How to make an ecologist #10

Monte_Vulture_Sept88

My occasional series of posts looking back over my career had reached Italy just in time for me to ruminate on the problems that would face Britain were it to leave the single market (see “How to make an ecologist #9”).   I did not get so far, in that post, to talk about why we had dragged so much equipment across Europe in the first place.

The project was a European Community (as it then was)-funded project to look at the vegetation history in the period following the last ice age; the standard way to do this is to collect a long core of sediment from the middle of a lake or bog, then to take samples from different depths along this core and examine the types of pollen grains that are present.  Because sediments are laid down sequentially over time, changes in the composition of the pollen as you move from the bottom to the top of the core provides a record of how the plants that were producing pollen in the area had changed over that time.

This was the period when global climate change was beginning to be recognised as a serious problem.   People had worked out that looking at the insights into vegetation in the past that pollen analysis offered could give many clues about climate at the time.   This, in turn, could be used to check the models that were being developed to predict climate change: in effect, if the models can “hindcast” climates that support vegetation known to exist at points in the past, then maybe we will also be able to “forecast” with greater confidence.  The problem was that most of the people doing this work were in the moist temperate parts of Europe and North America, where there are plenty of lakes and bogs from which to core.   Drier parts of the world, such as the Mediterranean Basin, had fewer lakes, a consequence of which was that there were fewer scientists with an interest in these techniques.   This also meant that there were fewer historical benchmarks in this region against which climate models could be tested, and our project set out to fill this gap.

One feature of peninsula Italy is that there are a number of lakes associated with the cones of extinct volcanoes, and this was had already raised the prospect of opportunities to collect cores that would help us understand how vegetation and climate had changed in this reagion.   We travelled first to Monte Vulture (photographed above), in the Basilicata region around the “ankle” of Italy, to collect cores from Lago Grande di Monticchio, one of the two lakes inside the crater of the volcano.   I included a photograph of us coring in the marsh area beside the lake in my previous post on this subject; the 33 m long core that we collected was passed on to Bill Watts at Trinity College Dublin to continue a study of the lake that started a few years earlier.   Subsequent visits by the Durham team and collaborators (after I had moved on) extended this glimpse into the past back to over 100,000 years ago.

The second location that we visited was a small crater lake, Lago di Martignano, just to the north of Rome.  We collected this with help from geologists from Edinburgh University who had a “Mackereth” corer.   This is a contraption that uses compressed air pumped from a boat to first push the corer into the soft sediments and then to slowly extract the core and bring it to the surface. The final stage, when the core is free from the sediment and filled with compressed air, results in a dramatic emergence of the core, cables, floats and other paraphernalia, which leap into the air above the lake surface before crashing back down.   Needless to say, capturing the event on camera is not easy, but everyone tries …

Martignano_Mackereth_corer

Using a Mackerth-type corer in Lago di Martignano, Lazio, Italy, September 1988.  The left hand picture shows the buoy marking the spot where the corer has been lowered, and the cables through which compressed air is pumped; the right hand image shows the corer breaking the surface of the lake once the core has been collected.

That core, from Lago di Martignano, was the one that I worked on for the next year, extracting the pollen with a cocktail of strong chemicals.  Our house was burgled during this time and the scene of crime investigator who was investigating to my fingerprints in order to eliminate these from his investigations.  He tried several times before telling me to take up a life of crime as I had no fingerprints and was, therefore, undetectable.  I attributed this to conditions in the rather basic laboratory that we were using at the time to prepare our samples.

Very roughly, the balance between pollen from trees associated with temperate climates, such as deciduous oak and beech, and pollen from the shrubs typical of the hot dry Mediterranean climate (see pictures below) allowed some insights into the climate that prevailed at the time that the sediment was laid down.   In the upper levels of the core, however, we also had to account for the effects of humans, removing trees and planting cereals and, in the process, upsetting the pure climate-driven signal that we were looking for. Unravelling this mix of influences made for an intriguing challenge, and also led to my first serious forays into statistical analyses, performed, in those days, on slow mainframe computers.

Maquis_vegetation_Italy88

Characteristic “maquis” plants, photographed during fieldwork in Italy during 1988.  Top left: Erica arborea (tree heather); top right: Pistachia lentiscus (pistachio); bottom left: Rosmarinus officinalis (rosemary); bottom right: Paliurus spina-christi (Jerusalem thorn / crown of thorns).

