No vultures at Druridge Bay, but a trip to Martian Spain finds some familiar plants.

Pete, Scott and I have had the great good fortune of a trip to Huesca, in northern Spain, for the 6^th European Pond Conference Network meeting. Huesca retains its romano-medieval feel, as if the heat has kept it from expanding beyond the old city walls into the deserts to the south or Pyrenees foothills to the north. Take the desert road south and you come to the county of Monegros, which looks ideal as a film set for Star war’s Tatooine, but instead is known for its spaghetti westerns. The roadside services even affect a wild-west feel with wood balustrades and canopied terraces from which to keep an eye of strangers riding into town. There are at least 140 saline wetlands, called “salades”, pock marking the terrain, largely the result of solution of the limestone and gypsum topography, with the wind also blowing out the hollows. The aquifers are saline too, the hydrology and topography creating a remarkable scatter of salt wetlands deep inland, many of them part of a Natura 2000 designation. They have characteristic vegetation, salt loving xerohalophytes (dry and salt loving), including Atriplex species higher on the edges around the dissolved out drepessions, then distinct zones down to Salicornia patula as the final outpost before the salt crust. The Atriplex are the shrubs in the photo foreground above, the Salicornia the bright green clumps before the open expanse of the salades floor. If you walk down below the line of bluffs around the salades the further horizons cannot be seen and it is easy to this could be Mars with a little bit of gentle terra forming. The fine sediment crusts of the hollows are loaded with the eggs of specialist crustacean such as fairy shrimps, waiting for the rains, and vivid red darter dragonflies perch like sundials on the crackling vegetation. Superficially all very different from the verdant greens of north-east England’s coastline, with its sea frets and northern winds. However Atriplex and Salicornia are familiar species along our coast. Different species, yes, but the same zonation with Salicornia the outer pioneer on salt marshes at Holy Island and Alnmouth, whilst Atriplex species are all along the coast and in the fields at Druridge. However, in Northumberland, no vultures drifting casually overhead though, keeping half an eye on the unwary salades tourists, in we became mired in the cracking salt crust.

The creeping up on red darter dragonflies time of year

 

Red Common Darter dragonflies, Sympetrum striolatum,  may not have the glamour of their bigger brethren such as piratical Emperor Dragonfly or gaudy Southern Hawkers but there is an everyday charm and confiding jauntiness to them that conjures up August (...with an ominous hint of approaching autumn too). They are fond of basking on wooden fences and tables in the sunshine and they soon circle back to their perches if you disturb them. Creep up carefully and you can get very close. Often they waggle their heads, sometimes holding an inquisitive sideways look at you as they try to work out what you are. Their huge eyes, made up of lots of separate single facets called ommaditia, are very good for detecting movement as the shadow you cast crosses from each facet to the next. If they are not in the mood for being crept up on they will depart but they seem to appreciate the warm days of high summer as much as we do and mostly can’t be bothered. Their larvae are rather squat, sprawling critters, again lacking the submarine menace of the larger species. Instead they clamber amongst the debris and submerged plants in ponds.  There are several very similar species of red darters, including migratory rarities such as the Red-Veined Darter, but this far north most of them are the Common red. this one has the typical large yellow splashes on the side of the thorax which are a good ID tip. Black Darters turn up along the Bay sometimes too: they are small and fidgety compared to their red cousins. Darter Dragonflies will last long into the autumn if the days stay warm, but right now are busy enjoying the sunshine, whipping in tight, dog-fighting circles as males vie for supremacy or hovering briefly on the look-out for a mate. Autumn can wait.

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"The small gilded fly doth lecher in my sight" (King Lear, nature lover)

Nature is famously good for us, with talk of “green gyms” (marketing speke for a walk in the countryside) and mental health.  The verdant green of a spring time woodland or flower strewn verge are a delight. I am less sure about the darkened woods of late summer as the leaves strip out all light or the wilder moors: Wuthering Heights, The Hound of the Baskervilles and Lorna Doon are not set high on the moors by accident. Nonetheless Druridge Bay has that overwhelming calm of sea and sky that King Lear could have done with instead of contemplating flies out in the storm. I have always assumed the “small gilded fly” he observed were Long-legged Flies, Dolichopodidae, perky, iridescent inhabitants of damp vegetation and exposed mud. They do a lot of letchering in sight (green bottles do not, so I’m ruling them out). The sun has brought out the more conspicuous Dolichopodiae in skipping, fizzing mobs. Most are very tricky to identify but one is not, Poecilobothrus nobilitatus, on account of the white wing tips of the males. These frantic suitors whirr and fan their wings to females, then hop and skip back and forth over the object of their amorous attention. However since they all tend to crowd together in the drying puddles and rims of the ponds the mob is a constant agitation of distracted flirting and collisions. As each fly shifts and twitches new neighbours jump into view so within seconds they seem to have lost sight of their intended.  They are also easily distracted trying to yank midge larvae out of the mud which they chew up with macerating mouth parts.  If you approach to abruptly the whole mess of flies scatters but lie down to watch and they will soon return to their choice patch of mud for another round of dancing.  They are flies of high summer’s hot days as the ponds dry down to squirming mud and a delight to watch.

