set amidst a wider area of meadows, where we refuelled at a small café serving the delicious local bean soup (“bob chorba”) before making our way across the meadow to the stream.

A haystack in a meadow near Rila Monestery, August 2017.

The Rila stream itself flowed through a densely-wooded channel, with a variety of substrates from coarse sand to moss-covered boulders.   The larger stones were mostly granite, reflecting the underlying geology of the region, which almost certainly means that the water was very soft.  The surrounding vegetation and low population density also mean that the water is probably as pure as we are likely to find anywhere in Europe.   I had a toothbrush and sample bottle in the bottom of my rucksack and scrubbed a few cobble-sized stones to remove the thin surface film and stowed this for the journey back down the valley.

Sampling Rila stream at Kirilova meadows, a few kilometres upstream from Rila Monestery in August 2017.   The photograph at the top of the post shows the scenery around Kirilova meadows.

It has taken until now for me to get around to looking at this sample, which turned out to have a large population of Gomphonema rhombicum, along with quite a lot of Achnanthidium minutissimum and relatives, confirming my suspicion of a circumneutral, low nutrient environment.   G. rhombicium is a relatively uncommon diatom, so I was intrigued to have a closer look.  It has a similar outline to G. pumilum, which is very common, but is larger and has a distinct broad lanceolate axial area and, consequently, relatively short striae.   The axial area broadens out a little further at the central area, where there is also a single stigmoid.  I wish now that I had had a look at the sample before digestion as many of the larger Gomphonema species have long mucilaginous stalks, whereas G. pumilum and relatives tend to be attached to the substrate by short mucilaginous pads.   I can find nothing in the literature that alludes to the habit of the living cell and, on this particular occasion, am in no position to judge the shortcomings of my peers.

By coincidence, the type location for Gomphonema rhombicum is given as “Appleby, Westmoreland”, which is just over an hour’s drive from where I live.   The most obvious place to hunt for G. rhombicum would be the River Eden; however, the scant details on the ecology of G. rhombicum that I can find suggest a preference for softer water than found here.  This is a geologically-complex area so there is a possibility of suitable habitat existing in a stream in the vicinity.  If the Eden was the location from which the original population of G. rhombicum was collected, then I suspect that it may have been a casualty of the agricultural intensification that has taken place in this area since it was first described.

Cleaned valves of Gomphonema rhombicum from Rila stream at Kirilova meadows, August 2017.  a. – g. show valve views; h. shows a girdle view.  The scale bar is 10 micrometres (= 100th of a millimetre).

That leaves me with just one option: a return to the Rila National Park.  I think I can just about live with that.   We stayed at Hotel Pchelina, a few kilometres down the valley from Rila Monestery and our dinner that evening was the most delicious grilled trout that I have ever tasted.  If a return visit was needed to solve the mystery of Gomphonema rhombicum’s habit then I think that is a hardship with which I can just about cope …


Iserentant, R. & Ector, L. (1996).  Gomphonema rhombicum M. Schmidt (Bacillariophyta): typification et description en microscopie optique.   Bulletin Français de la Pêche et de la Pisciculture 341/342: 115-124.

Ecology’s bear necessities

I found an old box of slides recently, which took me on a nostalgic journey back to British Columbia in 1980 and, in particular, to a weekend fishing trip with my cousin Steve.  We travelled north from Terrace, where he lived, along a series of unsurfaced roads through dense pine forest, passing the ethereal moonscape of Nisga’a Memorial Lava Bed to the Nass River where we cast lures and caught the salmon which became our dinner a few hours later.   The following morning we followed the road past an impressive Piedmont glacier, through the small town of Stewart and, a couple of miles beyond, passed an unmanned border post and entered Alaska.

The tiny settlement of Hyder sat just beyond the border, beyond which the forests close in again around the gravel track that followed a small stream into the hills.   When we pulled up beside the road and got out, however, the overwhelming sensory experience was not the landscape or even the sound of the stream tumbling out of the hills towards the fjord behind us.  It was the stench of rotting fish.   We were witnessing the spawning and subsequent death throes of the Pacific Salmon.   Unlike the Atlantic Salmon (Salmo salar) which can repeat their migration from the sea to freshwater several times, Pacific Salmon (Onchorhynchus spp.) spawn only once in their lifetime.   Exhausted after the exertions of the migration and what is euphemistically referred to as “big bang reproduction”, the salmon become easy prey for bears, one of whom emerged from the forest a hundred metres or so upstream of where we were standing.

