Grazing on algae …

I comment on the role that grazers play in controlling algal biomass in rivers in these posts and this is the time of year when I, myself, take a more participatory role.   As it is spring, Lemanea fluviatilis is thriving in our rivers (the cleaner ones, at least) and I could not resist grabbing a couple of handfuls whilst out in the field recently for culinary purposes.

This time, I followed the routine I described in “More from the Lemanea cookbook … ” and washed, air-dried and then cut-up some Lemanea filaments into short lengths (they need to be about a centimetre long, otherwise they can form clumps).   My experience is that the fishy taste of Lemanea is a fine complement to freshwater fish, so decided to use it in a warm potato salad which I then served underneath a salmon fillet seasoned and sprinkled with dill and then wrapped in foil and baked with a couple of knobs of butter.

The warm potato salad needs a mayonnaise made from one egg yolk and about 150 ml of olive oil into which a couple of tablespoons of lemon juice are stirred, along with salt and pepper.   Add a generous handful of dried Lemanea to this and leave to soften for about 20 minutes, and also add a teaspoon of capers and a small handful of land (or water) cress.  Cook and drain enough new potatoes for two, then cut these into small chunks and stir the mayonnaise and algae mixture into these.   Divide between two warmed bowls and place half the salmon fillet on top of each.  Finally, add a few fresh pea shoots as a garnish, along with a wedge of lemon, and serve.

Definitely worth repeating.

Warm potato salad with lemon and Lemanea, served with salmon fillets.

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More from the Lemanea cookbook …

My previous experiment with the culinary properties of the freshwater alga Lemanea took an Italian turn (see “Spaghetti alla Carbonara con Lemanea”) and this continues with my latest recipe, which combines Lemanea with a classic risotto to produce what is, in my opinion, the most flavoursome Lemanea-based dish I’ve yet encountered.   This is your last chance to cook with Lemanea this year, as it flourishes in late winter and early spring so its season is drawing to a close.   You need to collect a couple of good handfuls of Lemanea from a clean river, rinse it with cold running water in a sieve, and then spread it out on some kitchen paper to air-dry overnight.   At the end of this period, pick it over to make sure that there is no grit still adhering to the filaments, then chop it into short lengths with a pair of kitchen scissors.  As it dries, the gentle fishy aroma of the fresh filaments intensifies, inspiring the culinary imagination …

Lemanea_air_dried

Air-dried Lemanea, ready for cooking …

I have already tried Lemanea with pasta so today’s experiment was with risotto: one of my favourite Italian dishes both to eat and to cook.  I cooked a standard risotto bianco then, towards the end of the cooking period, added a handful of fresh prawns and a generous handful of chopped Lemanea (for two people).  I stirred it around whilst the prawns cooked, and to make sure that the Lemanea was distributed throughout the dish.   Once the stock had been absorbed, I removed the risotto from the heat and stirred in some butter and Parmesan cheese.   I used this time to pan-fry two trout fillets to serve with the risotto.

Risotto_with_Lemanea_&_trou

Risotto with Lemanea and prawns, served with pan-fried trout and a bottle of Durham Brewery’s Smoking Blonde ale.

Once again, the gently fishy flavour of the alga balances the taste of freshwater fish really well although, in retrospect, smoked fillets would have been better.  However, all my fishmonger had were some rather bland rainbow trout from a fish farm.   The prawns add extra flavour and texture to the dish and led me to wonder if the dish might also work really well with freshwater crayfish.

Rather than open a bottle of white wine with the risotto, we followed up a lesson we learned the evening before at Blackfriar’s restaurant in Newcastle, where we had a meal where every course was complemented by a carefully-selected beer.   The fish course was complemented superbly by Durham Brewery’s “Smoking Blonde”, a golden ale made with smoked wheat, which introduces to the beer the complex aromas I associate with Islay whisky.  I gain a double pleasure from recommending a beer from Durham Brewery: it is situated within walking distance of my house and they started in business at about the same time as me.   I first encountered them, in fact, on a course where we got a basic training in business methods together.   “Smoking Blonde” celebrates their 21st anniversary in business, so I guess it must celebrate Bowburn Consultancy’s “coming of age” too.

The complicated life of simple plants …

I have a theory, which I have touched on before in these posts, that the success in conveying the wonders of nature to non-biologists is easiest when the audience can relate what they see directly to their own experiences.   You only have to watch a typical David Attenborough documentary to see this principle at work: it may feature sumptuous photography in glorious landscapes, but the events portrayed are not so different to a typical Friday evening at the Bigg Market in Newcastle.   The BBC Natural History Unit would find plenty of courtship activities, territoriality and several kinds of violence here, much of it set around watering holes.   Who needs a plane ticket to an exotic location?