The method only worked, however, if we could “calibrate” our historical records against modern situations where the climate was already known.  The quest for pollen samples from a wide range of climates spilled over into holidays, with a memorable sampling trip during a trip to Jordan in 1989.   We drove into the Syrian desert on a dull, overcast day in search of Azraq Oasis, as sediment from the ponds here would have given us an insight into the pollen we might expect in semi-desert conditions.   There were more than just scientific reasons for wanting to make this trip: there is a 13th century castle at Azraq, built on the site of an earlier Roman fort.  We live close to Hadrian’s Wall and here, at Azraq, we were 4000 kilometres away at the opposite corner of the Roman Empire.  The castle is still largely intact and was, in fact, the headquarters for T.E. Lawrence’s operations against the Ottomans during the First World War, and little had changed since he wrote Seven Pillars of Wisdom.   I seem to recall that another Lawrence – D.H. this time – was cited in an early draft of the paper that arose from this study.   His travel memoir Etruscan Places had some references to the densely-forested landscape that had inhibited Roman soldiers in their forays against the Etrurians.  I thought that this corroborated our results; however, it had disappeared from the manuscript before it was submitted, probably for the best.   By that stage I was in Nigeria and too far away to fight my corner.  But that is jumping ahead …

Qasr_Azraq_Apr89

Qasr Azraq in the Syrian Desert in Jordan, photographed during our visit in spring 1989; the right hand image shows the Bedu custodian demonstrating the stone doors.

Reference

Kelly M.G. & Huntley B. (1991).   An 11,000-year record of vegetation and environment from Lago di Martignano, Latium, Italy.   Journal of Quaternary Science 6: 209-224.

 

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How to make an ecologist #9

fieldwork_in_Italy_1988

One of the minor pleasures of this year has been digging out old 35 mm slides, scanning them into a digital form and then using these to trigger memories of the twists and turns in my professional life (see “How to make an ecologist #8“).   I have not done this for some time, largely because other topics have seemed to be a higher priority to write about.   None more so in recent weeks than the forthcoming referendum on the UK’s membership of the European Union.   A serendipitous moment, however, led me to two boxes of slides documenting two periods of fieldwork in Italy in 1988 and, through these, to remember how difficult travelling around Europe used to be before the advent on the single market.

I visited Italy twice in 1988, as a postdoc on a project looking at Holocene vegetation history.  On both occasions we drove from northern England in a four wheel drive vehicle loaded with equipment.   I have two strong memories of those journeys: the distances we covered (Calais to northern Italy in a single day) and the hassle at every national border we crossed.   In those pre-open market, pre-Schengen agreement days we not only had to show passports at each frontier, we also had to queue up with the lorries and other commercial vehicles and go through a full customs check.   This had also entailed travelling to the Chamber of Commerce in Leeds shortly before we left to get a “Carnet de Passage en Douane”.   This was a document that allowed us to temporarily import our equipment for the duration of the project without the need to pay any customs or taxes at the border.   It entailed leaving a bond in the UK, which was returned if our Carnet de Passage was signed and stamped at every border to show that we had brought out the same as we had taken in a few days previously.  My memory is that the customs checks were not especially thorough; indeed, the officials rarely looked inside our vehicles.  But we did have to sit in the long queues awaiting our turn in order to get our carnet de passage signed.

sampling_in_Italy_1988

Fieldwork in Italy during 1988: sampling surface sediments from a lake somewhere in the Appenines with Brian Huntley during our spring visit (left) and using a Livingstone corer to collect a sediment core in the fens beside Lago di Monticchio in southern Italy in September 1988.

Almost thirty years later, I take for granted that I can travel around Europe for pleasure or business with almost no constraints.   In my own small way, I run a business that depends, to some extent, on “exports” to the European Union.   I had forgotten, until I dug out these memories, just what that entailed.  The irony is that establishing a tighter control on our borders will, almost inevitably, make crossing those same borders slower and will generate extra paperwork, particularly for those of us who travel on business.  Of course, once we are in Europe, the open borders will mean that our progress across the continent will not be impaired.   And the stated aspiration of the “leave” campaigners is that there will be a free trade agreement between UK and the EU which will mean that we can continue to do business.

