While going pond thrashing for my work experience with Matt, the third pond Matt and I needed to thrash was a large, open pond complex in the middle of what used to be an airfield. The area had been allowed to become overgrown and turned into a nature reserve, and the pond we were thrashing had used to be a gravel pit where a large tanker had once sat. We inspected the pond for potential habitats, which we would thrash to find the invertebrates in the pond. We found that the pond was filled with a pond weed called Crassula Helmsii, or New Zealand Pygmyweed, which is a highly invasive species that has taken over many ponds in Britain and killed of other pond flora. The far bank there is a large area of open water, free from pond weeds, and home to many of the smaller water beetles within the pond. It was easy to thrash this area of the pond, since it wasn’t strangled by Pygmyweed, and by stirring up the mud and slit beneath the surface of the water, we easily brought up a number of beetles.

On the far left there was an area that became shallow and clogged with mud, that made it difficult to thrash, and contained various tiny larvae, such as fly and mosquito young and bloodworms. Due to the difficulties we faced with the shallow mud in this pond, we used a different method to survey this habitat. This involved creating holes in the mud with our feet, so that water would flow into them, and we could use a fine sieve to pick out and organisms hiding amongst the dirt. Beyond the muddy section, just out of shot of the camera, was an area filled with Crassula, creating a swampy habitat, that many invertebrates such as boatmen larvae and backswimmers could live in, hiding under the cover of the weeds. This meant that we needed to search this area thoroughly until we could find no new species. Following thrashing the pond for nearly and hour, Matt and I had found water boatmen and their larvae, emperor dragonfly larvae, mayfly larvae, damselfly larvae, the shells of caddisly larvae, mosquito larvae, bloodworms, various water beetles, pond skaters and small pond snails. Interestingly, on the bank of the pond, we found evidence of solitary bee nests in the soft, red earth, although it was to windy for them to come out. Overall, this pond could be considered productive and diverse, with a great number of small water beetles and different larvae, although the presence of New Zealand Pygmyweed likely removed some of the diversity in the flora of this pond.

While doing pond surveys on my work experience, Matt and I arrived at a pond only to find that it was no longer there, leaving only a scattering of leaf litter and various aquatic mosses, surrounded by sedge and other plants. After the hot spring, the shallow woodland pond had dried out, and all of the invertebrates and other organisms had moved to other ponds or died out. Many ponds are temporary and will appear and disappear with the changes in the seasons, and the invertebrates in them, such as Mayflies and Caddisflies will move out to different ponds that are still around at the time, before returning when the pond refills, if it ever does. Such temporary ponds are essential to allow invertebrates and amphibians to thrive, since fish are unable to live there. This means that many species are preserved in such ponds, and the protection of these areas is essential too preserve the diverse ecology in British ponds. Unfortunately, it was not possible to survey this pond while dry, so we took a few photos of the area, and marked it down as dry when visited.

While pond thrashing on my work experience, Matt and I needed to thrash this woodland based pond. The first step in thrashing any pond is to locate the different habitats within the pond that might contain different organisms. After a quick search of this pond we found that there were three potential habitats. On the far left there is an open bank, where water from the pond has retreated after a particularly hot spring. There are spongy water mosses covering this bank and, out of shot, waterside plants mark where the pond used to be. On the far right side, there are large groups of bulrushes and other sedge plants. These rushes could easily provide cover for a number of invertebrates, including boatmen nymphs or mayfly larvae. These bulrushes also conceal a young willow sapling. Willow is known for destroying ponds, as the leaves it drops cause the pond to acidify and dry out. As this tree grows, this pond will likely become only a hole in the ground. At back, there is a more covered area, with several trees overhanging it. Much more leaf litter sits on the surface here, than in the other sections, and you can see gases bubbling to the surface, from the decomposition of the plant matter below. This habitat is often highly specialised, since the large amounts of decomposition, can often mean there is less oxygen in the water than most invertebrates can survive. Rat-Tail Maggots and other low oxygen creatures may live in this water, and so it is important to check this area meticulously.

After thrashing the pond for about 45 minutes, we collect a number of species, including boatmen larvae, mayfly larvae, bloodworms, leeches, several species of water beetle, caddisfly shells and pond snails. Notably we also found several types of dragonfly nymph and a diving spider. These finds indicated a productive but not very diverse pond, since it had ample amount of 1st trophic level invertebrates and top predators like hawker dragonflies.