As we lose that sense of empathy, so nature becomes “weird”.  A few of us find fascination in the weird but we are a minority.   Strangeness, however, brings problems, as I have commented before (see “Reflections from the trailing edge of science”) as stories cannot be conveyed using familiar metaphors drawn from our own experience.   The example I used in that earlier post was the concept of “alternation of generations” in plants and my recent encounter with the red alga Lemanea a couple of weeks ago (see “Spaghetti Carbonara con Lemanea”) reminded me of a set of wonderful photographs by Chris Carter that illustrate this concept very well.

That post contained a photograph of Lemanea from the River Ehen in Cumbria which shows some of the wiry filaments growing on the stream bed.   These filaments are, actually, hollow tubes of cells (see photograph in “The River Ehen in April”) along which there are a series of nodes.   The nodes, in this case, bear sexual cells at certain times of the year (see “Lemanea in the River Ehen”).

Lemanea-Rede-crosssection

A cross section of a filament of Lemanea from the River Rede, Northumberland (photo: Chris Carter).

Chris’ photographs shows how the Lemanea filaments are actually composed of a hollow tube of cells with an outer cortex.  However, the centre of this tube is not completely empty, and the clusters of cells that we can see inside the tube are spore-producing organs called “carposporophytes”.   At some point during the development of the carpospores, two cells fuse so that the carpospores is diploid (2n), rather than haploid (n).   The carpospores are released when the Lemanea filament dies back in late Spring and these then germinate into a filamentous sporophyte (2n) phase, called the “chantransia”.  At some point during the winter, these chantransia undergo meiosis, and the resultant haploid cells grow, still attached to the chantransia, into the next generation of gametophytes.

Lemanea-transp_CFC

Transapical view of a Lemanea filament; the arrows show the sporophytes (“carposporophytes”) inside (photo: Chris Carter).

Finally, I have included Chris’ high magnification photograph of some of the cells of this carposporophyte plant, looking very similar to simple red algal genera such as Audouinella, which prompted my original series of posts on alternation of generations.

These photographs capture my fascination with the algae: apparently simple, easily overlooked, but actually presenting sophisticated, highly-evolved solutions to survival under tough circumstances.   The constant current in rivers makes establishing and maintaining a population at one place hard enough, more so when a “population” actually consists of two discrete stages.   This has led some to suggest that the complexities of the red alga life cycle may be a form of “bet hedging”, spreading the risk of mortality between the life stages.   Having a large gametophyte phase, for example, gives the plants access to more light, making them more productive, but they are also exposed to the strong currents in the river, increasing their risk of loss due to scour.   On the other hand, the smaller sporophytes (the “chantransia”) are protected from the ravages of the current because they live close to rock surfaces, within a “boundary layer” where current velocity falls off due to drag.  It could be seen to be roughly parallel to the metamorphosis of butterflies and other insects, with phases of the life cycle optimised for different activities.

Lemanea faces a particular challenge: the gametophytes have “solved” (excuse the teleology) the challenge of living in very fast current speeds, where they have little competition from other plants and algae and, I would guess, little threat from grazing invertebrates.   This gives the genus plenty of scope to thrive in fast-flowing upland rivers.   There is normally a benefit to an organism of releasing spores and gametes into their immediate environment, as this encourages dispersal and cross-breeding. Were Lemanea to do this, the spores and gametes would be washed quickly downstream, away from their ideal habitat.  The practice of keeping the carposporophyte inside the thallus, rather than on the outside, increases the chances of some of the carpospores finding their way to the rocks in the immediate vicinity of the gametophyte and, thereby, ensuring that the chantransia are well-placed to produce a new gametophyte generation the following year.

It is all very complicated.  This is, I suspect, partly because systematic biologists have a fondness for obscure terminology that makes it hard for the non-initiate to follow the twists and turns of life cycles.  But it also, I suspect, a consequence of dealing with habits and life cycles that are unfamiliar and, more importantly, cannot be distilled down to simple, anthropomorphic metaphors.

Lemanea_Carpospores_CFC

High magnification view of carpospores of Lemanea (photo: Chris Carter).

Reference

Sheath, R.G. (1984).  The biology of freshwater red algae.  Progress in Phycological Research 3: 89-157.

Spaghetti alla Carbonara con Lemanea

Lemanea_Ehen_March16

Fieldwork in March brings out the forager in me, as lush growths of the red alga Lemanea smother the beds of our upland rivers at this time of year. Considered a delicacy in some parts of the Himalayas, I started my own culinary experiments with it and, last year, had my first success (see “Freshwater algae on the menu … again”). This year, I have branched out a little further, and offer you my own variant of the classic Italian dish Spaghetti alla Carbonara, which you can find in most Italian cookbooks (interesting theory for the origin of the dish if you follow this link. The twist to my recipe is to replace the bacon or pancetta with hot smoked salmon.

