Friday, 30 May 2014

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.

Tuesday, 13 May 2014

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.....