The burnet moths cyber noir day out

The July warmth has unleashed a very special day along the dunes around the Druridge Bay Country Park; the burnet moths have hatched. They are not rare nor unfamiliar, but well worth the time to creep up and admire. The newly emerged are shimmering black winged, whilst their bodies are the deepest sable fur. Vivid red spots blotch their wings, five or six spots per forewing depending on the species. Antennae stand proud, a filigree segmented hook of which the finest blacksmith would be proud. They seem slightly out of place on the dunes, dressed for Frank Millar's Sin City. Seen against the yellow of Birds Foot Trefoil or gaudy purple-pink of the Bloody Cranesbill, the burnet moths add to a remarkably colourful dune-scape. Maybe the Burnets are more fin de siècle Gustav Klimt that contemporary cyber noir. The males whirr, slightly clumsily, low through the marram stems or cluster on thistles. They can detect a female in her cocoon even before she emerges and the males wait around to mate even as she hauls herself out. Here are a pair with the females white cocoon as their foot hold. They shimmer in the sun. The high summer butterflies are also out in force. Common Blues fizz  past, the more tentative Small Heaths flitter away from out under your feet and Ringlets bob low amongst the stems as if on the end of invisible strings. Walk the dune path south of Druridge Bay Country Park and you will find these beautiful insects in abundance. The burnets do not last long, their extraordinary looks maybe burn out too soon, befitting their vanity, which deserves your attention.

The Hauxley time machine pond comparison website

The experimental ponds at Hauxley were dug in the autumn of 1994, to monitor the development of the animal communities from the very origins of the habitats. I had imagined this might go on for a few years but not twenty, but the value of the ponds as a study site increases with every passing year. The photo shows one of the original ponds at the front and, just behind, one of the new pools dug out by postgraduate Scott to explore the links between productivity, water chemistry and carbon accumulation in the sediments. In 1994 the old pond looked just as bare and abrupt as its new neighbour, the exposed clay base glistening in the June sunshine, stamped with heron footprints and jackdaw beak stabs. The old pond is now substantially infilled with debris and this is overlain with a sward of moss. Sticking up through are the stems of curl dock, Rumex crispus, their leaf edges conspicuously waved as if the growing leaves had expanded to some precise oscillation. These docks are common place but do not establish in properly submerged habitats. Here they are evidence of the increasing terrestrialisation of the old ponds. The new ponds have rapidly acquired the same pioneer animals that have now largely vanished from the old sites. In particular swarms of waterfleas, Daphnia obtusa, have appeared. The raw, new ponds seem to hold as many species as their twenty year old neighbours. It looks like the new ponds will follow the same trajectory of colonisations and extinctions as the older ponds.

The pond field is looking very beautiful. This year the greens are especially verdant, and the flowers radiate red, yellow and pink against this perfect backcloth. The clouds of pink are ragged robin, Lychnis flos-cuculi, their flowers seeming to hang in the air as if the slightest breeze can keep their confetti shape aloft.

The giant fly attack time of year

Summer now has the wetlands and dunes in its thrall. The warm, wet spring seems to have nurtured the richest greens and every flower is all the more intense against a backcloth of verdant meadow or hedge. At Hauxley yellow buttercups, Barbie doll pink ragged robin and purple spikes of orchids rocketing out of the fields compete to be the most garish. By mid June in some years the land already looks parched, the greens half hearted, but not this year. It is also an in-between time, with many birds having got their nestlings away and the occasional flourish of song suggesting a second brood might be on their minds. At Cresswell Lagoon young little gulls and sandwich terns are already hanging around waiting for something exciting to happen, or, at very least a fish to be brought back by parents who now look smaller than their indolent brood. For me high summer only begins when the meadow brown butterflies appear. Other insects are skipping, hopping, pinging and whirring from every footstep. Get down into the grasses and herbs and the sheer effervescence of life is shocking. as are flies as big as the one above, homing in on me. Nervous readers rest assured, it is not huge, high in the sky coming in from behind the tree, but somewhat smaller and probably disturbed as I crept up on a damselfly, whose turquoise body you can see out of focus bottom right. The marauder turned out to be an Empid (or Dance) fly, which often come with a conspicuous, rigid proboscis on which to skewer smaller brethren and suck them dry. They have perky, upright stance and are often furry too; if it was not for the vicious looking mouthparts they might pass as cute. During this same foray I saw an empid knock down a much larger cranefly and try to find purchase to spear its quarry, although its would be victim managed to buzz free and clamber up a stalk to re-launch itself. Judging by those raised legs and direct approach I got off lightly.