Gently fry a crushed garlic clove in a little olive oil whilst the pasta is cooking, then, add the salmon, cut into chunks (about 50 g per person), and turn for a couple of minutes.   Drain the pasta and add it to the pan with the salmon and garlic. Now take it off the heat and stir in a mixture of beaten eggs (two per person) and parmesan cheese (about a tablespoon per person) plus salt and pepper.   The key to a good Carbonara is to make sure that the eggs thicken to form a creamy sauce, and do not scramble.   I added chopped filaments of Lemanea, prepared as described last year, as a garnish on top of the pasta / egg / salmon mix, and served it with a rocket and water cress salad.   The alga has a distinctive fishy taste that complements, but does not overwhelm, the salmon.   Not only delicious, but also less than 20 minutes from putting the pasta into boiling water to sitting down to eat it.

Pasta_alla_carbonara_con_Le

Spaghetti alla Carbonara con Lemanea.

The photograph shows Lemanea growing on a submerged stone (about 20 cm across) in the River Ehen, Cumbria in March 2016.

Freshwater algae on the menu … again

The return of Masterchef to our screens at the same time that Lemanea is at its most abundant in our streams is too much of a coincidence for me.   I have already written about my culinary experiments with the red alga Lemanea (which is eaten in parts of northeast India) and have been wondering for some time how best to use it in British cooking (see “Trout with sorrel, watercress and … algae”).   This year, I followed my instincts, in the wake of my experiments with Welshman’s Caviar after the Green Man festival last summer (see “Gastronomy in the Welsh hills”) and found that it can really enhance the flavour of scrambled eggs.

This is how to do it: collect a few handfuls of young Lemanea from a stream.   It is only common in streams that are relatively unpolluted, though it is tolerant of heavy metal pollution, so it pays to avoid areas where you know there is a history of mining. Wash the filaments in cold water to remove any particles, shake it dry and then spread it out on a plate and leave it at room temperature overnight to dry.   Chop it roughly so that the fragments are about a centimetre in length. Finally, make your scrambled eggs in the usual way, but stir a generous handful of the dried Lemanea filaments into the mixture just as it starts to thicken. Cook whilst stirring for a couple of minutes, then serve on buttered toast.   The algae gives the scrambled eggs a nice, fishy flavour without overwhelming the dish.

scrambled_egg_with_Lemanea

Scrambled eggs with Lemanea.

By coincidence, I also found myself eating algae later in the day. I watched a small bowl filled with a tangle of narrow bright green strips trundled past on the conveyor belt whilst I was having a quick pre-cinema meal in YO! Sushi in Newcastle.   This was Kaiso salad, made from seaweed (Undaria, I think) marinated with sesame.   It looked too good to resist. Algae on the menu twice in one day … if I’m not careful, you’ll be thinking I’m obsessed …

kaiso_salad

Kaiso salad at YO! Sushi

Lemanea in the River Ehen

The rocks in the fastest-flowing sections of the lowermost of our four sample sites on the River Ehen were all smothered with the coarse filaments of Lemanea fluviatilis. Lemanea is another red alga (see “The schizophrenic life of red algae …”) but one that grows to a much larger size than Audouinella which I wrote about back in early February. I wrote about Lemanea last year (“The River Ehen in April”) but that was before I had an underwater camera. However, most of the Lemanea is attached to large, stable boulders located in sections of the river where the fast current made it almost impossible to photograph safely. Instead, I hunted around and found a smaller stone that was wedged in amongst these, and moved this to a shallow area where it was easier to photograph.

Lemanea_fluviatilis_in_Ehen

Lemanea fluviatilis from the River Ehen in March 2014. Scale bar: one centimetre.
If you look closely you will see that each of the filaments has a series of nodes along its length. Under the microscope, these nodes form darker patches, composed of smaller cells than the rest of the filament. These are, in fact, the reproductive structures, spermatangia, of the plant as Lemanea has a similar life-cycle to that of Audouniella, which I described in my earlier post. There is also a closely-related genus, Paralemanea, which looks like Lemanea but which has these spermatangia in rings rather than in patches. Older books do not recognise the distinction between Lemanea and Paralemanea.

Lemanea_fluviatilis_stack

Lemanea fluviatilis from the River Ehen, March 2014. a. low-power image showing the knobbly stems; b. close-up of a single stem showing the spermatangia patches associated with these protruberences (scale bar: 20 micrometres; 1/50th of a millimetre); c. close-up of a patch of spermatangia.
Lemanea is, in my experience, a very useful indicator of good quality aquatic ecosystems. Looking back through my own records, I see 88 per cent are associated with “high status” or “good status” conditions and the few instances where it is found associated with poorer quality conditions, it is always quite sparse. There is a site quite close to Durham where we used to find Lemanea despite the water being quite enriched with nutrients: though low down in the catchment there was an extensive riffle area with fast currents and, I suspect, few other organisms able to compete for Lemanea’s favourite conditions. Remember, too, that there are enormous reserves of Lemanea in the upper catchment of the River Wear, and plenty of opportunities for this to be scoured off boulders and carried downstream. The wise ecologist always works on “balance of evidence”, rather than making categorical judgements on the presence or absence of a single organism. There is, simply, too much that we still don’t know about the biology of these species.