Saturday, 14 September 2013

The pondweed's great time and space escape

Two inches of rain fell over parts of north east over the last week. Flash floods had motorists scrambling onto car roofs and the torrents carved out a gentle stream in the petite seaside resort of Saltburn into a mini canyon, ripping up tarmac and turning cars into dodgems. The end of august had seen most of the smaller ponds along Druridge bay dry and baked, with grim results for some animals and plants. For example the small leaved pondweed, Potamogeton berchtoldii, that had established in an isolated pond in the middle of an oil seed rape field in the wet summer of 2012 seemed lost (left hand photo, Blog, 2nd September). However the key to pond ecology is not to think of  a site in isolation, either in space or time. Pond-life has always had to come and go across the pondscape, finding entirely new sites as old ponds fill in or, over a shorter time scale, colonising or wiped out as the seasons and climate vary. The pond weed may have been lost from the arable pond (...although the real test will be next summer in case fragments of root or seeds sprout again from the apparently barren mud) but has turned up a kilometre away, this time in a pond in the middle of grazing pasture (right) , one of the few ponds to survive the summer drought due to an adjacent spring line.
This new site has been checked repeatedly over the preceding two years and the pondweed has not been found before, so this looks like a genuine colonisation. Repeatedly visiting sites over the years can feel like very mundane science, lacking the glamour of genetic code breaking or atom smashing, but long term monitoring is needed or else all we have are snap shots which may give a poor representation of the ecology.  The pondweed is doing perfectly well if you look across the years, but one year alone is too static; which year is representative? 2012,all pond inundated and the pondweed in amongst the arable crops or  2013, the ponds drying out, the pondweed in the pasture pond? No single year does this site justice

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