Impact Type: Deposition of pollutant
Stoneworts are a small group of freshwater and coastal, macroscopic non-vascular plants, which belong to the Class Characeae of the green algae (Chlorophyta) (a number of which are listed in the UKBAP). They mostly occur in unpolluted calcareous or brackish water. A few species, mostly in the genus Nitella, however can grow in acid water. The two most frequent species in base-poor waters are smooth stonewort (Nitella flexilis) and delicate stonewort (Chara virgata). These two species are relatively common in upland regions of the UK, but may be locally threatened at particular sites by acidification. Slender stonewort (Nitella gracilis) is the only red list charophyte typical of acid habitats (Stewart 1996). Recent records only exist for 6 UK sites, three in Wales and three in Scotland. Acid deposition in combination with conifer plantations may be a threat at 1 or 2 sites in south-west Scotland (Stewart 2001).
There is no published research on the effects of acidification on these species. The only red list charophyte that may be vulnerable to acidification is Nitella gracilis (Stewart 2001).
|Critical Load/ Level|
No estimate available