My first encounter with the USA.   The border is at the point where the metalled road ends and the gravel track starts.  The building on the left is the US Customs post.   

You can just make out the bear in the photograph at the top of the post (I’ve also circled in another version at the end).  At the time, my camera was a Kodak Instamatic, which had a semi-wide-angle lens.   We all have two appendages dangling from our hips that make up for many of the deficiencies of a wide-angle lens but, on that stream bank in Alaska, I decided that discretion was the better part of valour.   We watched from afar and the multisensory memory is rather more vivid than the somewhat faded Kodachrome slide that I found in the loft.

That would have been the end of the story except that, in the early years of the new millennium, scientific papers started to appear which turned this spectacle from an item on the wildlife tourist’s bucket list to an integral component of the engine that drives the forest ecosystems of the Pacific Northwest.    These forests, like most natural systems, are hungry for nutrients such as nitrogen and phosphorus and the salmon are, in effect, unwitting suppliers of the fertiliser that the trees need.   The Pacific Salmon spend up to five years in the ocean before moving to their spawning grounds.   Those strong muscles that they need to swim upstream and leap up waterfalls are largely protein which is built from nitrogen-containing molecules.  And nitrogen is, coincidentally, the nutrient that trees need most.

A view across Nisga’a Memorial Lava Bed in the Nass River valley, British Columbia.  The lava was the result of a volcanic eruption in about 1700.  This and other photographs in this post were taken with my Kodak Instamatic, which partially explains their poor quality.

By fishing the dying salmon from streams such as this (and even grabbing the leaping salmon before they get to their spawning grounds – see some spectacular footage from David Attenborugh’s Nature’s Great Events here) the bears become the agents by which the salmon’s nutrients are transferred from the Pacific Ocean to the forests.    It has been estimated that up to a quarter of the nitrogen needs of the forest around these streams is supplied in this way.   Indeed, some have suggested that this transfer of nutrients may be so essential to the functioning of this forest ecosystem that the salmon and bears are, in effect, “keystone species” and that their interaction has an effect that is greater than their contributions individually.

Brian Moss used to use this as a pithy illustration of the need to take a very broad view when managing ecosystems.   We all know that rivers flow into the sea but it is not always so obvious how the oceans can have an effect on terrestrial vegetation far inland.   Similarly, we understand how water flows across land and into stream channels but perhaps we have a hazier awareness of the movements in the opposite direction – from the river channel into the depths of the forest.   Salmon spawning in the Pacific Northwest is one of the world’s great wildlife spectacles, but it should also give us cause to pause and consider the complexities of interactions within natural habitats and, in turn, the dangers of meddling.

One more prosaic lessons that I learned from this short trip: if you are going to the USA, take a passport. Actually, I didn’t need one going into Alaska, but when we returned the Canadian border official had rolled out of bed after his Sunday lie-in  and almost didn’t let me back in!

Another species of hairy wildlife in search of salmon, this time on the Skeena River, British Columbia.   On this particular occasion, the salmon did not oblige and I had my first and only encounter with Kentucky Fried Chicken instead.  


Helfield, J.M. & Naiman, R.J. (2006).   Keystone interactions: salmon and bear in riparian forests of Alaska.  Ecosystems 9: 167-180.

Naiman, R.J., Bilby, R.E., Schindler, D.E. & Helfield, J.M.  (2002).  Pacific salmon, nutrients, and the dynamics of freshwater and riparian ecosystems.  Ecosystems 2: 399-417.

Quinn, T.P., Carlson, S.M., Gende, S.M. & Rich, H.B. (2009). Transportation of Pacific salmon carcasses from streams to riparian forests by bears.  Canadian Journal of Zoology 87: 195-203.

The scene near Hyder, Alaska, this time with the bear circled, just in case you didn’t believe me.