On Thursday 4th September after a rather wet day a small group assembled just outside Habberley to go pond dipping! A beautiful clear evening provided the perfect conditions for gazing into the water and seeing what we could find. Armed with sweep nets, trays and ID cards the group made their way around the pond seeing what we could find. The evening finished up with some bat watching, Common Pipistrelle, Soprano Pipistrelle, Brown Long-Eared and Noctules were seen and detected around the pond, with a pair of Soprano Pipistrelles putting on quite the show swooping above the pond.
Below is a write up of pond finds provided by group member and RVCWG committee member, Julian Livsey.
Following our Pond Dipping evening, a sample of water was looked at under the microscope. A single drop contained more species than I could possibly hope to identify so this is more of an overview of dominant species.
The organisms inhabiting the pond revealed a diverse ecosystem. The filamentous algae primarily consisted of Oedogonium species. Other algae strands included the occasional Spirogyra, Bulbochaete and Chaetophora. Diatoms are a group of silica-shelled algae, and while there weren’t huge numbers in the sample, there were a fair few different types. Most were from the Orders Naviculales and Cymbellales. These little glass organisms are part of the pond’s phytoplankton and play crucial roles in the aquatic food web. Desmids are green algae with two symmetrical half cells. They prefer nutrient poor water. Closterium gracile was by far the most abundant species – hundreds in each droplet of water. Other desmids present included Staurastrum, Cosmarium, and Pleurotaenium. Cyanobacteria are often referred to as blue-green algae. Harmful, like bacteria, but they are able to photosynthesise. They are one of the earliest forms of life and were found in the pond in a variety of forms: Microcystis colonies, strings of Oscillatoria, and Chroococcus. From such a small sample, this means they are capable of thriving within the pond.
A few other interesting organisms were recorded, including ostracods (seed shrimps), busy spinning Volvox colonies, and a large form of Heliozoa – which are protozoa related to amoeba, with characteristic sun-like axopodia. There was also a strong colony of Thuricola – a ciliate protozoa belonging to the family Vaginicolidae. Finally we recorded the cnidarian species Hydra viridissima – related to corals and jellyfish, they can only tolerate low levels of pollution.
During the evening we had lots of fun looking at diving beetles, dragonfly nymphs, water snails and newts, but peering at the pond through a lens reveals another aquatic environment every bit as complex and fragile.