ABSTRACT
Effects of fluoride (F(-)) emissions on previously unpolluted assemblages of saxicolous lichens, near an aluminium reduction works, are described. Lichens contained a mean 16 microg F(-) g(-1) dry weight in 1970 before emissions commenced. Subsequently, where annually monitored Ramalina contained >100microg g(-1) severe damage occurred, including loss of attachment to the rocky substratum. At sites within 1 km of the works well-exposed to emissions, fruticose (shrubby) lichens were eliminated, but in more sheltered locations 18% cover had survived by 1983. Some foliose (leaf-like) lichens tolerated >200 microg g(-1), while crustose (crust-like) species were least affected, 32% and 70% surviving, respectively. Concentrations of fluoride, and associated injury, decreased with increasing distance from the works. Fruticose and sensitive foliose species sustained 40-75% losses of cover up to 4 km NE, downwind of the works, where fluoride averaged 50-100 microg g(-1), but <40% losses were recorded in fruticose species up to 9 km, where concentrations averaged 35-50 microg. Saxicolous lichens were damaged less than corticolous species previously reported and, following decreased emissions, were also regrowing in sheltered and more distant locations by 1985.
ABSTRACT
Effects of emissions, from a new aluminium works, on previously unpolluted assemblages of corticolous lichens, are described. Injury symptoms included chlorosis, red colorations, necrosis and weakening of attachment of thalli to the bark substratum, resulting in reductions in % cover. Before emissions commenced in 1970, lichens contained <10microg fluoride (F(-)) g(-1) dry weight. Where concentrations in annually monitored samples of Ramalina reached >100microg F(-1) g(-1), within 4 km downwind of the works, severe injury occurred with >75% losses of cover of some species. At increasing distances, injury, and F(-) concentrations, decreased. The lichen flora was almost eliminated within 1 km of the works: after 15 years' operation, 37 species are absent within 650 m, but at least 43 survive at 900 m. A range of sensitivity was shown between, and within, morphological types. Fructicose (shrubby) lichens contained >600microg F(-1) g(-1) after 4 years and were the first, and most severely, affected (<1% cover surviving by 1975). Most foliose (leaf-like) species were sensitive (88% losses by 1977), but some were more tolerant, containing >400microg F(-1) g(-1) after 10 years. Crustose (crust-like) lichens were affected least, some growing markedly to occupy the space formed following elimination of more intolerant species. Since 1978, in response to decreasing emissions, there has been a recovery of some fruticose and foliose species in less-exposed locations.
