Hard cheese …

A day or so after my return from my trip to Orleans, The Guardian published an article on deadly algae on Brittany’s beaches.   The alga in question is Ulva, which I have written about a few times in the past.  It is a genus that is often associated with elevated concentrations of nutrients (see “Venice’s green fringe” and “News from Qingdao …”).  In Qingdao, the accumulations of algae caused problems during the 2008 Olympic sailing events but, in Brittany, there have actually been deaths associated with these growths.   Although green algae do not produce toxins themselves, the mats are so thick that the algae at the bottom cannot get the light and oxygen they need and so die and rot.   However, the thickness of the mats also means that the bacteria involved in breaking down dead plant matter are also starved of oxygen and, under such conditions, they can use sulphate as an energy source.  This, however, produces the toxic gas hydrogen sulphide which accumulates until released by, in this case, people stepping on the mats.

The problem in Brittany is concentrated on the north coast, close to where the Seine empties into the English Channel, rather than the south coast, where the Loire joins the Bay of Biscay.  Seine or Loire, the problem is similar: France has a large and vociferous farming lobby and inorganic nutrients, much deriving from agriculture, spill out of the rivers into the sea where they encourage the growth of algae.  It is not just green algae: there are also toxin-producing dinoflagellate blooms which can render shellfish dangerous for human consumption.  The combination of seashores piled high with rotting algae and restaurants unable to source local produce for their “fruits de la mer” is a major worry in a region where tourism makes a significant contribution to the economy.   It is also the classic environmental challenge, as economically-rational activities have malign consequences 100 km or more away, creating major headaches for policy-makers.

There is, however, good evidence from modelling studies that a reduction in the nitrogen in rivers that empty into the coast around Brittany will have positive effects.  One of these went so far as to envisage the adoption of organic farming in all agricultural areas of the Seine basin, leading to a halving of nitrogen load and a likely very significant reduction in the frequency of dinoflagellate blooms.   Another study indicated a likelihood of much less Ulva if river nitrate concentrations were much reduced.

That’s the theory. Putting such reductions into practice is a different matter because it means taking on the farming lobby.  There is a simple logic, in a farmer’s eyes, to raising output by adding more of the nutrient that limits growth.  The flaw in the argument is that nitrate is highly soluble and a proportion of the nutrient that a farmer spreads on his fields will be washed into nearby water courses when it rains.   No farmer wants to pay for fertilizer that is not nourishing his plants so there ought to be a solution that is agreeable to both them and the environment.   In reality, implementing policies that protect one sector (seafood harvesting, in this case), whilst not undermining another (agriculture), all within a framework in which market forces drive much of the decision-making is a fiendish challenge.

I think that this is one of the reasons why right-leaning politicians are rarely enthusiastic about the environment: simply leaving market forces to decide outcomes means that “externalities” – consequences of a commercial activity that are not reflected in the price – will be ignored.   Environmental regulation implies a need for interventions to control activities in order to protect wider interests, but that is an anathema to free market purists.  Regulation should, in theory, limit the “externalities” and create an environment in which sectors such as agriculture, seafood harvesting and tourism can co-exist.  Again that’s the theory but regulating the environment invariably results in labyrinthine bureaucracies that soak up money from taxes which free market purists would prefer not to have levied in the first place.

That’s why I really would encourage you to read Kate Raworth’s Doughnut Economics (see “The limits of science …”).  Every environmental scientist needs to reflect on how the changes they want to see need structural alterations that permeate throughout society, and not just technological fixes.  And, yes, those changes might affect our own lifestyle too. If French farmers use less fertiliser then they will produce less milk per hectare.  That, in turn, will result in less of the wonderful French cheeses that we all love and, probably, higher prices.  So, in the final analysis, it is not just the use of nitrate fertiliser that will have to change, it is our own aspiration.  Before we can make a difference we will have to live differently ourselves.  That’s the tough challenge we all have to face.


