Worcestershire Record No. 4 May 1998 p.6

STONEWORTS IN WORCESTERSHIRE

On 2nd May this year I attended the official opening of Grafton Wood nature reserve. After the speeches I joined a group to walk from Church Farm to the wood to look at the new reserve. On the way we passed a small shaded pool in pasture by the footpath and in it I noticed a stonewort growing. It was not one I was familiar with, but I immediately recognised that it belonged to the genus Tolypella, with incurved balls of fertile branchlets and longer straight sterile branchlets.

This was an exciting find, since Worcestershire only has one known site for any Tolypella: T. glomerata from Feckenham Wylde Moor. I collected a sample to check back at home. When I investigated the plant in detail, I concluded that it was not T .glomerata as I had expected but was instead T. intricata. This is a Red Data Book species (status vulnerable) with only four British sites confirmed since 1970 (Stewart & Church 1992). I have sent my specimen to the national referee for checking my identification. Stoneworts are not familiar even to many experienced naturalists so I thought a brief note about them would be helpful to local recorders. They are a separate class, Characeae, of the green algae but have a very complex structure which makes them easily mistaken for higher plants. The grow entirely underwater and have a main stem with whorls of branchlets which may be divided. The general appearance is rather like an aquatic horsetail. Many of the species become heavily encrusted with calcium carbonate, making them quite hard and brittle, which gives them their common name.

They grow in a variety of water habitats such as lakes, ponds, gravel pits and canals but very rarely in fast flowing water. Some grow in quite deep water while others may colonise shallow temporary pools. Most species prefer calcareous water and most are intolerant of pollution. They are poor competitors and are easily crowded out by aquatic vascular plants. They are quick to colonise from oospores buried in the mud or carried by birds and are most likely to be noticed in newly dug or cleared waterbodies. More details can be found in Moore (1986) and Stewart & Church (1992).

In Worcestershire they are not common. Nine species have been recorded (or ten if the new record is confirmed) but most have only a handful of records. Chara curta is another Red Data Book species (status insufficiently known) with one record from Westwood Great Pool. I am also only aware of single recent records for Chara aspera, C. contraria and Tolypella glomerata. I do not have details of the record for Chara virgata and there are very few sites for C. globularis, C. hispida and Nitella flexilis. The only species that is of reasonably frequent occurrence is Chara vulgaris.

I would like to get a better picture of the distribution of stoneworts in Worcestershire and I encourage all recorders to look out for them. Please keep your eyes open when looking for newts, dragonflies etc. Don't worry that you will not be able to identify them. Just pop a reasonable sized piece in a sealed plastic bag and send it to me with collection details (grid reference, date and collector) and I will look at it. If necessary I can send specimens to the national expert. 

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