Thursday, 7 December 2017

Green beer and Spirulina

A brewer on the shores of Lake Erie has produced a green beer, flavoured with kiwi fruit and with green tea added as colouring [1]. This unusual drink has received a favourable response from drinkers who like its fruity taste, but the brewers made the green beer to highlight a problem with their water supply that originates from Lake Erie. Unfortunately, the lake has recently suffered blooms of cyanobacteria (previously known as blue-green algae) that can be seen in satellite images (see below, from NOAA). Given that they are very primitive unicellular organisms, the numbers of individuals, and colonies, in these blooms are astonishing.

The cyanobacteria are fertilised by nutrients, especially phosphate, that are added to increase the growth of grass, or crops, and which run-off into the rivers and are then carried to the lake. Phosphate is a limiting nutrient in most fresh waters, so its addition causes the cyanobacteria to grow and multiply rapidly. Their numbers cannot be controlled by planktonic animals and cyanobacteria exude sticky polymers that provide a defence - the polymers also allow attachment of cells to form colonies, and enable some cells to propel themselves within the water column. As long as nutrients are available, blooms result and these inhibit the efficiency of drinking water treatment plants and, to add to the woe, some cyanobacteria produce toxins that are poisonous to humans and may be lethal to our pets.

So, are all cyanobacteria harmful to human activities? The answer is no, for without cyanobacteria and the evolution of their capacity to convert carbon dioxide and water into sugars using light energy – the process of photosynthesis – we would have no green plants and very little oxygen in the atmosphere. Indeed, we wouldn’t be here if it wasn’t for cyanobacterial evolution. The ancestors of single-celled algae ingested cyanobacteria and, by an unknown mechanism, some of these survived and became incorporated with the algal cell as chloroplasts. From single-celled algae came multicellular organisms and the complex aquatic, and terrestrial, plants that we know today.

Cyanobacteria also have a more obvious value to us, as some species are cultured in lagoons to produce intentional blooms that are then harvested. The collected mass is dried and compressed into cakes, pellets and powders that are marketed as Spirulina, being valued both as a health food and dietary supplement. There are many recipes that feature the cultured cyanobacteria [2,3] and Spirulina is even finding its way into “fine dining”, as viewers of the BBC’s Masterchef: The Professionals know. Of course, it is important to avoid harmful cyanobacteria when selecting those to be cultured for human consumption and I wouldn’t recommend harvesting the blooms from Lake Erie.

Monday, 20 November 2017

The kraken - and humpback whales

In his fascinating book Sea Monsters on Medieval and Renaissance Maps, Chet Van Duzer [1] gives a quote from Konungs skuggsjá (King’s Mirror), a mid-thirteenth century Old Norse book:

There is a fish not yet mentioned which it is scarcely advisable to speak about on account of its size, which to most men will seem incredible. There are, moreover, but very few who can tell anything definite about it, inasmuch as it is rarely seen by men; for it almost never approaches the shore or appears where fishermen can see it, and I doubt that this sort of fish is very plentiful in the sea. In our language it is usually called the “kraken”.. .. It is said, that when these fishes want something to eat, they are in the habit of giving forth a violent belch, which brings up so much food that all sorts of fish in the neighbourhood, both large and small, will rush up in the hope of getting nourishment and good fare. Meanwhile the monster keeps its mouth open, and inasmuch as its opening is about as wide as a sound or fjord, the fishes cannot help crowding in great numbers. But as soon as its mouth and belly are full, the monster closes its mouth and thus catches and shuts in all the fishes that just previously had rushed in eagerly to seek food.

This account puzzled me at first and then I realised it was probably a description of a behaviour shown by humpback whales that exhale streams of bubbles while swimming 3-5 m under the surface of the sea [2] to panic fish. Bubbles released as the whale swims in a tight circle cause the prey to become concentrated as the fish swim away from the disturbance in the water that is now partially surrounding them, creating a “bait ball”. The whale then lunges up through the mass of fish and, breaking the surface, closes its mouth to allow the release of water through the baleen plates [2]. This results in the capture of much larger numbers of prey than would be possible if humpbacks used the more linear feeding method used by other baleen whales, swimming through shoals at the water surface without lunging or producing bubbles.

