Silt Pond Thrashing

A very silty pond.

Matt and I needed to thrash this churned up pond during my work experience with him, and we found a wealth of interesting life hiding in the rising silt of the pond. Grazing animals such as cows and sheep often come into ponds like this to bath and drink, and as a result a lot of grit and animal faeces are stirred up and reveal some interesting life near the pond floor. We located two major habitats within the pond that we needed to thrash, one of which was the clear bank nearest to us, where we could see pond skaters and whirligigs Whirligig beetles are small predatory beetles that skim on the surface of water, and use a collection of air bubbles they carry around with them, in order to dive and catch small invertebrates. They get their peculiar name from the unmistakable circling pattern they make when moving on the surface of the water, which is reminiscent of the spinning tops that they are named after.

On the left and right sides of the pond, where there was more aquatic vegetation, we found smaller water beetles. The water was murky from the silt, making it hard to see anything below the surface, and Matt had to wade in quite deep to find any of the dragonfly or mayfly larvae, or to pick leeches off the surface of the sedge and pondweed. Thrashing this area was harder than the first, since we could not properly see where the weeds were below the surface, and they dragged into our nets. Despite this, we found a number of beetles we had not seen in any pond that day, and collected them to be dissected to identify their exact species.

An emperor dragonfly larvae we found in the pond.Silt from the pond. After thoroughly thrashing the pond for about an hour, Matt and I found water boatmen, water skaters, whirligigs, a nasal leech, emperor dragonfly larvae, mayfly larvae, caddisfly larvae cases, many small water beetles and bloodworms. The pond can be considered fairly productive, with a healthy foodweb, although it is likely that grazing animals wallowing in it has had a large effect on the ponds diversity.

Palmate Newt

An adult palmate newt.

While thrashing a pond full of newts on my work experience with Matt, we found an adult Palmate Newt hiding in the pondweeds nearby some common frogs. It is the smallest newt in Britain, 6 or 7cm smaller than the enormous Great Crested Newt, is common throughout West Europe, although it is actually extremely rare in Belgium and Holland. Palmate Newts are normally brown or pink in colour, with a slightly darker banded stripe across their eyes. They can have dark spots on their backs, but never as many as a Smooth Newt, and not as dark as those of a Great Crested Newt. Males possess webbed back feet, as well as a slight, smooth crest that will develop during mating season, which is around April.

These newts will eat most invertebrates smaller than them, crustaceans like freshwater shrimp, water fleas, frog or toad tadpoles, and occasionally, they will eat each other, making them the only cannibalistic newt in the UK. Palmate Newts only hunt at night, when the air is full of water, or the ground is particularly damp, spending the day and unsuitable nights underwater or beneath moist logs and stones. During the breeding season, the newts will also become active during the day, since they need to attract a mate and hunt.

The newt Matt and I found was a young female, and in relatively good health. We noted that Palmate Newts were present in the pond, and then moved away from where we found her, so that we wouldn’t disturb her and the other newts in the area again.

Great Crested Newts

The tadpole of a Great Crested Newt.

While thrashing an amphibian infested pond with Matt on my work experience, we found a large colony of rare great crested newts living by a bank of water mint. Of the three species of newt that live in Britain, the others being the Common and Palmate Newts, the Great Crested Newt is be far the largest and the rarest, measuring at around 15cm long, over 5cm longer than other British newts. The GC Newt, or Triturus Cristatus, can be recognised by the dark blotches on it’s body, which are unique to each individual, and the yellow or orange underbelly. Males also possess a silver or grey stripe that runs down their sides. During mating season, males will develop a large jagged crest, leading from the base of their head to the start of their tail, and a smoother crest along the whole of their tail. This crest is used to attract females to mate with.

Great Crested Newts mate during February and early March, and lay a couple of eggs every day from March to June, until roughly 250 eggs are produced. Eggs are normally placed on the leaves and branches of aquatic plants, such as the water mint in the pond Matt and I thrashed, and wrap the gently so as to protect them. The eggs hatch after about three weeks, creating a new batch of newt poles. The young are vulnerable to larger predators, such as fish or leaches, and so the adult newts normally lay in relatively safe ponds, avoiding rivers or lakes. After four months, the newt poles are able to leave the water and breath air, and after 2 or 3 years, they are ready to breed. A Great Crested Newt will live for about 10-15 years in the wild, but one newt has survived 28 years in captivity before dying.

