A year ago we had a team of excavators and dumpers working on our new dragonfly walk area as part of our SWaP project. The aims is improve some of the habitats of the reserve and increase the viewing pleasure of our many visitors.
This time last year, the last of nineteen new ponds was completed. The ponds are of different shapes, sizes and depths with four of them designed to hold water only through part of the year, they will be ephemeral. Ephemeral ponds often have distinct characteristics from nearby perennial ponds with different species assemblages, sometimes with a greater proportion of rarer species. Fish populations don’t build up and so predation pressure is often lower than more permanent ponds.
The ponds were completed at the end of August but were completely dry, even when it rained the moisture just seemed to disappear into the dust until finally at the end of September it rained. We had a month’s rainfall in a week, surely we’d come in one morning to brimming ponds? But even after all that the ponds looked 'splashy’ rather than like proper ponds.
One of our new ponds after a week’s worth of rain
The thought crossed my mind that we’d dug ponds that weren’t going to hold water. It would be a bit embarrassing if that was the case. Well there was no need to worry as it almost didn’t stop raining in October with almost 20% of the entire year’s rainfall in one month and the ponds filled and filled...and then overflowed.
After a wet October our concerns over filling the ponds dried up
They remained wet over the winter but April and May this year were some of the driest months on record, which caused the ponds to dry up quite significantly, but didn’t stop the explosion of life occurring. We’ve had some rain since and they have topped back up and could most definitely be described as ‘well colonised’.
One of the most obvious signs of life when walking round them a couple of weeks back were the gangs of whirligig beetles (Gyrinus substriatus) whizzing round on the surface. These beetles actually have two pairs of eyes, one that looks down underwater while the other looks above the water surface; they use both when hunting small insects.
You can’t really miss some of the plants either with sea club rush (Bolboschoenus maritimus), actually a sedge, and reed mace or bulrush (Typha latifolia) the most prominent in several of the ponds. Look closer and there are real rushes as well including spike rush???? (Eleocharis palustris) and grey club rush????. In the draw-down zone there was a classic wet edge colonist, celery-leaved buttercup (Ranunculus scleratus) and also red goosefoot (Oxybasis rubra), which has taken advantage of the bare mud caused by dropping water levels. There were also plants such as water crowfoot (of more than one species) starting to grow at the water’s edge and within some of the ponds.
Celery-leaved buttercup
Floating and submerged plants found included, fennel pondweed (Potamogeton pectinatus), a very small plant of spiked water milfoil (Myriophyllum spicatum) and small pondweed (Potamogeton pusilis).
One of the most interesting finds though were not flowering plants, or even plants but stoneworts. These are ‘complex algae’ and are simply quite fascinating - they build a skeleton of calcium carbonate for structural support instead of using cellulose, as do flowering plants and they have the longest cells known to science at up to 20cm! They are amongst the first to colonise new ponds and we appear to have three species present (there are thirty species in the UK). The most interesting was identified as the wonderfully named, hedgehog stonewort (Chara aculeolata).
Hedgehog stonewort
We had been considering planting the ponds up a little to give them a ‘headstart’ and make them more ‘pleasing to the eye’, but no longer. To see what has already colonised the ponds has been an eye-opener.
By way of animal life there weren’t just whirligigs either. In total 27 invertebrate species were found. Most, but not all, were flying species, which for fairly obvious reasons are usually the first to find new ponds - when ponds dry out these creatures seek out new water.
The non-flyers were a water hoglouse, a horse leech and an immature ramshorn snail, which most likely came in attached to a duck or a gull. Besides the whirligigs there were 15 other beetles including Agabus conspersus, which I must say is quite a smart looking beetle and is classed as nationally scarce and Octhebius marinus another localised brackish water beetle. It is likely the ponds have a saline influence as the older dragonfly ponds do, but salinity hasn’t been measured yet.
Agabus conspersus, one of 16 beetle species found in the new ponds and a pygmy backswimmer, Plea minutissima
There were four species of lesser water-boatmen, a common backswimmer, a backswimmer and a pygmy backswimmer – when I was a kid, to me they were all just water boatmen (and I wonder if I ever noticed a pygmy backswimmer!).
No doubt as the ponds mature the suite of species using them will change – a notable absence this year being dragonfly and damselfly larvae. Ovipositing adult common darter have been seen this year so it is possible that adults may emerge from the new ponds next summer.
I know it is said a lot, but, creating ponds must be one of the quickest ways to increase the biodiversity of an area. If you can do it in your garden, give it a go, I won’t bang on about how, there’ll be plenty of advice online, but it is truly fascinating to see what turns up.
Ed
Warden RSPB Saltholme