Sunday, 26 May 2013

Students of pond difference

I’ve spent the last week in the Lake District with our first year undergraduates on their annual field trip, a mix of core ecological skills for conservation and landscape in the UK (Phase 1 mapping, National Vegetation Classification), ping pong and stone circles human sacrifice re-enactments. They worked hard, twelve hour days, apart from the final night when they stayed up even longer to craft the data they had been collecting into presentations. Creating a pressed flower collection may not seem  the most compelling activity when you are 19, but I am confident those slightly mangled specimens of pignut and pink campion will one day be treasured possessions. Each student had a particular flower to find, hampered a bit by the late spring but also resulting in a bout of botanical blind man’s buff, watching them walk past their quarry. They have to do a group project too. One five-some, Ryan, Chloe, Dylan, Andrew and Jack took up the challenge of comparing the richness of invertebrate in two ponds compared to two streams. We’ve not tried this before but after several days of counting grasses in quadrats you can see the attraction. They took kick samples from two streams coming off the southern slopes of the Blencathra ridge up by Skiddaw, then samples from two nearby ponds. The streams yielded Heptagenidiae and Baetidae Mayflies, Leuctridae and Chloroperlidae stoneflies and a supporting caste of oligochaete worms and cranefly larvae. The two ponds were more of a surprise, both teeming with tadpoles but otherwise rather different, one pinging Copepoda zooplankton and creeping Nemouridae stoneflies, the other with Polycelis flatworms, Pseudocrangonyx gracilis shrimps and the giant Ramshorn snail Planorbis corneus. They used Jaccard’s Index of Similarity to summarise these patterns, essentailly a measure of how many taxa two sampels have in common ranging from none, 0%, to an identical inventory, 100%. The two streams were 50% similar to one another, the two ponds only 17% similar to each other, a neat demonstration of the heterogeneity of ponds in the landscape, and a neat demonstration that students can do good work given the opportunity plus  staff suffering from an overdose of Protestant work ethic and slightly sleepless nights.

Sunday, 19 May 2013

Spray time at Blakemoor

The subsidence ponds at Blakemoor Farm at the south end of the bay are so familiar to us that we forget how startling they can seem to visitors. The pond in the photo above swells across a hollow in the middle of a large arable field that is given over to oil seed rape of winter wheat. The extent of the water varies markedly with seasons and years. A dry summer can see the whole shallow basin exposed into a reticulated pavement of cracked mud, dotted with pineapple mayweed and knotweeds. A sudden rain storm can refill the whole hollow. This is one of the ponds over the ten abandoned seams of nearby Ellington pit. The coal measures extended far out under the sea, but were so near the sea bed that the miners could hear ships passing overhead. Many of these field ponds lie in suspicious rows across the fields, perhaps echoing the subterranean tunnels. The wet year of 2012 and dry winter of 2013 has left the crops stunted and patchy, much of the ground dried out to a tough crust. The crop sprayers have been out to catch the first sustained spring warmth. We are curious to find out if any of the farm management affects the productivity of the ponds. These arable field ponds black foetid mud of the deeper swamps which seems a better trap for organic carbon. However these field ponds can be carpeted by vivid turquoise and green crusts of algae, visibly fizzing trails of oxygen bubbles on sunny days, so may be briefly but intensely productive whilst the sumemr sunshien lasts. The sprayers do not drive through the cloying mud, perhaps nervous of just what lies beneath (or, more ominously, does not because it has all been dug out) from the days when mining dominated south east Northumberland.

Sunday, 12 May 2013

The cook, the core, its bung and his oven

After several decades working in the sciences I am still troubled by the awkward conventions of neutrality that were drummed into us as students, for example how we must not to write reports or academic articles in the first person. No “I” or “we”. “Data were collected” or “this report demonstrates”, as if data collects itself or reports self-publish. I let “I” sneak into work these days, partly as a reminder that research is carried out by people. For example Pete who, in the photo above, has our new corer wedged into the oven of his flat. The new corer is a marvel of practicality. The bottom end of the tube is sharpened and has cut through sediments that are reinforced with a lattice of bulrush rhizomes as easily as it does through softer muds. The top of the tube has extra flanges so you can push down with your foot too. A wooden plug allows the sediment to be pushed out, the plug attached to a calibrated rod so we can measure precise slices. It is this plunger which has caused trouble. It is beautifully cut to be flush with the inside circumference of the core tube, but the wood has swollen in the water and got stuck. Dave says this would not happen if it were made of mahogany wood. So, in addition to the elegant steel engineering we can perhaps add a touch of high class woodworking. Meantime Pete has stuck the core in the oven to dry out the bung. This is a fine example of the “we” in science. Dave designed the core; that is a real skill. Pete has been trying it out in ponds containing glutinous goo through to others solid with roots and rhizomes; that is a real skill too. Getting a corer that works slickly and effectively across all these pond types is important so that we can take equivalent cores and slice the columns of mud into similar sized discs to compare the amounts of organic material trapped through the varying depths of mud. Because the corer allows Pete to extract precise, replicate samples he has been able to work out the density of carbon buried in the sediments. Meantime I am glad he will have to explain why his remarkably well equipped kitchen has a mud corer stuck in the oven and not me. That is quite another skill.

Monday, 6 May 2013

The waterboatman's gaze

As spring begins to take hold it will soon be time for one of my favourite pond creatures to make its presence felt. This is a Greater Waterboatman, called the backswimmer in North America, one of the aquatic bugs. They are common enough, emerging from a net scoop of weed and debris with a twitchy, gangling urgency or to be watched hanging under the surface film of a pond, the occasional subtle scull to shift them in search of victims. They are predators, snatching prey with the first two pairs of legs and using that elegant proboscis you can see in the picture extending back from the head, to skewer prey and digest their innards. They are especially good at dispatching other insects that have got snarled in the meniscus or that bumble around at the surface. Amphibious beetles such as Helophorus are particularly vulnerable. The beetles have hard exoskeletons but the waterboatman stick their proboscis between the beetles’ head and thorax, resulting in a characteristic decapitation that you can use to count attacks as the forlorn, headless beetle bodies accumulate. Much like an expert wine waiter using a corkscrew. Mosquito larvae which need to rise to the surface to recharge their air supply or water fleas, twitching in the water column, are also an easy meal. So voracious are the waterboatmen that they can exterminate their chosen prey from small ponds, eventually turning cannibal when all the easy meals have been exhausted. Female waterboatmen lay batches of eggs on plants or stones (this varies a bit with species), which hatch into black specks of nymphs, rowing urgently in search of tiny prey or to avoid their older cousins. keep an eye out over the next few weeks as the race to eat and not be eaten hots up.