The chamber of earthly delights and a question of scale

 

 

Pete, Dave and Philip are unveiling the latest piece of field work kit. A fine example of the different scales at which people work: Pete seems to be taking a remote sensing view point, Dave bit more hands on, Philip going for the fine detail. The item they are revealing should allow us to work at the scale of whole ponds at Hauxley, the new arrival being a perspex chamber manufactured to fit over individual experimental ponds. This will allow Pete to monitor the gas exchanges from a whole pond, in addition to the more fine grained analyses with smaller floating chambers that we can position over small sections of distinct vegetation types. Initial data show that the individual ponds vary markedly, some ponds exhaling CO₂ and methane, others acting as sinks for those same gases at the very same time. The chamber looked surprisingly large when it arrived, (it looked surprisingly large when Pete tried to get it in his car at the factory). It is designed to extend either side of the ponds and wedge down into the surrounding vegetation to create a strong seal. Eventually the lure of bubble wrap got the better of us.

 

Dave, who is no mean craftsman himself is inspecting the workmanship. The chamber is a hefty and stout piece. The next step is to try this out in the field. We will put the chamber over a pond, and connect it up to the portable gas analyser which samples the air inside the chamber and gives real time measures of the changing concentrations. One unexpected outcome of this approach is the very concrete feel for the ecosystem's processes that you get from watching the numbers tick up on a display screen. Suddenly those invisible gases seem very real, the squidgy ground beneath our feet very lively, as if we are standing on some giant creature, submerged in the swamp.

 

What exactly do you do in that field? Sampling Hauxley's ponds

The experimental ponds at Hauxley have proved a revealing time machine. Since they were dug out in the autumn of 1994 their animals and plants have been monitored, allowing the changing communities to be tracked in detail. For the first ten years all thirty ponds were sampled in January and early summer (late April to early June, depending on how fast they were drying out). Since 2004 the animal life has only been checked in five of the ponds, simply because of the logistics, although it is a race between the science and my knees giving out. The sampling is used to record the presence and absence of taxa, first of all using a small, fine meshed aquarium net to sweep the open water, then a stout pond net to rake round the edges and through the plants. Each pond is sampled for between 2-3 minutes. I keep on doing this until no new taxa turn up in the white trays. Here I am crouched over the trays checking all the creatures wriggling and crawling.
As I do each tray I pour the contents into the blue box to hold the animals until I can put them back alive into their home pond.  Presence/absence is very basic but I like the idea of putting back the animals rather than killing them all in samples, though I suspect they are not keen on being dredged out in the first place. Many of the animals are small, but a hand-lens works well for identification although I do keep some beetles, Chironomid midges and Ostracods (pea shrimps)to check. All of the ponds are now choked with mosses and grass. The animals of the bare, raw ponds of 1995 and 1996 are largely gone and overall species richness has declined, probably a mix of predictable changes as ponds age but also degradation from increasing drying out after two very wet years early on in 1997 and 1998. Hunched over the trays has some benefits. Inquisitive stoats have crept up, perhaps wondering if I'd make a suitable meal. A local fox took to lying up next to the hedge to watch me with, I'd swear, an amused smirk on its face. In winter geese wheel away horrified to find a human crouched under their flyway. I probably miss even more wildlife baffled by this strange performance but those trays of animals do not sort themselves.

Monsoons... the pessimism of pollen trapping

Time underpins much of out work at Drurdige Bay: how does the number of ponds vary between seasons, what happens to the animal communities as rainfall patterns change with the years, how much organic carbon accumulates in the sediments since the ponds were dug? We have now added one of the classic methods for tracking the ecology back through time; pollen analysis. Pollen is tough stuff. The pollen spores of different species of plants linger in the sediments, undecayed. Each species, or, at least Family and Genus, has its own distinct spores, characterised by pits and spines, shape and size which can be identified with practice and patience under the microscope. Pollen analyses are the familiar science for characterising thousands of years or more, but we are exploring how fine a scale we can detect changes in the sediments of the experimental ponds at Hauxley in particular inter-annual changes which may be linked to wetter or drier times. Pippa is leading this work, which, like much of what we do, seems to involve digging. Here Pippa is not digging out a core for analysis. Instead she is putting in pollen traps to sample the rain of grains from the contemporary vegetation. Two sorts of traps are involved. The first looks like a minuature R2-D2 from Star Wars that has been sunk into the ground leaviung only its silver dome surmounted by an ornage or pink mesh cap. You can see one just below Pippa's hand. The second type of trap is a thinner tube held aloft from the ground on a stick. Apparently this is the sort of trap you need for monsoon conditions. I'm not expecting a monsoon, although after the deluge of the summer of 2012 it may be best to be prepared. Generally the coastal strip of Northumberland is dominated by rain shadow from the hills to the west, almost semi-arid by some measures. A monsoon would be new.....

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

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.

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.

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.

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.....