Freshwater Habitats and Associated Algal Flora
REPORT
Whitchurch Millennium Green Water Meadow: Freshwater Habitats and Associated Algal Flora
Vaucheria, as seen in the water at the south-east end of the Meadow
The freshwater algae growing in various aquatic habitats associated with a water-meadow close to Whitchurch village were sampled on 1st December 2009. These aquatic habitats were either supplied principally by spring water (including area of aquatic plant nursery) or by the ground water and surface run-off.
The following habitats were sampled:
(a) Spring-water fed stream flowing into the River Test and divided into a shallow ponded area close to Ninesprings House (<0.5 m deep), a mainly concrete lined outflowing channel giving way to a natural gravel/cobble lined stream with well-developed marginal vegetation, and flooded, shallow areas lined by polyethyhene sheeting overlain in places by fine, soft sediment;
Vaucheria, close-up, as seen in the water at the south-east end of the Meadow
(b) Small pond (‘scrape’) in the water meadow (<5 m across) with emergent marginal vegetation its floor lined by a stonewort;
(c) Flooded excavation below sluice with an early wood-lining. The most evident macroscopic algal growths were in the two non-flowing habitats sampled. (a map of these locations was added by the website administrator; the report continues after the map)
- Center of Millennium Meadow map
- map marker
- (a) Pond near Nine Springs house, The Weir
- map marker
- (b) Pond in Millennium Meadow
- map marker
- (c) Excavation below sluice
(a) Spring-fed Habitats
Verticillata, under magnification, found on the Millennium Meadow
The flowing water habitats had few evident macroscopic growths of algae, possibly reflecting to the relatively low light conditions associated with the winter months. Seasonal changes in day length is the key factor responsible for changes in algal diversity and abundance especially in spring-fed habitats where water chemistry, flow rate and water temperature tend to be relatively constant throughout the year. The water temperature close to a spring source in he British Isles is fairly constant, varying little over the year (frequently about 10-12°C) and usually has an alkaline pH in southern England; water temperature and pH was not measured during the visit.
Verticillata, under high magnification.
The only evident macroscopic growths of algae were purplish, mucilaginous clumps of the red alga Batrachospermum growing in the channel flowing from the ponded area and just upstream of a bridge crossing the channel. Some stages in sexual reproduction were detected but not all stages were evident so identification to species was not possible. Ocasionally growing on partially mud-buried flints and others surfaces lying in the main channel were bright green crusts of the filamentous green alga Gongrosira, possibly Gongrosira incrustans. Sediment mixed with algal fragments covered the frequently slightly lime-encrusted hard surfaces including stones, flints and submerged plant roots and other surfaces in the pond area close to the house. Sometimes brown-coloured diatoms and the occasionally green filaments of Cladophora glomerata were attached to these surfaces. No obvious algal growths were associated with the silt overlying the polythene sheeting in shallow areas within the nursery.
(b) Pond (‘scrape’)
The stonewort in the pond examined in the water meadow was Chara vulgaris (identified by Jenny Bryant).
(c) Flooded Excavation
Very extensive and sometimes loosely attached green, spongy clumps or mats of the siphonaceous filaments of Vaucheria were present in the channel (see photos). Roy Merrit (Vaucheria specialist) has grown samples of these mats in laboratory culture by Roy Merrit and these have produced organs of sexual reproduction so enabling him to identify the Vaucheria to species. The species is Vaucheria taylorii (=V. verticillata), a taxon rarely recorded in the British Isles. In conclusion, as expected the algal diversity was low and would be expectedly to increase significantly over the next summer. Experience surveying similar habitats in southern England suggests May to September to be the most productive period for carrying out a more comprehensive survey of the algal flora. List of Algae Chara vulgaris Linnaeus (Chlorophyta, Charales) Batrachospermum sp. (Rhodophyta) Gongrosira incrustans (Reinsch) Schmidle? (Chlorophyta, Chaetophrales) Cladophora glomerata (Linnaeus) Kützing (Chlorophyta, Zygnematales) Vaucheria taylorii Bloom (Xanthophyta) David M. John 16 January 2009