Humpback whales also use “bubble netting” to operate in groups, with the advantage that more fish are caught per individual than would be the case should the whales feed singly. It is thus of advantage to all individuals that partake, not only those that are closely related, and produces a larger, greater concentration of prey. Wiley et al. [3] monitored this group behaviour:

..humpback whales capture prey by engaging in complex feeding manoeuvres that are often accompanied by the apparently directed use of air bubbles.. .. Bubble use by humpback whales has been observed in many of their feeding habitats and is reported to occur in a variety of configurations. These bubble-feeding behaviours appear to vary in nature among both individuals and regions; for example, bubble clouds (the production of a single or multiple bursts of seltzer-sized bubbles) are commonly observed from humpback whales in the Gulf of Maine, but never in Alaskan waters.

Such differences point to behaviours learned by individuals in geographically-separated sub-populations, with groups of whales using two approaches to bubble netting - “upward spirals” and “double loops” [3]. The effect is the same - a bubble corral around very large numbers of fish - and the manoeuvrability required results from the large tail fluke and the high aspect ratio flippers (see below), that allow short turning circles and bursts of rapid movement to the surface. The evolution of form in humpback whales thus made bubble netting possible. 

It is spectacular for human whale watchers (see the video clip below), as is feeding by individuals,  and one can imagine the awe of thirteenth century explorers in their very small craft watching a kraken belching. As to the appearance of the kraken, we know that it was very large, but not with a mouth as wide as a sound or fjord. Clearly the observation of humpback whales resulted in descriptive stories that became elaborated with telling and the addition of some rich Nordic mythology.

[1] Chet Van Duzer (2013) Sea Monsters on Medieval and Renaissance Maps. London, The British Library.

[2] J.H.W.Hain, G.R.Carter, S.D.Kraus, C.A.Mayo and H.E.Winn (1982) Feeding behavior of the humpback whale, Megaptera novoaeangliae, in the Western North Atlantic. Fishery Bulletin 80: 259-268

[3] D.Wiley, C.Ware, A.Bocconcelli, D.Cholewiak, A.Friedlaender, M.Thompson and M. Weinrich (2011) Underwater components of humpback whale bubble-net feeding behaviour. Behaviour 148: 575-602.

Tuesday, 7 November 2017

The legendary Paignton cockles (and some recipes…)

I grew up in Paignton in South Devon and was always attracted to the sea, although only occasionally went swimming as I was more interested in walking along the beach to look at what had been washed up by the waves and tides. After the severe winter of 1962/63, I remember that the first storms brought masses of shells ashore, after the very low temperatures had killed a large number of molluscs (the sea froze in a few places). Although there were many common cockles, there were also some more unusual cockle shells, including those of the red-nosed cockle (below, upper) and the spiny cockle (below, lower). These species made Paignton Beach (shown above) famous in Victorian times, as their distribution around the coast of Great Britain is very local, the spiny cockle being largely confined to the shallow sandy sediments of the western part of Torbay.

Lovell wrote this about the red-nosed cockle (as Cardium rusticum) and spiny cockle (as Cardium aculeatum) in 1867 [1]:

[The red-nosed cockle].. rare and local in England. It is found on the Devonshire coast, at Paignton, and occasionally at Dawlish, and at certain times of the year, especially in the spring after a gale from the east, numbers may be gathered. On paying a visit to the Paignton sands, for the purpose of shell collecting, in the spring of 1862, the beach was quite strewn with broken single valves of this cockle, and there had evidently been quantities of live specimens washed up as well, as we met many persons returning home with their baskets heavily laden with them..