Passy, P., Le Gendre, R., Garnier, J., Cugier, P., Callens, J., Paris, F., … Romero, E. (2016). Eutrophication modelling chain for improved management strategies to prevent algal blooms in the Bay of Seine. Marine Ecology Progress Series 543: 107-125.  https://doi.org/10.3354/meps11533

Perrot, T., Rossi, N., Ménesguen, A., & Dumas, F. (2014). Modelling green macroalgal blooms on the coasts of Brittany, France to enhance water quality management. Journal of Marine Systems 132: 38-53. https://doi.org/10.1016/j.jmarsys.2013.12.010



The curious case of the red lake that isn’t …

From Venice, I crossed to the mainland to meet a colleague before driving two hours inland, first west across the flat lands of Veneto province, then into the increasingly mountainous terrain of Trentino and finally to the dramatic landscapes of the Dolomites. The last four or five kilometres were on a gravel track that brought us, eventually, to Lago di Toval, set in a beautiful location, 1178 metres above sea level, amidst wooded slopes, with rocky alpine peaks visible all around us.


Lago di Toval, Trentino Province, Italy, September 2014

We were here for a paper-writing workshop at a small limnological research station beside the lake, eating and sleeping at a small albergo a few hundred metres away.   Confusingly, for a hotel situated beside a perfectly blue lake, its name was “Albergo Lago Rosso” but there was a story behind this name as my Italian colleague, Marco Cantonati, later explained.

The name of the albergo becomes clear when you see photographs of the lake taken in the 1950s and early 1960s when the water in some parts was a bright red colour due to growths of a an alga called (at the time) Glenodinium sanguineum.   The species epithet comes from the Latin sanguis, meaning blood, an allusion to the red colour of the cells which lends the lake its distinctive colour.   This alga belongs to a group called the “dinoflagellates”, which we have not previously encountered on this blog. The red colour comes from the same pigment that we encountered in Haematococcus (see “An encounter with a green alga that is red”).


Albergo Lago Rosso, overlooking Lago di Toval, September 2014

For a long time, this alga was thought to exist in two forms, one of which was red, the other green.   However, the latest evidence suggests that there are at least three different forms, sufficiently different from one another to be assigned to separate genera. Two of these are only ever green whilst the third gives the lake its distinctive red colour.   This latter form was placed in new genus named after the lake where it was found, Tovellia.

Whilst the lake was famous for the distinctive red colouration that Tovellia sanguinea gave to it during late summer, this phenomenon has not been observed since 1964.   The other dinoflagellate species are still abundant, but T. sanguinea is now very rare.


A postcard of Lago di Toval probably dating from the 1950s or early 1960s, showing the red coloration.

There is no definitive explanation for this change in lake colour but it is thought that changes in land use and, in particular, the way cattle were housed in the catchment, may have reduced the already small quantities of phosphorus entering the lake and tipped the scales in favour of the two green dinoflagellates rather than T. sanguinea.   There are other hypotheses and, as ever, it is difficult to untangle causation and correlation from the available evidence.   There is, however, also evidence that T. sanguinea was also rare before the 1860s, which does lend weight to the suggestion that the reddening of the lake was a response to human factors.   If this is the case, then Lago di Toval represents a relatively rare case of a lake that is returning to a more natural state.   That, of course, poses another fraught question: what exactly do we mean by “natural”? But that is a topic for another day.


Borghi, B., Borsato, A., Cantonati, M., Corradini, F. & Flaim, G. (2006). Il fenomeno del mancato arrossamento del Lago di Tovel alla luce dei risultati emersi dal Progetto SALTO. Studi trentini di scienze naturali – Acta biologica 81 Supplement 2: 471-472.

Cavalca, L., Ferrari, P. & Andreoni, V. (2001). Glenodinium sanguineum March. and the reddening phenomenon of Lake Tovel: biological and environmental aspects. Annals of Microbiology 51: 159-177.

Flaim, G., Moestrup, Ø, Hansen, G. & d’andrea, M. (2006).   Da Glenodinium a Tovellia.   Studi trentini di scienze naturali – Acta biologica 81 Supplement 2: 447-457.

Hansen, G., Daugbjerg, N., Flaim, G. & D’andrea, M. (2006). Studies on woloszynskioid dinoflagellates II: On Tovellia sanguinea sp. nov., the dinoflagellate responsible for the reddening of Lake Tovel, N. Italy. European Journal of Phycology 41: 47-65.