The pond life in the acidic pools of Chailey Common

Posted by Graeme Lyons , Saturday, 16 September 2017 06:45

Last Saturday I ran a course for the Freshwater Habitats Trust's PondNet project up at Chailey Common. I've just got around to identifying everything. We only really had time to sample four ponds in detail but we also managed a quick diversion to a number of other sites around the common. We started with a couple of small man-made ponds full of Bog Pondweed, Floating Club-rush and Marsh St. John's-wort. These ponds are very acidic, with dark peaty water so we expected to find the more specialist aquatic invertebrates. I told everyone we would see the distinctive Notonecta obliqua, the most distinctive of our four backswimmers and it was indeed the commonest bug in the pools. We actually recorded all four of our backswimmers in these four pools. In the above image one of our (around 40) species of water boatman (this one of two species of Hesperocorixia recorded in this one pond) can be seen in the background. Most backswimmers are much bigger than water-boatmen, it helps to be bigger than things that you eat!

Nice to see some Marsh St. John's-wort and Floating Club-rush.

The first pool had two species of Dytiscus in and it was nice to be able to key these out in the field. Thanks to Fran Southgate for this photo of the commoner Dytiscus marginalis on the left and Dytiscus semisulcatus on the right. However the nationally scarce Hydrochus angustatus was perhaps the most interesting being a species I have not recorded before.

One pool had an adult 13-spot Ladybird in it and I'm pretty sure that this is also the larva but it looks a little bedraggled.

This is the most Floating Crystalwort Riccia fluitans (one of  our few aquatic liverworts) I have ever seen. You usually see a few little plants floating on the surface, not a huge mass like this!

We called in and had a look at the Marsh Gentians on Romany Ridge that have responded to the grazing there. A great success.

But the highlight for me has to be a diversion to Lane End to look for the Mud Snails that were relocated there last year after not being recorded for many years. The dried up woodland pool they were found in looked quite unsuitable for anything else. In fact next to nothing else was found in there but we did see two Mud Snails! This is typical for this scarce species. It was very dark and dingy in the woods by this time so apologies for the photo. Note to self: next time look for this first. Look at the state of the kit!

A big thank you to everyone who attended. a full species list will be send to the Freshwater Habitats Trust and the records synced with the SxBRC as always (I've nearly entered 10,000 records already this year!)

So, here is the full list which includes 14 aquatic bugs, 15 aquatic beetles but only two molluscs (acid sites are not so good for shell building). Here are my records for the day including a few random things like Devil's Fingers that are nothing to do with aquatic life.

Taxon group Species
annelid Erpobdella testacea
annelid Helobdella stagnalis
annelid Theromyzon tessulatum
crustacean Asellus aquaticus
crustacean Crangonyx pseudogracilis
flowering plant Water-plantain
flowering plant Downy Birch
flowering plant Callitriche sp.
flowering plant Star Sedge
flowering plant Floating Club-rush
flowering plant Marsh Gentian
flowering plant Floating Sweet-grass
flowering plant Marsh St John's-wort
flowering plant Yellow Iris
flowering plant Sharp-flowered Rush
flowering plant Bulbous Rush
flowering plant Compact Rush
flowering plant Soft-rush
flowering plant Water-purslane
flowering plant Purple Moor-grass
flowering plant Creeping Forget-me-not
flowering plant Small Pondweed
flowering plant Bog Pondweed
flowering plant Lesser Spearwort
flowering plant Ivy-leaved Crowfoot
flowering plant Thread-leaved Water-crowfoot
flowering plant Grey Willow
flowering plant Branched Bur-reed
fungus Devil's Fingers
insect - beetle (Coleoptera) Acilius sulcatus
insect - beetle (Coleoptera) Agabus bipustulatus
insect - beetle (Coleoptera) Anacaena limbata
insect - beetle (Coleoptera) Anacaena lutescens
insect - beetle (Coleoptera) Water Ladybird
insect - beetle (Coleoptera) Dytiscus marginalis
insect - beetle (Coleoptera) Dytiscus semisulcatus
insect - beetle (Coleoptera) Haliplus ruficollis
insect - beetle (Coleoptera) Haliplus flavicollis
insect - beetle (Coleoptera) Helochares punctatus
insect - beetle (Coleoptera) 13-spot Ladybird
insect - beetle (Coleoptera) Hydrobius fuscipes
insect - beetle (Coleoptera) Hydrochus angustatus
insect - beetle (Coleoptera) Hydroporus pubescens
insect - beetle (Coleoptera) Ilybius fuliginosus
insect - beetle (Coleoptera) Laccophilus minutus
insect - beetle (Coleoptera) Noterus clavicornis
insect - dragonfly (Odonata) Southern Hawker
insect - dragonfly (Odonata) Migrant Hawker
insect - dragonfly (Odonata) Emperor Dragonfly
insect - dragonfly (Odonata) Downy Emerald
insect - dragonfly (Odonata) Large Red Damselfly
insect - dragonfly (Odonata) Ruddy Darter
insect - dragonfly (Odonata) Common Darter
insect - moth Brown China-mark
insect - moth Broom Moth
insect - true bug (Hemiptera) Corixa punctata
insect - true bug (Hemiptera) Eurygaster testudinaria
insect - true bug (Hemiptera) Gerris gibbifer
insect - true bug (Hemiptera) Gerris odontogaster
insect - true bug (Hemiptera) Gerris thoracicus
insect - true bug (Hemiptera) Hesperocorixa castanea
insect - true bug (Hemiptera) Hesperocorixa linnaei
insect - true bug (Hemiptera) Hesperocorixa sahlbergi
insect - true bug (Hemiptera) Nepa cinerea
insect - true bug (Hemiptera) Notonecta glauca
insect - true bug (Hemiptera) Notonecta maculata
insect - true bug (Hemiptera) Notonecta obliqua
insect - true bug (Hemiptera) Notonecta viridis
insect - true bug (Hemiptera) Plea minutissima
insect - true bug (Hemiptera) Sigara limitata
liverwort Floating Crystalwort
mollusc Musculium lacustre
mollusc Omphiscola glabra
spider (Araneae) Pachygnatha clercki
spider (Araneae) Trochosa ruricola
spider (Araneae) Pirata latitans

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