.. There is another cockle found also at Paignton, which is even more scarce than Cardium rusticum, viz. Cardium aculeatum; it is larger and not so solid, with long spines on each rib, and is of a pale brownish-pink or flesh colour. It is very good to eat.

Lovell then describes the “Paignton method of cooking the red-nosed cockle” by frying them in a batter of breadcrumbs after they have been kept in clean water for a few hours to remove sand and other unwanted particles. We’ll come to more recipes later, but first a quote from Philp Henry Gosse, who lived in Torquay and knew the Torbay coast well. In his book A Year at the Shore (1865) Gosse writes [2]:

What is that object that lies on yonder stretch of sand, over which the shallow water ripples, washing the sand around it and presently leaving it to dry? It looks like a stone; but there is a fine scarlet knob on it; which all of a sudden has disappeared. Let us watch the moment of the receding wave, and run out to it.

It is a fine example of the great spinous cockle, for which all these sandy beaches that form the bottom of the great sea-bend of Torbay are celebrated. Indeed the species is scarcely known elsewhere; so that it is often designated in books as the Paignton cockle.. ..The creatures have not changed their habits nor their habitats, for they are still to be seen in the old spots just as they were a century ago: nor have they lost their reputation; they are indeed promoted to the gratification of more refined palates now, for the [Paignton] cottagers, knowing on which side their bread is buttered, collect the sapid cockles for the fashionables of Torquay, and content themselves with the humbler and smaller species.

For those who do not have access to the red-nosed, or spiny, cockles that the “fashionables of Torquay” were able to enjoy, the common cockle (Cardium edule) is still excellent to eat. They can be obtained from cockle “fisheries” in several estuaries, among the best being those from Penclawdd in Wales, where the shellfish are collected using hand rakes, rather than by more aggressive approaches. Cockles are gathered into sieves, washed to clean as much mud as possible from the shells, and then tipped into sacks for easy transport. There is much less occasional foraging than in Victorian times, although John Wright encourages us in his book Edible Seashore [3], in which he describes many edible plants and animals from both the landward and seaward parts of the shore. He recommends that cockles should not be collected during the summer months as this is when they spawn, but they are at their best through September and October.

Wright gives an excellent recipe for cooking cockles with chorizo, although they can be cooked using many of the recipes for clams [3]. Cockles with chorizo is easy to prepare: make sure that the cockles have had a chance to “clean themselves” in sea water overnight and then add them to a pot in which small pieces of chorizo have been sautéed to release their oil, with the addition of a little olive oil and a squeeze of lemon juice. Cover and cook until the shells open, garnish with parsley and then serve like mussels, with crusty bread to mop up the juices. If you are interested, further recipes are given below [4,5].

Should there be an excess of cleaned cockles, they can be prepared by placing them in a hot pan and then teasing the cockles away from their shells and placing them in a jar with just enough malt vinegar to cover. Pickled cockles will keep much longer than fresh cockles and they make a delightful snack at any dinner party (but make sure that they have had a chance to clean themselves of sand and silt…).

Do any readers out there, and especially those from Paignton, want to collect and cook cockles, or are you somehow put off by the thought?

[1] M. S. Lovell (1867) The Edible Mollusks of Great Britain and Ireland with recipes for cooking them. London, Reeve & Co.

[2] Philip Henry Gosse (1865) A Year at the Shore. London, Alexander Strahan.

[3] John Wright (2009) Edible Seashore: River Cottage Handbook No.5. London, Bloomsbury Publishing.

Monday, 30 October 2017

A Naturalist during the First World War

E Ray Lankester (shown above in an image from the Grant Museum of Zoology) wrote regular pieces on Biology and Natural History in the Daily Telegraph and these were collected into three volumes, the third of which is entitled Diversions of a Naturalist, Lankester liking the title Naturalist to describe his interests [1]. The Preface of this third collection was written in June 1915 and begins [2]:

At this time of stress and anxiety we all, however steadfast in giving our service to the great task in which our country is engaged, must, from time to time, seek intervals of release from the torrent of thoughts which is set going by the tremendous fact that we are fighting for our existence. To very many relief comes in splendid self-sacrificing action, in the joyful exercise of youthful strength and vigour for a noble cause. But even these, as well as those who are less fortunate, need intervals of diversion – brief change of thought and mental occupation – after which they may return to their great duties rested and refreshed.

