Wednesday, 30 April 2014

A short excursion to the pools of Avalon

High on the Northumberland coast, as the long shores of Druridge, Embleton and Beadnall turn into towards the Scottish border, lies Holy Island. Always an extraordinary place, whether the idling in a glittering June seascape or hunkered down against winter which reaches across from Scandinavia. Holy island may be an inspiration for Authurian Avalon. The Borders have a long claim on many elements of the Arthurian legend. Our trip was less romantic, though only slightly so as the sea fret plumes rolled in over the salt marsh and swallows strafed low for sluggish insects. Right by where the causeway road to the island dips from the mainland down to the tidal stretches there are a scatter of perfect salt marsh pans, usually in clusters just in front of the second world war anti-tank blocks. The pools are ideal for students to try out the ups and downs of sampling in the field: why do oxygen probes never seem to work coherently? Yes... you need to take the plastic cover of the pH probe before it will take a reading. We were testing for spatial patterns: for example are neighbouring pools more similar in their animal life than pools further and  were there salinity gradients as you go from the salt flats up into the pools amongst toppled tank traps.
The students pulled together some revealing data. Here they are piloting where exactly to take pH measures and whether the position of the samples in and around the pools alters the outcome. All of the pools showed marked brackish conditions, though declining slightly higher up the marsh amongst  the tank block pools. The fauna of adjacent pools was markedly more similar than further apart sites. Pond area seemed to bear no relation to overall numbers of taxa. Shrimps, mosquitoes, isopods slaters and gammarid shrimps were abundant, with beetles, copepods and fly larvae as bit part players. Towards midday the sun burnt away the thicker fret, although Holy island itself came and went as if anchored on the tide. High tide itself chased a few excited walkers back along the road to the safety of the mainland, just in time for an ice cream van to materialise through the last of the mist. A perfect day out on the marshes, between the incoming tide and an arc of skylarks singing over our heads throughout

Friday, 25 April 2014

The carbon dioxide devil is the small scale detail

 Science is good at generalising, sometimes even when it shouldn't. One of the twentieth century's great ecological insights, the ecosystem as a formal idea, is essentially a means of generalising habitats into a series of flows and reservoirs of gases, energy or nutrients. You can scale this up to a whole planet. Scaling down might be trickier. Pete is experimenting with scaling down, measuring carbon dioxide and methane exchange rates in different ponds. Here he is at Hauxley using the gas analyser (the yellow box) linked to a plastic chamber floating on one of the experimental ponds and allowing small scale measures as the gases exchange between the water under the box and air trapped inside. In this case carbon dioxide was bring dissolved down into the water. At the same time the pH in the pond was high, ~9.0 which is markedly more than you'd expect for a natural, clean pond in north east England. Except that this pond was being blasted by mid afternoon sunshine and, being full of plants, it is likely that photosynthesis was elevating the pH as the plants strip out HCO3 ions toget at the CO2 but in the process release  OH- ions into the water raising the pH. Here is the gas chamber with the pH probe just to the top left

Pete also tried the measures in the pond next door. This time the pond appeared to be a net releaser of  CO2 gas. Generalising for these two, adjacent ponds would be tricky. The variability of animals and plants between near by ponds is well established, one of the reasons they are such biodiveristy hot spots at the landscpae scale. It is beginning to look like they are just as variable in the way their gas fluxes work. the fine scale detail matters, whether it is counting up numbers of ponds, the variation of animal and plant communities between sites or the geochemistry.

Monday, 14 April 2014

From a small pond to the heavens

Whilst Pete and Scott have been trying out the elemental analyser in the lab the spring sunshine lures me back out into the field. Here is a perfect example of how field work stretches the imagination and challenges what is possible. The little ponds at Hauxley were dug out in 1994 to start off experiments tracking the changes to their wildlife over the years. I had not planned that the monitoring would last twenty years but it has. Better still the documented history of the ponds has been a boon for the new work exploring carbon capture: we are able to check the past hydrology and plant data from each pond to explore how those changes might influence carbon levels in the sediments. Neat. Meanwhile, overhead the last of the winter geese gather, stacking up in squadrons, circle to let stragglers catch up with the security and economy of the flying Vs. They will be off soon, a little piece of the Druridge Bay ecosystem unplugging itself and migrating to new lands. They will be carrying energy, microbes, maybe even the occasional plant seed or insect egg with them. Part of the Hauxley experiment will have gone away, not that the geese use the pond field much; it is the haunt of crows and teenage heron. If all the geese did choose to land in the pond field and bathe, graze and poo in the ponds the habitats would be much impacted. The experiment would have been changed, but perhaps in more intersting ways. The pond experiment is therefore not so neat. I cannot radio-control skeins of geese to migrate where I want them to, land them in a field of my choosing or slough off old feathers, seeds and eggs under my control. Field work has that unpredictable thread running through it, part of the appeal for me. Along with the wheeling geese and strengthening sun.