Like much of the rhetoric that surrounds the EU referendum, the reality is less certain than the protagonists suggest.  My own view is that leaving would be foolish but, if that is the outcome of the referendum, then a free trade agreement probably will be achieved, possibly on the lines of that currently enjoyed between Norway and the EU.   Brexiters such as Johnson, Farage and Duncan Smith talk glibly of this as if a deal strongly weighted in the UK’s favour was no more than a formality.   This is naïve: my own belief is that a free trade agreement will be contingent on the UK maintaining the “level playing field” for business which, in turn, will mean staying signed up to, amongst other things, key employment and environmental legislation.   It will also mean paying some money to Brussels to support the implementation of those aspects of EU law, and any other parts of the EU’s activities that are deemed beneficial (access to research funding, perhaps?).   That is something that the Brexiters have been rather quiet about over the past weeks.

Of course, I regard the prospect of the UK staying signed up to EU environmental legislation, in particular, as a small crumb of comfort in these worrying times.  That is partly down to self-interest, as helping with the implementation of EU legislation is a major part of my business.  But it is not just self-interest.  As I have written before (see “What has the EU ever done for us?”), I do genuinely believe that we get stronger environmental protection by being part of the EU than we would if we depended solely on Westminster and Whitehall.

I don’t expect that I will need a Carnet de Passage any time soon.  But remembering how things were, in the days before the European Economic Community morphed into the European Union and promoted genuinely free trade, is enough to remind of just how much we stand to lose after next week’s referendum.

Pinus_pinea_Italy88

A clump of umbrella pine, Pinus pinea, on a hillside, photographed during fieldwork in 1988.

Hindsight on the foreshore …

Angera_Feb16

Don’t be fooled by this photograph looking across Lago di Maggiore from the village of Angera, where I was staying during a visit to the European Commission’s Joint Research Centre at Ispra, a few kilometres away.   There had been two days of almost constant rain and temperatures little different to those in the UK and the sun came out just before we were due to head to the airport for the homeward journey.   Before the taxi came, however, I found time for a short walk along the lake front, during which time a silty foreshore littered with empty shells caught my eye.   The shells looked like cockle shells, common around our own coast yet this was a freshwater lake.   I scrambled down for a closer look.

The shells belonged to a bivalve mollusc and were an ochre colour, with darker markings and a series of concentric ridges.   I’m not an expert on molluscs but, after a little searching on the web, I think that they probably belong to the Asian clam (Corbicula fluminea), one of a number of alien mollusc species that has become established in Lago di Maggiore in recent years.   The shape of the cell, and the markings rule out the zebra and quagga mussels (Dreissena polymorpha, D. bugensis) whilst another recent invader, the Chinese pond mussel (Sinanodonta woodiana) is much larger (up to 30 cm).

Angera_foreshore_with_asiat

The foreshore at Angera littered with shells and (right) a close-up of the two halves of an Asian Clam shell.   Each is about 2 centimetres long.   February 2016.

There is an irony here, as I have written several blogs about an endangered freshwater bivalve (the pearl mussel – Margaritifera margaritifera, see “’Signal’ or ‘noise’?”) yet this group also contains some of the most notorious invasive species in the world. All originate from Asia but are now widespread in Europe and North and South America, where they cause a large amount of economic damage.

Like all bivalves, Asian clams are filter-feeders. They open their shells slightly and extend two tubes (“siphons”) from their bodies. Water is drawn in through one of these, across the gills, where particulate material is trapped, and out through the other. Fine cilia waft the particulates towards the clam’s mouth.   In a lake such as Maggiore, much of the particulate matter will be suspended algae (“phytoplankton”) and prolific growths of these invasive bivalves can actually reduce the quantities of phytoplankton to such an extent that they have been proposed as solutions to eutrophication problems under some circumstances. Because the phytoplankton, in turn, contains a lot of the phosphorus in the water, this has been referred to as “biological oligotrophication”. The benefits are partly a matter of perception: the bivalves have not removed the nutrients and algae, they have merely relocated them to another part of the lake.   That might bring short-term benefits, but it is not a solution per se.