Throughout Europe and in the UK in particular, the are numerous restrictions on what you can and can’t do with these newts. They are heavily protected, making it illegal to harm, keep, disturb or move one of these newts without the correct licence and the permission of the National or Wildlife Trust. Luckily, Matt and about 2000 others in the UK possess this licence, so we were able to carefully go about our work in the pond without harming the newts.

Newt Pond

A pond containing several species of newts.

While pond thrashing on my work experience with Matt, we went to a pond that was filled with numerous amphibians, such as frogs and newts. It had been listed as a fishing pond on the map, and the water was filled with healthy British plants, all of which point towards a diverse and productive pond. Upon reaching the pond, we could hear the croaking of marsh frogs, which are a non-native species, and shouldn’t have been in the pond. The most likely reason for their presence in this pond is that someone had them as pets, and chose to get rid of them by dumping them in a nearby pond. They are part of the genus Pelophylax, which contains the ‘green frogs’ of the Old World. We searched the pond’s banks for the different areas that we’d need to thrash for invertebrates, and found a few separate habitats. On the close bank, it was all open water, with few pondweeds and many larger snails floating in it, such as greater pond snails, and ramshorn snails. Water beetles and other smaller invertebrates lived in this area, with most of the larger, carnivorous invertebrates living deeper in the weeds.

On the left bank, there is a thicket of dense water mint, and lots of pondweeds in the water next to it. This is ideal habitat for newts, as they have covered areas to hunt and hide, as well as the large thicket of water mint, which is ideal for newts to lay their eggs on. We found two kinds of newt in the pond, including the rare and protected Great Crested Newt, which prevented us from disturbing that area of the pond further, to avoid agitating the newts. We also found a full grown Palmate Newt and a Common Frog and it’s tadpole hidden in the weeds and on the bank. On the far bank, there is an area of deep water, which can be seen by the lilies, which will only grow in places where the water is deep. The marsh frogs that Matt and I heard earlier jumped off of the bank and into the pond as we came past, although none of them sat on a lily pad. Thrashing in this section was fairly easy, and we found a good number of frog tadpoles and larvae.

The tadpole of a Great Crested Newt.

Matt and I thrashed the pond for nearly an hour before we stopped. We had found a large number of amphibians and invertebrates, including water boatmen, caddisfly larvae in their cases, mayfly larvae, dragonfly larvae, damselfly larvae, various small water beetles, water skaters, greater and lesser pond snails, ramshorn snails, palmate newts, great crested newt tadpoles, common frogs and marshfrogs. This was an extremely healthy and diverse pond, with numerous predatory vertebrates, many specimens of smaller invertebrates, and abundant local flora, such as the water mint.

New Zealand Pygmyweed

An example of Pygmyweed.

A gravel pit pond that I thrashed with Matt on my work experience was almost completely choked by New Zealand Pygmyweed, or Australian Swamp Stonecrop (Crassula Helmsii), an invasive species of pondweed that came in from abroad, and has taken over numerous British ponds, especially in south and midland England and most of Wales. The pondweed is particularly adaptable to it’s environment, being able to survive in both acidic and alkali conditions without detrimental effects, as well as surviving in semi-saline areas. As such it is able to grow in almost any body of still or slow moving freshwater it is introduced too, and often destroys the local subaquatic flora. This often leads to oxygen depletion within ponds, and invertebrates, fish and amphibians can quickly die out.

The Crassula in cannot create viable seeds in Britain, meaning that it must reproduce entirely through cuttings. The Pygmyweed can grow from a piece of leaf or stem as small as 5mm, which means that you must be very careful when fishing or surveying in a pond with Crassula in, so that you do not bring pieces of it to another pond which is not infested. This trait also makes it incredibly difficult to remove from habitats it has already taken over, and to this day it has not been successfully removed from any area.

Matt and I made care not to bring any of the New Zealand Pygmyweed with us when we went to the next pond, cleaning our nets, and the tray we used to search for invertebrates. Even a small piece of Crassula could have taken over another pond.

Solitary Bees

Solitary bee nests.

While thrashing a gravel pit pond on my work experience with Matt, we found the nests of some solitary bees in the ground around the pond’s bank. Solitary bees do not live in colonies and hives like other bees, such as honeybees and bumblebees, instead living along and raising their young in a single nest. There are over 225 different species of solitary bee in the UK alone, making it almost impossible to identify these ones, especially without having seen the bees themselves. If I were to guess what kind of bees lived here, I would say, it was a Tawny Mining Bee or a Red Mason Bee, since they are both very common, and often borrow their nests in the ground. Solitary bees often pad their nests with leaves and moss on the inside to insulate their young, and create the chambers of their nests. People can often mistake these nests for a colony, because many bees often live in the same area, since it is difficult to find an acceptable habitat, and this gives the impression that they are all living together in a single large hive.