Wednesday, 9 April 2014

Lab coat? check. Goggles? Check. Elemental Analyser? Check

The public image of science often plays to the idea of men in white coats. It can be women, but the cliché is generally male.  Labs are intimidating places. For our first year undergraduates one of my aims is to get them to enjoy being in labs, relax a little, not be intimidated by the hardware most of which I do not know how to use either. It is a tricky balance in the day to day struggle to detach 18-21 year olds from their mobile phones, which should be safely put away in lockers. Perhaps there is a specific psychology around labs versus field work. Put me in a swamp with mosquitoes, dragonflies and toads and I’m happy. The unpredictability of fieldwork (nudists, motorbike gangs, stoats trying to help....) is the charm. Field experiments and surveys are inherently prone to interesting (mis)fortune. The interplay between the predictable, systematic processes and the unexpected strikes me as an irresistible core to the natural world. Conversely I know scientists who find the uncertainty of nature troublesome but they are superb sleuths for the precision and detail that a lab allows. It is easy to paint this as a difference between whacky explorers versus OCD geeks but that is a daft conceit. Both outlooks represent a fascination with deep and troublesome problems, often working best when brought together.

Pete and Scott spend a great deal of time out in the field at Druridge Bay, slogging through the mud, digging out sediment  cold and battered by the wind, but are equally good in the lab. Here they are getting to grips with the new elemental analyser. This will allow them to measures organic carbon in their cores and wetlands much more exactly.  “Elemental analyser” is also hard to say. Try it out loud. Perhaps this is my lab-angst showing itself. I watched for a little while but was generally superfluous to the training. Scott and Pete have been working with undergraduate project students Paul White and Chris Maguire who are measuring sediment carbon from new sites along the Bay but also some restored peri-urban landscapes in Gateshead where wetlands have been engineered into old industrial sites. Two years ago those same undergrads might have been just as uncertain in the labs as our current first years, but, given the opportunity to get involved, flourish.

Thursday, 3 April 2014

The pond gas detective: tupperware and hi-tech

The new field season is underway at Druridge Bay. Pete has been experimenting with measurements of carbon dioxide and methane fluxing in and out of the wetlands. This needs a delicate mix of high-tech gas analysing kit cunningly attached to an upside down plastic sandwich box wrapped round with an old bicycle tyre inner-tube as a flotation device. Here is Pete gently positioning the floating box over the grassy shallows of a pond in a grazing meadow. The red and blue tubes allow gasses to be pumped through the analyser sitting snuggly in its black case perched on a plastic box (it does not like water), which records the changing concentrations. Pete's design uses a small floating chamber so that we can position the box over the distinct plant communities such as amphibious grasses or submerged pondweed in the ponds. There is something very immediate about watching the measures tick up on the digital displays. Suddenly the invisible chemistry is brought to life, the molecules in the air made apparent, complementing the seeping cold and the calls of the last winter geese, who did not approve of all this fiddling about in their field. The technology is, as usual, temperamental and easy to de-calibrate with one push of the wrong button but also very impressive when it switches from prima donna to primary data collection. Pete's first try outs showed steady carbon dioxide release with methane too, although at much lower concentrations. As Spring builds and the plant growth surges he will be aiming to capture gas fluxes from different pond types and plant communities. Early results show some pond types pumping out carbon dioxide whilst others are much less active. As with their plant and animal communities it seems that ponds represent a fine-grained diversity of geochemical drivers. If we can combine the flux measures for different pond types with data on the organic carbon trapped in the sediments we should be able to identify the wetlands that make the most powerful carbon sinks, perhaps even the role of different plant communities in these processes. Just so long as the wrong button does not get pressed.....