Unlike zebra mussels, however, Asian clams have an alternate mode of feeding: they extent a muscly foot to pull themselves into the sediments which, in the process, throws up fine particles that can be sucked through the siphons. This “pedal feeding” could play an important role in the functioning of lakes due to the disturbance it causes, allowing oxygen to penetrate the surface layers of the sediment. As phosphorus compounds are generally less soluble in the presence of oxygen than they are in anaerobic conditions, this can further reduce the effects of eutrophication by “locking” the phosphorus into the sediments. The oxygen also fuels microbial processes, including the breakdown of nitrogen compounds limiting the production of nitrous oxide, a potent greenhouse gas in the process. Yet, ironically, the distribution of Corbicula is strongly influenced by temperature and global warming is likely to increase its range.

Local scientists have concluded that eradication of Corbicula and other alien molluscs from Lago di Maggiore is probably impossible as any attempt to remove them will probably disrupt other littoral organisms too. Yet, at the same time, the role that Corbicula plays in the food chain is not clear and it is possible that the spread of this and other bivalves will have knock-on effects for local fisheries. The first record of C. fluminea in Lago di Maggiore was made in 2010. That means that the lake I looked across this week might look like the lake I looked across on my first visit about 10 years ago, but it is nonetheless a different lake under the surface. It’s not the same lake but, as Heroclitus also reminds us (see “What Constable never saw …”), I’m not the same man either.

References

Kamburska, L., Lauceri, R. & Riccardi, N. (2013a). Establishment of a new alien species in Lake Maggiore (Northern Italy): Anodonta (Sinanodonta) woodiana (Lea, 1834) (Bivalvia: Unionidae). Aquatic Invasions 8: 111–116.

Kamburska, L., Lauceri, R., Beltrami, M., Boggero, A., Cardeccia, A., Guarneri, I.Manca, M. & Riccardi, N. (2013b). Establishment of Corbicula fluminea (O.F. Müller, 1774) in Lake Maggiore: a spatial approach to trace the invasion dynamics. BioInvasions Records 2: 105–117.

McDowell, W.G., Benson, A.J. & Byers, J.E. (2014). Climate controls the distribution of a widespread invasive species: implications for future range expansion. Freshwater Biology 59: 847-857.

Vaughn, C.C. & Hakenkamp, C.C. (2001). The functional role of burrowing bivalves in freshwater ecosystems. Freshwater Biology 46: 1431-1446.

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

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

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.

lago_di_rosso

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.

References

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.

An impromptu sampling trip at Lago di Maggiore …

Image

Sampling diatoms from Lago di Maggiore.  Nigel Willby (left) and Sebastian Birk and, in the foreground, the sample collected in a plastic cup with a disposable toothbrush.

One of the inevitable quirks of the high-level overview of Europe’s ecology that intercalibration provided was that we spent most of our time staring at spreadsheets and relatively little time out in the field. The irony struck me as Lago di Maggiore came into view on the drive from the airport to JRC’s campus at Ispra: I’ve been here several times, always to discuss intercalibration, but I’ve never actually taken a sample from this huge lake right on JRC’s doorstep.

There was, however, a problem to overcome: I had travelled light so had nothing with which to collect or store a sample. Last night I had been given an emergency pack of toiletries by KLM, which included a toothbrush, but I had blithely discarded this. I did wonder if my own toothbrush could be pressed into service but there, waiting in my otherwise basically-equipped room at the Europa Hotel, was a toothbrush. What better sign did I need that this sampling trip was Meant To Happen?

In the gap between the end of the meeting and dinner, I pressed two colleagues who had the forethought to bring swimming trunks into service to collect stones from the littoral zone just in front of the hotel. Each had a thin slimy layer on the surface (the stones, not Nigel and Sebastian). I brushed this into a plastic cup, again filched from the hotel room, then left this on a shelf in the bathroom whilst we went to dinner so that the algae would settle at the bottom. When I got back, I poured off most of the overlying water and decanted the brown sludge at the bottom into a shampoo bottle which I had rinsed out thoroughly. A shot of grappa could have been pressed into service as a temporary preservative, but I did not think of that until it was too late.

The only obstacle that remains is airport security. I’ll have to hope that no-one questions this strange brown “shampoo” in my luggage and that, if forced to admit it is diatoms, the security staff don’t recall that fossil diatoms are a constituent of the soft, sedimentary rock “kieselguhr”, and, more particularly, that no-one ever told them that kieselguhr is one ingredient of TNT.