There are two main types of solitary bees, Miners and Leaf-Cutters. The miners, like the ones we found on the bank of the pond, will dig their nests in sandy or loose soil, stock up their nests with pollen and nectar to sustain the larvae, lay their young, and then seal the nests, leaving the babies to fend for themselves until they become adult bees, and dig out of the nests. Miner bees resemble honeybees closely, but you can tell the difference by looking for the pollen baskets on the back of the bee. The solitary miner bees lack these pollen baskets. Leaf-Cutter bees, will normally build their nests in dead plant matter such as stems or shallow roots, and cut out circular pieces of leaf and petal from nearby plants in order to construct their nests. Leaf-Cutter bees in particular are excellent pollinators, and are just as important to the pollination process and colonial bees.

Unfortunately, it was too windy for the bees on the day we discovered the nests, and they would not leave to let us have a better look at them, although we know they are definitely miner bees. After thrashing the pond, we left the bees as they were.

Gravel Pit Pond Thrashing

A gravel pit pond. 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. Matt and I creating holes in the mud to find organisms living there.Crassula weeds from the thrash. 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.

Dry Pond Thrashing

A dry 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.

Emperor Dragonfly

A selection of dragonfly larvae.

While thrashing a woodland pond for my work experience, I found several types of dragonfly larvae, including the larvae of the beautiful emperor dragonfly. In the pond Matt and I discovered three different species of dragonfly larvae, both hawkers and chasers. The hawker dragonfly on the right, can be recognised by it’s larvae’s larger, longer body, which will eventually turn into a dragonfly from one of the largest and fastest groups of dragonfly around. Hawkers generally fly well above head height, rarely settling, and diving down on prey like a hawk. They are the largest and fastest dragonfly, as well as the most prevalent type in Britain, with over seven species. I am not sure what species the larvae on the right is, but I suspect it is a Brown Dragonfly.

The chaser dragon fly in the middle, has a smaller and squatter body than the hawker’s, and will turn into a Four-Spotted or Broad-Bodied Chaser when it matures. Chasers sit on vegetation around ponds and rivers, waiting for their prey to fly past them, before taking to the air to hunt them down, giving them the name chasers.

The large dragonfly larvae on the left is that of an emperor dragonfly, which is extremely common in Britain, and can often be seen flitting around the edges of ponds, in Europe and parts of northern Africa. We can identify the larvae by the round shape of it’s head, as opposed to the more angular heads of the other larvae. It is also a hawker dragonfly, and has beautiful sky blue colourations when mature. They will prey mainly on butterflies, and other slow moving flying insects, which they dive down while they fly beneath them. They have been known to eat other species of dragonfly, particularly chasers and darters, which are slower and more vulnerable to their attacks. In the past, these dragonflies have been associated with witches and the devil, people claiming that they use their tails to sew up peoples eyes in the night. Obviously such tales are untrue and completely unfounded. The emperor dragonfly larvae pictured above is close to becoming a full adult, and will likely transform within a week, so we let him back into the water, keeping the other two larvae for identification under a microscope.

Diving Bell Spider

A diving spider.

While thrashing in a woodland pond on my work experience, one of my thrashings brought up an adult diving bell spider. These peculiar spiders live among reeds and weeds in ponds from Asia to Europe, including British ponds. They are the only type of spider to live their entire life under the water, in little web ‘diving bells’ containing air. In well oxygenated water, new oxygen will diffuse down the concentration gradient into the diving bell, removing the need for the spider to ever return to the surface to collect more oxygen. This means the spider will hunt and mate within the safety of these bells, without ever having to leave. They hunt mainly small invertebrates and crustaceans, such as nymphs and fresh water shrimp, which they dart out of their bells to catch.

This particular spider is a female, which can be seen by her small size and dark colouration. Unusually for spiders, the female is much smaller than the male, who has a far more active life of hunting then the female. A male also has much lighter yellowish colours and creates far smaller bells to live in. When the spiders want to mate, the male will build a new bell near the female’s bell, and will then weave a tunnel through into the female’s area, where they will mate. Typically 40 – 50 eggs are lain, and will hatch into baby diving bell spiders, most of which will be eaten by frogs and fish.

Rather than release this spider back into the pond, Matt took it with him, since a friend of his had been looking to keep one. They are fairly challenging to keep, requiring live prey, large spaces, and well oxygenated water. These are not recommended for beginner keepers.