I know that there are many who find a never-failing source of happiness in acquaintance with things belonging to that vast area of Nature which is beyond and apart from human misery, an area unseen and unsuspected by most of us and yet teeming with things of exquisite beauty; an area capable of yielding to man knowledge of inestimable value. Many are apt to think that the value of “Science” is to be measured mainly, if not exclusively, by the actual power which it has conferred on man – mechanical and electrical devices, explosives, life-saving control over disease. They would say of Science, as the ignoble proverb tells us of Honesty, that it is “the best policy.” But Honesty is far more than that, and so is Science. Science has revealed to man his own origin and history, and his place in this world of un-ending marvels and beauty. It has given him a new and unassailable outlook on all things both great and small. Science commends itself to us as does Honesty and as does great Art and all fine thought and deed – not as a policy yielding material profits, but because it satisfies man’s soul.

I offer these chapters to the reader as possible affording to him, as their revision has to me, a welcome escape, when health demands it, from the immense and inexorable obsession of warfare..

When Lankester wrote this Preface, the second Battle of Ypres had already begun - with the first use of poison gas - and even worse was to follow with the Battle of the Somme one year later. As Sargent's emotive painting of casualties of battle reminds us (above, upper [3]), it is doubtful that soldiers who fought in the trenches (above, lower [3]), thought too much about the wonders of the natural world. There is such a contrast between the "joyful exercise of youthful strength and vigour for a noble cause" and the dreadful reality of warfare. Lankester must have written that for patriotic reasons as, in a letter to H. G. Wells dated 29th June 1915 (just after he had written the Preface), he wrote this of his attitude to the War [1]: "[It] is too much for me. It has laid me flat. I am too old for it. I shall never recover."

People of many nations lost relatives in the First World War - sons, grandsons, brothers, husbands - and the ever-present anxiety of those at home needed relief. Lankester’s thoughts in the Preface must have been intended for this audience and many readers would appreciate that there is a wider realm than that just of humans, although human influence dominates everything. Nature can indeed be comforting.

While growing up, I had to cope with both the death of my mother (when I was 13) and father (when I was 21). Their funerals were both held at the local Baptist Church, followed by cremation, but I had already left organised religion and had no wish to attend either the church services or the delivery to the crematorium. Perhaps that was selfish, or a bad idea for me in coming to terms with the loss? It didn’t feel like that at the time as, on both occasions, I went for a walk in the Devonshire countryside before returning to join family and friends who had attended the funerals. There was something about the connection to the continuity of life that was all around me that appealed to my adolescent self and it made the immediate bereavement just a little easier to deal with.

A final point comes with Lankester’s statement that: “Science commends itself to us as does Honesty and as does great Art and all fine thought and deed – not as a policy yielding material profits, but because it satisfies man’s soul.” Too often we regard the natural world as something that we can exploit for human gain yet, with consideration and control, it is vital that we do exploit it. However, we also have a responsibility to maintain the quality of the environment and this would be easier if more of us had a sense of wonder about all that we see around us. I don’t mean that we should just receive information from polished Natural History programmes and documentaries, but have more of the “what’s that?” or “look at that” feeling that walks in nature provide – with no presenter, background music, tricks or high production values – yet an abundance of things to see, smell, hear and, occasionally, taste. And then there’s the additional pleasure of gentle physical exercise in the open air...

[1] Joe Lester (edited by Peter J. Bowler) (1995) E. Ray Lankester and the making of modern British Biology. British Society for the History of Science Monograph 9.

[2] Ray Lankester (1915) Diversions of a Naturalist. London, Methuen & Co.

[3] These illustrations are from the Imperial War Museum Collection